Novel environmental class 1 integrons and cassette arrays recovered from an on‐farm bio‐purification plant
ABSTRACT Rapid dissemination and emergence of novel antibiotic resistance genes among bacteria are rising problems worldwide. Since their discovery in clinical isolates in the late 1980s, class 1 integrons have been found in a wide range of bacterial genera and have been extensively studied as contributors to dissemination of antibiotic resistance. The present study aimed to investigate the presence and structure of class 1 integrons in plasmid‐carrying bacterial isolates obtained from a biopurification system used for decontamination of pesticide‐contaminated water as well as their possible role as reservoir of antimicrobial resistance gene cassettes. A total of 35 representative isolates were screened for the presence of class 1 integron integrase encoded by intI1. PCR and DNA sequencing revealed the presence of six class 1 integrons with four variable regions: 5′CS‐aadA1b‐3′CS, 5′CS‐aadA2‐3′CS, 5′CS‐aadA11c&Dgr;‐3′CS and 5′CS‐dfrB3‐aadA1di‐catB2‐aadA6k‐3′CS, the last two being unseen arrays of antimicrobial resistance gene cassettes associated with novel environmental alleles of intI1. These four class 1 integrons were identified as being present in four different genera, including Ochrobactrum, and Variovorax, where class 1 integrons have not been previously reported. The results provide evidence of the biopurification systems as a tank of class 1 integron carrying strains and novel environmental class 1 integron integrases associated with antimicrobial resistance gene cassette arrays.