RESUMEN
BACKGROUND: The spread of carbapenemase-producing Enterobacteriaceae (CPE) is a great problem of healthcare worldwide. Study of the spread for bla OXA-48-like genes coding epidemically significant carbapenemases among hospital pathogens is important for the regional and global epidemiology of antimicrobial resistance. METHODS: Antibacterial resistant isolates of Klebsiella pneumoniae (n = 95) from 54 patients, P. mirabilis (n = 32) from 20 patients, Enterobacter aerogenes (n = 6) from four patients, and Enterobacter cloacae (n = 4) from four patients were collected from January, 2013 to October, 2014 in neurosurgical intensive care unit (ICU) of the Burdenko Neurosurgery Institute, Moscow. Characteristics of the isolates were done using susceptibility tests, PCR detection of the resistance genes, genotyping, conjugation, DNA sequencing, and bioinformatic analysis. RESULTS: Major strains under study were multi drug resistant (MDR), resistant to three or more functional classes of drugs simultaneously-98.9 % K. pneumoniae, 100 % P. mirabilis, one E. aerogenes isolate, and one E. cloacae isolate. Molecular-genetic mechanism of MDR in K. pneumoniae and P. mirabilis isolates were based on carrying of epidemic extended-spectrum beta-lactamase bla CTX-M-15 gene (87.2 and 90.6 % accordingly), carbapenemase bla OXA-48-like gene (55.3 and 23.3 % accordingly), and class 1 (54.8 and 31.3 % accordingly) and class 2 (90.6 % P. mirabilis) integrons. The bla OXA-48-like-positive K. pneumoniae were collected during whole two-year surveillance period, while P. mirabilis and Enterobacter spp. carrying bla OXA-48-like genes were detected only after four and 18 months after the research start, respectively. The bla OXA-48-like gene acquisition was shown for P. mirabilis isolates collected from five patients and for E. cloacae isolate collected from one patient during their stay in the ICU, presumably from bla OXA-48-like-positive K. pneumoniae. The source of the bla OXA-244 gene acquired by E. aerogenes isolates and the time of this event were not recognized. CONCLUSIONS: The expanding of CPE in the surveyed ICU was associated with the spread of bla OXA-48 and bla OXA-244 carbapenemase genes documented not only among K. pneumoniae, well-known bacterial host for such genes, but among P. mirabilis, E. aerogenes, and E. cloacae.
Asunto(s)
Proteínas Bacterianas/genética , Enterobacter/enzimología , Infecciones por Enterobacteriaceae/microbiología , Klebsiella pneumoniae/enzimología , Proteus mirabilis/enzimología , beta-Lactamasas/genética , Biología Computacional , Conjugación Genética , ADN Bacteriano/química , ADN Bacteriano/genética , Enterobacter/genética , Infecciones por Enterobacteriaceae/epidemiología , Técnicas de Genotipaje , Humanos , Unidades de Cuidados Intensivos , Klebsiella pneumoniae/genética , Datos de Secuencia Molecular , Moscú/epidemiología , Reacción en Cadena de la Polimerasa , Proteus mirabilis/genética , Análisis de Secuencia de ADNRESUMEN
We compare (29)Si magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra from the two modifications of silicon nitride, alpha-Si(3)N(4) and beta-Si(3)N(4), with that of a fully ((29)Si, (15)N)-enriched sample (29)Si(3)(15)N(4), as well as (15)N NMR spectra of Si(3)(15)N(4) (having (29)Si at natural abundance) and (29)Si(3)(15)N(4). We show that the (15)N NMR peak-widths from the latter are dominated by J((29)Si-(15)N) through-bond interactions, leading to significantly broader NMR signals compared to those of Si(3)(15)N(4). By fitting calculated (29)Si NMR spectra to experimental ones, we obtained an estimated coupling constant J((29)Si-(15)N) of 20Hz. We provide (29)Si spin-lattice (T(1)) relaxation data for the (29)Si(3)(15)N(4) sample and chemical shift anisotropy results for the (29)Si site of beta-Si(3)N(4). Various factors potentially contributing to the (29)Si and (15)N NMR peak-widths of the various silicon nitride specimens are discussed. We also provide powder X-ray diffraction (XRD) and mass spectrometry data of the samples.