Phenotypic and Genotypic Characterization of Carbapenem-Resistant Acinetobacter baumannii
نویسندگان: Behnaz Deihim ©, Maryam Khorramizadeh
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Background and Aim
Antibiotic resistant Acinetobacter baumannii is one of the medical problems worldwide. In recent decades, carbapenem-resistant strains have emerged. One of the most common mechanisms of resistances is the production of carbapenemase enzyme, which in the present study we investigated their phenotypic and genotypic frequency in Dezful teaching hospital.
In this cross-sectional study, all strains of Acinetobacter baumannii were identified through biochemical and molecular methods. Antimicrobial susceptibility testing, Metalobetalactamase ( MBLs) and extended spectrum betalactamases ( ESBLs) were performed according to CLSI guidelines. Molecular detection of blaIMP, blaVIM, blaSPM, blaOXA-23, and blaOXA-24, blaOXA-58, blaGES genes were performed.
A total of 54 strains were isolated from respiratory tract ( 68.5%), urine ( 16.6%), wound ( 11.1%), and blood ( 3.7%). The highest resistance rate was against third-generation cephalosporins ( 98.1%) and ciprofloxacin( 94.2%), while about minocycline was 13%. Acinetobacter baumannii isolates exhibited 74% meropenem resistance. The most carbapenem-resistant strains were isolated from the endotracheal tubes. In phenotypic methods, 26% and 80% were ESBL and MBL producers, respectively. All of isolates were semi susceptibility against colistin ( MIC of less than 2 µg/mL). In 35 strains of carbapenem resistance A. baumannii ( CRAB) the most prevalent gene was blaOXA-23, followed by blaOXA-24, blaVIM , blaGES, blaIMP, and blaOXA-58 genes, but blaSPM gene not detected. These CRABs were classified into 11 patterns based on molecular detection. Six strains were positive for genes of class A, B and D and 18 strains were positive for B and D class genes.
Our report highlighted the existence of CRAB and semi-sensitivity to colistin and also co-existence of several genes from different carbapenemase classes in this region. Therefore, resistant strains should be identified promptly and specific treatment protocols should be devised to control the dissemination of resistance genes in therapeutic settings.
A. baumannii; Carbapenem resistance; Carbapenemase; Genotyping
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