Adherence and virulence genes of Escherichia coli from children diarrhoea in the Brazilian Amazon

The bacterial pathogen most commonly associated with endemic forms of childhood diarrhoea is Escherichia coli. Studies of epidemiological characteristics of HEp-2 cell-adherent E. coli in diarrhoeal disease are required, particularly in developing countries. The aim of this study was evaluate the presence and significance of adherent Escherichia coli from diarrhoeal disease in children. The prevalence of LA, AA, and DA adherence patterns were determined in HEp-2 cells, the presence of virulence genes and the presence of the O serogroups in samples obtained from 470 children with acute diarrhoea and 407 controls in Porto Velho, Rondônia, Brazil. E. coli isolates were identified by PCR specific for groups of adherent E. coli. Out of 1,156 isolates obtained, 128 (11.0%) were positive for eae genes corresponding to EPEC, however only 38 (29.6%) of these amplified bfpA gene. EAEC were isolated from 164 (14.1%) samples; of those 41(25%), 32 (19%) and 16 (9.7%) amplified eagg, aggA or aafA genes, respectively and aggA was significantly associated with diarrhoea (P = 0.00006). DAEC identified by their adhesion pattern and there were few isolates. In conclusion, EAEC was the main cause of diarrhoea in children, especially when the aggA gene was present, followed by EPEC and with a negligible presence of DAEC.

Comparison of multiplex PCR with serogrouping and PCR-RFLP of fliC gene for the detection of enteropathogenic Escherichia coli (EPEC)

Enteropathogenic Escherichia coli (EPEC) comprise one of the six categories of diarrhoeagenic E. coli (DEC). EPEC is subgrouped into typical (tEPEC) and atypical (aEPEC). The identification of DEC cannot be based only on cultural and biochemical criteria, since they are indistinguishable from the non-pathogenic E. coli commonly found in human feces. Several PCR methods, with both single and multiple target genes, have been reported for detecting the different DEC pathotypes. In the present study five hundred E. coli isolates from children with diarrhea were subjected into multiplex PCR. Furthermore the strains were typed serologically with O antisera and their fliC gene was characterized by PCR-RFLP. The results obtained revealed that overall 41 (8.2 percent) isolates could be detected as EPEC by this multiplex PCR assay. Of these isolates; 27 (66 percent) were typical (escv+, bfp+) and 14 (34 percent) atypical EPEC (escv+, bfp-). None of these 41 isolates contained the Stx1 and Stx2 genes. Among 37 (90 percent) typeable strains, nine different serogroups were present. The most common serogroups were O111, followed by O86, O55 and O119 and 10 different H types were found among these isolates. The multiplex PCR assay was found to be rapid and reliable in comparison to serological test; especially when screening the large number of isolates.

Principales características y diagnóstico de los grupos patógenos de Escherichia coli / Principal characteristics and diagnosis of the pathogenic groups of Escherichia coli

Escherichia coli colonizes the human intestinal tract within hours of birth and is considered a non-pathogenic member of the normal intestinal flora. However, there are six pathogenic groups that may produce diarrhea: enterotoxigenic (ETEC), enterohemorrhagic (EHEC), enteroinvasive (EIEC), enteropathogenic (EPEC), enteroaggregative (EAEC) and diffusely adherent (DAEC) groups. E. coli can be isolated and classified using traditional methods, by identifying its biochemical or serum characteristics. The pathogenic mechanisms may be studied in cell cultures and animal model assays, as well as more up to date molecular biology methods for study and diagnosis. The latter have proven that genes are involved in pathogenesis. The objective of the present work is to draw attention to the importance of E. coli as a pathogenic organism. This microorganism is an etiologic agent of sporadic cases of diarrhea, hemorrhagic colitis, dysentery, and hemolytic uremic syndromes and outbreaks. Diarrheic E. coli manifestations occur mainly among infants, and deep knowledge and understanding of this microorganism are crucial to better epidemiologic surveillance.

100 years of Widal test & its reappraisal in an endemic area.

A reappraisal of the Widal test was made for its diagnostic utility in typhoid fever in an endemic area of Central India. The significant basal antibody level in the normal population based on 1200 voluntary/relative blood donors at the cut-off titre of 80 or above was observed in 13.83 and 8.0 per cent for 'O' and 'H' antigens of Salmonella typhi respectively. A retrospective study (1991-1995) over 138 bacteriologically proven cases of typhoid showed a positivity of 64.49 and 78.26 per cent respectively for 'O' and 'H' antibodies at the titre of 80 or above and 44.2 and 63.04 per cent at the titre of 160 and above. The retrospective data also showed a greater positivity (46.41%) in 1991 which decreased to 25 per cent in 1995 and appeared to follow the incidence of multi drug resistant S. typhi over the period. The detection of 'H' antibodies is no less important than the 'O' antibodies in the present study. Our data bring out the diagnostic limitations of Widal test done on single samples collected in the early phase of illness (4-10 days) from patients suspected to have typhoid in an endemic area of Central India.