Comparative in vitro Activities of Different Antibiotics against Clinical Isolates of Gram-negative Bacilli

Objective: The local anti-microbial susceptibility profile plays a very critical role in guiding clinicians to choose the appropriate empiric therapies. This study was conducted to assess the pathogen characteristics and the in vitro susceptibility of different Gram negative isolates to commonly used antibiotics in our hospital settings.

Methods: A total of 110 Gram negative isolates were included in the study. A retrospective, observational analysis of antibiogram data was performed for four antimicrobial agents including CSE-1034 (ceftriaxone-sulbactam-EDTA), piperacillin-tazobactam (pip-taz), cefoperazone-sulbactam and meropenem.

Results: Of the 200 clinical specimens analysed, Gram negative isolates obtained from 110 samples were included in the final analysis. The most common Gram negative isolates were Klebsiella species (35.5%), E. coli (33.6%) and P. aeruginosa (21.8%). The overall susceptibility was highest to CSE-1034 (100%) followed by meropenem (66.4%), cefoperazone-sulbactam (56.4%) and pip-taz (45.5%). The MIC90 range of CSE-1034 for Enterobacteriaceae was ≤0.5-≤4μg/ml and ≤2μg/ml for susceptible P. aeruginosa isolates. The MIC90 of meropenem for 94.4% of meropenem-susceptible Enterobacteriaceae strains was <0.25μg/ml and 64.3% of P. aeruginosa were having MIC ≤0.25μg/ml. The MIC90 of pip-taz for 82.5% of the pip-taz susceptible Enterobacteriaceae strains was 4μg/ml and 63.6% of P. aeruginosa was ≤8.0μg/ml. The MIC90 of cefoperazone-sulbactam susceptible strains were between ≤8 to ≤16μg/ml and 45.8% isolates of susceptible P. aeruginosa were having MIC between ≤8 to ≤16μg/ml.

Conclusions: Overall, this in vitro surveillance study suggests that CSE-1034 can be considered an important therapeutic option for the treatment of various multi drug resistant Gram-negative bacterial infections and avert the threat of resistance to last resort antibiotics including carbapenems.