Isolation and Pattern of Antimicrobial Susceptibility Testing of Acinetobacter baumannii Clinical Isolates at Taksin Hospital: A Retrospective Study from 2019 to 2021

Objective: To determine the number of isolates and drug susceptibility testing of Acinetobacter baumannii at Taksin Hospital. Materials and Methods: A 3-year retrospective descriptive study was conducted between January 2019 and December 2021. Drug susceptibility testing of isolates to 13 drugs, which included amikacin, gentamycin, piperacillin/tazobactam, cefotaxime, ceftazidime, cefepime, three carbapenem drugs that were imipenem, meropenem, and doripenem, ciprofloxacin, trimethoprim-sulfamethoxazole, colistin, and tigecycline, were evaluated by standard disk diffusion method and automated microdilution method. Results: One thousand six hundred sixty-five non-duplicate A. baumannii isolates from different patients were detected and included 535 in 2019, 500 in 2020, and 630 in 2021. The patients’ ages ranged from three days to 100 years. The median age of patients was 70 years with an interquartile range of 56 to 80 years. A. baumannii was mostly found in patients aged older than 50 years old at 83.6%. They were isolated from sputum in 72.3%, urine in 9%, pus in 6.3%, tissue in 6.3%, and blood in 5.2%. Overall, A. baumannii demonstrated 91.5% and 79.8% susceptibility to colistin and tigecycline, respectively, but less susceptible to other drugs tested, with a range of 0.4% to 32.6%. Drug susceptibility to carbapenem such as imipenem, meropenem, and doripenem were 19.5%, 20%, and 20.9%, respectively. The carbapenem-resistant A. baumannii (CRAB) was found at 77.6%, 80%, and 79.1% in 2019, 2020, and 2021, respectively. For total isolates tested, the mean of CRAB was 78.9±1.2%. Conclusion: The present study results suggested the importance of monitoring A. baumannii at a hospital in Bangkok. Colistin and tigecycline had the high percentages of drug susceptibility rates in vitro. The antibiogram of susceptibility helps provide guidelines for clinician to consider empirical treatment.