Bacteriophages and the spread of antimicrobial resistance

One component of the human microbiome which is garnering more attention lately is the “phageome” or “virome”, that portion of our microbial ecosystem comprised of viruses (phages) that infect and replicate within bacteria. A recent Nature paper demonstrated that antibiotic treatment of mice resulted in an expansion of phages bearing antibiotic resistance genes that could then spread back to wild-type bacteria and confer resistance. In this month’s issue of Antimicrobial Agents and Chemotherapy, a group from Spain examined the phage DNA in fecal samples of 80 healthy adults. Almost 80% of the samples revealed one or more of the six genes they sought (genes encoding two beta-lactamases (TEM and CTX-M), methicillin resistance (mecA), high-level aminoglycoside resistance (armA) and quinolone resistance (qnrA and qnrS). 

Phages survive well in the environment, probably better than do their bacterial hosts. In addition, they aren’t detected using culture methods designed to find resistant bacteria. They almost certainly play a key role in the transmission of antimicrobial resistance genes.