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Emergence of carbapenem-resistant non-baumannii species of Acinetobacter harboring a blaOXA-51-like gene that is intrinsic to A. baumannii.

ABSTRACT: The bla(OXA-51)-like gene, originally intrinsic to Acinetobacter baumannii, had been detected in two clones of Acinetobacter nosocomialis and one clone of Acinetobacter genomic species "Close to 13TU." These bla(OXA-51)-like genes, all preceded by ISAba1, were located on plasmids that might have originated with A. baumannii. The plasmid-borne ISAba1--bla(OXA-51)-like confers a high level of carbapenem resistance and affects the accuracy of using bla(OXA-51)-like detection as a tool for differentiating A. baumannii from other Acinetobacter species.

SUBMITTER: Lee YT

PROVIDER: S-EPMC3264228 | biostudies-literature | 2012 Feb

REPOSITORIES: biostudies-literature

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Emergence of carbapenem-resistant non-baumannii species of Acinetobacter harboring a blaOXA-51-like gene that is intrinsic to A. baumannii.

Lee Yi-Tzu YT Kuo Shu-Chen SC Chiang Mei-Chun MC Yang Su-Pen SP Chen Chien-Pei CP Chen Te-Li TL Fung Chang-Phone CP

Antimicrobial agents and chemotherapy 20111114 2

The bla(OXA-51)-like gene, originally intrinsic to Acinetobacter baumannii, had been detected in two clones of Acinetobacter nosocomialis and one clone of Acinetobacter genomic species "Close to 13TU." These bla(OXA-51)-like genes, all preceded by ISAba1, were located on plasmids that might have originated with A. baumannii. The plasmid-borne ISAba1--bla(OXA-51)-like confers a high level of carbapenem resistance and affects the accuracy of using bla(OXA-51)-like detection as a tool for different ...[more]

PMID: 22083478

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Project description:Nosocomial infections caused by Acinetobacter spp. resistant to carbapenems are increasingly reported worldwide. Carbapenem-resistant Acinetobacter (CRA) is becoming a serious concern with increasing patient morbidity, mortality, and lengths of hospital stay. Therefore, the rapid detection of CRA is essential for epidemiological surveillance. Polymerase chain reaction (PCR) has been extensively used for the rapid identification of most pathogens. In this study, we have developed two multiplex real-time PCR assays to detect and differentiate A. baumannii and non-A. baumannii Acinetobacter spp, and common carbapenemase genes, including blaNDM, blaOXA-23-like, blaOXA-40-like, blaOXA-51-like, and blaOXA-58-like. We demonstrate the potential utility of these assays for the direct detection of blaNDM-, blaOXA-23-like-, blaOXA-40-like-, blaOXA-51-like-, and blaOXA-58-like-positive CRA in clinical specimens. Primers were specifically designed, and two multiplex real-time PCR assays were developed: multiplex real-time PCR assay1 for the detection of Acinetobacter baumannii 16S-23S rRNA internal transcribed spacer sequence, the Acinetobacter recA gene, and class-B-metalloenzyme-encoding gene blaNDM; and multiplex real-time PCR assay2 to detect class-D-oxacillinase-encoding genes (blaOXA-23-like, blaOXA-40-like, blaOXA-51-like,and blaOXA-58-like). The assays were performed on an ABI Prism 7500 FAST Real-Time PCR System. CRA isolates were used to compare the assays with conventional PCR and sequencing. Known amounts of CRA cells were added to sputum and fecal specimens and used to test the multiplex real-time PCR assays. The results for target and nontarget amplification showed that the multiplex real-time PCR assays were specific, the limit of detection for each target was 10 copies per 20 μL reaction volume, the assays were linear over six log dilutions of the target genes (r2 > 0.99), and the Ct values of the coefficients of variation for intra- and interassay reproducibility were less than 5%. The multiplex real-time PCR assays showed 100% concordance with conventional PCR when tested against 400 CRA isolates and their sensitivity for the target DNA in sputum and fecal specimens was 102 CFU/mL. Therefore, these novel multiplex real-time PCR assays allow the sensitive and specific characterization and differentiation of blaNDM-, blaOXA-23-like-, blaOXA-40-like-, blaOXA-51-like-, and blaOXA-58-like-positive CRA, making them potential tools for the direct detection of CRA in clinical specimens and the surveillance of nosocomial infections.

Project description:BackgroundWith an increase in the use of colistin methansulfonate (CMS) to treat carbapenem-resistant Acinetobacter baumannii infections, colistin resistance is emerging.MethodsPatients with infection or colonization due to colistin-resistant A. baumannii were identified at a hospital system in Pennsylvania. Clinical data were collected from electronic medical records. Susceptibility testing, pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) were performed. To investigate the mechanism of colistin resistance, lipid A was subjected to matrix-assisted laser desorption/ionization mass spectrometry.ResultsTwenty patients with colistin-resistant A. baumannii were identified. Ventilator-associated pneumonia was the most common type of infection. Nineteen patients had received intravenous and/or inhaled CMS for treatment of carbapenem-resistant, colistin-susceptible A. baumannii infection prior to identification of colistin-resistant isolates. The 30-day all-cause mortality rate was 30%. The treatment regimen for colistin-resistant A. baumannii infection associated with the lowest mortality rate was a combination of CMS, a carbapenem, and ampicillin-sulbactam. The colistin-susceptible and -resistant isolates from the same patients were highly related by PFGE, but isolates from different patients were not, suggesting evolution of resistance during CMS therapy. By MLST, all isolates belonged to the international clone II, the lineage that is epidemic worldwide. Phosphoethanolamine modification of lipid A was present in all colistin-resistant A. baumannii isolates.ConclusionsColistin-resistant A. baumannii occurred almost exclusively among patients who had received CMS for treatment of carbapenem-resistant, colistin-susceptible A. baumannii infection. Lipid A modification by the addition of phosphoethanolamine accounted for colistin resistance. Susceptibility testing for colistin should be considered for A. baumannii identified from CMS-experienced patients.

Dataset Information

Emergence of carbapenem-resistant non-baumannii species of Acinetobacter harboring a blaOXA-51-like gene that is intrinsic to A. baumannii.

Publications

Emergence of carbapenem-resistant non-baumannii species of Acinetobacter harboring a blaOXA-51-like gene that is intrinsic to A. baumannii.

Similar Datasets

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