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Objective(s):Antibiotic resistance in Acinetobacter baumannii and outbreaks caused by this organism have been reported from several areas of the world. The present study aimed at determining the antibiotic susceptibility profiles and the distribution of OXA-type beta-lactamases among Iranian Acinetobacter baumannii isolates from Qom of Iran. Materials and Methods: For this study, 108 non-duplicate A. baumannii isolates were obtained from clinical specimens in four teaching hospitals in Qom in the central of Iran. The antimicrobial susceptibility of isolates was tested by standard disk diffusion and prevalence of bla OXA genes was investigated by PCR method. Results: Among 97 carbapenem non-susceptible isolates of A. baumannii, 90.72% (88 isolates) isolates showed extensive drug resistance to multiple antibiotics. Among carbapenem resistant isolates, 100% carried blaOXA-51-like, 82.47% carried blaOXA-23-like, 55.67% carried blaOXA-58-like, 22.68% carried blaOXA-40-like and 14.43% had blaOXA-143-like resistance genes. Conclusion: This study demonstrated high genetic diversity of OXA genes among isolates of A. baumannii in Qom, Iran.

Acinetobacter baumannii produces carbapenemase-hydrolyzing class D β-lactamases (CHDLs) as one of the major drug resistance mechanisms. This investigation is thus aimed to assess the prevalence and to characterize the CHDL-producing strains of A. baumannii by both phenotypic assays and genotypic characterization. A total of 73 isolates of A. baumannii were phenotypically and genotypically characterized from patients (N = 1,000) with severe urinary tract infection. Tested strains were subjected to double disk synergy testing by Kirby–Bauer disk diffusion method with modified Hodge test (MHT) for carbapenemase production. Plasmid DNA was molecularly screened for CHDL-encoding bla oxa-51, bla oxa-23, and bla oxa-143 genes by polymerase chain reaction. Carbapenem-resistant profile showed 100%, 61.64%, and 67.12% resistance by Kirby–Bauer disk diffusion method that correlated with MHT positivity for 100% (n = 73), 80% (n = 36), and 78% (n = 38) of the isolates against imipenem, doripenem, and meropenem, respectively. The bla oxa-51 and bla oxa-23 were observed in 41.09% (n = 30) and 35.61% (n = 26) with co-occurrence in 4.10% (n = 3) of the isolates. MHT-positive isolates showed 100%, 91.66%, and 71.4% for bla oxa-51 and 91.78%, 51.11%, and 34.69% for bla oxa-23 with imipenem, doripenem, and meropenem resistance, respectively. None of the strains yielded bla oxa-143 gene. The findings of this study showed prevalence of carbapenem resistance and high frequency of bla oxa-51 and bla oxa-23 among A. baumannii. [ABSTRACT FROM AUTHOR]

Background: Carbapenem-resistant Acinetobacter baumannii (CRAb) is an important cause of nosocomial infections especially in intensive care units. This study aimed to assess clinical aspects and the genetic background of CRAb among ICU patients at a Brazilian teaching hospital., Methods: 56 critically ill patients colonized or infected by CRAb, during ICU stay, were prospectively assessed. Based on imipenem MIC≥4μg/mL, 28 CRAB strains were screened for the presence of genes encoding metallo-β-lactamases and OXA-type β-lactamases. The blaOXA-type genes were characterized by PCR using primers targeting ISAba-1 or -3. Genetic diversity of blaOXA-positive strains was determined by ERIC-PCR analysis., Results: Patient's mean age (±SD) was 61 (±15.1), and 58.9% were male. Eighty-percent of the patients presented risk factors for CRAb colonization, mainly invasive devices (87.5%) and previous antibiotic therapy (77.6%). Thirty-three patients died during hospital stay (59.0%). Resistance to carbapenems was associated with a high prevalence of blaOXA-23 (51.2%) and/or blaOXA-143 (18.6%) genes. ERIC-PCR genotyping identified 10 clusters among OXA-producing CRAb. Three CRAb strains exhibited additional resistance to polymyxin B (MIC≥4μg/mL), whereas 10 CRAb strains showed tigecycline MICs>2μg/mL., Conclusions: In this study, clonally unrelated OXA-123- and OXA-143-producing A. baumannii strains in ICU patients were strongly correlated to colonization with infected patients being associated with a poor outcome., (Copyright © 2016 Sociedade Brasileira de Infectologia. Published by Elsevier Editora Ltda. All rights reserved.)