Molecular features of heterogeneous vancomycin-intermediate Staphylococcus aureus strains isolated from bacteremic patients

<p>Abstract</p> <p>Background</p> <p>Heterogeneous vancomycin-intermediate <it>Staphylococcus aureus </it>(hVISA) bacteremia is an emerging infection. Our objective was to determine the molecular features of hVISA strains isolated from bacteremic patients and to compare them to methicillin resistant <it>S. aureus </it>(MRSA) and methicillin sensitive <it>S. aureus </it>(MSSA) blood isolates.</p> <p>Results</p> <p>We assessed phenotypic and genomic changes of hVISA (n = 24), MRSA (n = 16) and MSSA (n = 17) isolates by PCR to determine staphylococcal chromosomal cassette (SCC<it>mec</it>) types, Panton-Valentine leukocidin (PVL) and the accessory gene regulator (<it>agr</it>) loci. Biofilm formation was quantified. Genetic relatedness was assessed by PFGE. PFGE analysis of isolates was diverse suggesting multiple sources of infection. 50% of hVISA isolates carried SCC<it>mec </it>type I, 21% type II; 25% type V; in 4% the SCC<it>mec </it>type could not be identified. Among MRSA isolates, 44% were SCC<it>mec </it>type I, 12.5% type II, 25% type V, 12.5% were non-typable, and 6% were SCC<it>mec </it>type IVd. Only one hVISA isolate and two MSSA isolates carried the PVL. Biofilm formation and <it>agr </it>patterns were diverse.</p> <p>Conclusion</p> <p>hVISA isolates were diverse in all parameters tested. A considerable number of hVISA and MRSA strains carried the SCC<it>mec </it>type V cassette, which was not related to community acquisition.</p

Prevalence and Characteristics of Heteroresistant Vancomycin-Intermediate Staphylococcus aureus Bacteremia in a Tertiary Care Center

Infections with S. aureus with heterogeneous intermediate resistance to vancomycin (hVISA) are occurring more frequently. The detection of these infections, their prevalence, clinical characteristics, and significance are controversial. During 2003 and 2004, all blood culture isolates of methicillin-resistant Staphylococcus aureus (264 patients) at the Sheba Medical Center, Tel Hashomer, Israel, were assessed for hVISA by using the Etest macromethod. A total of 16 patients (6%) were positive for hVISA. Resistance to teicoplanin alone and to vancomycin alone using the Etest macromethod was found in 14 and 10 patients, respectively. Standard MICs to vancomycin were between 1 to 4 mg/ml. Most of these isolates (12 of 16 [75%]) would have been missed without specific testing. The median number of bacteremic days was 4. Seven patients had positive blood cultures for more than 5 days. Twelve patients died, and for eight of these the deaths were directly related to hVISA sepsis. We found that hVISA bacteremia was prevalent in our institution, and we suggest seeking hVISA in patients with persistent S. aureus bacteremia

Genetic and Phenotypic Characterization of a Salmonella enterica serovar Enteritidis Emerging Strain with Superior Intra-macrophage Replication Phenotype.

Salmonella enterica serovar Enteritidis (S. Enteritidis) is one of the ubiquitous Salmonella serovars worldwide and a major cause of food-born outbreaks, which are often associated with poultry and poultry derivatives. Here we report a nation-wide S. Enteritidis clonal outbreak that occurred in Israel during the last third of 2015. Pulsed field gel electrophoresis and whole genome sequencing identified genetically related strains that were circulating in Israel as early as 2008. Global comparison linked this outbreak strain to several clinical and marine environmental isolates that were previously isolated in California and Canada, indicating that similar strains are prevalent outside of Israel. Phenotypic comparison between the 2015 outbreak strain and other clinical and reference S. Enteritidis strains showed only limited intra-serovar phenotypic variation in growth in rich medium, invasion into Caco-2 cells, uptake by J774.1A macrophages, and host cell cytotoxicity. In contrast, significant phenotypic variation was shown among different S. Enteritidis isolates when biofilm-formation, motility, invasion into HeLa cells and uptake by THP-1 human macrophages were studied. Interestingly, the 2015 outbreak clone was found to possess superior intra-macrophage replication ability within both murine and human macrophages in comparison to the other S. Enteritidis strains studied. This phenotype is likely to play a role in the virulence and host-pathogen interactions of this emerging clone

Genetic and Phenotypic Characterization of a Salmonella enterica serovar Enteritidis Emerging Strain with Superior Intra-macrophage Replication Phenotype.

Salmonella enterica serovar Enteritidis (S. Enteritidis) is one of the ubiquitous Salmonella serovars worldwide and a major cause of food-born outbreaks, which are often associated with poultry and poultry derivatives. Here we report a nation-wide S. Enteritidis clonal outbreak that occurred in Israel during the last third of 2015. Pulsed field gel electrophoresis and whole genome sequencing identified genetically related strains that were circulating in Israel as early as 2008. Global comparison linked this outbreak strain to several clinical and marine environmental isolates that were previously isolated in California and Canada, indicating that similar strains are prevalent outside of Israel. Phenotypic comparison between the 2015 outbreak strain and other clinical and reference S. Enteritidis strains showed only limited intra-serovar phenotypic variation in growth in rich medium, invasion into Caco-2 cells, uptake by J774.1A macrophages, and host cell cytotoxicity. In contrast, significant phenotypic variation was shown among different S. Enteritidis isolates when biofilm-formation, motility, invasion into HeLa cells and uptake by THP-1 human macrophages were studied. Interestingly, the 2015 outbreak clone was found to possess superior intra-macrophage replication ability within both murine and human macrophages in comparison to the other S. Enteritidis strains studied. This phenotype is likely to play a role in the virulence and host-pathogen interactions of this emerging clone

Rapid Detection of blaKPC Carbapenemase Genes by Internally Controlled Real-Time PCR Assay Using Bactec Blood Culture Bottles ▿

Rapid detection of drug-resistant bacteria in clinical samples plays an instrumental role in patients' infection management and in implementing effective infection control policies. In the study described in this report, we validated a multiplex TaqMan real-time quantitative PCR (qPCR) assay for the detection of blaKPC genes and the human RNase P gene in Bactec blood culture bottles. The MagNA Pure LC (version 2.0) instrument was utilized to extract nucleic acids from the inoculated broth, while bovine serum albumin (BSA) was utilized as the PCR inhibitor reliever. The multiplex assay, which was specific for the detection of blaKPC genes, had a limit of detection of 19 CFU per reaction mixture with human blood-spiked Bactec bottles. Of the 323 Bactec blood culture sets evaluated, the same 55 (17%) blood cultures positive for carbapenem-resistant bacteria by culture were also positive by the validated qPCR assay. Thus, the sensitivity, specificity, positive predictive value, and negative predictive value of the qPCR assay compared to the results of culture were all 100%. blaKPC genes were also detected from the same Bactec bottle broth after manual extraction with a QIAamp DNA minikit; however, there was an average 3-threshold-cycle delay in the qPCR readings. With the limited therapeutic options available, the accurate and rapid detection of blaKPC-possessing bacteria by the described blaKPC/RNase P assay will be a crucial first step in ensuring optimal clinical outcomes and infection control