Acinetobacter baumannii which is gram-negative rod and infecting hospitalized patient often develops multiple drug
resistance patterns and causes serious problem in treatment. The aim of this study is to determine the relationship
between this serious problem in treatment and Presence of some β-lactamase genes in the A. baumannii. 100 isolates
of Acinetobacter collected from hospitalized patients in Tehran. First their resistance to different antibiotics were
determined using disk agar diffusion test then the MICs of all resistant isolates determined by Etest .In the second
stage we screened all resistance isolates for β-lactamase gene existence by double-disk synergy test and finally
prevalence of β-lactamase encoding genes such as IMP-1,SIM-1,OXA-23,OXA-24 and OXA-58 were determined
by PCR. According those tests the most efficient treatment was achieved by Colistin, Gentamicin, and Imipenem.
Disk synergy test with 0.1M EDTA determined 23 % of isolates as metalo β-lactamase producers. Prevalence of β-
lactamase encoding genes was: 4%, 0%, 38%, 32%, and 1% respectively. According to this study efficient treatment
will be influenced by OXA β-lactamase more than the other genes which have been studied. This is the first report
of SIM type among MBL-producing A. baumannii in Iran
