Rapid Detection of Carbapenem Resistance in Acinetobacter baumannii Using Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry

Rapid detection of carbapenem-resistant Acinetobacter baumannii strains is critical and will benefit patient care by optimizing antibiotic therapies and preventing outbreaks. Herein we describe the development and successful application of a mass spectrometry profile generated by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) that utilized the imipenem antibiotic for the detection of carbapenem resistance in a large series of A. baumannii clinical isolates from France and Algeria. A total of 106 A. baumannii strains including 63 well-characterized carbapenemase-producing and 43 non-carbapenemase-producing strains, as well as 43 control strains (7 carbapenem-resistant and 36 carbapenem-sensitive strains) were studied. After an incubation of bacteria with imipenem for up to 4 h, the mixture was centrifuged and the supernatant analyzed by MALDI-TOF MS. The presence and absence of peaks representing imipenem and its natural metabolite was analyzed. The result was interpreted as positive for carbapenemase production if the specific peak for imipenem at 300.0 m/z disappeared during the incubation time and if the peak of the natural metabolite at 254.0 m/z increased as measured by the area under the curves leading to a ratio between the peak for imipenem and its metabolite being <0.5. This assay, which was applied to the large series of A. baumannii clinical isolates, showed a sensitivity of 100.0% and a specificity of 100.0%. Our study is the first to demonstrate that this quick and simple assay can be used as a routine tool as a point-of-care method for the identification of A. baumannii carbapenemase-producers in an effort to prevent outbreaks and the spread of uncontrollable superbugs

Extensively drug-resistant ArmA-producing acinetobacter baumannii in an Italian intensive care unit

© 2018 by EDIMES - Edizioni Internazionali Srl. All rights reserved. We describe the spread of 12 carbapenem-resistant Acinetobacter baumannii isolates in hospitalized patients. All strains showed an extensively drug-resistant phenotype and high-level of aminoglycoside resistance, harboring the ArmA gene and blaoxa-23 downstream of ISAba1 (transposon Tn2008 arrangement) where both were located on the chromosome. These strains carry a class 1 integron containing the gene cassette aacA4-catB8-aadA1. Molecular analysis revealed that all isolates belonged to the same sequence type (ST) 2 clone. The spread of ArmA-producing A. baumannii strains limit the treatment options showing the dramatic situation which requires novel therapies to limit high mortality rates

Epidemiological characterization and distribution of carbapenem-resistant Acinetobacter baumannii clinical isolates in Italy

This study was aimed at tracing the molecular characteristics of carbapenem-resistant Acinetobacter baumannii (CRAB) clinical isolates in Italy with both pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Two hundred and two CRAB isolates were collected during 2004-2009, in two different surveillance periods, from 22 Italian hospitals that were representative for both distribution and infection. PFGE was performed, and the MLST scheme used was based on the gene sequence as published on the MLST Pasteur website. Representatives of the major European clones&nbsp;I (RUH&nbsp;875) and II (RUH&nbsp;134) were used as controls. The two groups of isolates were characterized for their carbapenem resistance genes: 154 of 202 carried blaOXA-58 alone, 21 of 202 also carried blaOXA-23, and 27 of 202 carried blaOXA-23 alone. No isolates were positive for blaOXA-24. Genotype analysis of all isolates identified four distinct patterns by PFGE, which correlated with four distinct sequence types (STs) by MLST. The distribution of these four clusters in Italy confirmed the propensity of A.&nbsp;baumannii for nosocomial cross-transmission in a vast geographical area. We observed that clones&nbsp;A and B had similarities with European clone&nbsp;II and I respectively. By MLST, clone&nbsp;A was ST2, like European clone&nbsp;II, and clone&nbsp;B was ST1, like European clone&nbsp;I. PFGE and MLST showed the same discriminatory power and reproducibility. In addition, the two methods were concordant in defining CRAB Italian clones and in correlating them with the two pan-European clones. © 2011 The Authors. Clinical Microbiology and Infection © 2011 European Society of Clinical Microbiology and Infectious Diseases

Dynamics of colistin and tobramycin resistance among Enterobacter cloacae during prolonged use of selective decontamination of the digestive tract

Background A high prevalence of colistin resistance among E. cloacae isolates in two intensive care units (ICU) (of 16 and 6 beds) using selective digestive decontamination (SDD) since 1990 instigated a retrospective and prospective investigation to quantify the role of clonal transmission. SDD is topical application of colistin and tobramycin and systemic use of cefotaxime during the first days of ICU-admission. Methods Multi-resistant E. cloacae (MREb) was defined as ESBL production and/or tobramycin non-susceptibility and/or colistin non-susceptibility. Incidence of acquisition and prevalence of carriage with MREb was determined from microbiological culture results. Results Colistin-resistant E. cloacae was first detected in November 2009 and carriage was demonstrated in 141 patients until October 2014. Mean incidence of MREb acquisition was 4.61 and 1.86 per 1000 days at risk in ICUs 1 and 2, respectively, and the mean monthly prevalence of MREb in both ICUs was 7.0 and 3.1%, respectively, without a discernible trend in time. Conversion rates from carriage of colistin-susceptible to resistant E. cloacae were 0.20 and 0.13 per 1000 patient days, respectively. Whole genome sequencing of 149 isolates revealed eight clusters, with the number of SNPs of the largest two clusters ranging between 0 and 116 for cluster 1 (n = 49 isolates), and 0 and 27 for cluster 2 (n = 36 isolates), among isolates derived between 2009 and 2014. Conclusions This study demonstrates a stable low-level endemicity of MREb in two Dutch ICUs with prolonged use of SDD, which was characterized by the persistent presence of two clusters, suggesting incidental clonal transmission