Investigation into clinical isolates of resistance genes in carbapenem resistant Acinetobacter baumannii by using molecular methods

Acinetobacter baumannii, one of the most important infectious agents spread in hospitals, is an opportunistic, Gram-negative, aerobic, and nonfermentative pathogen that causes outbreaks often in intensive care units, causing difficulties in treatments due to multiple antibiotic resistance characteristics. Carbapenems reported with increasing resistance rates worldwide are significant representatives of the group β-lactamases that are used in the treatment of Acinetobacter baumannii. Acinetobacter baumannii has the most common type of OXA gene family(OXA-23, OXA-24, OXA-51 and OXA-58) responsible for carbapenem resistance. In this study, Acinetobacter baumannii isolates collected from the respiratory tract samples obtained from the patients receiving treatment between June 2017 and January 2018 at the intensive care unit in T. C. Ministry of Health Amasya University Sabuncuoğlu Şerefeddin Training and Research Hospital were identified by VITEK-2 device and microbiological with molecular analyses were performed in collected samples. Resistance profiles of carbapenem resistant strains against to ceftazidime, ciprofloxacin, levofloxacin, amikacin, gentamicin, tetracycline, tigecycline and colistin antibiotics were determined by disk diffusion and minimum inhibition concentration (MIC) tests. The expressions of OXA-23, OXA-24, OXA-51, and OXA-58 genes responsible for carbapenem resistance, were investigated by RT-PCR (reverse transcriptase olymerase chain reaction) and real-time PCR methods. Identified 50 Acinetobacter baumannii isolates were found to be 100% resistant to imipenem, meropenem, cefepim, ceftazidime and ciprofloxacin, 94% for levofloxacin, 68% for amikacin, 78% for gentamicin, 88% for tetracycline and 6% for tigecycline. It was detected that all samples are susceptible to colistin and showed multiple antibiotic resistance. As a result of molecular analyses, it was determined that the expressions of only OXA-23 and OXA-51 genes in all isolates. This study is one of the first reports in our region where OXA genes are investigated in Acinetobacter baumannii by RT-PCR and real-time PCR method. The obtained findings are expected to contribute to empirical treatments.