Marques PX, O'Donovan J, Souda P, Gutierrez J, Williams EJ, Worrall S, McElroy M, Proctor A, Brady C, Sammin D, Basset H, Whitelegge JP, Markey BK, Nally JE (2011) Amniotic and allantoic fluids from experimentally infected sheep contain immunoglobulin specific for Chlamydophila abortus, Veterinary Immunology and Immunopathology 140 (1-2) pp. 1-9
Chlamydophila abortus, the aetiological agent of enzootic abortion of ewes (EAE), replicates in trophoblast cells leading to their destruction and dissemination of the bacterium to foetal organs. To further understand the pathogenesis of EAE, amniotic and allantoic fluids were collected from experimentally infected pregnant ewes at 30 (7 samples from each fluid), 35 (8 samples from each fluid), 40 (10 samples from each fluid) and 43 (6 amniotic fluids and 7 allantoic fluids) days post-infection to determine pathogen numbers and other markers of infection. Whilst experimentally infected ewes had characteristic placental lesions, only two amniotic and seven allantoic fluid samples were positive for C. abortus by real-time PCR. In contrast, all amniotic and allantoic fluids were positive for immunoglobulin. Immunoglobulins were generally detected earlier in allantoic fluid than in amniotic fluid and the numbers of samples containing immunoglobulins increased as infection progressed. IgG in amniotic and allantoic fluids was shown to be specific for C. abortus, and reacted with the major outer membrane proteins, polymorphic outer membrane protein and macrophage infectivity potentiator protein. A comparison of two-dimensional immunoblots using purified IgG from the allantoic fluid, amniotic fluid, ewe serum and foetal serum of a C. abortus infected animal at 40 days post infection indicated a pattern of reactivity intermediate between that of the ewe serum and the foetal serum. Results suggest that a maternal source of immunoglobulin is predominant at 30 days post-infection but that foetal derived antibodies may be contributed at a later stage. © 2010 Elsevier B.V.
Gutierrez J, Barry-Ryan C, Bourke P (2008) The antimicrobial efficacy of plant essential oil combinations and interactions with food ingredients., Int J Food Microbiol 124 (1) pp. 91-97
The objective of this study was to evaluate the efficacy of plant essential oils (EOs) in combination and to investigate the effect of food ingredients on their efficacy. The EOs assessed in combination included basil, lemon balm, marjoram, oregano, rosemary, sage and thyme. Combinations of EOs were initially screened against Bacillus cereus, Escherichia coli, Listeria monocytogenes and Pseudomonas aeruginosa using the spot-on-agar test. The influence of varying concentrations of EO combinations on efficacy was also monitored using E. coli. These preliminary studies showed promising results for oregano in combination with basil, thyme or marjoram. The checkerboard method was then used to quantify the efficacy of oregano, marjoram or thyme in combination with the remainder of selected EOs. Fractional inhibitory concentrations (FIC) were calculated and interpreted as synergy, addition, indifference or antagonism. All the oregano combinations showed additive efficacy against B. cereus, and oregano combined with marjoram, thyme or basil also had an additive effect against E. coli and P. aeruginosa. The mixtures of marjoram or thyme also displayed additive effects in combination with basil, rosemary or sage against L. monocytogenes. The effect of food ingredients and pH on the antimicrobial efficacy of oregano and thyme was assessed by monitoring the lag phase and the maximum specific growth rate of L. monocytogenes grown in model media. The model media included potato starch (0, 1, 5 or 10%), beef extract (1.5, 3, 6 or 12%), sunflower oil (0, 1, 5 or 10%) and TSB at pH levels of 4, 5, 6 or 7. The antimicrobial efficacy of EOs was found to be a function of ingredient manipulation. Starch and oils concentrations of 5% and 10% had a negative impact on the EO efficacy. On the contrary, the EOs were more effective at high concentrations of protein, and at pH 5, by comparison with pH 6 or 7. This study suggests that combinations of EOs could minimize application concentrations and consequently reduce any adverse sensory impact in food. However, their application for microbial control might be affected by food composition, therefore, careful selection of EOs appropriate to the sensory and compositional status of the food system is required. This work shows that EOs might be more effective against food-borne pathogens and spoilage bacteria when applied to ready to use foods containing a high protein level at acidic pH, as well as lower levels of fats or carbohydrates.
Basanta A, Herranz C, Gutiérrez J, Criado R, Hernández PE, Cintas LM (2009) Development of bacteriocinogenic strains of Saccharomyces cerevisiae heterologously expressing and secreting the leaderless enterocin L50 peptides L50A and L50B from Enterococcus faecium L50, Applied and Environmental Microbiology 75 (8) pp. 2382-2392
A segregationally stable expression and secretion vector for Saccharomyces cerevisiae, named pYABD01, was constructed by cloning the yeast gene region encoding the mating pheromone ±-factor 1 secretion signal (MF±1 s) into the S. cerevisiae high-copy-number expression vector pYES2. The structural genes of the two leaderless peptides of enterocin L50 (EntL50A and EntL50B) from Enterococcus faecium L50 were cloned, separately (entL50A or entL50B) and together (entL50AB), into pYABD01 under the control of the galactoseinducible promoter PGAL1. The generation of recombinant S. cerevisiae strains heterologously expressing and secreting biologically active EntL50A and EntL50B demonstrates the suitability of the MF±1 s-containing vector pYABD01 to direct processing and secretion of these antimicrobial peptides through the S. cerevisiae Sec system. Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Gutierrez J, Rodriguez G, Barry-Ryan C, Bourke P (2008) Efficacy of plant essential oils against foodborne pathogens and spoilage bacteria associated with ready-to-eat vegetables: antimicrobial and sensory screening., J Food Prot 71 (9) pp. 1846-1854
The objectives of this study were to evaluate the antimicrobial activity of plant essential oils (EOs) against foodborne pathogens and key spoilage bacteria pertinent to ready-to-eat vegetables and to screen the selected EOs for sensory acceptability. The EOs basil, caraway, fennel, lemon balm, marjoram, nutmeg, oregano, parsley, rosemary, sage, and thyme were evaluated. The bacteria evaluated were Listeria spp., Staphylococcus aureus, Lactobacillus spp., Bacillus cereus, Salmonella, Enterobacter spp., Escherichia coli, and Pseudomonas spp. Quantitative antimicrobial analyses were performed using an absorbance-based microplate assay. Efficacy was compared using MIC, the half maximum inhibitory concentration, and the increase in lag phase. Generally, gram-positive bacteria were more sensitive to EOs than were gram-negative bacteria, and Listeria monocytogenes strains were among the most sensitive. Of the spoilage organisms, Pseudomonas spp. were the most resistant. Oregano and thyme EOs had the highest activity against all the tested bacteria. Marjoram and basil EOs had selectively high activity against B. cereus, Enterobacter aerogenes, E. coli, and Salmonella, and lemon balm and sage EOs had adequate activity against L. monocytogenes and S. aureus. Within bacterial species, EO efficacy was dependent on strain and in some cases the origin of the strain. On a carrot model product, basil, lemon balm, marjoram, oregano, and thyme EOs were deemed organoleptically acceptable, but only oregano and marjoram EOs were deemed acceptable for lettuce. Selected EOs may be useful as natural and safe additives for promoting the safety and quality of ready-to-eat vegetables.
