Phenotypic and genotypic characteristics of Escherichia coli strains of non-enteropathogenic E-coli (EPEC) serogroups that carry eae and lack the EPEC adherence factor and shiga toxin DNA probe sequences

This study was conducted to characterize the virulence potential of 59 Escherichia coli strains carrying eae and lacking the enteropathogenic E. coli adherence factor and Shiga toxin probe sequences. in hybridization studies, all strains carried the locus of enterocyte effacement (LEE)-associated DNA sequences. of the other 15 virulence DNA sequences tested, hly was the most frequent (44.1%); 17 combinations of these sequences were found, but strains carrying eae only (eae profile) were the most frequent (35.6%). Except for 1 cytodetaching strain, all others adhered to HeLa and Caco-2 cells, most of which (similar to 75.0%) showed variations of the localized adherence pattern. Actin accumulation was detected in 75.9% of the nondetaching strains. Most strains had LEE, probably inserted in pheU (49.2%), and presented a nontypeable intimin (83.1%). Translocated intimin receptor-derived DNA sequences correlated with enteropathogenic and enterohemorrhagic E. coli in 61.0% and 32.0% of the strains, respectively. Thirty-five different serotypes were found. Only strains with the eae profile were associated with diarrhea (P = .039).Universidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol Imunol & Parasitol, BR-04023062 São Paulo, BrazilUniv São Paulo, Inst Butantan, Lab Especial Microbiol, São Paulo, BrazilUniv São Paulo, Inst Adolfo Lutz, Secao Bacteriol, São Paulo, BrazilUniv São Paulo, Hosp Clin, Inst Crianca, São Paulo, BrazilUniv Estado Rio de Janeiro, Dept Microbiol, Rio de Janeiro, BrazilUniv London Imperial Coll Sci Technol & Med, Dept Biochem, London, EnglandUniversidade Federal de São Paulo, Escola Paulista Med, Dept Microbiol Imunol & Parasitol, BR-04023062 São Paulo, BrazilWeb of Scienc

Acquired and Congenital Ocular Toxoplasmosis Experimentally Induced in Calomys callosus (Rodentia, Cricetidae)

An experimental model for acquired and congenital ocular toxoplasmosis as well as a model to induce experimental autoimmune uveitis (EAU) was investigated in Calomys callosus. Toxoplasma gondii, ME-49 strain, was used to infect males and pregnant- and not pregnant-females while S-antigen, a major glycoprotein of the retinal photoreceptor cell, was used to induce EAU. The ocular lesions elicited by T. gondii were characterized by the presence of cysts, free tachyzoites and inflammatory cells in the retina or related tissues. In the congenital form, 40% of the fetus presented ocular lesions, i.e., presence of cysts in the retina, vitreous, and extra-retinal tissues. In the acquired form, 75% of the females and 50% of the males presented unilateral ocular cysts both at 21 and 47 days post-infection. It was also demonstrated that S-antigen was not uveitogenic in the C. callosus model. No lesion was observed in the animals exclusively immunized with this retinal component, even when jacalin was used as additional adjuvant for polyclonal response to the retinal antigen. It can be concluded that C. callosus may constitute in a promising model for study both acquired and congenital ocular toxoplasmosis, particularly when it is important to make sure that a non autoimmune process is involved in the genesis of the ocular infection