Characterization and anti-microbial susceptibility of gram-negative bacteria isolated from bloodstream infections of cancer patients on chemotherapy in Pakistan

Purpose: Bloodstream infection remains a major cause of morbidity and mortality in patients undergoing treatment for cancer. Severe infections due to Gram-negative bacilli staphylococci are common in cancer patients. Altered gut flora because of frequent antibiotic administration and damage of epithelial surfaces contribute to the development of infection. To access the use of new potent antibiotics against bloodstream infection in cancer patients and to determine the cross resistance of Gram-negative bacterial strains. Materials and Methods: We studied the bacterial spectrum antimicrobial susceptibility pattern of cephalosporins, fluoroquinolones, carbapenems and aminoglycosides against Gram-negative bacterial strains in cancer patients. The susceptibility was determined by broth dilution method according to National Committee for Clinical Laboratory Standards (NCCLS) now called Clinical Laboratory Standards Institute (CLSI) during study period (July 2006 to Jan 2007). Results: A total of 60 Gram-negative bacterial blood cultures were examined. Among these, Pseudomonas aeruginosa was the most common (38). The Minimum Inhibitory Concentration at which 50 (MIC50) and 90 (MIC90) of Enterobacteriaceae and P. aeruginosa inhibited were found. Resistance in P.aeruginosa against cefepime, meropenem, ciprofloxacin, ceftriaxone, tobramycin, cefoperazone and imipenem was 60, 13, 80, 67, 40, 90 and 10 respectively while for Enterobacteriaceae 80, 20, 88, 72, 20, 90 and four per cent resistance was observed. Meropenem was found to be the most effective antimicrobial against Gram-negative bacteria. Conclusion: High resistance observed in this study warrants the needs of surveillance of resistant pattern of antimicrobial agents. Due to increased level of drug resistance, carbapenem would be a prudent choice in high- risk cases.