Antibiotic-Resistant Microorganisms and Multiple Drug Resistance Determinants in Pseudomonas Bacteria from the Pushchino Wastewater Treatment Facilities

The work presents characterization of antibiotic-resistant strains isolated by direct plating of five samples collected at different treatment stages from the Pushchino water treatment facilities in April 2015. Primary analysis of resistance of the collection (~800 strains) to the following antibiotics was carried out: carbenicillin, kanamycin, streptomycin, amikacin, tobramycin, chloramphenicol, rifampicin, gentamicin, tetracycline, ceftazidime, cefepime, and meropenem. Antibiotic-resistant bacteria most common in the Pushchino wastewater treatment facilities were found to belong to the genera Pseudomonas and Alcaligenes. Occurrence of tetracycline resistance genes was investigated, and predominance of the tetA/tetC genes responsible for active transport of this antibiotic from the cell were found to be predominant among the studied strains. The strains containing the genes associated with type I integrons (intI1, qacE/qacEΔ1, and sul1) constituted 25% of the studied ones. Four Pseudomonas strains were found to contain the IncN plasmids, while seven strains of this genus contained plasmids of the P-9 incompatibility group (e-subgroup). Three IncP-9 plasmids were conjugative and carried simultaneously the determinants of tetracycline, streptomycin, and gentamicin resistance, which has not been previously reported for the e-subgroup of IncP-9 plasmids.