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In May 1981 an outbreak of typhoid fever occurred in a small village on a southwestern United States Indian reservation. Five of the six culture-proven cases, but only 2 of 15 community, age-matched controls, had eaten food prepared for a party held in the village on 20 April (chi-square = 4.3; P less than 0.05). Food histories obtained from 16 persons who ate food at the party suggested that chicken with chili (P = 0.03) and potato salad (P = 0.09) were possible vehicles. Eleven adults who attended the party, 5 of whom helped prepare an implicated food, were studied with one or more stool cultures and serum for Vi antibody by using enzyme-linked immunosorbent assay (ELISA) and hemagglutination techniques. All initial stool cultures were negative for Salmonella typhi; however, one subject, a 70-year-old female foodhandler, had a Vi antibody titer of 1:320 by ELISA. Subsequent cultures from this subject were positive for S. typhi. ELISA for Vi antibody directed the investigators to a single individual as the most probable carrier source and obviated the need for multiple fecal cultures from the other potential carriers identified by the epidemiological investigation.

In early 1983, an outbreak of illness caused by raw milk contaminated with multiple-antimicrobial-resistant Salmonella typhimurium occurred in Arizona. One of the cases involved a 72-year-old woman who died with Salmonella enteritis and sepsis that had not responded to treatment with chloramphenicol. The S typhimurium isolates from this patient, from other ill persons, and from raw milk were resistant to ampicillin, chloramphenicol, kanamycin sulfate, streptomycin, sulfonamide, and tetracycline. These resistances were mediated by a 105-megadalton R plasmid. During the epidemic period, 43% of the S typhimurium isolates submitted to the Arizona Department of Health Services were resistant to chloramphenicol, and 80% of these possessed the same plasmid resistance. Although there was evidence of spread of the S typhimurium in the community, there was no evidence of spread of this Salmonella R plasmid to the normal flora of patients or their family members a median of 14 weeks after the infection. This outbreak demonstrates the ability of drug-resistant Salmonella to spread from the animal to the human reservoir and, in a suitable host, produce a fatal infection.

From June through September 1979, diarrheal illness occurred in an estimated 1,850 persons who had camped at a private campground in Arizona. Illness occurred more frequently among campers at that campground than among those in the adjacent State park (P less than 0.0001). The same well served both the private and the State campgrounds as the source of drinking water, but that water was distributed to the two campgrounds through separate lines. Illness was significantly associated with drinking water at the campsite (P less than 0.0001), drinking larger quantities of campsite water (P less than 0.001), and camping on the southwest side of the campground (P less than 0.001). Samples of the water collected from the system during January through June contained no coliform bacteria. However, all those samples had been collected from the State park only. Of the 11 water samples submitted for bacteriological analyses during the summer, 3 had high levels of bacteria. Excavation of the water system uncovered a direct cross connection between the potable water system and a sewage-effluent irrigation system. This outbreak calls attention to the importance of designing, maintaining, and monitoring potable water systems properly, especially those proximate to wastewater re-use systems.