Haemophilus parasuis is an early colonizer of the porcine upper respiratory tract and is the etiological agent of Glasser's disease. The factors responsible for H. parasuis colonization and systemic infection are not yet well understood, while prevention and control of Glasser's disease continues to be challenging. Recent studies on innate immunity to H. parasuis have demonstrated that porcine ...

Four virulent strains of Venezuelan encephalitis virus attained higher concentrations of infectious virus in bloods of adult hamsters than two benign strains when given subcutaneously. One benign virus, the attenuated TC83 vaccine strain, reached higher concentrations in bone marrow and Peyer's patches than virulent subtype I strains, and another benign virus, subtype IV, grew to lower levels. ...

Opsonization by Abs represents a critical component of the host immune response against many pathogens. The mechanisms by which virulent microbes evade this protective response are not completely understood. In disease mediated by Francisella tularensis, Ab can effectively protect against infections with attenuated strains, for example, LVS, but not virulent strains such as SchuS4. Thus, it is ...

Hemadsorbing (HA+) virulent Mycoplasma pneumoniae and spontaneously derived nonhemadsorbing (HA-) avirulent mutants were compared by biochemical and ultrastructural techniques in an attempt to understand the molecular basis for cytadsorption. Lactoperoxidase-catalyzed iodination of intact mycoplasmas indicated that both virulent and avirulent mycoplasmas displayed similar surface protein patter...

By experimental infection, host-specific Salmonella serotypes were shown to demonstrate specificities for chickens, mice, and other laboratory animals. Following oral inoculation, four strains of Salmonella gallinarum and two S. pullorum strains, isolated from diseased poultry, were more virulent for chickens than for mice. By contrast, four strains each of S. choleraesuis and S. dublin, isolat...

in this study, immunohistochemistry was used to clarify the early stages of viral kinetics and cycliccourse of ibdv, ir499, which has been described earlier as a very virulent strain (vvibdv). fifteen, 4-week-old spf chickens were inoculated with 10³ eid50 of vvibdv, ir499, via oculo/nasal route. five birdsserved as controls, and inoculated with phosphate buffered saline (pbs). the birds were t...

Salmonellae with differences only in the O-antigenic polysaccharide of their lipopolysaccharide were previously shown to differentially activate complement via the alternative pathway, causing them to be ingested at different rates by the mouse macrophage-like cell line J774. We now show that this mechanism could explain the different virulence of these strains in vivo. Mouse peritoneal macroph...

The disease is caused by a mycoplasma known as Mycoplasma gallisepticum (MG).The strains of MG may differ markedly in virulence, that is, in the degree of their disease-producing power. Some strains of MG are mild while others are highly virulent (very harmful). Mycoplasma is similar to bacteria, but lacks a cell wall. Lack of wall makes MG extremely fragile. They are easily killed by disinfect...

A simple alfalfa model was developed as an alternative infection model for virulence studies of the Burkholderia cepacia complex. Symptoms of disease were observed in wounded alfalfa seedlings within 7 days following inoculation of 10(1) to 10(5) CFU of most strains of the B. cepacia complex. Strains from seven genomovars of the B. cepacia complex were tested for virulence in the alfalfa model,...