Aims: One of the drug resistant organisms in the worldwide hospitals is Acinetobacter baumannii. The aim of this study was to investigate the expansion of drug-resistant Acinetobacter baumannii-calcoaceticus population, extensively drug-resistant (XDR) and pan-drug resistant (PDR) strains, and the ability of carbapenemases production, as well as to determine imipenem MIC in its isolates.

Materials & Methods: In the cross-sectional study, 48 samples of the patients hospitalized in different wards of the hospitals in Shiraz were collected and cultured on clinical microbiological media during 10 months from July 2014 to April 2015. Specific non-fermentative bacteria API 20NE system and biochemical tests were used to confirm the isolates finally. Based on CLSI 2014 protocol, disc diffusion method was used to investigate the antibiotic sensibility. Modified hodge test was used to determine the strains producing carbapenemases enzymes. E-test method was used to determine imipenem MIC.

Findings: All the isolates were sensitive to coloistin antibiotic. None of the isolate answered carbapenemases (ertapenem, imipenem, and meropenem). Beside multi-drug resistant characteristics, all the isolates were with expanded drug resistant characteristics. However, there was no pan-drug resistant isolate. Levels of sensitivity to minocycline and ampicillin-sulbactam were 14.3 and 10.7%, respectively. Phenotypic modified Hodge test was positive in all the isolates. Imipenem MIC was higher than 32 units in all the isolates. 

Conclusion: Combined drug regimens are effective on the treatments of XDR and MDR Acinetobacter strains.