EMERGENCE OF IMIPENEM RESISTANT ACINETOBACTER BAUMANNII ISOLATES FROM VARIOUS CLINICAL SAMPLES IN A TERTIARY CARE HOSPITAL IN

to determine the prevalence of imipenem resistant

In the recent past carbapenems had been drugs of choice for serious infections with Acinetobacter baumannii, but carbapenem resistant strains are rapidly emerging as a potential threat. There are several factors leading to carbapenem resistance(CRAB) in Acinetobacter baumannii, most important being the acquisition of carbapenem hydrolysing β-lactamases. Other mechanisms include the presence of mobile genetic elements, reduced expression of outer membrane proteins, altered affinity or expression of penicillin-binding proteins and multidrug efflux pumps. 3 However, increased resistance to carbapenem class of antibiotics has been reported worldwide. Results from studies have reported carbapenem resistance rate of A. baumannii as 40-75 per cent throughout India. 4 The main objectives of this study is to determine the prevalence of the Acinetobacter infections from various clinical samples and to investigate imipenem resistant A. baumannii strains isolated from patients in a tertiary care hospital.

Bacterial Isolates
This study was conducted in the Department of Microbiology, in a tertiary care hospital in Kanchipuram district, chennai. Acinetobacter baumannii isolated from various clinical samples over a period of one year (November 2017 to November 2018). Out of 734 samples, Acinetobacter baumannii was isolated from 191 clinical samples such as urine, pus, sputum, miscellaneous (body fluids and others ) and blood were collected from patients. Informed consent was obtained from the participants before starting the procedures. The samples received in the laboratory were inoculated on 5% Sheep Blood agar and Mac Conkey agar and incubated overnight aerobically at both 37•C and 44•C. All isolates were further processed and identified by routine microbiological and biochemical tests as per standard methodology. 5

Bacterial identification and purification
In case of urine samples, the isolates were subjected to biochemical tests only if the colony count was significant (>10 5 CFU/ml). In order to ensure that all isolates were pure, they were cultured three times. To confirm that all these isolates belonged to Acinetobacter baumannii characteristic colonies (Non Lactose-fermenting, glistening, small mucoid colonies) were subjected to Gram stain (Gram negative coccobacilli), motility ( non-motile) and standard biochemical reactions (Catalase, Oxidase, Oxidation-fermentation test, Indole production, Methyl Red(MR), Voges-Proskauer (VP), Citrate utilization, reaction in Triple Sugar Iron medium, Mannitol Motility test, Urease activity). 5

Antibiotic Susceptibility of A. baumannii
After identification by phenotypic methods, antibiotic susceptibility was performed for each isolate by the Kirby Bauer disc diffusion method on Mueller-Hinton agar using 0.5 MacFarland turbidity standard and comparing zone sizes with control strain Pseudomonas aeruginosa ATCC 27853. 6 The antimicrobial agent used were carbapenem group imipenem. Carbapenem resistant was tested by using commercially available imipenem disc (10μg) by Kirby Bauer disc diffusion method. Antibiotic susceptibility results were interpreted by measuring the zone diameters produced and correlating them with the CLSI standards. 7

Statistical analysis:-
The statistical analysis was performed using the SPSS version statistics 20. The Chi 2 (x 2 ) test was used to compare the percentages of Acinetobacter baumannii prevalence and imipenem resistance rates from different clinical samples. The p values < 0.05 were considered statistically significant.

Statistical analysis:-
Data were recorded and statistical analyses were performed by SPSS version 20 software using chi-square test. Hence, P value < 0.05 was considered as the statistically significance level.

Discussion:-
In the recent years, A. baumannii infection has become a critical challenge to healthcare systems and has contributed to increased morbidity and mortality among patients in Tamil nadu. Control of A. baumannii infections is always difficult because A. baumannii is resistant to several antimicrobial agents, including imipenem, which remains as the drug of choice, even though frequency of IRAB isolates are reported to be on the rise worldwide. 8 Among 191(26%) strains, 56% isolates were from males and 44% from females. In correlation with this study, Nadheema et al.,(2013) 9 showed A. baumannii isolates were recovered from 75 patients; 67 (89%) men and 8(11%) women. In contrast to this study Anuradha et al., (2015) 10 reported that Acinetobacter was isolated most commonly from females.
In the present study Acinetobacter baumannii was isolated from various clinical samples including urine, pus, sputum, miscellaneous (body fluids and others) and blood. The total percentage of distribution of Acinetobacter baumannii among the culture samples showed more distribution among urine samples (35%) followed by pus (23%), sputum (19%), miscellaneous (body fluids and others) (15%) and blood (8%  9 the proportion of imipenem resistant A. baumannii (IRAB) isolates was found to be 77.27% from sputum specimens followed by 74.07%, 56.67%, 37.5% and 16.67% from wounds, blood, urine and burns specimens respectively, which is not in agreement with the present study.

Conclusion:-
Acinetobacter is a common threat in hospital acquired infections. In this study Acinetobacter baumannii were found to be 49% imipenem resistant. Emergence of carbapenem resistance is troublesome nowadays. It is a great challenge for physicians to treat Acinetobacter baumannii infections which is associated with high mortality, highlighting the need for strict infection control strategies.
To avoid antibiotic resistance, antibiotics should be used sensibly and alternative therapy should be considered for each hospital according to the resistance rates in the hospital… IPM(10