Mohammad Ahanjan - Mazandaran University of Medical Sciences

Introduction and Objectives: Since carbapenems are the last line treatment option for multi-drug resistant Enterobacteriaceae, increasing resistance to these antibiotics has been an important concern around the world. Thus, the aim of this study was to investigate the phenotypic and genotypic prevalence of carbapenemase-producing Enterobacteriaceae. Materials and Methods: One hundred non-repeated clinical samples were collected from patients hospitalized in Intensive Care Units of four teaching and treatment hospitals of Sari, North of Iran. The API 20E system was used to identification of the Enterobacteriaceae. Also, the minimum inhibitory concentration (MIC) of the carbapenems was detected by E-test. The phenotypic Modified Hodge Test (MHT) and Combined Disk Test (CDT) were used to determine the carbapenemase producer clinical isolates, and the polymerase chain reaction (PCR) method was done to study the presence of NDM-1, VIM and OXA-48 genes in chromosomes of the isolates. Results: The most enterobacterial isolates in the present study included Escherichia coli (37%), Klebsiella pneumoniae (21%), and Serratia rubidaea (10%), respectively. The most and least effective antibiotics against the clinical isolates were amikacin and meropenem with resistance rates of 24% and 73%, correspondingly, while 51% of the isolates were imipenem resistant. Also, 58 isolates were detected as multi-drug resistant (MDR) of which all of them were carbapenem-resistant. Among 73 carbapenem-resistant isolates, 35 (47.9%) and 33 (45.2%) of them were MHT and CDT positive, respectively. Moreover, 30.1%, 31.5%, and 38.3% of these isolates contained VIM, NDM-1, and OXA-48 carbapenemase encoding genes, correspondingly. Conclusions: This study showed that the MHT is not a reliable test for the study of strains producing OXA-48 or VIM carbapenemases. Also, there was a significant relationship between the presence of carbapenem resistance genes and Klebsiella pneumoniae isolates. It seems that the presence of at least two of these genes can be one of the main reasons for resistance to carbapenems in Enterobacteriaceae.

Enterobacteriaceae, Carbapenem, NDM-1, VIM, OXA-48.