For study of the role of lipopolysaccharide (LPS) character in colonization of the mouse large intestine, use was made of S. typhimurium strain SL5316, which is streptomycin resistant and smooth (wild-type LPS) but nonvirulent because it is Aro- (aromatic dependent). Several rough variants of different LPS chemotype derived from strain SL5316 comprised: an rfb deletion transductant making type ...

Toxoplasma gondii is the causative agent of toxoplasmosis in human and animals. In a mouse model, T. gondii strains can be divided into three groups, including the virulent, intermediately virulent, and nonvirulent. The clonal type I, II, and III T. gondii strains belong to these three groups, respectively. To better understand the basis of virulence phenotypes, we investigated mouse gene expre...

Escherichia coli strains of serogroup O26 comprise two distinct groups of pathogens, characterized as enteropathogenic E. coli (EPEC) and enterohemorrhagic E. coli (EHEC). Among the several genes related to type III secretion system-secreted effector proteins, espK was found to be highly specific for EHEC O26:H11 and its stx-negative derivative strains isolated in European countries. E. coli O2...

Newcastle disease is one of the main concerns of poultry farmers. Detection of virulent strains of Newcastle disease virus (NDV) has a great impact on control measures against the disease. In this study RT-PCR was optimized in high sensitivity in order to differentiate the virulent from non-virulent NDV isolates directly in tissue homogenates. The vaccinal NDV strain and known field isolates we...

The biological activities in vivo and in vitro of 59 motile Aeromonas spp. isolated from fish and water tanks were simultaneously analyzed in poikilothermic and homoiothermic systems. A total of 64.3% of the isolates tested were pathogenic for fish, and 62% of Aeromonas hydrophila and A. sobria isolates either virulent or nonvirulent for fish were enterotoxigenic. Although the majority of the s...

Helicobacter pylori-induced gastritis is a risk factor for developing gastric pathologies. Here, we report the complete genome sequence of a multidrug-resistant H. pylori strain isolated from a chronic gastritis patient in Mexico City, Mexico. Nonvirulent VacA and cag-pathogenicity island (PAI) genotypes were found, but the presence of a potential mobilizable plasmid carrying an IS605 element i...

Helcococcus kunzii, a nonvirulent member of the human skin flora, has recently been implicated in causing infections in immunosuppressed patients. We report a case of breast abscess associated with H. kunzii in an immunocompetant patient and discuss the criteria used in its identification and our observations of susceptibility testing for this species.

Two kinds of prophage deletions of the Salm.onella phage P22 were isolated. One type of deletion was isolated by simultaneously selecting for loss of a host gene (pro) adjacent to the integrated prophage and for survival at the nonpermissive temperature of a temperature-inducible (tse2) lysogen. The second type of deletion was isolated by transduction to tetracycline resistance using high-frequ...