Prevalence of carbapenem-resistant gram-negative bacilli producing carbapenemase by modified carbapenem inactivation method in an educational hospital in Tehran

Introduction: Regarding the crucial role of geographic factors in different mechanisms underlying bacterial antibiotic resistance worldwide, it is necessary to design and conduct studies to determine the prevalence and specific underlying mechanisms of this phenomenon. Objectives: This study was performed to assess the prevalence of carbapenem-resistant gram-negative bacilli which produce carbapenemase, in Loghman Hakim hospital, Tehran. Patients and Methods: In this cross-sectional study, antibiotic resistance of 300 samples of gram-negative bacilli from different patients was evaluated; 145 of which were identified as carbapenem-resistant. Carbapenemase enzyme production in these samples was assessed by the modified carbapenem inactivation method (mCIM). Results: About 81% of the samples were collected from the intensive care unit. In terms of sample type, most samples were obtained from trachea and urine culture. Acinetobacter baumannii (43%) was the most common carbapenem-resistant strain. Klebsiella pneumoniae (38%) and Pseudomonas aeruginosa (11%) ranked as the second and third most common strains, respectively. Based on mCIM evaluation, 82% of carbapenem resistance was due to the presence of carbapenemase enzyme which showed no significant difference neither between the both genders nor in various sample types. However, among carbapenemase-resistant bacilli, the presence of carbapenemase enzyme was significantly higher in A. baumannii (92%) and Escherichia coli (80%) and also in patients older than 50 years old. Conclusion: The findings of the present study showed that half of the collected gram-negative bacilli were resistant to carbapenem, of which 82% was due to the carbapenemase enzyme. The presence of the carbapenemase enzyme was higher in older patients as well as in Acinetobacter baumannii and Escherichia coli strains.