Gutierrez J, O'Donovan J, Williams E, Proctor A, Brady C, Marques PX, Worrall S, Nally JE, McElroy M, Bassett H, Sammin D, Buxton D, Maley S, Markey BK (2010) Detection and quantification of Toxoplasma gondii in ovine maternal and foetal tissues from experimentally infected pregnant ewes using real-time PCR, Veterinary Parasitology 172 (1-2) pp. 8-15
A real-time PCR (rt-PCR) targeting the 529-bp repeat element (RE) of Toxoplasma gondii was used to detect and quantify the parasite burden in maternal and foetal tissues in 18 seronegative ewes infected with 3000 toxoplasma oocysts on day 90 of pregnancy. The infected ewes were sacrificed in groups of 4-6 at 21, 25, 33 and 35 days post-challenge. Ten sham inoculated pregnant ewes were used as controls. T. gondii was not detected in the control ewes or their foeti. The parasite was only detected in the maternal tissues in a few of the challenged ewes on a small number of occasions where it was identified in spleen and uterine lymph nodes. T. gondii was detected in the foetal spleen and liver at the early sacrifice times but only sporadically thereafter. In the case of amniotic, allantoic and foetal aqueous humor samples T. gondii was only detected on a small number of occasions. However, it was found in the majority of the foetal lung and placentome samples throughout the study period, while placentomes and foetal brains contained high levels of the parasite during the later stages. Histopathological examination of placentome and brain tissue from the foeti in the present study revealed a strong correlation between histopathological lesions and quantities of the parasite DNA detected. These results indicate that the cotyledonary component of the foetal membranes is the sample of choice for the diagnosis of T. gondii by rt-PCR, followed by foetal lung and brain. © 2010 Elsevier B.V.
Criado R, Gutiérrez J, Martín M, Herranz C, Hernández PE, Cintas LM (2006) Immunochemical characterization of temperature-regulated production of enterocin L50 (EntL50A and EntL50B), enterocin P, and enterocin Q by Enterococcus faecium L50., Appl Environ Microbiol 72 (12) pp. 7634-7643
Polyclonal antibodies with specificity for enterocin L50A (EntL50A), enterocin L50B (EntL50B), and enterocin Q (EntQ) produced by Enterococcus faecium L50 have been generated by immunization of rabbits with chemically synthesized peptides derived from the C terminus of EntL50A (LR1) and EntL50B (LR2) and from the complete enterocin Q (EntQ) conjugated to the carrier protein keyhole limpet hemocyanin (KLH). The sensitivity and specificity of these antibodies were evaluated by a noncompetitive indirect enzyme-linked immunosorbent assay (NCI-ELISA) and a competitive indirect ELISA (CI-ELISA). The NCI-ELISA was valuable for detecting anti-EntL50A-, anti-EntL50B-, and anti-EntQ-specific antibodies in the sera of the LR1-KLH-, LR2-KLH-, and EntQ-KLH-immunized animals, respectively. Moreover, these antibodies and those specific for enterocin P (EntP) obtained in a previous work (J. Gutiérrez, R. Criado, R. Citti, M. Martín, C. Herranz, M. F. Fernández, L. M. Cintas, and P. E. Hernández, J. Agric. Food Chem. 52:2247-2255, 2004) were used in an NCI-ELISA to detect and quantify the production of EntL50A, EntL50B, EntP, and EntQ by the multiple-bacteriocin producer E. faecium L50 grown at different temperatures (16 to 47 degrees C). Our results show that temperature has a strong influence on bacteriocin production by this strain. EntL50A and EntL50B are synthesized at 16 to 32 degrees C, but production becomes negligible when the growth temperature is above 37 degrees C, whereas EntP and EntQ are synthesized at temperatures ranging from 16 to 47 degrees C. Maximum EntL50A and EntL50B production was detected at 25 degrees C, while EntP and EntQ are maximally produced at 37 and 47 degrees C, respectively. The loss of plasmid pCIZ1 (50 kb) and/or pCIZ2 (7.4 kb), encoding EntL50A and EntL50B as well as EntQ, respectively, resulted in a significant increase in production and stability of the chromosomally encoded EntP.
Gutierrez J, Barry-Ryan C, Bourke P (2009) Antimicrobial activity of plant essential oils using food model media: Efficacy, synergistic potential and interactions with food components, Food Microbiology 26 (2) pp. 142-150
The aim of this study was to optimise the antimicrobial efficacy of plant essential oils (EOs) for control of Listeria spp. and spoilage bacteria using food model media based on lettuce, meat and milk. The EOs evaluated were lemon balm, marjoram, oregano and thyme and their minimum inhibitory concentrations (MIC) were determined against Enterobacter spp., Listeria spp., Lactobacillus spp., and Pseudomonas spp. using the agar dilution method and/or the absorbance based microplate assay. MICs were significantly lower in lettuce and beef media than in TSB. Listeria strains were more sensitive than spoilage bacteria, and oregano and thyme were the most active EOs. EO combinations were investigated using the checkerboard method and Oregano combined with thyme had additive effects against spoilage organisms. Combining lemon balm with thyme yielded additive activity against Listeria strains. The effect of simple sugars and pH on antimicrobial efficacy of oregano and thyme was assessed in a beef extract and tomato serum model media. EOs retained greater efficacy at pH 5 and 2.32% sugar, but sugar concentrations above 5% did not negatively impact EO efficacy. In addition to proven antimicrobial efficacy, careful selection and investigation of EOs appropriate to the sensory profile of foods and composition of the food system is required. This work shows that EOs might be more effective against food-borne pathogens and spoilage bacteria when applied to foods containing a high protein level at acidic pH, as well as moderate levels of simple sugars. © 2008 Elsevier Ltd. All rights reserved.
