Comparison of Beta-Lactamase Profiles and Epidemiology of Multi-Drug Resistant Acinetobacter baumannii Isolates in Southwest Turkey: 2011 vs. 2019 Study

Background: The most significant problem encountered with hospital infections caused by multi-drug resistant Acinetobacter baumannii isolates is the difficulty in treatment. Defining resistance mechanisms is important for the development of treatment strategies. Objectives: The aim of this study was to investigate the beta-lactamase genes and clonal relationship in multi-drug resistant A. baumannii isolates in Mugla, Turkey, as no data are currently available for this province. Methods: Total 96 multi-drug resistant A. baumannii isolates obtained from hospitalized patients, between 2011 - 2012 period (n = 61) and in year 2019 (n = 35) were investigated and compared for antibiotic susceptibilities, beta-lactamase enzyme encoding genes by polymerase chain reaction (PCR) method. Repetitive extragenic palindromic (REP) PCR was made for dendrogram analysis to illustrate hierarchical relationship between isolates. Results: Overall, 74.0% of the isolates were obtained from patients in intensive care units. All multi-drug resistant isolates were found resistant to ciprofloxacin, piperacillin, piperacillin-tazobactam, meropenem, and imipenem by the disk diffusion method. The minimum inhibitory concentration values indicated that all isolates were resistant to imipenem, while colistin resistance was determined as 21.9%. The ISAba-I insertion element was present in all isolates. BlaOXA-23-like was present in 96.9%, and blaOXA-24-like was detected in three (3.1%) isolates. blaNDM positivity was shown in 5.2% of isolates. The indistinguishable or closely related isolates ratio was detected as 29.5% for the 2011 - 2012 period and 80% for 2019. Conclusions: Our findings showed that antibiotic resistance rates were high in A. baumannii, particularly isolated from intensive care unit patients in Mugla province. The prevalence of beta-lactamase and metallo-beta-lactamase genes has been increasing year by year, with the blaOXA-23-like gene region being the most prevalent. Additionally, the co-existence of these genes among strains is also on the rise. These findings from two different periods may provide useful reference data for future studies.