https://imcjms.com Ibrahim Medical College Journal of Medical Science https://imcjms.com/registration/journal_full_text/221 Thu, 18 May 2017 09:55:59 +0000 Acinetobacter species are aerobic Gram variable coccobacilli that are now emerging as an  important nosocomial pathogen. Infections caused by them are difficult to control due to multidrug resistance. The purpose of this study was to detect virulence factors namely gelatinase production, biofilm formation and antibiotic susceptibility of Acinetobacter species. Two hundred fifty six clinical samples collected from Bangabandhu Sheikh Mujib medical University (BSMMU) and from burn unit of Dhaka Medical College Hospital were included in the study. Gelatinase production was seen on Luria Bertani agar media containing gelatin (30 gm/l) and biofilm formation was detected in microtiter plate assay. Out of 256 clinical samples, 52 (20.3%) were Acinetobacter species. Out of 52 Acinetobacter isolates, none were gelatinase producer but 39 (75%) were found biofilm producers. Acinetobacter isolates were 100% resistant to ceftazidime, cefotaxime cefuroxime and ceftriaxone. High level of resistance was also recorded for amoxicillin (98.1%), aztreonam (98.1%), gentamicin (90.4%), ciprofloxacin (73.1%), amikacin (57.6%), netilmicin (53.8%) and imipenem (44.2%). Susceptibility to colistin was maximum (96.2%). The present study demonstrated a high propensity of biofilm formation by the clinical isolates of Acinetobacter species and most of the Acinetobacter  were multidrug resistant. Address for Correspondence:Dr. Azizun Nahar, Senior lecturer, Department of Microbiology, Bangladesh Medical College, Dhaka, Bangladesh.  E mail: drnahar.a_26@yahoo.com   Acinetobacter species are Gram negative, strongly aerobic, catalase positive, oxidase negative, non motile encapsulated coccobacilli. Acinetobacter are widely distributed in nature and are commonly found as a part of normal flora of human skin and occasionally in the respiratory tract, genitourinary tract, gastrointestinal tract and conjunctiva.1,2 Although Acinetobacter species are considered to be relatively of low virulence pathogens, certain characteristics of these organisms may enhance the virulence of the strains involved in infections. These characteristics include (i) the property of adhesion to human epithelial cells in the presence of fimbriae and / or capsular polysaccharide, (ii)  lipopolysaccharide component of the cell wall and the presence of lipid A, (iii) biofilm formation and (iv) gelatinase production. Gelatinase is a protease that is capable of hydrolyzing gelatin, collagen, casein, haemoglobin, and other bioactive peptides.5 The potential ability of Acinetobacter baumannii to form biofilms might also explain its outstanding antibiotic resistance, survival properties and increased virulence and further dissemination in the hospital setting.6,7 The presence of indwelling medical devices increases the risk for biofilm formation and subsequent infection especially in the ICU. Therefore, the aim of the present study was to detect gelatinase production, biofilm formation and antimicrobial susceptibility of Acinetobacter species isolated from various clinical specimens. Material and Methods Microbiological methods b. Gelatinase activity: Gelatinase production was detected by inoculating Acinetobacter isolates on the Luria Bertani agar media containing gelatin (30 g/l). After inoculation the plates were incubated overnight at 370C and then cooled for 5 hours at 40C. The appearance of a turbid halo around the colonies was considered positive for gelatinase production.5 Serratia spp. was used as positive control and E. coli was used as negative control in this test. d. Antimicrobial susceptibility tests: All the isolated Acinetobacter species were tested for antimicrobial susceptibility testing by disc diffusion method using the Kirby-Bauer technique11 and as per recommendations of the National Committee for Clinical laboratory Standards (NCCLS).12 Amoxicillin (10µg), ciprofloxacin (5 µg), gentamicin (10µg), ceftriaxone (30µg), ceftazidime (30µg), cefuroxime (30µg), cefotaxime (30µg), amikacin (30µg), aztreonam (30µg), imipenem (10µg), netilmicin (30µg) and colistin (10µg) discs were used. Results     Discussion In this current study, out of 52 Acinetobacter isolates, none produced gelatinase while 75% was positive for biofilm production. Sechi et al found no gelatinase activity and biofilm formation by 80% Acinetobacter isolates.13 Cevahir et al detected gelatinase activity in 14.0% and biofilm formation in 74.4% Acinetobacter isolates.14 Acinetobacter isolated from CVC blood, peripheral blood and tracheal aspirates showed higher biofilm production (84-100%). The presence of indwelling medical devices increases the risk for biofilm formation and subsequent infection especially in the ICU.7 Biofilm production in Acinetobacter species might promote increased colonization and persistence leading to higher rate of device related infections. A greater understanding of the nature of biofilm production by Acineotbacter spp, their role in pathogenicity and in serious infections will help in development of more effective treatment for Acinetobacter infections. 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APMIS 2007; 115: 891-9. 12.National Committee for Clinical Laboratory Standards. (2001) Performance standards for Antimicrobial Susceptibility Tests. Eleventh informational supplement. NCCLS document M100-S11 NCCLS. Wayne, Pennsylvania, USA. 14.Cevahir N, Demir M, Kaleli I, Gurbuz M, Tikvesli S. Evaluation of Biofilm production, gelatinase activity and mannose- resistant hemagglutination in Acinetobacter baumannii strains. J of Microbiology, Immunology and Infection 2008; 41: 513-518. 2026 Ibrahim Medical College. All rights reserved.