Background and study aim: The last decade was marked by the emergence and spread of carbapenemases. The study aims to ‎compare three phenotypic methods with PCR for rapid detection of carbapenemase in carbapenem ‎resistant gram negative bacteria.
Material and Methods: This study was conducted on 50 carbapenem-resistant gram negative bacteria. clinical isolates in Central ‎Microbiology Laboratory, Ain Shams University Hospitals. All isolates were tested for ‎carbapenemase encoding genes (blaKPC, blaIMP, blaOXA-48, blaVIM and blaGES) using PCR.  ‎Phenotypic detection of carbapenemases was made by chromID® CARBA SMART Agar ‎‎(CARB/OXA), Modified Hodge test and Blue-Carba test‎‎‎.‎
Results: The 50 isolates included Klebsiella spp. (28/50, 56%) and Acinetobacter spp. (22/50, 44%). All ‎Klebsiella isolates were positive for one or more genes coding for carbapenemase by PCR, with ‎predominance of blaOXA-48 gene, while 20/22 (90.9%) of Acinetobacter isolates were positive for one ‎or more genes coding for carbapenemase by PCR with predominance of blaOXA-48 gene. ‎Chromogenic media gave positive results in 98% (49/50) of isolates with sensitivity 100% and ‎specificity 0% for detection of carbapenemase producers. MHT gave positive results in 45 isolates ‎out of 48 PCR positive isolates with a sensitivity of 93.8% and specificity 0% for detection of ‎carbapenemase production. Blue carba test gave positive results in 48 isolates out of 48 PCR ‎positive isolates with a sensitivity of 100% and specificity 100% for detection of carbapenemase ‎production‎‎‎‎‎‎‎.
Conclusion: Blue carba test agreed with PCR with a sensitivity of 100% and specificity 100%, However it failed to detect ‎the carbapenemases detected by other phenotypic tests‎ ‎ ‎‎‎‎‎‎‎‎.