Phenotypic Detection and Molecular Characterization of Metalo-Beta-lactamases in Carbapenem Resistant Pseudomonas Aeruginosa in Zagazig University Hospitals

Abstract

Background: Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic nosocomial pathogen that acquires resistance to conventional  anti-pseudomonal antibiotics especially carbapenems. Due to the existing lack of choices, treating individuals infected with MBL-resistant  pseudomonas is difficult.

Objective: The aim of the present study was to evaluate the performance of different phenotypic methods for  the detection of metallo-beta-lactamase (MBL) producing P. areuginosa in comparison with polymerase chain reaction (PCR) for MBLs  genes.

Patients and methods: This study was conducted two hundred and twenty-five (225) samples obtained in ICUs in Zagazig  University Hospitals, 80 samples were P. aeruginosa positive of age group between 39-70 years, including 50 males and 30 females.  

Results: The antimicrobial resistant pattern of P. aeruginosa isolates by disc diffusion method. Among the 80 P. aeruginosa isolates, all  isolates were resistant to CAZ and CTX. While 75 isolates (93.8%) were resistant to IPM, MEM and TBZ. All cases were negative regarding  the presence of IMP gene. VIM gene was positive in 48% of cases. While NDM-1 gene was positive in 60% of cases. Both VIM and NDM-1  genes were positive in 29.3% of cases. CDST is more sensitive, while DDST with both concentration of EDTA is less sensitive but more  specific. Sensitivity, specificity, PPV and NPV of DDST (taking the presence of any MBL gene as a reference test were 96.6%, 94.1%, 98.2%  and 88.9% respectively.

Conclusion: The ICU was a highly dispersed location for MBL-producing P. aeruginosa, which is one of the main  sources of resistance to carbapenem and other antimicrobial drugs.