Abstract:
Objective: To determine, the susceptibility pattern of carbapenamase producing enterobacteriaceae (CPE) against
polymyxinB, tigecycline and fosfomycin.
Study Design: Descriptive cross sectional.
Place and Duration of Study: The study was carried out in the Department of Microbiology PNS Shifa Karachi,
from 26 Sep 2013 to 25 Mar 2014.
Material and Methods: All specimens were inoculated on blood and macConkey agar, incubated aerobically at
35oC - 37oC for 18 to 24 hours. After identification of gram negative rods by colony morphology, Gram's staining
and biochemical reactions, these were screened for Carbapenems resistance with imipenem and meropenem 10
ƒÊg discs along with routine first and second line antibiotics by Kirby-Bauer disc diffusion technique according to
Clinical Laboratory Standard Institute (CLSI) guide lines. All isolated CPE were saved and then inoculated on
Mueller-Hinton agar (MHA). Antimicrobial susceptibility against polymyxin B, Tigecycline and Fosfomycin was
done by Kirby-Bauer disc diffusion method using disc polymyxin B 300 units, Tigecycline 15ƒÊg and Fosfomycin
200ƒÊg. Zone diameters greater than 24 mm were taken as sensitive for Tigecycline 15ƒÊg, 16mm for Fosfomycin
200 ƒÊg and 12 mm for polymyxin B 300 units.
Results: Clinical specimens of 171 patients who fulfilled the inclusion criteria were included in our study. Mean }
SD of age was 42.02 } 22.367 with C.I (38.65 - 45.40). Out of 171 patients 110 (64%) were male and 61 (36%) were
female. In vitro susceptibility results revealed that all the 171 (100%) CPE isolates susceptible to PolymyxinB,
while susceptibility against Fosfomycin and Tigecycline was 132 (77%) and 49 (29%) respectively.
Conclusion: CPE were found to be 100% susceptible to polymyxinB, while for Fosfomycin and Tigecycline
susceptibility was 77% and 29% respectively.
