Phenotypic Characterization of Antimicrobial Resistance Mechanisms Among the Clinical Isolates of Acinetobacter spp. in a Tertiary Care Hospital, Nepal: A Descriptive Cross-Sectional Study

The global emergence and spread of multidrug-resistant Acinetobacter spp. have become a significant challenge for managing and treating their infections effectively. The aim of this study was to explore the prevalence of antimicrobial resistance phenotypes (MDR, ESBL, AmpC β-lactamases, MBL, KPC) among Acinetobacter spp. and to determine their antimicrobial susceptibility patterns. A descriptive cross-sectional study was conducted from December 2021 to May 2022 at Nepal Medical College Teaching Hospital, Nepal on 55 non-repetitive clinical isolates of Acinetobacter spp. Isolation, identification and antimicrobial susceptibility testing was done following standard microbiological techniques. Different β-lactamases (ESBLs, AmpC β-lactamase, MBL and KPC) were detected by standard phenotypic tests. Out of 6,344 clinical specimens processed, 1025 (16.16%) showed bacterial growth. The prevalence of Acinetobacter spp. among the grown isolates was of 5.36% (n=55). The highest positivity rate among the processed sample was found in the sputum sample (3.21%) followed by pus (1.21%), body fluids (0.51%), urine (0.47%), and blood (0.31%). The rate of isolation of Acinetobacter spp. was higher among the isolates from inpatient (n=378) than the isolates from out-patients (n=647) (10.05% vs 2.63%). The prevalence of MDR, ESBL, AmpC β-lactamases and MBL producing Acinetobacter spp. was 67.27 % (n=37), 25.45% (n=14), 14.55% (n=8), and 34.54% (n=19), respectively. Two isolates were detected as KPC phenotypes. Six isolates (10.91%) showed both ESBL and AmpC B-lactamase co-producers. All isolates were susceptible to polymixins and colistin sulphates. Tigecycline resistance was among 29.09 % of isolates. More than 70.00 % of the isolates were resistant to most commonly used first line antibiotics (cefixime - 80.00%, ceftazidime - 78.12%, cefotaxime - 76.36%, ciprofloxacin - 72.72%, ofloxacin - 70.90%, cotrimoxazole - 81.82%). Almost half of the isolates were resistant to carbapenems (imipenem -46.64%, meropenem - 41.82%), piperacillin-tazobactam (49.00%) and amikacin (54.55%). The study shows a high proportion of Acinetobacter spp. as MDR with significant presence of ESBL, MBL, AmpC and KPC resistant phenotypes in our set-up. Over 70% resistance to the commonly used antibiotics further highlights the therapeutic challenges posed by these pathogens. The findings from the study emphasize the need for continuous monitoring and implementation of effective control strategies to curb the spread of resistant Acinetobacter infections.