Abstract:
Objective: To determine the types of pathogens causing blood stream infections and their drug susceptibility profile in
immunocompromised patients.
Study Design: Cross-sectional, observational study.
Place and Duration of Study: Department of Microbiology, Armed Forces Institute of Pathology, Rawalpindi, from
January to September 2012.
Methodology: Blood culture bottles received from immunocompromised patients were dealt by two methods, brain heart
infusion (BHI) broth based manual method and automated BACTEC system. The samples yielding positive growth from
either of two methods were further analyzed. The identification of isolates was done with the help of biochemical reactions
and rapid tests. Antimicrobial susceptibility of the isolates was carried out as per recommendations of Clinical and
Laboratory Standards Institute (CLSI).
Results: Out of the 938 blood culture specimens received from immunocompromised patients, 188 (20%) yielded positive
growth. Out of these, 89 (47.3%) isolates were Gram positive and Gram negative each, while 10 (5.3%) isolates were fungi
(Candida spp.). In case of Gram positive isolates, 75 (84.3%) were Staphylococcus spp. and 51 (67%) were Methicillin
resistant. Amongst Gram negative group 49 (55.1%) isolates were of enterobacteriaceae family, while 40 (44.9%) were
non-lactose fermenters (NLF). In vitro antimicrobial susceptibility of Staphylococci revealed 100% susceptibility to
vancomycin and linezolid. The enterobacteriaceae isolates had better susceptibility against amikacin 85.7% compared to
tigecycline 61.2% and imipenem 59.2%. For NLF, the in vitro efficacy of aminoglycosides was 72.5%.
Conclusion: The frequency of Gram positive and Gram negative organisms causing blood stream infections in
immunocompromised patients was equal. Vancomycin in case of Gram positive and amikacin for Gram negative
organisms revealed better in vitro efficacy as compared to other antibiotics.
