Determination and molecular analysis of antibiotic resistance in Gram-negative enteric bacteria isolated from Pelophylax sp. in the Eastern Black Sea Region

Abstract

Abstract The aim of this study was to evaluate the prevalence and types of antimicrobial resistance among Gram-negative enteric bacteria isolated from Pelophylax sp. Fifty-four frogs were collected from six provinces in the Eastern Black Sea Region of Turkey. In the cloacal swab cultures, bacteria from 160 different colonies were identified by biochemical tests, automated systems, and matrix-assisted laser desorption ionisation-time of flight mass spectrometry. The antimicrobial susceptibility tests were performed by the disk diffusion method. The observed drug resistance rate was the highest to ampicillin and cefazolin, while the lowest against ciprofloxacin and tetracycline. In the molecular assays, bla TEM (8 Citrobacter spp.), bla SHV (2 Escherichia coli, 1 Hafnia alvei, and a Serratia liquefaciens), tetA genes (E. coli and Klebsiella spp.) and a class 1 integron without any gene cassette (E. coli) were detected. Among the strains, no plasmid-mediated quinolone resistance [qnrA, qnrB, qnrS, qepA and aac (6 ′)-Ib-cr] was found. However, two of three quinolone-resistant Klebsiella strains showed the novel amino acid substitution in the gyrA gene resulting in Ser83Asp and Asp87Glu.The clonality between E. coli isolates was also examined by pulsed-field gel electrophoresis. We consider that multidrug-resistant Gram-negative enteric bacteria in the intestinal microbiota of a cosmopolitan frog species might be a reservoir for antibiotic resistance genes.