RESUMEN
The MALDI Biotyper Selective Testing of Antibiotic Resistance-ß-Lactamase (MBT STAR-BL) assay, which analyzes bacterial induced hydrolysis of cefotaxime using MALDI-TOF MS, correctly identified 100.0% of extended-spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae as positive and 94.7% of non-ESBL producers as negative in 80 strains tested.
Asunto(s)
Infecciones por Enterobacteriaceae/microbiología , Escherichia coli/aislamiento & purificación , Klebsiella pneumoniae/aislamiento & purificación , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/métodos , Resistencia betalactámica , Cefotaxima/química , Hospitales Universitarios , Japón , Tamizaje Masivo/métodosRESUMEN
This study investigated the molecular and phenotypic characteristics of carbapenemase-producing Klebsiella pneumoniae, and identified the risk factors underlying its acquisition. We evaluated K. pneumoniae isolated in Nagasaki University Hospital between January 2009 and June 2015. The presence of carbapenemase genes and plasmid characteristics were investigated. We performed multilocus sequence typing (MLST), and generated a dendrogram based on the results of pulsed-field gel electrophoresis (PFGE) for carbapenemase-producing strains. We also performed a case-control study of patients. Of the 88 K. pneumoniae strains that showed minimum inhibitory concentration ≥1 µg/mL for imipenem and/or meropenem, and that were available from our bacterial collection, 18 had the IMP-type carbapenemase gene, all of which were IMP-1 according to sequencing analysis. Strains included seven different sequence types (STs), of which the most common was ST1471. A dendrogram showed the significant similarity of some strains with relationships in PFGE patterns, STs, and the wards in which they were isolated. Plasmid incompatibility group was similar among the IMP-1 producers. Regarding risk factors, multivariate analysis showed that liver disease and previous uses of carbapenems and anti-fungal drugs were significant factors for the acquisition of IMP-1-producing strains. Our results demonstrate that IMP-1 is a major carbapenemase produced by K. pneumoniae. The PFGE results indicated the possibility of transmission in the hospital. The identified risk factors should be considered for appropriate antibiotic therapy and infection-control measures.
Asunto(s)
Antibacterianos/farmacología , Carbapenémicos/farmacología , Infecciones por Klebsiella/epidemiología , Klebsiella pneumoniae/genética , Centros de Atención Terciaria/estadística & datos numéricos , Anciano , Antibacterianos/uso terapéutico , Técnicas de Tipificación Bacteriana/métodos , Carbapenémicos/uso terapéutico , Estudios de Casos y Controles , Niño , Preescolar , Farmacorresistencia Bacteriana Múltiple/genética , Femenino , Humanos , Lactante , Control de Infecciones/métodos , Control de Infecciones/estadística & datos numéricos , Japón/epidemiología , Infecciones por Klebsiella/tratamiento farmacológico , Infecciones por Klebsiella/microbiología , Infecciones por Klebsiella/transmisión , Klebsiella pneumoniae/aislamiento & purificación , Masculino , Pruebas de Sensibilidad Microbiana , Persona de Mediana Edad , Tipificación de Secuencias Multilocus/métodos , Estudios Retrospectivos , Factores de Riesgo , beta-LactamasasRESUMEN
The MALDI Biotyper Selective Testing of Antibiotic Resistance-ß-Lactamase (MBT STAR-BL) assay enables rapid detection of ß-lactamase activity using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry. The assay is based on analysis of bacterially induced hydrolysis of ß-lactam antibiotics. We investigated the performance of the MBT STAR-BL assay for detecting IMP metallo-ß-lactamase (MBL) activity in Enterobacteriaceae. A total of 145 strains (30 Escherichia coli, 43â¯Klebsiella pneumoniae, and 72 Enterobacter cloacae complex) were evaluated using meropenem hydrolysis assays. The MBT STAR-BL correctly identified all 48 IMP MBL producers as positive, even those exhibiting a low minimal inhibitory concentration (MIC) (1⯵g/mL) for meropenem. Conversely, all non-IMP MBL producers, including strains with higher MICs (4 or 8⯵g/mL), were correctly identified as negative. The MBT STAR-BL is a rapid, accurate, and reliable system for detecting IMP MBL activity in Enterobacteriaceae.
