Prevalence and Molecular Characterization of Carbapenemase Producing P. aeruginosa from Clinical Isolates in Tertiary Care Hospital

Carbapenemases are β-lactamases with hydrolytic capacities and can hydrolyze penicillin, monobactams, carbapenems, and cephalosporins. Bacteria producing these β-lactamases renders many β-lactams ineffective and thus may cause serious infections. This study was designed to investigate the prevalence and molecular characterization of Carbapenemase producing Pseudomonas aeruginosa from clinical isolates in tertiary hospital to identify its prevalence. This study was conducted at the department of Microbiology, Microbiology Research Laboratory of Quaid-i-Azam University. Antibiotic susceptibility testing and phenotypic screening for MBLs were performed on 150 P. aeruginosa isolates which were collected from department of Microbiology Shaheed Zulfiqar Ali Bhutto Medical University, Islamabad Pakistan. MICs were determined and Carbapenemase genes were sought by PCR. The resistant rate to imipenem was 34.6 %. The resistance rates of P. aeruginosa to levofloxacin, ciprofloxacin, tobramycin, Ceftazidime, Meropenam, Aztreonam, Amikacin, cefaperazone/sulbactam and piperacillin/tazobactam were 43.3%, 40.1%, 40.1%, 34.6%, 34.6%, 26.6%, 25.3%, 20.1% and 15.3% respectively. Piperacillin+tazobactum (15.3%) were observed to be the most effective. The point prevalence of Multi-Drug-Resistant (MDR) P. aeruginosa showed 56%, The MIC of 35 isolates showed no zone of inhibition under the potential range of E-test strips and thus have MIC > 32 µg/ml showing the high level of resistance to imipenem. Modified Hodge Test (MHT) was used for screening of Carbapenemase which showed 71% (n=37 out of 52) and for Metallo-beta-lactamase (MBL) screening with EDTA it showed 100% positive. PCR was used for the confirmation of 52 positive samples which indicated that 23 (44%) of the isolates were positive for (IMP) gene. A total of 11 isolates (21%) were positive for (VIM) resistant gene while 7 isolates were identified positive for IMP and VIM genes showing a high prevalence of MDR strains.