SEWAGE EFFLUENT - LIKELY SOURCE OF SALMONELLA-ENTERITIDIS, PHAGE TYPE-4 INFECTION IN A COMMERCIAL CHICKEN LAYER FLOCK IN SOUTHERN CALIFORNIA

Following the diagnosis of Salmonella enteritidis, phage type 4, infec tion in a commercial layer flock in southern California, effluent from a nearby sewer treatment plant was investigated as a potential source of infection. Between July 1994 and March 1995, 68 Salmonella isolati ons, comprising 27 serotypes, were made from the inflow (raw sewage) a nd effluent (treated sewage). Thirty-nine of 68 (57%) isolations yield ed six serotypes, which consisted of S. enteritidis 12% (8/68), S. cer ro 10% (7/68), S. typhimurium 7.4% (5/68), S. tennessee 7.4% (5/68), S . give 7.4% (5/68) S. mbandaka 7.4% (5/68), and S, panama 6% (4/68). T he remaining 43% (29/68) isolations were represented by 21 serotypes. Seventeen S. enteritidis isolates originating from the effluent (creek water), resident feral animals (rodents, stray cats, skunks), and chi ckens (organs, eggs) of the affected flock were subjected to plasmid p rofile and restriction endonuclease analysis. Twelve of the 17 isolate s had identical plasmid profile and restriction digestion patterns. Tw o of 17 isolates showed similar patterns but both differed from the re st; and 1 of 17 did not yield plasmids. Two other isolates were found to be different from each other and from the rest of the group.