Evaluation of Carba NP Method for Rapid Detection of Pseudomonas aeruginosa Isolates Producing Carbapenemase Enzymes

Recently, increased resistance to carbapenem antibiotics among Pseudomonas aeruginosa has raised concerns. The Carba NP test is used for detection of carbapenemase types. This study aimed at applying Carba NP method for rapid detection of P. aeruginosa isolates producing carbapenemase enzymes. A total of 97 clinical specimens was collected from patients in educational hospitals between November 2017 and May 2018 in Hamadan, Iran. Antibiotic susceptibility test was performed by disc diffusion method and MIC for imipenem was done by E-test. In order to detect carbapenemases enzymes, combined disk (CDT), CarbaNP, Modified Hodge (MHT), and Polymerase chain reaction (PCR) were performed. Statistical analysis was performed using SPSS V16. The highest and lowest levels of resistance were found to be to Ceftriaxone 65 (67%) and Piperacilin/Tazobactam 38 (39.2%), respectively. Among 97 clinical isolates of P.aeruginosa,
49 (50.51%) were positive for carbapenemase genes by PCR test from which 48 (97.95%) were positive for CarbaNP test. There were 48 (49.48%) PCR negative isolates of which all (100%) showed negative results for CarbaNP test. Compared to PCR, the sensitivity and specificity of this test was 98% and 100%, respectively. This study showed that a high percentage of P. aeruginosa was resistant to Carbapenem antibiotics and the CarbaNP method was highly sensitive and specific for detection of carbapenemase enzymes.