Worrall S, Sammin DJ, Bassett HF, Reid CR, Gutierrez J, Marques PX, Nally JE, O'Donovan J, Williams EJ, Proctor A, Markey BK (2011) Interferon-³ expression in trophoblast cells in pregnant ewes challenged with Chlamydophila abortus, Journal of Reproductive Immunology 90 (2) pp. 214-219
Pregnant ewes were challenged with Chlamydia abortus at 91-98 days of gestation and euthanised at 14, 21 and 28 days post-challenge. IFN³ mRNA labelling appeared to be co-localised with Chlamydial lipopolysaccharide within trophoblast cells in discrete areas lining the primary villi in the limbus and hilar zone of the placentomes from challenged sheep on days 21 and 28 post-infection. The presence of IFN³ was also demonstrated by immunohistochemistry. No labelling was seen in tissues from the non-infected ewes. The presence of IFN³ in trophoblast cells from infected ewes may indicate an attempt to restrict the replication of the organism and be an important trigger for the inflammatory responses that develop on the fetal side of the placenta in enzootic abortion. © 2011 Elsevier Ireland Ltd.
Martín M, Gutiérrez J, Criado R, Herranz C, Cintas LM, Hernández PE (2007) Chimeras of mature pediocin PA-1 fused to the signal peptide of enterocin P permits the cloning, production, and expression of pediocin PA-1 in Lactococcus lactis., J Food Prot 70 (12) pp. 2792-2798
Chimeras of pediocin PA-1 (PedA-1), a bacteriocin produced by Pediococcus acidilactici PLBH9, fused to the signal peptide of enterocin P (EntP), a sec-dependent bacteriocin produced by Enterococcus faecium P13, permitted the production of PedA-1 in Lactococcus lactis. Chimeric genes encoding the EntP signal peptide (SP(entP)) fused to mature PedA-1 (pedA), with or without its immunity gene (pedB), were cloned into the expression vector pMG36c to generate the recombinant plasmids pMPP9 (SP(entP):pedA) and pMPP14i (SP(entP):pedA + pedB). Transformation of competent L. lactis subsp. lactis IL1403, L. lactis subsp. cremoris NZ9000, and L. lactis subsp. lactis DPC5598 with the recombinant plasmids has permitted the detection and quantitation of PedA-1 and the coproduction of nisin A and PedA-1 in supernatants of producer cells with specific anti-PedA-1 antibodies and a noncompetitive indirect enzyme-linked immunosorbent assay. Recombinant L. lactis hosts carrying pMPP9 or pMPP14i displayed antimicrobial activity, suggesting that mature PedA-1 fused to SP(EntP) is the minimum requirement for the synthesis, processing, and secretion of biologically active PedA-1 in L. lactis. However, the production and antimicrobial activity of the PedA-1 produced by L. lactis was lower than that produced by the P. acidilactici control strains.
Gutiérrez J, Criado R, Citti R, Martín M, Herranz C, Nes IF, Cintas LM, Hernández PE (2005) Cloning, production and functional expression of enterocin P, a sec-dependent bacteriocin produced by Enterococcus faecium P13, in Escherichia coli., Int J Food Microbiol 103 (3) pp. 239-250
The cloning and expression of enterocin P (EntP), a sec-dependent bacteriocin produced by Enterococcus faecium P13, was studied in Escherichia coli. PCR-amplified products of the preenterocin P gene (entP) or entP plus the putative EntP immunity gene (entiP), were cloned in plasmid pETBlue-1 under the control of the inducible T7lac promoter. Although target genes in derivative plasmids pJG01 (entP) and pJG02 (entP plus entiP) did not generate products with antimicrobial activity after an in vitro combined transcription/translation reaction, they were expressed as biologically active products following transformation and induction in the E. coli Tuner(DE3)pLacI host. The use of specific antibodies and an ELISA permitted the detection and quantification of EntP in the supernatant (SN), cellular soluble protein fraction (CSF), and inclusion bodies (IB) of E. coli Tuner(DE3)pLacI cells transformed with either pJG01 or pJG02. Functional EntP from the supernatants of E. coli Tuner(DE3)pLacI (pJG01) cultures grown in a complex medium was recovered, at a high efficiency, by immunoaffinity chromatography in a single step. A purification method based on hydrophobic adsorption and reverse-phase chromatographies also permitted the recovery of active EntP from the supernatants of the same cultures grown in a minimally defined medium. The E. coli Tuner(DE3)pLacI (pJG01) cells would merit consideration as an alternative experimental model for the heterologous production and functional expression of EntP, as well as for the fast and efficient recovery of this bacteriocin from the supernatant of this recombinant producer.
Criado R, Gutiérrez J, Budin-Verneuil A, Hernández PE, Hartke A, Cintas LM, Auffray Y, Benachour A (2008) Molecular analysis of the replication region of the pCIZ2 plasmid from the multiple bacteriocin producer strain Enterococcus faecium L50., Plasmid 60 (3) pp. 181-189
The sequence analysis of the 7383 bp plasmid pCIZ2 from Enterococcus faecium L50 enabled the identification of a DNA region involved in its replication. The structural organization of the pCIZ2 replication region is highly similar to those of well-known theta-replicating plasmids. It contains an untranslated region, the putative replication origin (ori), constituted by two sets of direct repeats of 12 and 22 bp (iterons), and followed by three open-reading frames (orf8 to orf10). orf8 encodes the replication initiation protein (RepE). The transcriptional start site of the replication locus was identified 13 nucleotides upstream of the repE start codon. A two-dimensional agarose gel electrophoresis analysis revealed pCIZ2 intermediates profile typical of the theta-type replication mechanism. Subcloning of different DNA fragments of the pCIZ2 replication region in Escherichia coli and, subsequently, in the plasmidless E. faecium L50/14-2 allowed the determination of the minimal replicon on a 1.2kb DNA fragment containing only the overall ori and repE which also act in trans. The involvement of orf9 in the plasmid copy number and in the plasmid stability was investigated. The pCIZ2 recombinant plasmids constitute narrow-host range shuttle cloning vectors (E. coli-E. faecium) that could be very useful for enterococcal genes studies, allowing an easy identification due to their histochemical recognition.
Martín M, Gutiérrez J, Criado R, Herranz C, Cintas LM, Hernández PE (2007) Cloning, production and expression of the bacteriocin enterocin A produced by Enterococcus faecium PLBC21 in Lactococcus lactis., Appl Microbiol Biotechnol 76 (3) pp. 667-675
Replacement of the leader sequence of enterocin A (EntA), a bacteriocin produced by Enterococcus faecium PLBC21, by the signal peptide of enterocin P (EntP), a sec-dependent bacteriocin produced by E. faecium P13, permitted production of EntA in Lactococcus lactis. Chimeras encoding the EntP signal peptide (SP( entP )) fused to mature EntA (entA), with or without its immunity gene (entiA), were cloned into the expression vector pMG36c to generate the recombinant plasmids, pMPA15 (SP( entP ):entA) and pMPA10i (SP( entP ):entA + entiA). Transformation of competent L. lactis subsp. lactis IL1403 and L. lactis subsp. cremoris NZ9000 with the recombinant plasmids permitted production of EntA by the transformed cells, and the co-production of nisin A and EntA by the L. lactis subsp. lactis DPC5598 transformants. Mature EntA fused to SP(EntP) is the minimum requirement for synthesis, processing and secretion of biologically active EntA in L. lactis. The production of EntA by most recombinant L. lactis hosts was larger than in the E. faecium control strains. All L. lactis derivatives showed antimicrobial activity against Listeria spp., and L. lactis (pMPA15) displayed the highest antilisterial effect.
