Drug Resistance Mechanism among Acinetobacter Species

S Jayashree,K.G Rajeshwari,Mita D Wadekar

doi:10.22207/jpam.15.2.44

Abstract

Acinetobacter species cause infections that are difficult to control due to multi-drug resistance and are noted for their intrinsic resistance to antibiotics and for their ability to acquire genes encoding resistance for the production of beta-lactamases and Aminoglycoside-modifying enzymes. MBLs are molecular class B and functional group 3 beta-lactamases which have the capability of hydrolyzing all β-lactams except the Monobactam, Aztreonam. Of several MBLs, only IMP, VIM and SIM types have been detected in these species. To analyze the antibiotic resistance patterns among Acinetobacter isolates and to detect Carbapenemase and MBL among MDR Acinetobacter isolates. The descriptive study of all phenotypically identified strains and multidrug-resistant strains of Acinetobacter species was conducted. A total of 303 isolates were isolated from various samples. They were processed and identified by standard Microbiological procedures. The antibiotics susceptibility testing was performed by Kirby- Bauer disc diffusion method using CLSI guidelines. Carbapenemase production was detected by employing 3 phenotypic test methods (MHT, CDM and DDST). Of 6355 samples processed, 303 were found to be Acinetobacter species, among those 50 were multidrug-resistant strains. The highest isolation of MDR Acinetobacter was from endotracheal tube tip (42%) and pus sample (32%). The majority of MDR Acinetobacter infection was found in male patients 36 (72%) compared to female patients 14 (28%). The majority of the strains were isolated from patients >/ 60 years of age group (%). A number of these isolates were more from ICU wards (30%) followed by Surgery wards (24%). Higher resistance for the Piperacillin/tazobactam ((82%), followed by Ceftazidime (80%), Imipenem (76%) etc. and the most susceptible drug was found to be the Tigecycline (82%) followed by Colistin (80%). Carbapenemase production was detected by MHT and 24 (48%) isolates were MHT positive. MBL production was detected by CDM and 34 (68%) isolates were CDM positive and by DDST 30 (60%) isolates were positive. Acinetobacter species are increasingly important nosocomial pathogens and are capable of rapid adaptation to the hospital environment. The variety of potential source of contamination or infection with these species in the hospital environment makes control of outbreaks caused by these difficult.

Highlights

The genus Acinetobacter contains strictly aerobic, non-motile, Gram-negative, coccobacillary rods that are oxidase negative, nitrate negative and do not ferment sugars[1]
Acinetobacter species cause infections that are difficult to control due to multi-drug resistance and are noted for their intrinsic resistance to antibiotics and for their ability to acquire genes encoding resistance for the production of beta-lactamases and Aminoglycoside-modifying enzymes
The antibiotic susceptibility testing was performed by KirbyBauer disc diffusion method using Clinical and Laboratory Standard Institute (CLSI) guidelines[15]

Summary

Introduction

The genus Acinetobacter contains strictly aerobic, non-motile, Gram-negative, coccobacillary rods that are oxidase negative, nitrate negative and do not ferment sugars[1] This species is the second most frequent nonfermenter encountered in clinical laboratories but with only about 1/10th the frequency of Pseudomonas aeruginosa[2]. The property of adhesion to human epithelial cells in the presence of fimbriae and / or capsular polysaccharide[4,5] These species cause infections that are difficult to control due to multi-drug resistance. They are noted for their intrinsic resistance to antibiotics and for their ability to acquire genes encoding resistance for the production of beta-lactamases and Aminoglycoside-modifying enzymes[6]. Resistance to fluoroquinolones is correlated with point mutations of genes encoding DNA gyrase and topoisomerase IV

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Discussion

Conclusion