Pigs could be the key to understanding how antibiotic resistant bacteria persist in Intensive Care Units in hospitals.
NSW Department of Primary Industries (NSW DPI) Immunology & Molecular Diagnostic Research Unit Team Leader, Dr James Chin, says it is commonly believed that each time an antibiotic is used only pathogens or disease-causing bacteria will be killed.
"Antibiotic use in hospitals is often perceived to be solely directed against only bad bacteria.
"In reality, antibiotics also act against entire microbial communities, including the good bacteria which can protect patients from pathogenic bacteria.
"Antibiotics do not just eliminate bad bacteria", Dr Chin said. "They also maintain a pool of antibiotic resistance genes within the microbial community of patients treated with antibiotics."
Using pigs as a model, Dr Chin and Dr Toni Chapman at NSW DPIs Elizabeth Macarthur Agricultural Institute have examined how E.coli bacteria a common cause of diarrhoea in pigs and humans - respond to treatment by antibiotics.
Dr Chin told the 2007 Australian Society for Microbiologys annual conference in Adelaide in July that: "The current theory of antibiotic resistance is that the fittest bacteria, that is, those carrying genes for resistance, are the most likely to survive.
"Because antibiotic treatment will never kill all bacteria, bad or good, there will always be a pool of antibiotic resistance bacteria that can potentially transfer resistance to incoming pathogens.
"It is important to identify the antimicrobial resistant gene pool in entire microbial communities before antibiotic treatment.
Dr Chin said this has been tested with E. coli in pigs.
"Our research shows clearly that use of one antibiotic to treat E. coli not only increases resistance against that antibiotic but also increases the carriage of resistance genes against other classes of antibiotics.