Heterogeneity of species isolated from serial stool specimens of Egyptian children using pulsed field gel electrophoresis.

BACKGROUND

The genus spp. is a common cause of human acute bacterial enteritis and travellers' diarrhoea worldwide.

OBJECTIVE

To determine whether multiple serial isolations of spp., when obtained from a single child, represented the same or a different organism.

METHODS

In a birth cohort study conducted in Egypt, numerous children showed serial isolations of spp. Of these, 13 children were selected from different households based on the successive isolation of six or more isolates from stool samples.

RESULTS

Eighty isolates were recovered and identified as either ( = 25) or ( = 55). Pulsed-field gel electrophoresis (PFGE) revealed the presence of 38 unique and 24 profiles at a similarity level of ≥ 90%. Although no serially-identical isolates were detected in six children, others demonstrated at least one identical couple of isolates; all identified serially between one to six weeks. Two children demonstrated > 80% similar couples of isolates that appeared seven months apart. PFGE could be a useful tool for differentiating reinfection, relapse and convalescent excretion phases.

CONCLUSION

Our data suggest that infection in children is a complex process; children are exposed to multiple species in endemic environments and strains of the same bacterium appear to be shed serially between one to six weeks after the first exposure. Isolates that persisted for longer periods were relatively less similar, as shown from the results of this study.