Susceptibility Pattern and Distribution of Oxacillinases and bla (PER-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.