blaKPC and rmtB on a single plasmid in Enterobacter amnigenus and Klebsiella pneumoniae isolates from the same patient

Enterobacter amnigenus (EA76) and Klebsiella pneumoniae (KP76) isolates with multidrug-resistant (MDR) patterns were identified from the same patient in the neurosurgery department of our hospital. An outbreak of MDR K. pneumoniae had also occurred in this department. To characterize the resistance mechanism and molecular epidemiology of these isolates, sequential experiments including antimicrobial susceptibility testing, polymerase chain reaction (PCR), plasmid analysis, pulsed field gel electrophoresis (PFGE), and multilocus sequence typing (MLST) were performed. EA76 and KP76 were resistant to all of the antibiotics tested, except colistin and tigecycline. blaKPC-2, blaTEM-1, blaSHV-12, blaCTX-M-3, blaCTX-M-14, and rmtB genes were identified in both isolates, with blaKPC-2, blaTEM-1, blaCTX-M-14, and rmtB being co-carried on one plasmid in each isolate. Further analysis showed different restriction patterns between the two KPC-carrying plasmids. Of the 11 carbapenem-resistant isolates found in the outbreak, all were resistant to all of the β-lactams tested, with 63.64% (7/11) also exhibiting resistance to aminoglycosides and 72.73% (8/11) exhibiting resistance to quinolones. PCR analysis and molecular typing of the 11 K. pneumoniae strains revealed that the seven aminoglycoside-resistant isolates shared the same antibiotic-resistant gene pattern and identical or one-band-difference PFGE profiles relative to KP76. In addition, all of the eight aminoglycoside-resistant isolates, including KP76, belonged to the national epidemic clone ST11. The overall results indicate the emergence of E. amnigenus and outbreak of ST11 K. pneumoniae, with both co-harboring blaKPC and rmtB genes on a single plasmid in our neurosurgery wards

Tobramycin at subinhibitory concentration inhibits the RhlI/R quorum sensing system in a <it>Pseudomonas aeruginosa </it>environmental isolate

<p>Abstract</p> <p>Background</p> <p>Antibiotics are not only small molecules with therapeutic activity in killing or inhibiting microbial growth, but can also act as signaling molecules affecting gene expression in bacterial communities. A few studies have demonstrated the effect of tobramycin as a signal molecule on gene expression at the transcriptional level and its effect on bacterial physiology and virulence. These have shown that subinhibitory concentrations (SICs) of tobramycin induce biofilm formation and enhance the capabilities of <it>P. aeruginosa </it>to colonize specific environments.</p> <p>Methods</p> <p>Environmental <it>P. aeruginosa </it>strain PUPa3 was grown in the presence of different concentrations of tobramycin and it was determined at which highest concentration SIC, growth, total protein levels and translation efficiency were not affected. At SIC it was then established if phenotypes related to cell-cell signaling known as quorum sensing were altered.</p> <p>Results</p> <p>In this study it was determined whether tobramycin sensing/response at SICs was affecting the two independent AHL QS systems in an environmental <it>P. aeruginosa </it>strain. It is reasonable to assume that <it>P. aeruginosa </it>encounters tobramycin in nature since it is produced by niche mate <it>Streptomyces tenebrarius</it>. It was established that SICs of tobramycin inhibited the RhlI/R system by reducing levels of C4-HSL production. This effect was not due to a decrease of <it>rhlI </it>transcription and required tobramycin-ribosome interaction.</p> <p>Conclusions</p> <p>Tobramycin signaling in <it>P. aeruginosa </it>occurs and different strains can have a different response. Understanding the tobramycin response by an environmental <it>P. aeruginosa </it>will highlight possible inter-species signalling taking place in nature and can possible also have important implications in the mode of utilization for human use of this very important antibiotic.</p

Extended-spectrum beta-lactamase-producing Klebsiella spp. in a neonatal intensive care unit: risk factors for the infection and the dynamics of the molecular epidemiology

The extended-spectrum beta-lactamase (ESBL)-producing Klebsiella spp. cause worldwide problems in intensive care units. The aim of this study was to investigate the molecular epidemiology of ESBL-producing Klebsiella pneumoniae and K. oxytoca strains in a neonatal intensive care unit (NICU) in Budapest, Hungary and to determine the risk factors of the infections and the epidemiological features. Infections with Klebsiella spp. were analyzed retrospectively by reviewing the medical records between January 2001 and December 2005. Antibiotic susceptibility tests, isoelectric focusing, pulsed field gel electrophoresis, plasmid analysis, PCR for bla(TEM) and bla(SHV) and DNA sequencing analysis were performed on ESBL-producing Klebsiella isolates. A total of 45 babies were found to be infected with non-ESBL-producing Klebsiella spp. and 39 with ESBL-producing Klebsiella spp. Of the parameters analyzed, including sex, gestational age, twin pregnancy, birth weight, presence of central vascular catheter, mechanical ventilator use, parenteral nutrition, polymicrobial infection, caesarean section, transfusion and mortality, we found no statistically significant difference between the ESBL and the non-ESBL groups, or between the K. pneumoniae and K. oxytoca species. Further characterization of the ESBL-producing K. pneumoniae and K. oxytoca strains isolated between February 2001 and January 2003 revealed three distinct PFGE patterns of SHV-5-producing K. pneumoniae (A, B, E) and two distinct patterns of SHV-12-producing K. oxytoca (C,D) isolates; these had different plasmid profiles. From July to November 2005, a new SHV-5 producing K. oxytoca (F) was isolated. The molecular epidemiology of ESBL-producing organisms in a NICU over time shows substantial shifts in predominant strains. The ESBL production of the infected organisms has an impact on the survival of newborn babies with infections caused by Klebsiella spp