Cork institute on trail of drug-resistant bacteria

The molecular diagnostics unit of Cork Institute of Technology has turned its attention from the clinical minimalism of the hospital…

The molecular diagnostics unit of Cork Institute of Technology has turned its attention from the clinical minimalism of the hospital to the smorgasbord of the food industry.

The group, which is led by Dr Seamus Fanning, has been tracking antibiotic resistance in bacteria for more than 10 years, initially looking at pathogens in the hospital environment.

"When the Government brought in legislation to set up the Food Safety Authority of Ireland three years ago, they contacted us and asked us to shift emphasis towards food-borne pathogens," he said.

The MDU, a small unit with two postdoctoral researchers Dr Mairead Daly and Dr Fiona Halloran, one PhD student, Brigid Lucey, and a number of MSc students, is investigating genetic mechanisms involved in the transmission of multi-drug resistance, focusing on "jumping genes" or transposons/integrons.

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These carry discrete packages of multi-drug resistance genes capable of being transmitted among a wide variety of unrelated bacteria.

Samples from three main sources - infected humans, animals, and food - are analysed by the unit.

At least seven integron structures have been identified in Salmonella typhimurium, a bacterium associated with food poisoning.

Surveillance and control of multi-drug resistant food-borne pathogens from farm to fork, using modern scientific methods, is essential, according to Dr Fanning.

"When we began to investigate we started to see huge numbers of organisms resistant to more than two, and up to five, antibiotics. If you take Salmonella typhimurium DT104, it can be resistant to five prominent antibiotics: ampicillin, chloramphenicol, streptomycin, sulphonamide, and tetracylcine. These are common household-name antibiotics.

"If someone is healthy, there's no major problem. In many cases, antibiotic intervention is not warranted but in specific circumstances the old, the very young, and the immuno-compromised can be vulnerable."

However, the good news is that, in a major two-year study (199698), the MDU found no resistance to Ciprofloxacin, the antibiotic commonly used against Salmonella typhimurium infections.

The study also investigated drug resistance in another food poisoning organism - Campylobacter - and found evidence of multi-drug resistance, although the profile was a little different.

The group were the first researchers to suggest the existence of a possible integron-like structure in Campylobacter.

Microbiological safety of food is of increasing concern to consumers but concomitant demand for food production by modern animal husbandry has resulted in increased dependence on the use of antibiotics to promote animal growth.

The greatest threat to the continued use of anti-microbial agents for human therapy is the development of resistance among pathogenic micro-organisms, especially those that can be acquired from the consumption of infected food produce, Dr Fanning said.

The EU has banned the use of certain anti-microbials for animals, but the ban needs to be more rigid, Dr Fanning believes.

Food processors, retailers and consumers can also play their part in reducing multi-drug resistance, by conforming to good hygiene practices.

Prudent prescription of antibiotics by general practitioners is also important.

The MDU is now trying to discover new types of multi-drug resistant clusters in non-DT104 Salmonella typhimurium. This has not been shown to date, says Dr Fanning.

"We need to predict and implement measures to prevent the spread of multi-drug resistance, in order to preserve the usefulness of antibiotics," he said.