Bacteriological data collected from various field studies involving irrigation water, field crops, and soils were studied with respect to sources and magnitude of fecal contamination associated with cultivation, harvesting, and marketing of fruits and vegetables. Other reports concerned with contamination during agricultural activities were reviewed. Fecal coliform densities proved to be a better measurement of the probable occurrence of waterborne pathogens than any single test for a specific pathogenic group. When the fecal coliform density per 100 ml was above 1,000 organisms in various stream waters, Salmonella occurrence reached almost 100 per cent frequency. These data support the establishment of the proposed limit of 1,000 fecal coliforms per 100 ml of irrigation water, but approved sanitation practices must accompany (or supplement) use of this bacteriological standard. A concept of multiple safeguards to limit the public health hazard associated with poor quality irrigration water, irrigation farming practices, and market preparation of produce is discussed from the microbiological viewpoint.

Summary A study has been made of coli‐aerogenes bacteria isolated from 251 soil samples collected from 26 States and 3 foreign countries. Based on land use, the soils were classified in 8 classes of the undisturbed group and one additional group of soils which were known to have been exposed to various kinds of faecal pollution. Faecal coli‐aerogenes organisms were usually absent, or present in comparatively small numbers only, in undisturbed soils, with most counts being less than 1.8/g. There was a marked increase in the numbers in soils of the polluted group, with a density of between 3,300 and 49,000/g. Intermediate types represented 76% of the 2,348 strains isolated from the undisturbed soil classes, as contrasted with only 17% of 665 polluted soil strains. The IMViC reactions of the predominant type from the undisturbed group were ‐ + ‐ +, and this type represented 48% of the 2,348 strains isolated. The sanitary significance of the ‐ + ‐ + intermediate type as a soil coli‐aerogenes organism, in relation to data on types from faecal samples and certain remote mountain streams, suggests that the strains giving these IMViC reactions, and which are 45° negative, may possibly be considered as a type characteristic in unpolluted soils but relatively infrequent where faecal pollution has occurred. Since soil contains high numbers of organisms, other than coli‐aerogenes bacteria, which frequently produce false positive reactions by the ‘confirmed test’ procedure, the ‘completed test’ method is recommended for the examination of soils for coli‐aerogenes organisms.

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