Catalase and superoxide dismutase (SOD) activities of virulent and nonvirulent isolates of Staphylococcus aureus were compared. The mean value of catalase activity for intact cell suspensions was 2,773 +/- 1,049 Kat f units (Kat f is defined as the ratio of the velocity constant of catalase at 0 min to the protein content in grams per milliliter); that of nonvirulent isolates was 154 +/- 92 Kat...

Entamoeba histolytica is a human parasite that requires iron (Fe) for its metabolic function and virulence. Bovine lactoferrin (B-Lf) and its peptides can be found in the digestive tract after dairy products are ingested. The aim of this study was to compare virulent trophozoites recently isolated from hamster liver abscesses with nonvirulent trophozoites maintained for more than 30 years in cu...

The propensity of RNA viruses to revert attenuating mutations contributes to disease and complicates vaccine development. Despite the presence of virulent revertant viruses in some live-attenuated vaccines, disease from vaccination is rare. This suggests that in mixed viral populations, attenuated viruses may limit the pathogenesis of virulent viruses, thus establishing a virulence threshold. H...

Virulent and avirulent strains of swine vesicular disease virus (SVDV), a picornavirus, have been characterized previously. The major determinants for attenuation have been mapped to specific residues in the 1D-2A-coding region. The properties of the 2A proteases from the virulent and avirulent strains of SVDV have now been examined. Both proteases efficiently cleaved the 1D/2A junction in vitr...

Several environmental factors regulate the expression of virulence genes under certain conditions and the expression of bacterial virulence determinants. Cytolethal distending toxin (CDT) is an important virulence determinant secreted by Campylobacter jejuni (C. jejuni), a leading cause of gastrointestinal bacterial pathogen worldwide. Therefore, the aim of the study was to investigate the effe...

the importance of the role played by bacteria in the pathogenesis of pulpal and apical disease has been established. one of the characteristics of apical periodontitis is apical bone resorption, which is due to apical immune response to bacterial infection. recently, novel bacterial complex lipid called phosphorylated dihydroceramides has been discovered to be of inflammatory activators. the ba...

Introduction: Biofilm formation on implants is the primary factor for implant loss. Porphyromonas gingivalis a highly virulent pathogen that contributes to development of periodontal disease and failure.

a bacterial septicaemia occurred in 3-female oscars (astronotus ocellatus) of about 2-year old held in 300l freshwater aquaria in south tehran. the external signs of infected fish consisted of lethargy, anaemia, distension (clinical dropsy), exophthalmia and cataract. internally there was a large amount of red-ascitic fluid accumulated in the abdominal cavity with haemorrhages/ hyperaemia of in...