Microbiologica最新文献

A mechanism involved in the plaque enhancement effect of foot-and-mouth disease viruses (FMDV) by the addition of sodium thiosulfate (Hypo) in the agar overlay medium (AOM) previously reported was studied. It was experimentally proved that the diffusion of virus particles through agar overlay medium was enhanced when this salt was incorporated. Accordingly, the enlarged plaque formation was assumed to be caused by the enhanced diffusion of viral progenies produced in infectious centers during plaque assays.

The pathogenetic potential and the true extent of human T leukemia/lymphotropic virus type I (HTLV-I) and type II (HTLV-II) infection are unknown. To find out more about HTLV-I/II seroepidemiology and the risks of iatrogenic transmission, we performed a serological study, screening 4086 healthy blood donors. A surprisingly high percentage of serum reactivity to HTLV-I/II antigens was observed by commercial ELISA (2.08%) and immunoblotting (IB) (0.85%) analysis, although none of the samples satisfied the (IB) criteria for positivity based on detection of gag protein p24 and at least one env gene product, either gp46 or gp61/68. To clarify these inconclusive results, we performed polymerase chain reaction (PCR) analysis for HTLV-I and HTLV-II provirus detection in peripheral blood lymphocytes, obtained from individuals with an apparent pattern of seropositivity. The data obtained by PCR failed to reveal evidence of HTLV-I/II provirus integration in peripheral blood cells, ruling out the possibility of a viral infection in these cases, and pinpointing the limitations of both serological methods used. Our observations suggest that serological assays alone are not a reliable tool for blood donor screening of HTLV-I/II infection and raise the important question of interpreting inconclusive results.

The ability of some bacterial strains to obtain iron from ethylenediamine di-o-hydroxyphenylacetic acid (EDDA) or iron-free transferrin, and accordingly grow in their presence, was studied. Growth of Staphylococcus aureus and Yersinia pseudotuberculosis was inhibited by EDDA or by iron-free transferrin. Growth of Streptococcus faecalis, however, was inhibited by iron-free transferrin, but not by EDDA. The other bacterial strains, i.e.; Escherichia coli, Salmonella typhimurium and Shigella dysenteriae were able to grow both in the presence of EDDA or iron-free transferrin. All of the above bacterial strains grow in the presence of iron-saturated transferrin which was not able to bind the iron of the medium and accordingly left the iron of the medium available to them.

The ability of Micromycetes strains to produce extracellular phenoloxidases was examined on solid malt agar medium using ten different reagents. We established a POx index summarizing the global activity given by the ten reagents used. The results indicated a wide variability depending on the taxonomic groups, the genera and the species. Some groups were relatively homogeneous, either no and low producers of phenoloxidases (Yeasts, Zygomycetes, genera Aspergillus and Penicillium) or medium and high producers of phenoloxidases (Basidiomycetes, Coelomycetes, Tuberculariales and Dematiaceae), while other groups were very heterogeneous (Ascomycetes, Mucedinaceae). The POx index was significantly higher for strains recently isolated than for strains kept in the fungi collection for a long time.

Three methods for the concentration of poliovirus from oyster homogenates were compared. The adsorption-elution-precipitation method gave the lowest average virus recovery (24.1%), while the beef extract elution-acid precipitation method and the non-fat dry milk elution-acid precipitation methods gave recoveries of 47.2% and 39.6%, respectively. Although the overall recovery rates with these methods were lower than those reported in previous studies, recoveries of 40-47% obtained with the elution-precipitation methods used in the present study are considered to be above average in terms of recovery efficiency.

Three enzyme-linked immunosorbent assays (EIA) designed for the detection of human respiratory syncytial virus (RSV) were evaluated for the detection of bovine respiratory syncytial virus (BRSV) in bovine lungs and the results were compared with those obtained by a direct fluorescent antibody assay (DFA). The EIA tests used were Directigen EIA, Kallestad Pathfinder EIA, and Abbott RSV EIA. Homogenates of lung tissues obtained from 64 cattle that had died of respiratory disease were used; 32 were positive by DFA and 32 were negative. All EIA's varied in the amount of labor and time involved but their relative sensitivities were similar ranging between 59 and 66% when compared with DFA. The specificity of Pathfinder EIA was lower than those of the Directigen and Abbott tests. The overall agreement between the three EIA's and the DFA was 66-77% indicating that DFA is still the test of choice for detecting BRSV infection in lung tissues of cattle.

This study was undertaken to evaluate the in vitro effects of cefonicid on phagocyte functions such as phagocytosis and intracellular killing of phagocytosed bacteria. At concentrations of half the MIC cefonicid caused human macrophages to ingest and kill Klebsiella pneumoniae at a greater rate than did drug-free macrophages. Bacteria pretreated with subinhibitory concentrations of cefonicid became more susceptible to the phagocytic and bactericidal activity of macrophages than untreated microorganisms. Sub-MIC cefonicid pretreatment of macrophages did not reduce phagocytosis and killing, confirming the inability of beta-lactam antibiotics to cross biological membranes.

The viral susceptibility of a cell line, named KSEK6, newly established from the kidney cortex of swine embryo was tested for the indication of CPE occurrences and also plaque formations. The multiplication of porcine adenoviruses was considerably high in the cells among the virus strains tested though plaques of these viruses were hardly visible under agar overlay medium. Two strains of swine enteroviruses, Aujeszky's disease virus and hemagglutinating encephalomyelitis virus also multiplied well in a similar order to those received in the other cells employed.

Bacillus licheniformis has been found to be one of the dominant nosocomial species of Bacillus: laboratories dealing with nosocomial infections must be able to identify Bacillus up to the species level. To date, no DNA probes have been isolated for B. licheniformis although there is a clear need for a direct detection by polymerase chain reaction. The isolation of a B. licheniformis-specific DNA probe, as described in this paper, represents the first step toward accomplishing this goal.

One hundred stool samples from children with acute diarrhoea were examined by six commercial latex and immunoenzymatic assays for the diagnosis of rotavirus infection in four different laboratories. Samples were also analyzed by solid-phase immune electron microscopy using a rabbit anti-group A rotavirus antiserum. With electron microscopy as a basis for comparison, sensitivity and specificity for the latex and ELISA assays varied from 91.1 to 92.9% and from 94.2 to 99.4%, respectively. Statistically significant differences were revealed in the confirmation rate of electron microscopy-negative samples between different commercial assays. Significant variability was also found between results obtained by the laboratories taking part in the study.