Research by scientists at Kansas State University and North Carolina State University found a high prevalence of antibiotic resistant bacteria in the intestines of house flies and German cockroaches as well as in pig faeces – all from the same farms.

For the study, which was conducted on two commercial swine operations in Kansas and North Carolina, scientists isolated the common gut bacteria Enterococcus faecalis and Enterococcus faecium from the digestive tract of house flies, and the feces of German cockroaches and pigs.

“Our data showed that enterococci were common from all three sources and frequently carried antibiotic resistance genes,” said K-State associate professor of microbial ecology, Ludek Zurek. “The bacteria were found to be frequently resistant to tetracycline, erythromycin, streptomycin and kanamycin, which are common antibiotics used to treat infections in humans.”

Other collaborators on the study were K-State postdoctoral research associates Aqeel Ahmad and Anuradha Ghosh in Zurek’s research group and North Carolina State University distinguished professor, Coby Schal.

The research was published in the BioMed Central journal BMC Microbiology on 26 January 2011.

“Because antibiotics are widely used as growth promoters in US swine operations, the digestive tract bacteria in pigs are often exposed to selective pressure and many become resistant to antibiotics,” Professor Zurek said. “Insects such as house flies and German cockroaches can move freely between animal waste and food and may play a significant role in the dissemination of antibiotic resistant bacteria within and between animal production farms and residential settings.”

The study showed that cockroaches and house flies shared some of the same enterococcal clones that were detected in the swine manure, indicating that insects acquired enterococci from swine manure.

Professor Zurek said that this study was the first analysis of antibiotic resistance and virulence of enterococci associated with insect pests in swine farms.

“Since we found such a good match in enterococci, it is possible these insects acquire other bacteria from swine faeces with even greater public health significance and could disseminate them to the surrounding environment. This research will enhance our understanding of the role insects play in the ecology of antibiotic resistant and virulent bacteria and in public health. Flies and cockroaches may be more than just a nuisance and insect pest management should be a part of pre-harvest food safety and security programmes,” Professor Zurek said.