Criado R, Diep DB, Aakra A, Gutiérrez J, Nes IF, Hernández PE, Cintas LM (2006) Complete sequence of the enterocin Q-encoding plasmid pCIZ2 from the multiple bacteriocin producer Enterococcus faecium L50 and genetic characterization of enterocin Q production and immunity., Appl Environ Microbiol 72 (10) pp. 6653-6666
The locations of the genetic determinants for enterocin L50 (EntL50A and EntL50B), enterocin Q (EntQ), and enterocin P (EntP) in the multiple bacteriocin producer Enterococcus faecium strain L50 were determined. These bacteriocin genes occur at different locations; entL50AB (encoding EntL50A and EntL50B) are on the 50-kb plasmid pCIZ1, entqA (encoding EntQ) is on the 7.4-kb plasmid pCIZ2, and entP (encoding EntP) is on the chromosome. The complete nucleotide sequence of pCIZ2 was determined to be 7,383 bp long and contains 10 putative open reading frames (ORFs) organized in three distinct regions. The first region contains three ORFs: entqA preceded by two divergently oriented genes, entqB and entqC. EntqB shows high levels of similarity to bacterial ATP-binding cassette (ABC) transporters, while EntqC displays no significant similarity to any known protein. The second region encompasses four ORFs (orf4 to orf7), and ORF4 and ORF5 display high levels of similarity to mobilization proteins from E. faecium and Enterococcus faecalis. In addition, features resembling a transfer origin region (oriT) were found in the promoter area of orf4. The third region contains three ORFs (orf8 to orf10), and ORF8 and ORF9 exhibit similarity to the replication initiator protein RepE from E. faecalis and to RepB proteins, respectively. To clarify the minimum requirement for EntQ synthesis, we subcloned and heterologously expressed a 2,371-bp fragment from pCIZ2 that encompasses only the entqA, entqB, and entqC genes in Lactobacillus sakei, and we demonstrated that this fragment is sufficient for EntQ production. Moreover, we also obtained experimental results indicating that EntqB is involved in ABC transporter-mediated EntQ secretion, while EntqC confers immunity to this bacteriocin.
O'Donovan J, Proctor A, Gutierrez J, Worrell S, Nally J, Marques P, Brady C, McElroy M, Sammin D, Buxton D, Maley S, Bassett H, Markey B (2012) Distribution of Lesions in Fetal Brains Following Experimental Infection of Pregnant Sheep With Toxoplasma gondii, Veterinary Pathology 49 (3) pp. 462-469
Six ovine fetal brains were harvested 33 to 35 days postchallenge from 5 ewes, each of which was given 3000 Toxoplasma gondii oocysts on day 90 of pregnancy. Histopathologic examination of transverse sections taken at 13 levels in the fetal brains revealed the presence of toxoplasmosis-related lesions in all 6 brains. However, lesions were not randomly distributed (P=.007); they were most numerous at the level of the optic tract, the rostral margin of the pons, and 4 mm caudal to the ansate sulcus and were absent in all sections at the level of the caudal cerebellum. Lesion distribution may be due to hemodynamic factors, differences in the expression of endothelial surface receptor molecules at the level of the blood-brain barrier, or the presence of localized permissive/inhibitory factors within the brain. The results have implications for the selection of areas of brain from aborted ovine fetuses to be examined histopathologically for laboratory diagnosis. © The Author(s) 2012.
Gutierrez J, Williams EJ, O'Donovan J, Brady C, Proctor AF, Marques PX, Worrall S, Nally JE, McElroy M, Bassett HF, Sammin DJ, Markey BK (2011) Monitoring clinical outcomes, pathological changes and shedding of Chlamydophila abortus following experimental challenge of periparturient ewes utilizing the natural route of infection, Veterinary Microbiology 147 (1-2) pp. 119-126
Enzootic abortion of ewes (EAE) caused by Chlamydophila abortus is an important disease resulting in significant lamb loss in most sheep producing countries. Ewes are considered to be naturally infected with C. abortus via the oral-nasal route and may become persistent carriers, shedding during subsequent oestrous cycles and at lambing. The aim of this study was to monitor the clinical outcomes, pathological changes and shedding of C. abortus in 18 periparturient orally infected sheep for two breeding seasons. In the first season, C. abortus was detected by real-time PCR (rt-PCR) in 13/18 conjunctival swabs at oestrus. Three out of the 15 pregnant ewes gave birth to 1 live and 1 dead lamb, and 2 of them aborted. Following parturition/abortion, C. abortus was detected in 12/15 vaginal swabs and in all the collected foetal membranes. However, only those membranes containing high copy numbers of the bacterium displayed the EAE typical lesions. In the second season, none of the 13 pregnant ewes aborted, and 5 of them gave birth to dead or weak lambs. C. abortus was not detected in conjunctival or vaginal swabs at oestrus or parturition. The bacterium was detected at low levels in 36% of the foetal membranes, but with no evidence of histopathological lesions. These results indicate that C. abortus can be detected in a large proportion of animals during the first pregnancy after oral infection. However, this proportion is reduced at the subsequent breeding season, confirming the occurrence of a chronic low level persistent infection in post-abortion/lambing ewes. © 2010 Elsevier B.V.
Gutiérrez J, González-Pérez S, García-García F, Daly CT, Lorenzo O, Revuelta JL, McCabe PF, Arellano JB (2014) Programmed cell death activated by Rose Bengal in Arabidopsis thaliana cell suspension cultures requires functional chloroplasts., J Exp Bot 65 (12) pp. 3081-3095
Light-grown Arabidopsis thaliana cell suspension culture (ACSC) were subjected to mild photooxidative damage with Rose Bengal (RB) with the aim of gaining a better understanding of singlet oxygen-mediated defence responses in plants. Additionally, ACSC were treated with H2O2 at concentrations that induced comparable levels of protein oxidation damage. Under low to medium light conditions, both RB and H2O2 treatments activated transcriptional defence responses and inhibited photosynthetic activity, but they differed in that programmed cell death (PCD) was only observed in cells treated with RB. When dark-grown ACSC were subjected to RB in the light, PCD was suppressed, indicating that the singlet oxygen-mediated signalling pathway in ACSC requires functional chloroplasts. Analysis of up-regulated transcripts in light-grown ACSC, treated with RB in the light, showed that both singlet oxygen-responsive transcripts and transcripts with a key role in hormone-activated PCD (i.e. ethylene and jasmonic acid) were present. A co-regulation analysis proved that ACSC treated with RB exhibited higher correlation with the conditional fluorescence (flu) mutant than with other singlet oxygen-producing mutants or wild-type plants subjected to high light. However, there was no evidence for the up-regulation of EDS1, suggesting that activation of PCD was not associated with the EXECUTER- and EDS1-dependent signalling pathway described in the flu mutant. Indigo Carmine and Methylene Violet, two photosensitizers unable to enter chloroplasts, did not activate transcriptional defence responses in ACSC; however, whether this was due to their location or to their inherently low singlet oxygen quantum efficiencies was not determined.
