A Microbiological Study of Acinetobacter calcoaceticus baumannii with Special Reference to Multidrug Resistance

Abstract

Introduction The outbreak of Acinetobacter calcoaceticus baumannii ( ACB ) is mainly reported to be a notorious pathogens at health-care settings. It is the major problem on the health-care system with high morbidity and mortality rates because of the broad range of antibiotic resistance and lack of understanding the mechanism of developing new antibiotic resistance rapidly. It emphasizes the importance of local surveillance in describing or understanding and predicting microbial resistance patterns so that there will be limited use of antibiotics by developing strategies to control the extensive use of antimicrobial chemotherapy in clinical environment, which is still considered as one of the factors in the emergence of multidrug resistance microorganisms. Objectives The study aims to detect the occurrence rate of ACB infections from various clinical samples, identify the resistance levels to different groups of antimicrobial agents, and the occurrence rate of multidrug resistant (MDR) ACB clinical isolates from a tertiary hospital in Durgapur, West Bengal, India. Material and Methods The study was performed in the Department of Microbiology of the IQ City Medical College and Hospital, Durgapur, West Bengal, India, for the 24 months duration, that is, from January 1, 2018 to December 31, 2019. Altogether 15,800 clinical samples consisting of endotracheal tube aspirates, sputum, pus, blood, catheter tips, urine, tissue, and other body fluids were studied. ACB from clinical samples were identified by its characteristic colonies (nonlactose fermenting, glistening, small mucoid colonies), Gram-staining pattern (Gram-negative coccobacillus), and standard biochemical reactions. It was further confirmed in the Department of Microbiology of the Healthworld Hospital, Durgapur, West Bengal, India, by Vitek2 compact system (bioMerieux, Inc., Durham, North Carolina, United States). Antibiotic susceptibility testing was performed using automated broth microdilutions by Vitek2 compact system (bioMerieux, Inc.) and Kirby-Bauer disk diffusion test on Mueller-Hinton Agar (HiMedia). Results Nonrepetitive 289 ACB were isolated from various clinical samples. A total of 277 (96%) isolates of ACB were MDR strains. Conclusion ACB was mostly isolated from the intensive care unit department and was found to be the most MDR type in the tertiary care hospital by this study.

Keywords: Acinetobacter calcoaceticus baumannii; MDR strains; Vitek2 compact system; antibiotic susceptibility testing.

Fig. 1

Venn diagram showing association between three classes of antibiotics namely aminoglycosides (amikacin), folate pathway antagonists (co-trimoxazole), and tetracycline (tigecycline). Within the Venn diagram circles are 284 isolates representing varying degrees of antibiotic resistance (moderate resistance or fully resistant), while there are 5 isolates outside the Venn diagram, representing the susceptible isolates. Together, these constitute the entire population of Acinetobacter calcoaceticus baumannii complex isolates examined in this study (i.e., N  = 284 + 5 = 289 isolates).