Phenotypic and Genotypic Methods for Detection of Metallo - Beta - Lactamase ( MβL ) Producing Pseudomonas Aeruginosa

Abstract

Aeruginosa, MβL, IMP-EDTA CDT, PCR Background: The occurrence of a MβL-positive isolate in a hospital setting represents a therapeutic problem, as well as a serious concern for infection control management. The accurate identification and reporting of MβL-producing P. aeruginosa will aid infection control practitioners in preventing the spread of these multidrug-resistant isolates. Objectives: This study aimed to detect and characterize MβL producing P. aeruginosa in Benha and to evaluate IMP- EDTA CDT as phenotypic screening method for MβL detection. Methodology: This study was conducted on 100 P.aeruginosa strains isolated from 220 different clinical specimens collected from patients admitted to Benha University Hospital and Benha Teaching Hospital. The isolated P. aeruginosa strains were subjected to antibiotic susceptibility testing by disc diffusion test and MβL detection both phenotypically by IMP- EDTA CDT and genotypically by multiplex PCR. Results: Out of 100 P.aeruginosa isolates, 25 strains (25%) were imipenem resistant and 15 strains of them (60%) were carrying genes responsible for MβL production (15% of the total number of P.aeruginosa). Thirteen strains (13%) were carrying VIM gene while two strains (2%) were carrying both VIM and SPM genes together. IMP, GIM-1, SIM-1 genes were not detected. None of the imipenem sensitive strains were carrying genes of MβL production. Nearly all MβL producers were resistant to most antibiotics used while all strains were sensitive to colistin and polymyxinB. There is very good strength of agreement between IMP-EDTA CDT and PCR. The sensitivity & specificity of the IMPEDTA CDT in relation to PCR was 93.3% and 100% respectively. Conclusion: MβL producers is a serious problem as they are highly resistant to most antibiotics used making treatment options very limited, VIM gene is the most prevelant one in comparison with other genes of MβL production and IMP-EDTA CDT is a good and sensitive test in detecting MβL production.