Gonzalez-Perez S, Gutierrez J, Garcia-Garcia F, Osuna D, Dopazo J, Lorenzo O, Revuelta JL, Arellano JB (2011) Early Transcriptional Defense Responses in Arabidopsis Cell Suspension Culture under High-Light Conditions, PLANT PHYSIOLOGY 156 (3) pp. 1439-1456 AMER SOC PLANT BIOLOGISTS
Gutierrez J, Bourke P, Lonchamp J, Barry-Ryan C (2009) Impact of plant essential oils on microbiological, organoleptic and quality markers of minimally processed vegetables, Innovative Food Science and Emerging Technologies 10 (2) pp. 195-202
The objectives of this study were to evaluate the efficacy of plant essential oils (EOs) for control of the natural spoilage microflora on ready-to-eat (RTE) lettuce and carrots whilst also considering their impact on organoleptic properties. Initial decontamination effects achieved using EOs were comparable to that observed with chlorine and solution containing oregano recorded a significantly lower initial TVC level than the water treatment on carrots (p
Gutiérrez J, Criado R, Martín M, Herranz C, Cintas LM, Hernández PE (2005) Production of enterocin P, an antilisterial pediocin-like bacteriocin from Enterococcus faecium P13, in Pichia pastoris., Antimicrob Agents Chemother 49 (7) pp. 3004-3008
The gene encoding mature enterocin P (EntP), an antimicrobial peptide from Enterococcus faecium P13, was cloned into the pPICZalphaA expression vector to generate plasmid pJC31. This plasmid was integrated into the genome of P. pastoris X-33, and EntP was heterologously secreted from the recombinant P. pastoris X-33t1 derivative at a higher production and antagonistic activity than from E. faecium P13.
Gutiérrez J, Criado R, Citti R, Martín M, Herranz C, Fernández MF, Cintas LM, Pablo E H (2004) Performance and applications of polyclonal antipeptide antibodies specific for the enterococcal bacteriocin enterocin P, J Agric Food Chem
Polyclonal antibodies with specificity for enterocin P (EntP) have been generated by immunization of rabbits with two chemically synthesized N-terminal peptides (P1 and P2) and a C-terminal peptide (P3) of this bacteriocin conjugated to the carrier protein KLH. The sensitivity and specificity of the peptide-KLH-generated antibodies were evaluated by a noncompetitive indirect enzyme-linked immunosorbent assay (NCI-ELISA) and a competitive indirect (CI)-ELISA. The NCI-ELISA but not the CI-ELISA was valuable for detecting the existence of EntP specific antibodies in the sera of the P2-KLH and P3-KLH immunized animals and to detect and quantify the EntP in the supernatant of producer strains. The anti-P2-KLH sera cross-reacted with the supernatant of a strain producer of sakacin A, a bacteriocin closely related to EntP. Immunoaffinity chromatography columns with anti-P2-KLH or anti-P3-KLH immunoglobulins retained the EntP from the supernatant of the producer strain. Western blotting of EntP with the anti-P2-KLH-generated antibodies suggests that purified EntP tends to the formation of aggregates with no antimicrobial activity. Monitoring the purification of EntP with antipeptide antibodies suggests that while the performance of the evaluated purification procedures would be reasonably acceptable in terms of recovery of the antimicrobial activity of the bacteriocin, their yield is far from attractive in terms of recovery of the initial concentration of enterocin P.
Marques PX, Souda P, O'Donovan J, Gutierrez J, Williams EJ, Worrall S, McElroy M, Proctor A, Brady C, Sammin D, Basset HF, Whitelegge JP, Markey BE, Nally JE (2010) Identification of immunologically relevant proteins of Chlamydophila abortus using sera from experimentally infected pregnant ewes (Clinical and Vaccine Immunology (2010) 17, 8, (1274-1281)), Clinical and Vaccine Immunology 17 (9)
Gutiérrez J, González-Pérez S, García-García F, Lorenzo O, Arellano JB (2011) Does singlet oxygen activate cell death in Arabidopsis cell suspension cultures? Analysis of the early transcriptional defense responses to high light stress, Plant Signaling and Behavior 6 (12) pp. 1937-1942
Can Arabidopsis cell suspension cultures (ACSC) provide a useful working model to investigate genetically-controlled defense responses with signaling cascades starting in chloroplasts? In order to provide a convincing answer, we analyzed the early transcriptional profile of Arabidopsis cells at high light (HL). The results showed that ACSC respond to HL in a manner that resembles the singlet oxygen ( 1O 2)-mediated defense responses described for the conditional fluorescent (flu) mutant of Arabidopsis thaliana. The flu mutant is characterized by the accumulation of free protochlorophyllide (Pchlide) in plastids when put into darkness and the subsequent production of 1O 2 when the light is on. In ACSC, 1O 2 is produced in chloroplasts at HL when excess excitation energy flows into photosystem II (PSII). Other reactive oxygen species are also produced in ACSC at HL, but to a lesser extent. When the HL stress ceases, ACSC recovers the initial rate of oxygen evolution and cell growth continues. We can conclude that chloroplasts of ACSC are both photosynthetically active and capable of initiating 1O 2-mediated signaling cascades that activate a broad range of genetically-controlled defense responses. The upregulation of transcripts associated with the biosynthesis and signaling pathways of OPDA (12-oxophytodienoic acid) and ethylene (ET) suggests that the activated defense responses at HL are governed by these two hormones. In contrast to the flu mutant, the 1O 2-mediated defense responses were independent of the upregulation of EDS1 (enhanced disease susceptibility) required for the accumulation of salicylic acid (SA) and genetically-controlled cell death. Interestingly, a high correlation in transcriptional expression was also observed between ACSC at HL, and the aba1 and max4 mutants of Arabidopsis, characterized by defects in the biosynthesis pathways of abscisic acid (ABA) and strigolactones, respectively. © 2011 Landes Bioscience.
