In preceding papers of this series (Smith, 1950a, b, 1951a; Smith, Harris-Smith & Stanley, 1951) the virulence-enhancing action of mucin has been shown to be a synergic combination of a viscous medium, a particulate residue Iand a more specific 'third factor'. The activity of the latter, in a biological assay in which the other two factors were kept constant (Smith et al. 1951), was shown to re...

Several novel Legionella pneumophila virulence genes were previously discovered by use of signature-tagged mutagenesis (P. H. Edelstein, M. A. Edelstein, F. Higa, and S. Falkow, Proc. Natl. Acad. Sci. 96:8190-8195, 1999). One of these mutants appeared to be defective in multiplication in guinea pig lungs and spleens, yet it multiplies normally in guinea pig alveolar macrophages. Here we report ...

The concept or notion of virulence factor-activity relationships (VFAR) is an approach for identifying an analogous process to the use of qualitative structure-activity relationships (QSAR) for identifying new microbial contaminants. In QSAR, it is hypothesized that, for new chemical contaminants, their potential acute or chronic toxicity may be reasonably estimated on the basis of structural r...

In this paper, we attempted to define the role of phagocytosis in the virulence of Entamoeba histolytica. We have isolated, from a highly phagocytic and virulent strain, a clone deficient in phagocytosis. Trophozoites of wild-type strain HM1:IMSS were fed with Escherichia coli strain CR34-Thy- grown on 5-bromo,2'-deoxyuridine. The trophozoites that had incorporated the base analog through phago...

Background & Objective: Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), represent serious nosocomial and community infections. Biofilm formation as an important virulence factor may be affected by sub-inhibitory levels of antibiotics. Few studies examined the effects of all therapeutic antimicrobial agents on...

Virulence genes in Listeria monocytogenes are coordinately expressed under the control of the transcriptional activator PrfA, encoded by prfA, a member of the cyclic AMP (cAMP) receptor protein (CRP)/FNR family of bacterial regulators. Strain P14-A is a spontaneous mutant of L. monocytogenes serovar 4b which produces elevated levels of virulence factors (M. T. Ripio, G. Domínguez-Bernal, M. Suá...

Serum opacity factor (SOF) is a cell surface virulence factor made by the human pathogen Streptococcus pyogenes. We found that S. pyogenes strains with naturally occurring truncation mutations in the sof gene have markedly enhanced beta-hemolysis. Moreover, deletion of the sof gene in a SOF-positive parental strain resulted in significantly increased beta-hemolysis. Together, these observations...

Various strains of E. coli. and Salmonella typhimurium were studied in vitro for the presence plasmids controlling haemolysin, drug resistance, serum resistance colonization factor etc. They also tested mice to determine probable role on host pathogenicity. To effect associated R-factor pathogenicity virulence S. typhimurium, antibiotic sensitive resistant mice. The experiments showed that enha...

background: escherichia coli is the most causative agent of urinary tract infections (utis). apart from all human infectious diseases, uti have a high prevalence and in most cases, escherichia coli is a dominance bacterium which can cause pyelonephritis and cystitis. the aim of the study was to determine the occurrence of some virulence genes expressing fimbriae, production of hemolysin and aer...