Complex genomic and phenotypic characterization of the related species Staphylococcus carnosus and Staphylococcus piscifermentans.
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On the basis of numerical analysis of 100 phenotypic features, the strains of two species, Staphylococcus carnosus and Staphylococcus piscifermentans, were differentiated into two separate phenons corresponding with the macrorestriction patterns of their genomic DNA, as well as with the results of ribotyping and PCR amplification of enterobacterial repetitive intergenic consensus sequences. One of the S. carnosus strains, the F-2 strain, was shown to be marginal, exhibiting the lowest genomic and phenotypic similarity to the S. carnosus type strain DSM 20501T. Two of the strains studied (strains S. carnosus SK 06 and S. piscifermentans SK 05) were phenotypically convergent, forming a separate phenon. They were phenotypically similar, even though the genomic DNA of one of them was homologous with that of the S. carnosus type strain, whereas that of the other was homologous with the genomic DNA of the S. piscifermentans type strain. In such cases, fingerprinting methods (particularly macrorestriction analysis and ribotyping) served as important correctives, as they allow phenotypically convergent strains to be distinguished on the basis of their genomic profiles. The results of this paper support the proposal for the new species Staphylococcus condimenti as well as the new subspecies Staphylococcus carnosus subsp. utilis. (+info)
Species identification and phylogenetic relationships based on partial HSP60 gene sequences within the genus Staphylococcus.
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The phylogenetic relationships among 36 validly described species or subspecies within the genus Staphylococcus were investigated by cloning and sequencing their 60 kDa heat-shock protein (HSP60) genes using a set of universal degenerate HSP60 PCR primers. The cloned partial HSP60 DNA sequences from nine Staphylococcus aureus strains were highly conserved (97-100% DNA sequence similarity; mean 98%), indicating that the HSP60 gene of multiple isolates within the same species have little microheterogeneity. At the subspecies level, DNA sequence similarity among members of S. aureus, Staphylococcus schleiferi, Staphylococcus cohnii and Staphylococcus capitis ranged from 91 to 98%. At the interspecies level, sequence similarity among 23 distinct species of staphylococci ranged from 74 to 93% (mean 82%). By comparison, the highest sequence similarity of Bacillus subtilis and Escherichia coli with members within the genus Staphylococcus was only 70 and 59%, respectively. Importantly, phylogenetic analysis based on the neighbour-joining distance method revealed remarkable concordance between the tree derived from partial HSP60 gene sequences and that based on genomic DNA-DNA hybridization, while 16S rRNA gene sequences correlated less well. The results demonstrate that DNA sequences from the highly conserved and ubiquitous HSP60 gene offer a convenient and accurate tool for species-specific identification and phylogenetic analysis of staphylococci. (+info)
Serum amyloid A, cytokines, and corticosterone responses in germfree and conventional mice after lipopolysaccharide injection.
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To determine why germfree mice are less susceptible to lipopolysaccharide (LPS) than conventional mice, we studied serum levels of serum amyloid A (SAA), tumor necrosis factor (TNF), interleukin 1 (IL-1), IL-6, and corticosterone in mice after treatment with LPS. A single injection of LPS caused an elevation of SAA, an acute-phase protein in the mouse, in both conventional and germfree IQI mice, and the response was significantly less in germfree mice. LPS-induced elevations of serum TNF, IL-1, and IL-6 levels were also significantly less in germfree mice, while serum corticosterone levels were greater in germfree mice than in conventional mice. These results suggest that the lower susceptibility to LPS and a smaller response of SAA elevation by LPS in germfree mice may result from less elevation in serum of these cytokines in these mice, which are known to mediate the acute phase response of SAA. High levels of serum corticosterone in germfree mice may be partly responsible for the lower responsiveness of these inflammatory cytokines to LPS in these mice. (+info)
In vitro activities of linezolid against important gram-positive bacterial pathogens including vancomycin-resistant enterococci.
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The emergence of resistance in gram-positive bacteria has necessitated a search for new antimicrobial agents. Linezolid is an oxazolidinone, a new class of antibacterial agents with enhanced activity against pathogens. We compared the activity of linezolid to those of other antimicrobial agents against 3,945 clinical isolates. Linezolid demonstrated potent activity against all isolates tested. For all vancomycin-susceptible enterococci, staphylococci, and streptococci, the activity of linezolid was comparable to that of vancomycin. Against oxacillin-resistant staphylococci and vancomycin-resistant enterococci, linezolid was the most active agent tested. In summary, linezolid appears to be a promising new antimicrobial agent for the treatment of gram-positive infections. (+info)
The essential Staphylococcus aureus gene fmhB is involved in the first step of peptidoglycan pentaglycine interpeptide formation.