Gutierrez J, O'Donovan J, Proctor A, Brady C, Marques PX, Worrall S, Nally JE, McElroy M, Bassett H, Fagan J, Maley S, Buxton D, Sammin D, Markey BK (2012) Application of quantitative real-time polymerase chain reaction for the diagnosis of toxoplasmosis and enzootic abortion of ewes, Journal of Veterinary Diagnostic Investigation 24 (5) pp. 846-854
Toxoplasma gondii and Chlamydophila abortus are the 2 most common infectious causes of ovine abortion worldwide. These obligate intracellular pathogens are associated with severe placentitis leading to abortion or stillbirth in pregnant ewes, and resulting in significant economic losses. The objectives of the current study were the development, validation, and application of a duplex real-time polymerase chain reaction (PCR) assay capable of quantifying the burden of infection by T. gondii and C. abortus in material submitted for diagnostic purposes. The validation was carried out using samples from ewes experimentally infected with these organisms. Based on the numbers of genome copies detected, an arbitrary cutoff level was established to correlate with significant pathological changes sufficient to give rise to abortion. When the PCR assay was applied to samples from 66 Irish farms with naturally occurring outbreaks of ovine abortion, toxoplasmosis and enzootic abortion of ewes (EAE) accounted for 14% and 20% of the farms, respectively, while on 6% of the farms, there was evidence of dual infection. When standard diagnostic techniques including histopathological examination, serological analysis, chlamydial antigen detection, and bacteriological culture, were used on samples from the same farms, toxoplasmosis was diagnosed in 17% of farms, and EAE in 12%; dual infection was diagnosed on 3% of the farms. In general, good agreement was found between the PCR and the standard methods. The duplex real-time PCR assay developed in this study has proved to be a very sensitive and rapid tool that might provide a valuable addition to the methods currently available for routine diagnosis of ovine abortions. © 2012 The Author(s).
Gutiérrez J, Larsen R, Cintas LM, Kok J, Hernández PE (2006) High-level heterologous production and functional expression of the sec-dependent enterocin P from Enterococcus faecium P13 in Lactococcus lactis., Appl Microbiol Biotechnol 72 (1) pp. 41-51
Enterocin P (EntP), a sec-dependent bacteriocin from Enterococcus faecium P13, was produced by Lactococcus lactis. The EntP structural gene (entP) with or without the EntP immunity gene (entiP) was cloned in (1), plasmid pMG36c under control of the lactococcal constitutive promoter P32, (2) in plasmid pNG8048e under control of the inducible PnisA promoter, and (3) in the integration vector pINT29. Introduction of the recombinant vectors in L. lactis resulted in production of biologically active EntP in the supernatants of L. lactis subsp. lactis IL1403 and L. lactis subsp. cremoris NZ9000, and the coproduction of nisin A and EntP in L. lactis subsp. lactis DPC5598. The level of production of EntP, detected and quantified by specific anti-EntP antibodies and a noncompetitive indirect enzyme-linked immunosorbent assay, by the recombinant L. lactis strains depended on the host strain, the expression vector, and the presence of the entiP gene in the constructs of the recombinant L. lactis strains. The highest amount of EntP was produced with derivatives containing entP and entiP, for both L. lactis IL1403 and L. lactis NZ9000. These derivatives produced up to five- to six-fold more EntP than E. faecium P13. Mass spectrometry analysis revealed that EntP purified from L. lactis IL1403 (pJP214) has a molecular mass identical to that purified from E. faecium P13, suggesting that the synthesis, processing, and secretion of EntP progresses efficiently in recombinant L. lactis hosts.
Marques PX, Souda P, O'Donovan J, Gutierrez J, Gutierrez EJ, Worrall S, McElroy M, Proctor A, Brady C, Sammin D, Basset HF, Whitelegge JP, Markey BE, Nally JE (2010) Identification of immunologically relevant proteins of Chlamydophila abortus using sera from experimentally infected pregnant ewes, Clinical and Vaccine Immunology 17 (8) pp. 1274-1281
Chlamydophila abortus is an intracellular pathogen and the etiological agent of enzootic abortion of ewes (EAE). C. abortus has a biphasic development cycle; extracellular infectious elementary bodies (EB) attach and penetrate host cells, where they give rise to intracellular, metabolically active reticulate bodies (RB). RB divide by binary fission and subsequently mature to EB, which, on rupture of infected cells, are released to infect new host cells. Pregnant ewes were challenged with 2 × 106 inclusion forming units (IFU) of C. abortus cultured in yolk sac (comprising both EB and RB). Serum samples were collected at 0, 7, 14, 21, 27, 30, 35, 40, and 43 days postinfection (dpi) and used to identify antigens of C. abortus expressed during disease. Additionally, sera from fetal lambs were collected at 30, 35, 40, and 43 dpi. All serum samples collected from experimentally infected pregnant ewes reacted specifically with several antigens of EB as determined by one-dimensional (1-D) and 2-D gel electrophoresis; reactive antigens identified by mass spectrometry included the major outer membrane protein (MOMP), polymorphic outer membrane protein (POMP), and macrophage infectivity potentiator (MIP) lipoprotein. Copyright © 2010, American Society for Microbiology. All Rights Reserved.
Martín M, Gutiérrez J, Criado R, Herranz C, Cintas LM, Hernández PE (2006) Genes encoding bacteriocins and their expression and potential virulence factors of Enterococci isolated from wood pigeons (Columba palumbus)., J Food Prot 69 (3) pp. 520-531
Samples of the intestinal content and carcasses of wood pigeons (Columba palumbus) were evaluated for enterococci with antimicrobial activity. Enterococcus faecium comprised the largest enterococcal species with antagonistic activity, followed by Enterococcusfaecalis and Enterococcus columbae. PCR amplification of genes coding bacteriocins and determination of their nucleotide sequence, and the use of specific antipeptide bacteriocin antibodies and a noncompetitive indirect enzyme-linked immunosorbent assay, permitted characterization of enterococci coding that described bacteriocins and their expression. The efaAfm determinant was the only virulence gene detected in E. faecium, whereas E. faecalis showed a larger number of virulence determinants, and E. columbae did not carry any of the virulence genes examined. Although all E. faecalis isolates manifested a potent direct antimicrobial activity, no activity was detected in supernatants of producer cells. Purification of the antagonistic activity of E. columbae PLCH2 showed multiple chromatographic fragments after matrix-assisted laser desorption-ionization time-of-flight mass spectrometry analysis, suggesting the active peptide(s) had not yet purified to homogeneity. Bacteriocinogenic E. faecium and E. columbae isolates may be considered hygienic for production of enterocins and potentially safe due to their low incidence of potential virulence genes and susceptibility of most relevant clinical antibiotics. However, the presence among the enterococci of E. faecalis strains with a potent antagonistic activity and multiple virulence factors is an issue that must be considered further.
