FREQUENCY OF CARBAPENEMASE AND METALLO-BETALACTAMASE RESISTANCE AND OXA- 48, OXA-23, AND NDM GENES IN CLINICAL ISOLATES OF ACINETOBACTER BAUMANNI IN 2017

One of the most important problems in treatment centers is the infectious diseases
caused by antibiotic resistant Acinetobacter Bumanni. This study aimed to isolate and identify
carbapenemase and metallo-beta-lactamase producing strains using phenotypic and molecular methods.
Materials & Methods: In this study 79 strains of Acinetobacter Bumanni were isolated from patients
hospitalized in Tehran Heart Hospital and identified by biochemical tests. Antibiotic susceptibility of
isolates was performed by disc diffusion method. Phenotypic methods such as combined disk test
(CDT), double disk synergy test (DDST), and Modified Hodge test (MHT) were performed to identify
carbapenemase and metallo-beta-lactamase activity. PCR was performed using specific primers for
OXA- 48, OXA-23, and NDM genes.
Results: In this study, the highest resistance in A. baumanii was observed to imipenem and ertapenem
by disk diffusion method. By CDT, 96.2% of isolates showed carbapenemase activity and 94.93%
showed metallo-beta-lactamase activity in presence of imipenem. Also, by DDST, 86.07% and 91.13%
of isolates showed Carbapenemase and metallo-beta-lactamase activity, respectively, and 91.14% of
isolates were positive by MHT. The molecular method showed that OXA-48 gene was in 100% of
isolates and OXA-23 gene was in 98.73% of isolates and NDM gene did not exist in isolates.
Conclusion: Based on the results, CDT has high susceptibility in other phenotypic methods for
identifying carbapenemase and metallo-beta-lactamase activity. Frequency of OXA-48 and OXA-23
genes revealed antibiotic resistance in A. baumanii isolates