Asunto(s)
Infecciones por Enterobacteriaceae/diagnóstico , Infecciones por Enterobacteriaceae/microbiología , Enterobacteriaceae/clasificación , Enterobacteriaceae/efectos de los fármacos , Pruebas de Sensibilidad Microbiana , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Resistencia betalactámica , Enterobacteriaceae/enzimología , Humanos , Inosina Monofosfato/metabolismo , Pruebas de Sensibilidad Microbiana/métodos , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/métodos , beta-Lactamasas/metabolismoRESUMEN
BD Phoenix™ is an automated bacterial identification and susceptibility testing system. Here, its performance in screening IMP-producing Enterobacteriaceae was evaluated. The system identified 97.8% of IMP producers as being nonsusceptible to imipenem or meropenem, which was higher than that identified by the broth microdilution method (91.3%, imipenem; 41.3%, meropenem).
Asunto(s)
Automatización de Laboratorios/métodos , ADN Bacteriano/genética , Enterobacter cloacae/aislamiento & purificación , Infecciones por Enterobacteriaceae/diagnóstico , Inosina Monofosfato/metabolismo , Klebsiella pneumoniae/aislamiento & purificación , Antibacterianos/farmacología , Proteínas Bacterianas/genética , Carbapenémicos/metabolismo , Enterobacter cloacae/efectos de los fármacos , Enterobacter cloacae/enzimología , Infecciones por Enterobacteriaceae/microbiología , Imipenem/farmacología , Klebsiella pneumoniae/efectos de los fármacos , Klebsiella pneumoniae/enzimología , Meropenem/farmacología , Pruebas de Sensibilidad MicrobianaRESUMEN
The Verigene Gram-Negative Blood Culture Nucleic Acid Test (BC-GN) is a microarray-based assay that enables rapid detection of 9 common Gram-negative bacteria and 6 resistance determinants directly from positive blood cultures. We compared the performance of BC-GN with currently used automated systems, testing 141 clinical blood cultures and 205 spiked blood cultures. For identification of BC-GN target organisms in clinical and spiked blood cultures, the BC-GN assay showed 98.5% (130/132) and 98.9% (182/184) concordance, respectively. Of 140 resistance genes positively detected in clinical and spiked blood cultures with the BC-GN test, 139 (99.3%) were confirmed by PCR, and the detection results were consistent with the resistance phenotypes observed. The BC-GN assay, thus, can potentially improve care for sepsis patients by enabling timely detection and targeted antimicrobial therapy.
Asunto(s)
Bacteriemia/diagnóstico , Bacteriemia/microbiología , ADN Bacteriano/análisis , Bacterias Gramnegativas/efectos de los fármacos , Bacterias Gramnegativas/aislamiento & purificación , Pruebas de Sensibilidad Microbiana/métodos , Técnicas de Diagnóstico Molecular/métodos , Automatización de Laboratorios/métodos , ADN Bacteriano/genética , Bacterias Gramnegativas/clasificación , Humanos , Factores de TiempoRESUMEN
A Monte Carlo (MC) study is made of the persistence length q and the binary cluster integral ß (or the excluded-volume strength B) for polyelectrolytes by the use of the discrete Kratky-Porod wormlike chain with hard-core-effective Debye-Hückel electrostatic pair potentials. The quantity q is determined from the initial decay rate of the bond correlation function after preliminary confirmation of the validity of this procedure using the chain with Lennard-Jones pair potentials. The quantity B is determined from the mean-square radius of gyration along with q by the use of the quasi-two-parameter (QTP) excluded-volume theory. They are evaluated for two model cases of polyelectrolytes, sodium hyaluronate as an example of semiflexible polymers and poly(sodium 4-styrenesulfonate) as a typical example of flexible polymers, both in aqueous sodium chloride. The behavior of MC data so obtained for q and B as functions of added salt concentration c is examined in detail, comparing them with the Odijk-Skolnick-Fixman theory of q and the Fixman-Skolnick (FS) theory of B and also with literature experimental data. In particular, the MC values of B are in almost complete agreement with the FS theory for large c, although the latter still overestimates B somewhat for small c. The values of B themselves and also the validity of the QTP theory in general are discussed in comparison with the case of nonionic polymers.
RESUMEN
A Monte Carlo study is made of the mean-square radius of gyration