Arellano JB, Li H, González-Pérez S, Gutiérrez J, Melø TB, Vacha F, Naqvi KR (2011) Trolox, a water-soluble analogue of ±-tocopherol, photoprotects the surface-exposed regions of the photosystem II reaction center in vitro. Is this physiologically relevant?, Biochemistry 50 (39) pp. 8291-8301
Can Trolox, a water-soluble analogue of ±-tocopherol and a scavenger of singlet oxygen ( 1O 2), provide photoprotection, under high irradiance, to the isolated photosystem II (PSII) reaction center (RC)? To answer the question, we studied the endogenous production of 1O 2 in preparations of the five-chlorophyll PSII RC (RC5) containing only one ²-carotene molecule. The temporal profile of 1O 2 emission at 1270 nm photogenerated by RC5 in D 2O followed the expected biexponential behavior, with a rise time, unaffected by Trolox, of 13 ± 1 ¼s and decay times of 54 ± 2 ¼s (without Trolox) and 38 ± 2 ¼s (in the presence of 25 ¼M Trolox). The ratio between the total (k t) and chemical (k r) bimolecular rate constants for the scavenging of 1O 2 by Trolox in aqueous buffer was calculated to be
Gutiérrez J, Bourque D, Criado R, Choi YJ, Cintas LM, Hernández PE, Míguez CB (2005) Heterologous extracellular production of enterocin P from Enterococcus faecium P13 in the methylotrophic bacterium Methylobacterium extorquens., FEMS Microbiol Lett 248 (1) pp. 125-131
Enterocin P (EntP), a strong antilisterial pediocin-like bacteriocin from Enterococcus faecium P13, was produced by Methylobacterium extorquens. For heterologous expression of EntP in the methylotrophic bacterium M. extorquens, a recombinant plasmid was constructed. The gene encoding the EntP structural gene (entP) was cloned into the plasmid vector pCM80, under control of the methanol dehydrogenase promoter (P(mxaF)), to generate plasmid pS25. When M. extorquens ATCC 55366 was transformed with pS25, EntP was detected and quantified in supernatants of the recombinant M. extorquens S25 strain by using specific anti-EntP antibodies and a non-competitive indirect enzyme-linked immunosorbent assay (NCI-ELISA). Purification of EntP by hydrophobic adsorption and reverse-phase (RP-FPLC) chromatographies, permitted recovery of active EntP from the supernatants of M. extorquens S25 grown in a synthetic defined medium.
Marques PX, O' Donovan J, Williams EJ, Gutierrez J, Worrall S, McElroy M, Proctor A, Brady C, Sammin D, Bassett H, Buxton D, Maley S, Markey BK, Nally JE (2012) Detection of Toxoplasma gondii antigens reactive with antibodies from serum, amniotic, and allantoic fluids from experimentally infected pregnant ewes, Veterinary Parasitology 185 (2-4) pp. 91-100
Toxoplasma gondii, an intracellular protozoan parasite, is one of the major causes of infectious abortion in sheep. To further understand the pathogenesis of toxoplasmosis, serum, amniotic and allantoic fluids and foetal stomach contents were collected from experimentally infected pregnant ewes to determine pathogen numbers and other markers of infection. Fifteen pregnant ewes (90 days of gestation) were each orally inoculated with 3000 sporulated oocysts of T. gondii. Serum samples were collected weekly following challenge. Amniotic and allantoic fluids and foetal stomach contents were collected at 21, 25, 28, 33 and 35 days post-infection. Characteristic placental lesions were detected in 1 of 4 challenged ewes at day 25, 3 of 4 challenged ewes at day 28 and in all challenged ewes at days 33 and 35 post-infection. T. gondii was detected only sporadically in amniotic and allantoic fluids before 35 days of infection, by real-time PCR, and only in ewes with placental lesions. At 35 days post-infection, high numbers of parasite were detected in both amniotic and allantoic fluids. An increase in the number of fluids from challenged animals with IgM and IgG was detected over time, except for IgG in allantoic fluid, which was detected in all samples from day 21 post-infection. IgG in amniotic and allantoic fluids was shown to be specific for T. gondii, and reacted with antigens with an apparent molecular mass of approximately 22. kDa and 30. kDa. Results suggest a maternal source of immunoglobulin in the allantoic fluid and a foetal source of immunoglobulin in the amniotic fluid early in infection but that both sources may contribute immunoglobulin to both fluids at a later stage. © 2011 Elsevier B.V.
Brachyspira are the causative agent of avian intestinal spirochaetosis, a gastrointestinal disease common in layer hens and broiler breeders. This disease costs the UK laying industry approximately £18 million per annum, resulting from reduced egg production and poor egg quality. Prevalence of Brachyspira is increasing, and due to the poor understanding of this pathogen, mitigation strategies have been largely unsuccessful. Therefore, preventative measures are essential.
These studies aimed to improve the understanding of Brachyspira pathobiology and investigate Lactobacillus probiotics as a suitable mitigation strategy. Brachyspira and Lactobacillus species were characterised using phenotypic and genotypic methods. Four Lactobacillus isolates were selected for their inhibition of Brachyspira in vitro and demonstrated inhibition by a number of mechanisms.
Secreted metabolites in Lactobacillus cell free supernatant inhibited Brachyspira (p value
Pro-inflammatory responses to Brachyspira in HD11 avian macrophages were dominated by upregulation of IFNg (p value
infection and Lactobacillus isolates were able to protect against the mortality associated with Brachyspira isolates (p value
The studies here demonstrated that Lactobacillus probiotics are a suitable mitigation strategy against Brachyspira. A number of mechanisms were identified, however future studies are required to explore these mechanisms in a more relevant in vivo chicken model.
Natural antimicrobials are of interest to replace traditional food decontamination methods: they are milder and maintain desirable sensory characteristics. However, efficacy can be affected by food structure/composition, thus structural effects in a co-culture pathogen/microflora system are investigated.
Listeria was grown planktonically (liquid broth) or on a biphasic viscoelastic system, in monoculture with/without artificial nisin, or in co-culture with L. lactis (nisin/non-nisin producing). Microbial growth kinetics were monitored and advanced microscopy techniques were utilised to quantify cellular interactions and spatial organisation.
Microstructural effects are observed on the kinetics, with differences in monoculture/co- culture. Significant microscopic differences are observed in spatial organisation and colony size. We are the first to observe changing growth location for all species in monoculture/co- culture, with differences in colony size/organisation through stationary phase.
This study provides insight into the environmental stress response/adaptation of Listeria grown on structured systems in response to L. lactis and natural antimicrobials.
