Patterns and persistence of antibiotic resistance in fecal indicator bacteria from freshwater recreational beaches

Aims: This study was conducted to determine antibiotic susceptibility patterns<br>among the faecal indicator bacteria (FIB), Escherichia coli and enterococci, and<br>to determine the potential for freshwater beaches to serve as reservoirs of<br>resistance genes where transfer of resistant phenotypes takes place or de novo<br>resistance may evolve.<br>Methods and Results: One hundred and forty-seven E. coli and 150<br>enterococci collected from sand and water at recreational beaches along Lake<br>Huron, Michigan, USA were screened against commonly used antibiotics.<br>Resistance was apparent in both E. coli (19% resistant) and enterococci (65%<br>resistant). Antibiotic-resistant E. coli were capable of growing in beach sand<br>microcosms and were able to transfer a plasmid-encoded kanamycin-resistance<br>gene in sand microcosms. Furthermore, resistant phenotypes were stable in the<br>sand environment even in the absence of the corresponding antibiotic.<br>Conclusions: Antibiotic-resistant FIB were prevalent and persistent in the beach<br>habitat.<br>Significance and Impact of the Study: Active populations of FIB at beaches<br>express antibiotic resistance phenotypes and have the ability to transfer<br>antibiotic resistance. These human-associated bacteria may be intermediaries in<br>the movement of resistance between environmental and clinical reservoirs.