Pattern of Bacterial Pathogens and Their Antimicrobial Susceptibility from Blood Culture Specimens in a Tertiary Care Setting

Abstract

The objective of this paper is to find out the pattern of bacterial pathogens and their antimicrobial susceptibility from blood culture specimens received from a tertiary care referral setting. This cross-sectional observational study was carried out at the Department of Microbiology, Armed Forces Institute of Pathology, from July 2011 through June 2012. Blood culture specimens were dealt with brain heart infusion broth based manual method and automated BACTEC system. The specimens yielding positive growth were further analyzed and antimicrobial susceptibility carried out as per CLSI recommendations. Out of 2921 blood culture specimens, 465 (16%) yielded growth. Out of these, 245 (53%) isolates were Gram positive, 209 (45%) Gram negatives while 11 (2%) were yeast. Among Gram positive isolates, 208 (85%) were Staphylococcus spp. and among these 158 (76%) were methicillin resistant. Amongst Gram negative group, 115 (55%) isolates were members of enterobacteriaceae family and E. coli was the leading pathogen, while 94 (45%) were non-fermenters (NF). Among these, Acinetobacter spp. and Pseudomonas aeruginosa were common pathogens. In vitro antimicrobial susceptibility of staphylococci revealed that 100% isolates were susceptible to vancomycin and linezolid. The organisms of family enterobacteriaceae revealed better susceptibility to amikacin (68.7%) and imipenem (64.3%). The NF group showed better in vitro susceptibility to tazobactam/piperacillin (65%). Gram positive organisms were predominantly causing blood stream infections. Vancomycin and linezolid in case of Gram positive and amikacin and tazobactam/piperacillin against Gram negative organisms revealed better in vitro efficacy.