Viridans streptococci (VS) are responsible for several systemic diseases, such as endocarditis, abscesses, and septicemia. Unfortunately, species identification by conventional methods seems to be more difficult than species identification of other groups of bacteria. The aim of the present study was to evaluate the use of cell matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) for the rapid identification of 10 different species of VS. A total of 99 VS clinical isolates, 10 reference strains, and 20 strains from our in-house culture collection were analyzed by MALDI-TOF-MS. To evaluate the mass-spectrometric discrimination results, all strains were identified in parallel by phenotypic and genotypic methods. MALDI-TOF-MS identified 71 isolates as the mitis group, 23 as the anginosus group, and 5 as Streptococcus salivarius.Comparison of the species identification results obtained by the MALDI-TOF-MS analyses and with the phenotypic/genotypic identification systems showed 100% consistency at the species level. Thus, MALDI-TOF-MS seems to be a rapid and reliable method for the identification of species of VS from clinical samples.Established methods for bacterial identification in clinical microbiology are often time-consuming and do not always lead to a reliable differentiation of closely related species. Hence, there is an increasing need for alternative procedures that allow the rapid and reliable identification of microorganisms. Bacterial identification by matrix-assisted laser desorption ionization-time of light mass spectrometry (MALDI-TOF-MS) holds the potential to serve this need.Viridans streptococci (VS) are commensal bacteria of the human oral cavity and the respiratory, gastrointestinal, and genitourinary tracts. On the other hand, they are responsible for several systemic diseases, including subacute infective endocarditis, septicemia, meningitis, and pyogenic infections (1, 9, 17). The heterogeneous group of VS currently includes more than 30 species. They form five major groups, namely, the mutans, salivarius, anginosus, mitis, and bovis groups (16). The accurate species-level identification of isolates from relevant clinical specimens, like blood and abscess material, is important in understanding the pathogenic mechanisms of the particular species. Unfortunately, species identification seems to be more difficult for VS than for other groups of bacteria, possibly because VS are competent bacteria and, thus, may readily take up DNA from the environment.Phenotypic test systems do not always allow the accurate identification of some species in this heterogeneous group of bacteria (3, 10). Several molecular methods for the identification of VS to the species level have been developed. The targets of the molecular methods are, e.g., the 16S RNA gene, the 16S-23S rRNA gene intergenic spacer region (7), the Dalanine-D-alanine ligase gene (11), hyaluronate lyase genes (27), and the glucosyltransferase gene (14). Species of the mitis group are especially difficult t...

This neglected pathogen causes a large portion of these infections.

Oral streptococci are a heterogeneous group of human commensals, with a potential to cause serious infections. Activation of plasminogen has been shown to increase the virulence of typical human pathogenic streptococci such as S. pneumoniae. One important factor for plasminogen activation is the streptococcal α-enolase. Here we report that plasminogen activation is also common in oral streptococci species involved in clinical infection and that it depends on the action of human plasminogen activators. The ability to activate plasminogen did not require full conservation of the internal plasminogen binding sequence motif FYDKERKVY of α-enolase that was previously described as crucial for increased plasminogen binding, activation and virulence. Instead, experiments with recombinant α-enolase variants indicate that the naturally occurring variations do not impair plasminogen binding. In spite of these variations in the internal plasminogen binding motif oral streptococci showed similar activation of plasminogen. We conclude that the pathomechanism of plasminogen activation is conserved in oral streptococci that cause infections in human. This may contribute to their opportunistic pathogenic character that is unfurled in certain niches.

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The molecular mode of cell killing by the antiviral drug (E)-5-(2-bromovinyl-2Ј-deoxyuridine (BVDU) was studied in Chinese hamster ovary (CHO) cells stably transfected with the thymidine kinase gene (tk) of varicella zoster virus (CHO-VZVtk). The colony-forming ability of the cells was reduced to Ͻ1% at a concentration of ϳ1 M BVDU, whereas for nontransfected cells or cells transfected with tk gene of herpes simplex virus type 1 (CHO-HSVtk), a 1000-fold higher dose was required to achieve the same response. BVDU inhibited thymidylate synthase in CHO-VZVtk but not in CHO-HSVtk and control cells. On the other hand, the drug was incorporated into DNA of VZVtk-and HSVtk-expressing cells to nearly equal amounts. Because coexposure of CHO-VZVtk cells to exogenous thymidine protected them from BVDU-induced cell killing, the cells obviously die because of thymidine depletion. At highly cytotoxic BVDU doses (50 M) and longer exposure times (24 -48 h), VZVtk cells were blocked to some extent in S and G2/M phase and underwent apoptosis (48 -72 h). Not only apoptosis but also necrosis was induced. The findings also show that the drug causes the induction of c-Jun and the activation of activator protein-1 resulting in increased level of Fas ligand (FasL) and caspase-8/-3 activation. Bid and poly(ADP-ribose) polymerase were cleaved by caspases. Expression of Bax increased, whereas Bcl-2/Bcl-x L remained unchanged. Transfection of dominant-negative Fas-associated death domain and inhibition of caspase-8 by N-benzyloxycarbonyl-IETD-fluoromethyl ketone strongly abrogated BVDU-induced apoptosis, indicating Fas/FasL to be crucially involved. Thus, BVDU-triggered apoptosis differs significantly from that induced by ganciclovir, which induces in the same cellular background the mitochondrial damage pathway.(E)-5-(2-Bromovinyl)-2Ј-deoxyuridine (BVDU) is a pyrimidine nucleoside analog exhibiting potent antiviral activity especially against herpes simplex virus (HSV) type 1 and varicella zoster virus (VZV) infections. It is licensed (in Germany) for oral therapy of these virus diseases. Similar to most other antiherpetic drugs, the antiviral activity of BVDU relies on selective monophosphorylation by herpesvirus-encoded thymidine kinases (TKs), whereas cellular thymidine kinases, owing to their much more stringent substrate specificities, do not phosphorylate this nucleoside analog (Cheng et al., 1981). In herpesvirus-infected cells BVDU monophosphate (BVDU-MP) is phosphorylated to the diphosphate by a thymidylate kinase that is associated with certain herpesviral thymidine kinases (e.g., those of HSV-1 and VZV) (Cazaux et al., 1998). The thymidylate kinase function of the viral TK is essential for the antiviral activity of BVDU because the drug is inactive in cells infected with herpesviruses in which TKs lack the thymidylate kinase function (e.g., HSV type 2) (Fyfe, 1982;Mayo, 1982). Finally, BVDU diphosphate The work was supported by Deutsche Forschungsgemeinschaft Grants KA 724/7-3 and 7-4 (to B.K.) and TH 670/1-3 (to R.T.)...