Distribution of Class D Carbapenemase and Extended-Spectrum β-Lactamase Genes among Isolated from Burn Wound and Ventilator Associated Pneumonia Infections.

Introduction: Resistance to is dramatically on the rise in Iran. Therefore, it is important to study resistance pattern among isolates which is a common cause of nosocomial infections.

Aim: To investigate antibiotic resistance patterns and the role of resistant genes and biofilm formation in the induction of resistance among isolated from burn wound and ventilator associated pneumonia infections.

Materials And Methods: Total 103 isolates such as 33 burn samples from Rasool Akram Hospital and 70 isolates from ventilated patients in Shahid Motahhari Hospital were identified with . using biochemical method, and then identified to species level with PCR of and gene. Antibiotic sensitivity pattern for β-lactam and carbapenem antibiotics was assessed using Agar disc diffusion test and E-test. The presence of different carbapenemase and metalo-β-lactamase (, , , , , , , , , , ), extended-spectrum β-lactamases (, ) and two insertion sequences genes (, ) was assessed. Biofilm formation of all isolates was then assessed. Chi-square analysis or Fisher's-exact tests were used for statistical analysis. A p-value <0.05 was considered statistically significant.

Results: Colistin was the most effective antimicrobial agents, although 10.7% (11/103) of the isolates were resistant. The high rate of resistance to meropenem (93.2%) and imipenem (90.3%) was determined. Also, with exception of ampicillin-sulbactam, surprisingly the resistant rate was 28.2%, the resistance to β-lactam antibiotic was dramatically increased. Co-existence of two and three blaOXA genes was also determined. The blaOXA-58 was detected in only one isolate. The blaTEM and blaOXA-23 was the most prevalent Extended-Spectrum β-Lactamases (ESBL) gene. All isolates were biofilm producers.

Conclusion: Antibiotic resistance is increasing among A. baumannii isolates which is due to excessive use of antibiotics and also acquired resistant genes and biofilm production. Resistance to nearly all antimicrobial agents especially colistin as end choice for treatment of multiple drug resistance A. baumannii is a big concern.