enteropathogenic E. coli and Shigella sp. They can be transmitted by means of contaminated food, although the relative importance of this route compared with water contamination or direct person-to-person transmission is unknown. Other bacterial pathogens, such as Campylobacter jejuni or vibrios also could be transmitted by food in developing countries. It is also likely that certain viral pathogens, such as 27nm viruses like Norwalk virus, and parasitic agents, such as Entamoeba histolytica, Giardia lamblia, or Cryptosporidium sp. are often ingested with food. The offending organism may be present in raw foodstuffs or it may be introduced during food preparation or storage. It then replicates under suitable temperature and pH conditions. These conditions, which can also occur because of critical defects in food handling in developed countries, are very common in household settings in developing countries. Bacterial multiplication may be particularly important for some pathogens, such as enterotoxigenic E. coli or vibrios, that require a large ingested dose to cause disease.
Food control investigations often use enumeration of indicator organisms, rather that isolation of pathogens (Frank and Barnhart, 1986). These organisms, predominantly E. coli, are indicators of fecal contamination, since that is their usual origin. Coliform or fecal coliform indicators have been used extensively to assess water quality, and the presence of any coliforms in water is considered unacceptable for potable water (APHA, 1989). The presence of indicator bacteria in food simply suggests that there is a risk that food also is contaminated with an enteropathogen. In settings with poor sanitation and hygiene, that risk of contamination is determined in part by the frequency of enteropathogens in the stools of healthy people, and the prevalence of diarrhea during which higher numbers of enteropathogens are excreted.
In studies done in Bangladesh, El Salvador, India, Indonesia, Jamaica, Peru, and The Gambia, high levels of fecal bacteria were found in the milk or formula given to infants (Barrell and Rowland, 1979; Black et al., 1982b; Black et al., 1989). A similar hazard of fecal contamination has also been demonstrated with traditional weaning foods (Black et al., 1982a, 1989; Rowland et al., 1978). Cereal gruels and other foods specially prepared for infants were the most frequently and heavily contaminated. Pathogens, namely, enterotoxigenic E. coli and Salmonella sp. and possible pathogens, including Aaromonas hydrophila and Vibrio cholerae non-O group one, have been isolated from foods consumed by infants in studies done in The