Could the food we eat be contributing to the continuing rise of antibiotic-resistant infections? Harmless and even beneficial bacteria that exist in our food supply may also be carrying genes that code for antibiotic resistance. Once in our bodies, could they transmit the resistance genes to disease-causing bacteria?
"The data indicate that food could be an important avenue for antibiotic-resistant bacterial evolution and dissemination. The role of commensals, especially food-borne microbes, in transmitting resistance genes are becoming a concern to the scientific community," says Hua Wang of the Ohio State University, presenting May 23, 2007 at the 107th General Meeting of the American Society for Microbiology (ASM) in Toronto.
The culprit is a process known as horizontal gene transfer, in which bacteria in close proximity to each other can share genetic information, including genes that code for antibiotic resistance. Horizontal gene transfer between disease-causing bacteria in the hospital setting has already been recognized as an important avenue for the exchange of antibiotic-resistance genes among pathogens.
Research has also already demonstrated that pathogenic bacteria have the ability to engage in horizontal gene transfer with various commensal bacteria and even beneficial bacteria, including those from the food chain. What concerns scientists is that the size and diversity of the gene pool represented by commensal bacteria increases the likelihood of gene transfer and some commensals possess high frequency gene transfer mechanisms.
"We have demonstrated not only that organisms carrying such intrinsic mechanisms have the potential to become an important reservoir for antibiotic resistance genes but, more importantly, that these intermediate organisms can disseminate antibiotic resistance genes in subsequent events much more effectively than the parental donor strain," says Hua.