Probing for integron–encoded antibiotic resistance among fecal indicator bacteria.

Priscila Rodríguez, Glendalis Vargas and Carlos Rodríguez, Industrial Biotechnology, Biology Department, University of Puerto Rico at Mayaguez.

Traditionally fecal bacteria have been used as indicators of water quality. Based on their detection, it is inferred that fecal contamination has occurred and that potential harmful microorganisms might be present at the tested site. However with this culture-based approach, it is not possible to evaluate inconspicuous risks to human health posed by the presence of transmissible genetic determinants that increase the pathogenic potential of their hosts. Recently, integrons, a genetic system carried by bacteria, have been implicated in the establishment and dispersal of antibiotic resistance, or ABR, traits which include protection mechanisms against the most important antibiotics used for the treatment of infection in humans. To evaluate the presence of integron-encoded resistance among indicator bacteria, axenic cultures presumptively characterized as coliforms, with n= 66, and enterococci, with n=66, were recovered from coastal environments with a history of wastewater impact. These were submitted to an integron-targeted PCR assay for the retrieval of antibiotic resistance genes. Six coliform isolates and six enterococci strains were positive for the presence of ABR genes encoded by class 1 integrons. DNA sequencing analyses revealed the presence of genes 99-100% identical to determinants conferring resistance against beta-lactam antibiotics, trimethoprim, and quaternary ammonium compounds. Our results indicate that exposure to environments impacted by wastewater contamination may constitute a risk for human health as resistance mechanisms which compromise the effectiveness of treatment options for bacterial infections were found in viable bacteria outside healthcare settings. We give thanks to BioMinds which has sponsored part of this investigation.

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