Because of their better immunogenicity and the improved protection they afford, live attenuated vaccines derived from serial passaging in an abnormal host are widely used to protect humans or animals from certain pathogens. Here, we used a virulent and a chicken embryo-attenuated duck hepatitis A virus genotype 1 to compare the different regulated immune responses induced by viruses with differ...

Newcastle disease virus [NDV (avian paramyxovirus type 1 [APMV1])] isolates were recovered from imported exotic birds confiscated following importation into the United States, from waterbirds in the United States, and from poultry. The exotic birds probably originated from Central and South America, Asia, and Africa. The NDV isolates were initially characterized as highly virulent because of a ...

Newcastle disease is a viral disease of birds caused by avian paramyxovirus 1 (APMV-1). For official control purposes, this disease is currently defined as the most severe form of the illness, which is caused only by certain viral strains. Many less virulent strains of APMV-1 also circulate among domesticated and wild birds. These viruses usually cause much milder clinical signs or infect birds...

Staphylococcus aureus is a commensal inhabitant of skin and mucous membranes in nose vestibule but also an important opportunistic pathogen of humans and livestock. The extracellular proteome as a whole constitutes its major virulence determinant; however, the involvement of particular proteins is still relatively poorly understood. In this study, we compared the extracellular proteomes of poul...

Streptococcus suis serotype 2 is an important porcine bacterial pathogen and emerging zoonotic agent mainly responsible for sudden death, septic shock, and meningitis, with exacerbated inflammation being a hallmark of the infection. However, serotype 2 strains are genotypically and phenotypically heterogeneous, being composed of a multitude of sequence types (STs) whose virulence greatly varies...

Newcastle disease is a viral disease of birds caused by avian paramyxovirus 1 (APMV-1). For official control purposes, this disease is currently defined as the most severe form of the illness, which is caused only by certain viral strains. Many less virulent strains of APMV-1 also circulate among domesticated and wild birds. These viruses usually cause much milder clinical signs or infect birds...

Farming practices have changed dramatically over the years. The industrialization of farming has provided parasites with an abundance of hosts and is thought to have influenced parasite evolution. For example, the parasite that causes the highly contagious poultry disease, Marek's disease, has evolved over the past 60 years into a highly virulent pathogen. It is assumed that the industrializati...

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 were fo...

Newborn mice of several inbred strains develop few or no tumors following inoculation with highly tumorigenic strains of polyomavirus. Here we show that such resistant strains can be divided into two groups based on the responses of adult mice to radiation followed by virus inoculation. Most strains show a radiation-sensitive form of resistance (Rr-s) and develop tumors following radiation and ...

Macrophages from the mouse peritoneal cavity were examined by electron microscopy at various time intervals up to 24 h after intraperitoneal administration of each of three strains of staphylococci different in virulence for mice: high-virulent, low-virulent, and avirulent strains. After engulfment, avirulent bacteria were highly liable to intracellular digestion, resulting in almost complete d...