Evidence for the presence of a type III secretion system in diffusely adhering Escherichia coli (DAEC).

Diffusely adhering Escherichia coli (E. coli) strains (DAEC) represent a potential cause of diarrhoea in infants, and the detection of type three secretion system (TTSS) genes in DAEC would substantiate their pathogenic nature. In this work, four isolates of DAEC, recovered from stools of diarrhoeic children, were analysed by PCR, in order to detect the presence of TTSS genes. Primers targeted to the escC, escJ, escN and escV, some of the most conserved TTSS genes in enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC and EHEC), were used in order to verify the occurrence of homologous genes in our DAEC isolates. By this approach, we were able to characterise DNA fragments corresponding to putative escJ and escN genes in all DAEC isolates. Furthermore, DNA fragments homologous to the escC and escV genes were also amplified from all isolates. Besides the similarity found among the DAEC esc homologues with EPEC and EHEC esc genes, the nucleotide sequence analysis of the flanking regions of the amplified DNA fragments suggests that the putative DAEC esc genes are organised in the same manner as observed in EPEC and in EHEC strains. The results described here provide strong evidence for the presence of a TTSS in the DAEC strains analysed, implicating a pathogenic nature of these isolates.

Liver levels of retinol in unselected necropsy specimens: a prevalence survey of vitamin A deficiency in Recife, Brazil.

Total retinol was analyzed in 517 necropsy specimens from children 0 to 14 yr of age, deceased of various causes in Recife, Brazil, and from eight persons, 10 to 59 yr of age, who died violently. Age and nutritional status, in that order, were found to be the major determinants of the prevalence of low reserves, children less than 1 yr of age showing the highest prevalence of deficient values. These data were extrapolated to the live population less than 5 yr of age, categorized by age and nutritional status. By using the criteria that liver reserves of vitamin A less than 5 and 20 micrograms/g denote states of high risk and inadequacy, respectively, approximately 3 and 17% of children 0 to 4 yr of age in the live population of Recife were estimated to fall in the high risk and inadequate status group, respectively. None of the persons who died violently was at high risk and only one had inadequate reserves. These estimates agree with previous prevalence figures from clinical and biochemical surveys. Thus, the direct assessment of concentrations of vitamin A in the liver at necropsy is a simple, inexpensive, and noninvasive procedure for estimating the vitamin A status of children.