Half of the 50 chicken samples from supermarkets, street markets, and butchers contained phages able to perform this gene transfer. Phages are the viruses that infect bacteria.

"Our work suggests that such transfer could spread antibiotic resistance in environments such as food production units and hospitals and clinics," said corresponding author Friederike Hilbert, a professor in Vienna.

"One quarter of all phages isolated were able to transduce [transfer] one or more of the five antimicrobial resistances under study," said Professor Hilbert.

These included resistances to tetracycline, ampicillin, kanamycin, and chloramphenicol, as well as resistance to extended spectrum betalactam antibiotics.

The results suggest that the number of phages that can transduce antibiotic resistance genes must be far higher, since the experiments were restricted to resistance to only five antibiotics via five randomly chosen phages per sample of chicken, said Professor Hilbert.

"Strategies to combat antimicrobial resistance have enjoyed only limited success, and there are still many questions relating to how and when resistance transfer occurs," Hilbert writes.

"The presence of phages that transfer antimicrobial resistance could explain the failures to combat antimicrobial resistance."

Until recently, transduction of antibiotic resistance via phage was assumed to be a very minor source of the spread of resistance, said Professor Hilbert. "New information from the sequencing of bacterial DNA has shown that transduction must be a driving force in bacterial evolution, and thus, quite common."

In the study, the investigators rinsed the chicken they had purchased, and then isolated coliphage, using the International Organization for Standardization (ISO) method for isolating such viruses from water, said Professor Hilbert.

Unlike bacteria, which are true living creatures, viruses, including phages, can be thought of more as complex molecular machinery.

As such, the latter are much more resistant to disinfectants, including those used in the food industry. Alcohol, in particular, is harmless to most viruses.

"It is thus highly likely that phages survive under routine conditions of disinfection, not only in the food industry," Professor Hilbert wrote.

The research, Hilbert concludes, demonstrates that transduction is an efficient way to transfer antimicrobial resistance to E. coli in different environments. That, she says, needs to be addressed for concerns related to hygiene, sanitation, and public health.

The research is published in Applied and Environmental Microbiology, a journal of the American Society for Microbiology.