MOLECULAR BIOLOGICAL APPROACHES TO THE EPIDEMIOLOGY OF DIARRHEAL DISEASES IN DEVELOPING-COUNTRIES

Diarrhoea in developing countries is caused by an increasingly long list of bacterial, viral, and parasitic pathogens with rotavirus, enterotoxigenic Escherichia coli, Campylobacter, Shigella, and Salmonella heading the list. Using methods to detect most of the known enteropathogens, one or more enteropathogen(s) is isolated in two-thirds of diarrhoeal illnesses in the developing world. Many of these enteropathogens are also frequently isolated from children without diarrhoea. An aetiologic agent is more frequently isolated from cases of invasive diarrhoea than from those with secretory diarrhoea. Deoxyribonucleic acid probes have proved very useful in detecting pathogens such as enterotoxigenic (ETEC), enteroinvasive (ETEC), and enteropathogenic E. coli (EPEC), but have not yet proved to be particularly rapid or less expensive. Molecular biology has proved useful in epidemiological studies as a means of strain identification. Plasmids were initially used as convenient markers and proved useful in identifying epidemic strains of bacteria. Other molecular markers, such as ribotyping, are accurate enough to be used as taxonomic tools.