Integron-bearing Gram-negative bacteria in lake waters

The aim of the study was to determine the occurrence of integron-bearing Gram-negative bacteria in the water of four lakes located in Wielkopolski National Park, Poland. Altogether, 17 isolates harbouring class 1 or class 2 integrons were found. The integron-bearing bacteria were identified as Escherichia coli, Klebsiella pneumoniae, Pasteurella multocida and Aeromonas hydrophila. The variable regions of the class 1 integrons contained aadA1 and dfrA1-aadA1 gene cassettes, whereas class 2 integrons carried dfrA1-sat2-aadA1 gene cassette array. The isolates were resistant to 3-20 antimicrobials. One of them produced SHV-type extended-spectrum β-lactamase.

Integrons play a major role in the spread of antibiotic resistance among bacteria. They are frequently found in clinical bacterial strains, but are also detected in environmental isolates in sites affected by anthropogenic pressure. Little is known, however, about the presence and characteristics of integrons in bacteria living in water environments in areas of nature preservation. To the best of our knowledge, this is the first study focused on detection and characterization of integrons in bacteria living in water ecosystems in a national park.