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The factor catalyzing the first step in the synthesis of the characteristic pentaglycine interpeptide in Staphylococcus aureus peptidoglycan was found to be encoded by the essential gene fmhB. We have analyzed murein composition and structure synthesized when fmhB expression is reduced. The endogenous fmhB promoter was substituted with the xylose regulon from Staphylococcus xylosus, which allowed glucose-controlled repression of fmhB transcription. Repression of fmhB reduced growth and triggered a drastic accumulation of uncrosslinked, unmodified muropeptide monomer precursors at the expense of the oligomeric fraction, leading to a substantial decrease in overall peptidoglycan crosslinking. The composition of the predominant muropeptide was confirmed by MS to be N-acetylglucosamine-(beta-1,4)-N-acetylmuramic acid(-L-Ala-D-iGln-L-Lys-D-Ala-D-Ala), proving that FmhB is involved in the attachment of the first glycine to the pentaglycine interpeptide. This interpeptide plays an important role in crosslinking and stability of the S. aureus cell wall, acts as an anchor for cell wall-associated proteins, determinants of pathogenicity, and is essential for the expression of methicillin resistance. Any shortening of the pentaglycine side chain reduces or even abolishes methicillin resistance, as occurred with fmhB repression. Because of its key role FmhB is a potential target for novel antibacterial agents that could control the threat of emerging multiresistant S. aureus. (+info)
Risk of infection from heavily contaminated air.
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In a factory processing shea nuts the dust concentrations were found to be up to 145 mg/m3 [80% respirable (1--5 micrometer)]. Bacterial examination of the dust revealed that under the worst conditions observed a worker might inhale 350,000 bacteria per 8 h. Of these, 3,000 were Ps. aeruginosa and 1,500 Salmonella spp. of nine different types. The possible health effects of these findings are discussed. (+info)
Identification of a gene in Staphylococcus xylosus encoding a novel glucose uptake protein.
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By transposon Tn917 mutagenesis, two mutants of Staphylococcus xylosus were isolated that showed higher levels of beta-galactosidase activity in the presence of glucose than the wild type. Both transposons integrated in a gene, designated glcU, encoding a protein involved in glucose uptake in S. xylosus, which is followed by a glucose dehydrogenase gene (gdh). Glucose-mediated repression of beta-galactosidase, alpha-glucosidase, and beta-glucuronidase activities was partially relieved in the mutant strains, while repression by sucrose or fructose remained as strong as in the wild type. In addition to the pleiotropic regulatory effect, integration of the transposons into glcU reduced glucose dehydrogenase activity, suggesting cotranscription of glcU and gdh. Insertional inactivation of the gdh gene and deletion of the glcU gene without affecting gdh expression showed that loss of GlcU function is exclusively responsible for the regulatory defect. Reduced glucose repression is most likely the consequence of impaired glucose uptake in the glcU mutant strains. With cloned glcU, an Escherichia coli mutant deficient in glucose transport could grow with glucose as sole carbon source, provided a functional glucose kinase was present. Therefore, glucose is internalized by glcU in nonphosphorylated form. A gene from Bacillus subtilis, ycxE, that is homologous to glcU, could substitute for glcU in the E. coli glucose growth experiments and restored glucose repression in the S. xylosus glcU mutants. Three more proteins with high levels of similarity to GlcU and YcxE are currently in the databases. It appears that these proteins constitute a novel family whose members are involved in bacterial transport processes. GlcU and YcxE are the first examples whose specificity, glucose, has been determined. (+info)
Outbreak of mupirocin-resistant staphylococci in a hospital in Warsaw, Poland, due to plasmid transmission and clonal spread of several strains.
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An outbreak of mupirocin-resistant (MuR) staphylococci was investigated in two wards of a large hospital in Warsaw, Poland. Fifty-three MuR isolates of Staphylococcus aureus, S. epidermidis, S. haemolyticus, S. xylosus, and S. capitis were identified over a 17-month survey which was carried out after introduction of the drug for the treatment of skin infections. The isolates were collected from patients with infections, environmental samples, and carriers; they constituted 19.5% of all staphylococcal isolates identified in the two wards during that time. Almost all the MuR isolates were also resistant to methicillin (methicillin-resistant S. aureus and methicillin-resistant coagulase-negative staphylococci). Seven of the outbreak isolates expressed a low-level-resistance phenotype (MuL), whereas the remaining majority of isolates were found to be highly resistant to mupirocin (MuH). The mupA gene, responsible for the MuH phenotype, has been assigned to three different polymorphic loci among the strains in the collection analyzed. The predominant polymorph, polymorph I (characterized by a mupA-containing EcoRI DNA fragment of about 16 kb), was located on a specific plasmid which was widely distributed among the entire staphylococcal population. All MuR S. aureus isolates were found to represent a single epidemic strain, which was clonally disseminated in both wards. The S. epidermidis population was much more diverse; however, at least four clusters of closely related isolates were identified, which suggested that some strains of this species were also clonally spread in the hospital environment. Six isolates of S. epidermidis were demonstrated to express the MuL and MuH resistance mechanisms simultaneously, and this is the first identification of such dual MuR phenotype-bearing strains. The outbreak was attributed to a high level and inappropriate use of mupirocin, and as a result the dermatological formulation of the drug has been removed from the hospital formulary. (+info)