Mechanisms of resistance to carbapenems among Acinetobacter isolates

Objectives: To identify carbapenem resistance mechanism in Acinetobacter isolates from clinical samples. Methods: Eighty six isolates of Acinetobacter spp obtained from various samples were included in the study. Antibiotic susceptibility was determined by Kirby-Bauer disc diffusion method. Isolates showing resistance to Meropenem were further tested for Amp C beta lactamase production by Amp C disc test and Metallobetalactamase (MBL) production by disc potentiation test. Results: Among eighty six isolates of Acinetobacte r sp , forty eight strains (55%) were found to be resistant to Meropenem by disc diffusion method. Out of forty eight resistant strains, twenty nine strains (60%) were isolated from intensive care units,10 strains (20%) from medical wards and 9 (19%) from surgical wards. Among these resistant strains, six (12%) were found to be Amp C betalactamase producers, 39 strains (81%) produced MBL, 3 strains (6%) were negative for both Amp C and MBL. Conclusion: In our study we found that meropenem resistance in Acinetobacter was more in Intensive care units and the major resistance mechanism to carbapenem among Acinetobacter isolates was due to production of metallobetalactamase.