Phylogenetic characterization, antimicrobial susceptibilities, and mechanisms of resistance in bacteria isolates from a poultry waste-polluted river, southwestern Nigeria

Bacteria resistance to antibiotics has become a worldwide problem impacted partly by antibiotics use in livestock production. The present study investigated the pattern and mechanisms of resistance in 21 bacteria species isolated from a river used as a waste-dump by a poultry farm in Ogbomoso, southwestern Nigeria. Bacteria were isolated on nutrient agar supplemented with 50 μg/mL of tetracycline, their identities were determined by PCR amplification, and sequencing of their 16s rRNA genes and their susceptibility to 6 antimicrobials determined by broth dilution. The molecular basis of resistance among the isolates was also investigated by the PCR amplification of class 1 and 2 integrons, tetA, tetB, tetC, tetD, tetE, tetG, tetL, tetW, tetM, tet37, blaTEM, aadA1, strA, strB, sul2, sul3 and a 550bp gene fragment encoding a multidrug resistance efflux transporter of the resistance nodulation division (RND) family. All the isolates were resistant to the tested antimicrobials with MIC ranging from 16 μg/mL to 512 μg/mL. class 2 integrons tetB, tetC, tetD, tetE, tetG, tetL, tetW, tetM, tet37, aadA1, and sul3 could not be detected in any of the isolates. However, 2 isolates were positive for class 1 integrons, 1 each for blaTEM and tetA, 3 for sul2, and 2 for strA and strB. Seven of the isolates were positive for the RND efflux pump. Results of the present study showed that polluted aquatic ecosystemsmay serve as a reservoir of transferable antibiotic resistance.