Tracking ISAba1 element associated with blaOXA genes increasing carbapenem resistance in clinical isolates of Acinetobacter baumannii: The first report of a novel OXA carbapenemase group in Iran

سال انتشار: 1397
نوع سند: مقاله کنفرانسی
زبان: انگلیسی
مشاهده: 373

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شناسه ملی سند علمی:

ICCM12_003

تاریخ نمایه سازی: 1 دی 1397

چکیده مقاله:

Introduction and Objectives: Carbapenem-resistant Acinetobacter baumannii (CRAB) has emerged as a serious challenge and poses a threat to public health worldwide. The present study was conducted to determine the prevalence of blaOXA-type carbapenemases and the presence of ISAba1 sequences in upstream of blaOXA genes in clinical isolates of CRAB.Materials and Methods: A total of 65 A. baumannii isolates were obtained from burn wounds and evaluated for antimicrobial susceptibility by disc agar diffusion method. CRAB isolates were assessed against imipenem, meropenem, polymyxin B, colistin, and tigecycline using broth microdilution method. PCR assay was performed to determine distribution of blaOXA genes and the presence of ISAba1 enhancer upstream of corresponding oxacillinase-encoding genes in CRAB isolates. The expression of the OXA-type carbapenemases was quantified by real-time PCR (RT-PCR).Results: Overall, 96.92% and 72.3% of A. baumannii isolates were multi-drug resistant (MDR-AB), and extensively-drug resistant (XDR-AB). CRAB strains accounted for 96.92% of total isolates. Polymyxin B, colistin, and tigecycline were the most effective agents in CRAB isolates, with a susceptibility rate of 100%, 87.3%, and 65.08%, respectively. CRAB isolates carrying oxacillinase genes accounted for as follow: blaOXA-51-like; 100%, blaOXA-23-like; 74.6%, blaOXA-24/40-like; 47.62%, and blaOXA-235-like; 12.69%. This is the first epidemiological study reporting detection of blaOXA-235-like-harboring CRAB isolates from Iran, which has been deposed in the GenBank under the accession numbers AXH79648 and AXH79649. ISAba1, ISAba1-blaOXA-23-like, and ISAba1-blaOXA-51-like were detected in 100%, 41.26% and 1.58% of CRAB isolates. Co-occurrence of blaOXA determinants or inserted ISAba1 upstream of corresponding genes was associated with increased minimum inhibitory concentrations (MICs) (≥128 μg/ml) to carbapenems. The qRT-PCR showed overexpression of OXA-group enzymes with an upstream ISAba1 in CRAB.Conclusions: The presence of the ISAba1 promoter sequence associated with the blaOXA genes in A. baumannii leads to an increase in the expression of carbapenemase enzymes for hydrolyze of carbapenems and increasing resistance to them. Emergence of high-level carbapenem-resistant strains with blaOXA and ISAba1-blaOXA family in burn patients is a matter of increasing clinical concern, re-emphasizing need to infection control efforts to limit such problematic bacteria.

نویسندگان

Sajjad Yazdansetad

Department of Microbiology , School of Medicine, Golestan University of Medical Sciences, Gorgan, Iran

Abdollah Ardebili

Department of Microbiology , School of Medicine, Golestan University of Medical Sciences, Gorgan, Iran

Ezzat Allah Ghaemi

Department of Microbiology , School of Medicine, Golestan University of Medical Sciences, Gorgan, Iran

Ehsan Najjari

Department of Microbiology , School of Medicine, Golestan University of Medical Sciences, Gorgan, Iran