Susceptibility Pattern and Distribution of Oxacillinases and blaPER-1 Genes among Multidrug Resistant Acinetobacter baumannii in a Teaching Hospital in Iran

Acinetobacter baumannii (A. baumannii) is an important nosocomial pathogen in healthcare institutions. β-Lactamase-mediated resistance is the most common mechanism for carbapenem resistance in A. baumannii. The aim of this study was to determine the antibiotic resistance pattern, to detect OXA encoding genes, class A, bla PER-1, and to detect the presence of ISAba1. A total of 124 A. baumannii isolates were collected from hospitalized patients in a teaching hospital in Kashan, Iran. The susceptibility of isolates to different antibiotics was determined by disk-diffusion method. PCR was used to detect bla PER-1, bla OXA-23, bla OXA-24, bla OXA-51, bla OXA-58, and ISAba1 genes. All isolates were resistant to ceftazidime, ceftriaxone, and cefotaxime. All of the isolates revealed susceptibility to polymyxin B and colistin. Ninety-six percent of the isolates were extensive drug resistance (XDR), 5.6% extended spectrum beta-lactamase (ESBL), and 54.8% metallo-beta-lactamase (MBL). All isolates were positive for bla OXA-51 and ISAba1. bla OXA-23,  bla OXA-24, and bla OXA-58 were found in 79.8%, 25%, and 3.2%, respectively. The frequency rate of bla PER-1 gene was 52.4%. Multidrug resistant A. baumannii isolates are increasing in our setting and extensively limit therapeutic options. The high rate presence of class D carbapenemase-encoding genes, mainly bla OXA-23 carbapenemases, is worrying and alarming as an emerging threat in our hospital.