Wildlife poses a significant burden for the complete eradication of bovine tuberculosis (bTB). In particular, wild boar (Sus scrofa) is one of the most important reservoirs of Mycobacterium bovis, the causal agent of bTB. Wild boar can display from mild TB lesions, usually found in head lymph nodes, to generalized TB lesions distributed in different anatomical regions; but rarely clinical signs, which complicates the diagnosis of Mycobacterium bovis infection and bTB control. Among the possibilities for this variability in lesion distribution is the influence of the host-beneficial commensal-primed immune barrier. In this respect, beneficial microbes may delay bTB dissemination as a consequence of an antagonistic competition for nutrients and phagocytes. In order to explore this possibility, we have tested whether typical commensals such as lactobacilli have the capacity to reduce the survival rate of the surrogate M. bovis strain Bacillus Calmette-Guerin (BCG); and to modulate its phagocyte intake.
Three Lactobacillus species, L. casei, L. plantarum, and L. salivarius, isolated from wild boar feces displayed a pH-dependent inhibitory activity against BCG and influenced its intake by porcine blood phagocytes in a species-dependent manner. All lactobacilli showed a very significant bactericidal effect against BCG at low pH, but only isolates of L. plantarum and L. casei displayed such antimycobacterial activity at neutral pH. The genomes of these isolates revealed the presence of two-peptide bacteriocins whose precursor genes up-regulate in the presence of BCG cells. Furthermore, L. plantarum reduced significantly the BCG phagocytic intake, whereas L. casei had the opposite effect. L. salivarius had no significant influence on the phagocytic response to BCG.
Our in vitro results show that lactobacilli isolated from wild boar antagonize BCG as a consequence of their antimycobacterial activity and a competitive phagocytic response. These findings suggest that commensal bacteria could play a beneficial role in influencing the outcome of bTB dissemination. Further work with lactobacilli as a potential competitive pressure to control bTB will need to take into account the complex nature of the commensal microbiome, the specific immunity of the wild boar and the in vivo infection context with pathogenic strains of M. bovis.
The aim of this study was to determine the reliability of lactic acid bacteria (LAB) as heterologous hosts for the expression of MPB70 and MPB83, two Mycobacterium bovis antigens that possess diagnostics and immunogenic properties, respectively. We therefore generated recombinant cells of Lactococcus lactis and Lactobacillus plantarum that carried hybrid genes encoding MPB70 and MPB83 fused to signal peptides that are specifically recognized by LAB. Only L. lactis was able to secrete MPB70 using the L. lactis signal peptide Usp45, and to produce MPB83 as an immunogenic membrane protein following its expression with the signal peptide of the L. plantarum lipoprotein prsA. Inactivated cells of MPB83-expressing L. lactis cultures enhanced NF-ºB activation in macrophages. Our results show that L. lactis is a reliable host for the secretion and functional expression of antigens that are naturally produced by M. bovis, the causative agent of bovine tuberculosis (bTB). This represents the first step on a long process to establishing whether recombinant LAB could serve as a food-grade platform for potential diagnostic tools and/or vaccine interventions for use against bTB, a chronic disease that primarily affects
cattle but also humans and a wide range of domestic and wild animals.
Minimal processing for microbial decontamination, such as the use of natural antimicrobials, is gaining interest in the food industry as these methods are generally milder than conventional processing, therefore better maintaining the nutritional content and sensory characteristics of food products.
The aim of this study was to quantify the impact of (i) structural composition and complexity, (ii) growth location and morphology, and (iii) the natural antimicrobial nisin, on the microbial dynamics of Listeria innocua.
More specifically, viscoelastic food model systems of various compositions and internal structure were developed and characterised, i.e. monophasic Xanthan gum-based and biphasic Xanthan gum/Whey protein-based viscoelastic systems. The microbial dynamics of L. innocua at 10oC, 30oC and 37oC were monitored and compared for planktonic growth in liquid, or in/on (immersed or surface colony growth) the developed viscoelastic systems, with or without a sublethal concentration of nisin. Microscopy imaging was used to determine the bacterial colony size and spatial organisation in/on the viscoelastic systems.
Selective growth of L. innocua on the protein phase of the developed biphasic system was observed for the first time. Additionally, significant differences were observed in the colony size and distribution in the monophasic Xanthan gum-based systems depending on (i) the type of growth (surface/immersed) and (ii) the Xanthan gum concentration. Furthermore, the system viscosity in monophasic Xanthan gum-based systems had a protective role against the effects of nisin for immersed growth, and a further inhibitory effect for surface growth at a suboptimal temperature (10oC).
These findings give a systematic quantitative insight on the impact of nisin as an environmental challenge on the growth and spatial organisation of L. innocua, in viscoelastic food model systems of various structural compositions/complexities. This study highlights the importance of accounting for system structural composition/complexity when designing minimal food processing methods with natural antimicrobials.
Bovine tuberculosis (bTB) caused by Mycobacterium bovis is the most serious endemic disease affecting
livestock in the UK. The European badger (Meles meles) is the most important wildlife reservoir of bTB transmission to
cattle, making eradication particularly difficult. In this respect, oral vaccination with the attenuated M. bovis vaccine Bacillus
Calmette-Guerin (BCG) has been suggested as a wide-scale intervention to reduce bTB infection in badgers. However,
experimental studies show variable protection. Among the possibilities for this variation is that the resident gut bacteria
may influence the success of oral vaccination in badgers; either through competitive exclusion and/or inhibition, or via
effects on the host immune system. In order to explore this possibility, we have tested whether typical gut commensals
such as Lactic Acid Bacteria (LAB) have the capacity to impact on the viability and survival rate of BCG and to modulate
the immune response to BCG using an in vitromodel.
Twelve LAB isolated from badger faeces displayed inhibitory activity to BCG that was species-dependent.
Weissella had a bacteriostatic effect, whereas isolates of enterococci, lactobacilli and pediococci had a more bactericidal
activity. Furthermore, BCG-induced activation of the pro-inflammatory transcription factor NF-ºB in human THP-1
macrophages was modulated by LAB in a strain-dependent manner. Most pediococci enhanced NF-ºB activation but
one strain had the opposite effect. Interestingly, isolates of enterococci, lactobacilli and weissella had different effects as
immunomodulators of BCG-induced macrophage responses as some had no significant influence on NF-ºB activation,
but others increased it significantly.
Our in vitro results show that LAB isolated from badgers exhibit significant inhibitory activity against BCG
and influence the immune activation mediated by BCG in a human macrophage assay. These findings suggest that gut
commensal bacteria could play a role in influencing the outcome of oral BCG vaccination. Inactivated cells of LAB, or
LAB that are bacteriostatic but have a synergistic immunostimulatory effect with BCG, could be potential adjuvants to
be used for oral vaccination in badgers. Further work is needed to take into account the complex nature of the gut
microbiome, specific immunity of the badger and the in vivo context.