Dr Alison Cottell

Non-enteric Gram-negative bacteria associated with nosocomial infections

There has been a recent and significant increase in infections caused by this group of bacteria among certain vulnerable patient groups, such as those with cystic fibrosis, and those in intensive care, neonatal wards, and burns units. 

Important genera include Pseudomonas, Stenotrophomonas, Burkholderia and Sphingomonas species. These pathogens are problematic due to their intrinsic resistance to many common antibiotics, and their ability to form biofilms on medical devices. 

Current research interests in this area include characterising the outer membrane structure of clinical strains with acquired antibiotic resistance determinants, to identify changes in outer membrane protein and lipopolysaccharide profiles.   

Bacterial co- and cross-resistance between biocides and antibiotics

The use of disinfectants has increased substantially, particularly in the domestic environment, due to increasing concerns about hygiene and the increasing availability of products such as kitchenware, dentrifices and cosmetics that contain antimicrobial agents. 

At high concentrations bacteria are easily killed by disinfectants, but these chemicals are often diluted to sub-inhibitory concentrations following disposal. At low concentration some biocides, such as triclosan, have been shown to attack specific targets in bacterial cells and at sub-inhibitory concentrations it has been demonstrated that bacteria can become resistant to them. Although biocide-tolerant strains of bacteria are not resistant enough to survive at-use concentrations of biocides, they may be cross-resistant to antibiotics: fatty acid biosynthesis, for example, is inhibited by low concentrations of triclosan, and therapeutic concentrations of the anti-tuberculosis antibiotic isoniazid. Alternatively, bacterial strains can become hypersusceptible to one or more antimicrobial agents following exposure to a chemically unrelated agent.

Current interests in this area include dynamics of resistant phenotypes in stepwise-trained antimicrobial resistant organisms, and reversion to wildtype MICs of bottlenecked populations.