Antibiotic Resistance Pattern and Evaluation of Metallo-Beta Lactamase Genes Including bla- IMP and bla- VIM Types in Pseudomonas aeruginosa Isolated from Patients in Tehran Hospitals.

Samira Aghamiri,Hossein Samadi Kafil,Babak Fouladtan,Nour Amirmozafari,Jalil Fallah Mehrabadi

doi:10.1155/2014/941507

Abstract

Beta-lactamase producing strains of Pseudomonas aeruginosa are important etiological agents of hospital infections. Carbapenems are among the most effective antibiotics used against Pseudomonas infections, but they can be rendered infective by group B β-lactamase, commonly called metallo-beta lactamase. In this study, the antimicrobial sensitivity patterns of P. aeruginosa strains isolated from 9 different hospitals in Tehran, Iran, as well as the prevalence of MBLs genes (bla-VIM and bla-IMP) were determined. A total of 212 strains of P. aeruginosa recovered from patients in hospitals in Tehran were confirmed by both biochemical methods and PCR. Their antimicrobial sensitivity patterns were determined by Kirby-Bauer disk diffusion method. Following MIC determination, imipenem resistant strains were selected by DDST method which was followed by PCR tests for determination of MBLs genes: bla-IMP and bla-VIM. The results indicated that, in the DDST phenotypic method, among the 100 imipenem resistant isolates, 75 strains were MBLs positive. The PCR test indicated that 70 strains (33%) carried bla-VIM gene and 20 strains (9%) harbored bla-IMP. The results indicated that the extent of antibiotic resistance among Pseudomonas aeruginosa is on the rise. This may be due to production of MBLs enzymes. Therefore, determination of antibiotic sensitivity patterns and MBLs production by these bacteria, can be important in control of clinical Pseudomonas infection.

Highlights

Pseudomonas aeruginosa is one of the commonest causes of infection in burn patients and an important agent for hospital acquired infections and death in immunocompromised such as cystic fibrosis and cancer patients [1]
The first MBLs enzymes were IMP-1 which was initially found in S. marcescens in Japan (1991), VIM-1 originally detected in Italy (1997), SPM-1 first detected in Brazil (1997), and GIM detected in Germany (2002) [5, 6]
Because the genes for MBLs are often carried on plasmids and class I integron, they can rapidly spread among different species of this bacterium and ISRN Microbiology other bacteria [7, 8]

Summary

Introduction

Pseudomonas aeruginosa is one of the commonest causes of infection in burn patients and an important agent for hospital acquired infections and death in immunocompromised such as cystic fibrosis and cancer patients [1]. This bacterium is often resistant to many antimicrobial agents. MBLs can potently hydrolyze all betalactam antibiotics except azetreonam These enzymes require zinc ion as cofactor [9]. Several phenotypic methods are available for detection of MBLs producing bacteria All these methods are based on the ability of metal chelators such as EDTA to inhibit the activity of MBLs. The double disk synergy test method was employed in this investigation [9]. The goal of this study was to determine the antibiotic resistance pattern in P. aeruginosa species isolated from nine hospitals in Tehran, Iran, and evaluate the prevalence of MBLs genes, bla-VIM and bla-IMP, in imipenem resistance strains

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Conclusion