https://imcjms.com Ibrahim Medical College Journal of Medical Science https://imcjms.com/registration/journal_full_text/61 Tue, 02 Aug 2016 11:44:47 +0000 Vancomycin and high level gentamicin resistant enterococci detection is important for effective treatment and control of nosocomial infection. The present study was undertaken to determine the species distribution of Enterococcus and the rate of vancomycin and high level gentamicin resistant enterococci (HLGRE) in clinical samples in a tertiary care hospital of Dhaka city. Enterococci were identified to species level by standard biochemical and serological methods. Their susceptibilities to antibiotics were determined by disc diffusion method according to CLSI guideline. Minimum inhibitory concentration (MIC) of vancomycin and gentamicin were determined by agar dilution method. The study was conducted from July 2009 to February 2010. The study indicated high prevalence of HLGRE in our hospital population. MIC method was more accurate in detecting high level gentamycin resistant enterococci compared to disc diffusion method with 120 µg gentamicin disc. However, none of the enterococcal strains showed resistance to vancomycin. HLGRE should be monitored regularly in clinical samples as it is difficult to treat. Key word: Enterococcus, HLGRE, VRE Address for Correspondence:Prof. J. Ashraful Haq, Professor of Microbiology & Principal, Ibrahim Medical College 122 Kazi Nazrul Islam Avenue, Shahbagh, Dhaka-1000. E-mail: jhaq54@yahoo.com   Enterococcus is a leading cause of nosocomial infections and important for its ability to acquire antibiotic resistance determinant from other organisms. Enterococcus includes more than 17 species. Enterococcus faecalis (90-95%) and Enterococcus faecium (5-10%) are the two species commonly present in human intestine as commensal. Other species account for less than 5% of clinical isolates. Enterococci are estimated to cause 5-15% of all cases of bacterial endocarditis.1 Recently, the treatment of enterococcal infections is increasingly become difficult due to emegernce of antibiotic resistant strains. E. faecium represents most vancomycin resistant enterococci, but vancomycin resistant strains of E. faecalis also occur. Vancomycin resistant enterococci (VRE) are now a common cause of hospital-acquired infection and are difficult to treat pathogen with currently available antibiotics.2,3 Combination of a cell wall active antibiotic such as penicillin and an aminoglycoside such as gentamicin is essential for severe enterococcal infection. Although enterococci have intrinsic low-level resistance to aminoglycoside, they have synergistic susceptibility when treated with a cell wall acting antibiotic and an aminoglycoside. However, some aminoglycosides are not susceptible to synergism.4,5 Emergence of high level resistance to gentamicin (MIC of >500 µg/ml) by some enterococci has caused the failure of synergistic effects of combination therapy.6   Study place, samples and organisms   All samples collected during the above period were routinely cultured on blood agar media. All suspected colonies of enterococci were identified by Gram staining, cultural characteristics, motility, growth in bile esculin media and in media containing 6.5% NaCl, catalase, litmus milk reduction and L-arabinose hydrolysis tests using the standard microbiological techniques.7 Specific antiser (Streptex, Ramel Europe Ltd. UK) was used to determine the serogroups. Antibiotic susceptibility testing   A total of eighty enterococci were isolated during the study period. Of the 80 Enterococcus isolates, 71 were from urine, 8 from wounds/pus and 1 from tracheal aspirate. Among 80 isolates, 76 (95%) were Enterococcus faecalis and 4 (5%) were E. faecium. The detail antimicrobial susceptibility pattern of the 80 isolates to different antibiotics is shown in Table-1. Most of the isolates were sensitive to the tested antibiotics except ciprofloxacin and cotrimoxazole. About 82-95% enterococci was sensitive to penicillin and ampicillin. Out of 80 isolates, 72 (90%) were sensitive while 8 (10%) were intermediate resistant to vancomycin (30 µg) by disc diffusion method. But all the intermediate resistant isolates were found susceptible by agar dilution method. The MIC range of those 8 intermediate resistant enterococci was 2-4 µg/ml. Of the 80 isolates, 49 (61.25%) were sensitive while 31 (38.75%) were resistant to gentamicin by disc diffusion method. All 31 gentamicin resistant enterococci by disc diffusion method showed high level resistance (MIC > 500 µg/ml) by agar dilution method (Table-2). But, out of 49 gentamicin sensitive isolates by disc diffusion method, six isolates showed high level resistance to gentamicin. Both MIC50 and MIC90 of vancomycin were 2 µg/ml while for gentamicin it was 64 µg/ml and 4096 µg/ml respectively (Table 2). Table-1: Antimicrobial susceptibility patterns of Enterococcus by disk diffusion method (n=80)    Table 2: Comparative susceptibility pattern of isolated enterococci to vancomycin and gentamicin by disc diffusion and agar dilution MIC method   Discussion The results of the study indicated the absence of VRE and high prevalence of HLGRE in tertiary care hospital of Dhaka city. Enterococci have both an intrinsic and acquired resistance to antibiotics, making them important nosocomial pathogens. As VRE and HLGRE are difficult to treat, resistance should be monitored regularly in a wide range of clinical samples. References 2.    Leclercq R, Derlot E, Duval J, Courvalin P. Plasmid-mediated resistance to vancomycin and teicoplanin in E. faecium. N. Engl. J. Med. 1988; 319: 157-161. 4.    Swenson JM, Ferraro MJ, Sahm DF, et al. Multi laboratory evaluation of screening methods for detection of high-level aminoglycoside resistance in enterococci. Journal of Clinical Microbiology 1995; 33: 3008-18. 6.    Levine DP. Vancomycin: a history. Clinical Infectious Diseases 2006; 42: S5–12. 8.    Bauer AW, Kirby WMM, Sherris JC, and Turek M. Antibiotic sensitivity testing by a standardized single disk method. American Journal of Clinical Pathology 1966; 45: 493-496. 10.  Washington JA, II: Suscptibility tests: agar dilution. In EH Lennette, A. Balows,W.J. Hausler and HJ Shadomy (eds), Manual of Clinical Microbiology. 4th ed. American Society for Microbiology, Washington DC 1985; 967-971. 12.  Love R M. Enterococcus faecalis – a mechanism for its role in endodontic failure. Int Endod J 2001; 34: 399–40. 14.  Adhikari L. High-level aminoglycoside resistance and reduced susceptibility to vancomycin in nosocomial enterococci. J Glob Infect Dis 2010; 2: 231–235. 15.   Chenoweth CE, Bradley SF, Terpenning MS, Zarins LT, Ramsey MA, Schaberg DR, Kauffman CA. Colonization and transmission of high level gentamicin-resistant enterococci in a long-term care facility.  Infection Control and Hospital Epidemiology 1994; 15: 703-709. 2026 Ibrahim Medical College. All rights reserved.