Comparison of Various Methods for the Detection of Extended Spectrum Beta Lactamase in Klebsiella Pneumoniae Isolated from Neonatal Intensive Care Unit, Ahmedabad

Background & objectives: Several outbreaks of neonatal septicemia by extended spectrum beta lactamases (ESBL) producing isolates are not uncommon & are associated with increased mortality. Moreover, detection of ESBL in isolates that produce Amp C beta lactamases is problematic. So, clinical laboratories need to develop quick screening methods for detection of ESBL producing strains. Materials & methods: Out of 600 samples of blood culture from neonatal intensive care unit (NICU) patients, 54 Klebsiella pneumoniae were tested for ESBL by screening & confirmatory tests recommended by clinical laboratory standard institute (CLSI). In addition, double disk synergy test (DDST), modified double disk synergy test (MDDST), direct modified three dimensional tests (DMTDT) & indirect modified three dimensional tests (IMTDT) were evaluated for optimum detection of ESBL in Amp C producing isolates. Results: From 54 Klebsiella pneumoniae, 48 were screen positive for ESBL by CLSI criteria. ESBL detection was confirmed in 44 isolates. Phenotypic confirmatory disk diffusion method (PCDDT) by CLSI detected ESBL in 41/48 isolates. DDST using amoxicillin-clavulanic acid detected the same in 36/48 cases. MDDST using cefepime & piperacillin-tazobactam detected ESBL in 44/48 cases, including 3 isolates having Amp C enzyme which was confirmed by modified three dimensional tests for Amp C enzyme. DMTDT detected only 4 isolates with ESBL production. IMTDT detected all 44 ESBL producing isolates. Conclusion: The prevalence of ESBL producing Klebsiella pneumoniae in our NICU was 81.48%. MDDST & DMTDT seem to be superior to PCDDT, DDST & IMTDT for detection of ESBL in Amp C producing isolates.