Molecular characterization of antibiotic resistance in corynebacterium strains isolated from clinical samples

Objective: In this study, it was aimed to perform the molecular characterization of antibiotic resistance of 117 strains of the genus Corynebacterium isolated as clinical agents from various samples sent from different clinics to Karadeniz Technical University, Faculty of Medicine, Medical Microbiology laboratory between January 2017 and February 2020. Method: Bacteria identification was performed with MALDI-TOF MS. For the molecular characterization of antibiotic resistance genes, in accordance with EUCAST recommendations, erythromycin, clindamycin, penicillin, ciprofloxacin, gentamicin and tetracycline, rifampicin, vancomycin and linezolid resistance were demonstrated phenotypically by KirbyBauer disk diffusion method and the genes responsible for resistance to these antibiotics (ermB, ermA, ermX, ampC, mefA/E, gyrA, tetM, acc(3)-XI), the presence of polymerase chain reaction (PZR) and the gyrA gene mutations responsible for quinolone resistance were determined by DNA sequence analysis. Conclusion: Forty-six (39,3%) strains were isolated from respiratory tract samples, 38 (32,4%) were isolated from intensive care units, and 95 (81%) were identified as C. striatum. Of the strains, 114 (97,4%) were penicillin and ciprofloxacin, 112 (95,7%) clindamycin, 105 (90,5%) tetracycline 89 (76%) gentamicin, and 68 (58%) strains were resistant to erythromycin, and sensitivity to vancomycin and linezolid was 100%. The presence of ermX gene in 116 (99,1%) strains, ermB gene in 10 (8,5%) and acc(3)-XI gene in 103 (88,1%) strains were found to be ermA, tetM, ampC and mefA/E genes were not detected. Mutations in gryA genes were screened in 50 (42,7%) of the strains, and 87-phenylalanine and 91-alanine mutations in 17 (33,3%) strains; In 22 (43,1%) 87-phenylalanine and 91-glycine mutations were detected. The 99-proline mutation of the gyrA genes of one C. striatum and five C. aurimucosum strains was detected for the first time in the literature in this study, and it was observed that the 87-isoleucine mutation together with this mutation increased the MIC of ciprofloxacin and moxifloxacin compared to the 99-proline mutation alone. It was determined that ciprofloxacin and moxifloxacin decreased the MIC value when this mutation occurred with the valine mutation in the 87th region.