Evaluation of AmpC Gene Expression in Carbapenem Resistant Pseudomonas aeruginosa Strains Isolated from Severely Burned Patients With Secondary Infection in Hospitals

Abstract

Background: Pseudomonas aeruginosa is an opportunistic pathogen mostly affecting hospitalized and immunodeficient patients. Considering the extent of attention paid to the issue of antibiotic resistance and the origin of such resistance and the growing number of treatment failures in patients with burn injury, it seems that investigating the degree of ampC gene expression could be beneficial for the treatment of patients with severe burn injury. Objectives: The present study focused on identifying different antibiotic patterns, detecting carbapenem resistant Pseudomonas aeruginosa strains isolated from severely burned patients and investigating AmpC gene expression as one of the important mechanisms associated with drug resistance. Materials and Methods: A total of 189 clinical isolates of carbapenem resistant Pseudomonas aeruginosa, isolated from patients with severe burn injuries, were identified by bacteriological methods followed by determination of their antibiotic resistance patterns by the standard protocol of Kirby–Bauer. The expression of ampC gene was determined by quantitative real-time PCR. Results: Based on our findings, 94.2% of the isolates were resistant to imipenem, 99.5% were resistant to meropenem, and all were resistant to ertapenem. The level of ampC gene expression in carbapenem resistant Pseudomonas aeruginosa isolates, compared to standard carbapenem sensitive strains, was significantly increased. Conclusions: Our data showed that the over-expression of ampC gene is an important mechanism of resistance in carbapenem resistant Pseudomonas aeruginosa strains isolated from severely burned patients with secondary infections.