Phenotypic, biochemical, and molecular techniques for detection of metallo-β-lactamase NDM in Acinetobacter baumannii

Matrix-assisted laser desorption ionization-time of flight (maldi-tof) mass spectrometry for detection of antibiotic resistance mechanisms: from research to routine diagnosis

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been successfully applied as an identification procedure in clinical microbiology and has been widely used in routine laboratory practice because of its economical and diagnostic benefits. The range of applications of MALDI-TOF MS has been growing constantly, from rapid species identification to labor-intensive proteomic studies of bacterial physiology. The purpose of this review is to summarize the contribution of the studies already performed with MALDI-TOF MS concerning antibiotic resistance and to analyze future perspectives in this field. We believe that current research should continue in four main directions, including the detection of antibiotic modifications by degrading enzymes, the detection of resistance mechanism determinants through proteomic studies of multiresistant bacteria, and the analysis of modifications of target sites, such as ribosomal methylation. The quantification of antibiotics is suggested as a new approach to study influx and efflux in bacterial cells. The results of the presented studies demonstrate that MALDI-TOF MS is a relevant tool for the detection of antibiotic resistance and opens new avenues for both clinical and experimental microbiology.

Gram-negative bacteria that produce carbapenemases causing death attributed to recent foreign hospitalization

Overseas travel, as a risk factor for the acquisition of infections due to antimicrobial-resistant organisms, has recently been linked to carbapenemase-producing Gram-negative bacteria. Multiresistant Klebsiella pneumoniae, Escherichia coli, and Acinetobacter baumannii strains were isolated from a wound of a Canadian patient with a recent history of hospitalization in India. This resulted in the initiation of outbreak management that included surveillance cultures. Epidemiological and molecular investigations showed that NDM-1-producing K. pneumoniae ST16 and OXA-23-producing A. baumannii ST10 strains were transmitted to 5 other patients, resulting in the colonization of 4 patients and the death of 1 patient due to septic shock caused by the OXA-23-producing A. baumannii strain. The high rate of false positivity of the screening cultures resulted in additional workloads and increased costs for infection control and clinical laboratory work. We believe that this is the first report of an infection with carbapenemase-producing Gram-negative bacteria resulting in death attributed to a patient with recent foreign hospitalization. We recommend routine rectal and wound screening for colonization with multiresistant bacteria for patients who have recently been admitted to hospitals outside Canada.

Detection of New Delhi metallo-β-lactamase (encoded by blaNDM-1) in Acinetobacter schindleri during routine surveillance

A carbapenem-resistant Alcaligenes faecalis strain was isolated from a surveillance swab of a service member injured in Afghanistan. The isolate was positive for bla(NDM) by real-time PCR. Species identification was reevaluated on three identification systems but was inconclusive. Genome sequencing indicated that the closest relative was Acinetobacter schindleri and that bla(NDM-1) was carried on a plasmid that shared >99% identity with one identified in an Acinetobacter lwoffii isolate. The isolate also carried a novel chromosomally encoded class D oxacillinase.

Rapid and simultaneous detection of blaKPC and blaNDM by use of multiplex real-time PCR

The increasing incidence of carbapenem nonsusceptibility among clinically important species is of global concern. Identification of the molecular mechanisms underlying carbapenem nonsusceptibility is critical for epidemiological investigations. In this report, we describe a real-time PCR-based assay capable of simultaneously detecting blaKPC and blaNDM, two of the most important carbapenemases, directly from culture in less than 90 min. The assay was validated with blaKPC- and blaNDM-carrying clinical isolates and demonstrated 100% concordance with the Carba NP test.

Detection of SPM-1-producing Pseudomonas aeruginosa and class D β-lactamase-producing Acinetobacter baumannii isolates by use of liquid chromatography-mass spectrometry and matrix-assisted laser desorption ionization-time of flight mass spectrometry

This study evaluates the accuracy of liquid chromatography-mass spectrometry (LC-MS) and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) for detecting carbapenem hydrolytic activity among SPM-1-, GIM-1-, and GES-5-producing Pseudomonas aeruginosa isolates and OXA-143-, IMP-10-, and OXA-58-producing Acinetobacter baumannii isolates. Class A and B carbapenemase activities were rapidly detected by MALDI-TOF in a 2-h assay. However, an extended incubation time was necessary for detection of carbapenem-hydrolyzing class D β-lactamase (CHDL) activity in Acinetobacter spp.

Wide dissemination of GES-type carbapenemases in Acinetobacter baumannii isolates in Kuwait

Acinetobacter baumannii is an opportunistic pathogen that is an important source of nosocomial infections. Production of extended-spectrum β-lactamases (ESBLs) of the GES type in A. baumannii has been increasingly reported, and some of these GES-type enzymes possess some carbapenemase activity. Our aim was to analyze the resistance determinants and the clonal relationships of carbapenem-nonsusceptible A. baumannii clinical isolates recovered from hospitals in Kuwait. A total of 63 isolates were analyzed, and all were found to be positive for bla(GES)-type genes. One isolate harbored the bla(GES-14) gene encoding an ESBL with significant carbapenemase activity, whereas the other isolates harbored the bla(GES-11) ESBL gene. Thirty-three isolates coharbored the bla(OXA-23) and bla(GES-11) genes. Analyses of the genetic locations indicated that the bla(GES-11/-14) genes were plasmid located. It is noteworthy that the bla(OXA-23) and bla(GES-11) genes were colocated onto a single plasmid. Nine different pulsotypes were observed among the 63 isolates. This study showed the emergence of GES-type ESBLs in A. baumannii in Kuwait, further suggesting that the Middle East region might be a reservoir for carbapenemase-producing A. baumannii.

Dissemination of New Delhi metallo-β-lactamase-1-producing Acinetobacter baumannii in Europe

Multidrug-resistant and New Delhi metallo-β-lactamase 1 (NDM-1) -producing Acinetobacter baumannii are increasingly reported. A collection of five NDM-1-positive A. baumannii isolates recovered in four European countries were analysed. Genotyping was performed by pulsed-field gel electrophoresis, multiplex PCR sequence typing, Diversilab and multilocus sequence typing. Three distinct sequence types were identified. All isolates harboured a chromosomally located bla(NDM-1) gene within a Tn125-like transposon. One isolate co-expressed another unrelated carbapenemase OXA-23. This report constitutes the first epidemiological study of NDM-1-producing A. baumannii from four countries.