Streptococcus suis is an important zoonotic pathogen. However, identification of virulent S. suis strains is complicated because of the high diversity of the species. Here we evaluated the genetic difference among S. suis strains using comparative genomic hybridization (CGH) and virulence variation in vivo and in vitro. We showed that different clades differed in their ability to activate TLR2/...

infectious bursal disease (ibd) is a highly contagious disease of chickens caused by the infectious bursal disease virus (ibdv). this study was conducted to characterize three ibdv strains from iran. a reverse transcriptase-polymerase chain reaction (rt-pcr) procedure was used to amplify a 715-bp fragment of the vp1 gene from ibdv strains. amplified vp1 fragments of the three iranian ibdv strai...

Yersinia pestis, the highly virulent agent of plague, is a biological weapon. Strategies that prevent plague have been sought for centuries, and immunization with live, attenuated (nonpigmented) strains or subunit vaccines with F1 (Caf1) antigen is considered effective. We show here that immunization with live, attenuated strains generates plague-protective immunity and humoral immune responses...

In this study, twenty-five strains of Mycobacterium tuberculosis resistant to isoniazid (INH) were isolated from patients with tuberculosis (TB). Nine strains (36%) were found to be virulent in guinea-pigs [root index virulence (RIV» 1 ]. The remaining sixteen strains (64%) were non-virulent (RIV <1). Of the nine strains resistant to INH as well as virulent to guinea-pigs, eight of them wer...

Could some vaccines drive the evolution of more virulent pathogens? Conventional wisdom is that natural selection will remove highly lethal pathogens if host death greatly reduces transmission. Vaccines that keep hosts alive but still allow transmission could thus allow very virulent strains to circulate in a population. Here we show experimentally that immunization of chickens against Marek's ...

Haemophilus parasuis is a commensal bacterium of the upper respiratory tract of healthy pigs. It is also the etiological agent of Glässer's disease, a systemic disease characterized by polyarthritis, fibrinous polyserositis and meningitis, which causes high morbidity and mortality in piglets. The aim of this study was to evaluate biofilm formation by well-characterized virulent and non-virulent...

The MS character of polio-virus particles is described. Strains that produced relatively large plaques, up to 6 mm. in diameter, on a monkey stable (MS) cell line, were classified as MS(+). Such strains were found to include the highly virulent poliovirus strains. Attenuated strains appeared deficient in this gene, for they produced tiny plaques less than 1 mm. in size, or no visible plaques at...

background and aims: infectious laryngotracheitis virus (iltv) infection causes a highly contagious respiratory disease in poultry leads to significant economic losses in the poultry industry. the genomic and antigenic characteristics between virulent and vaccine strains of iltv are very similar. the ability of embryonated chicken neural stem (cns) cell for differential diagnosis of iltv strain...