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Contamination of eggs by Salmonella Enteritidis has been a prominent cause of human illness for several decades and is the focus of a recently implemented national regulatory plan for egg-producing flocks in the United States. Salmonella Heidelberg has also been identified as an egg-transmitted pathogen. The deposition of Salmonella strains inside eggs is a consequence of reproductive tract colonization in infected laying hens, but prior research has not determined the relationship between the numbers of Salmonella that colonize reproductive organs and the associated frequency of egg contamination. In the present study, groups of laying hens in two trials were experimentally infected with large oral doses of strains of Salmonella Enteritidis (phage type 13a), Salmonella Heidelberg, or Salmonella Hadar. Reproductive tissues of selected hens were cultured to detect and enumerate Salmonella at 5 days postinoculation, and the interior contents of eggs laid between 6 and 25 days postinoculation were tested for contamination. Significantly more internally contaminated eggs were laid by hens infected with Salmonella Enteritidis (3.58%) than with strains of either Salmonella Heidelberg (0.47%) or Salmonella Hadar (0%). However, no significant differences were observed between Salmonella strains in either isolation frequency or the number of colony-forming units (CFU) isolated from ovaries or oviducts. Salmonella isolation frequencies ranged from 20.8% to 41.7% for ovaries and from 8.3% to 33.3% for oviducts. Mean Salmonella colonization levels ranged from 0.10 to 0.51 log CFU/g for ovaries and from 0.25 to 0.46 log CFU/g for oviducts. Although parallel rank-orders were observed for Salmonella enumeration (in both ovaries and oviducts) and egg contamination frequency, a statistically significant relationship could not be established between these two parameters of infection.

Internal contamination of eggs laid by hens infected with Salmonella enteritidis has been a prominent international public health issue since the mid-1980s. Considerable resources have been committed to detecting and controlling S. enteritidis infections in commercial laying flocks. Recently, the Centers for Disease Control and Prevention also reported a significant association between eggs or egg-containing foods and S. heidelberg infections in humans. The present study sought to determine whether several S. heidelberg isolates obtained from egg-associated human disease outbreaks were able to colonize reproductive tissues and be deposited inside eggs laid by experimentally infected hens in a manner similar to the previously documented behavior of S. enteritidis. In two trials, groups of laying hens were orally inoculated with large doses of four S. heidelberg strains and an S. enteritidis strain that consistently caused egg contamination in previous studies. All five Salmonella strains (of both serotypes) colonized the intestinal tracts and invaded the livers, spleens, ovaries, and oviducts of inoculated hens, with no significant differences observed between the strains for any of these parameters. All four S. heidelberg strains were recovered from the interior liquid contents of eggs laid by infected hens, although at lower frequencies (between 1.1% and 4.5%) than the S. enteritidis strain (7.0%).

By conventional trayliner (hatcheries) and drag swab assembly (broiler houses) culture methods, the isolation distribution of Salmonella serotypes from five commercial broiler hatcheries (three sample times) and 13 broiler farms (eight sample times) was evaluated. A total of 11 different Salmonella serotypes were isolated from hatcheries, with Salmonella heidelberg (9/30) and Salmonella kentucky (6/30) accounting for 50% of the total isolations. Of 700 chick paperpad trayliners sampled, regardless of lot (breeder flock source) or hatchery, 12% were positive for Salmonella. When 10 individual trayliners were cultured from individual lots (same breeder flock source), Salmonella was detected in 24/57 lots (42%). Multiple serotypes were simultaneously isolated from the same lot on three occasions (6%). Of the 21 lots that were serially sampled, the Salmonella serotype detected was different within lots eight times (38%) on at least one occasion of two or more sampling times. Of the 196 individual broiler houses sampled, 44 were positive for Salmonella (42%). Twelve different serotypes were isolated from broiler houses during this study. The serotypes isolated most frequently were S. heidelberg (34/94) and S. kentucky (22/94). These two serotypes accounted for 59.6% (56/94) of the total broiler house isolations. Of the 38 houses that were serially sampled, two or more serotypes were detected in the same broiler house on 20 occasions (53%). Of the 38 serially sampled houses (four or more times), a consistent Salmonella serotype was detected in five houses (13%). In only 5 of the 38 (13%) serially sampled houses did we fail to detect Salmonella on four or more samplings. No significant difference in Salmonella isolation frequency was observed between poultry houses using new or used litter. These data support previous findings indicating that paratyphoid Salmonella serotypes are prevalent in some broiler hatcheries and houses. Further, the observation of multiple serotypes simultaneously and serially isolated from the same breeder hatchery lots suggests that breeder flocks may be infected with more than one serotype, possibly providing a source for multiple serotype infections in progeny grower flocks.

participate in the study. The surface of the manure pile in one house on each ranch was sampled by drag swabbing. The drag swabs were tested for Salmonella using a most probable number procedure that had a detection level of one to five Salmonella per drag swab. In 12 ranches (32.4%), the drag swabs were negative for Salmonella; the remaining had Salmonella counts in the range of 1 to over 1700 per swab. Twenty-two different serotypes were found. Salmonella heidelberg and Salmonella cerro represented the majority of the typed isolates. Salmonella enteritidis (SE) was found on only one ranch. This study found SE to be rare in California egg ranches, which implies that these ranches are not a major source of S. enteritidis.

Young turkey poults were experimentally infected with Salmonella heidelberg to evaluate the standard tube agglutination test (TAT) and direct fluorescent antibody test (DFAT), and to correlate results of these procedures with the spread pattern of the organisms in the feces using conventional culture procedures for the detection and isolation of S heidelberg from cloacal swabs. The DFAT test detected fecal excretors considerably longer than bacterial isolation and gave better results. The cultural method was not the most reliable and sensitive method, especially when compared with the DFAT. All control birds remained negative bacteriologically serologically, and with the DFAT during the observation period.

Domestic fowl may constitute a major reservoir of Salmonella among animals (4). Between 1934 and 1963 more than two-thirds of the approximately 20,000 Salmonella cultures isolated from animals were from domestic fowl (5). For the past several years Salmonella heidelberg in this country has been ranked as second in incidence of various Salmonella isolated from animals (nonhuman), and one of the top four in incidence from human beings. S. heidelberg was first recovered from man by Habs, in 1933 (9), and was reported in ducks by Kauffman in 1953 (10). It was first reported in England in 1951 (6), and in Canada in 1952 (3). Several times, this serotype has surpassed S. typhimurium as the number one cause of human Salmonella infections in Canada. It is believed that the increase in human infection due to S. heidelberg was associated with the presence of the organism in foodstuffs containing egg products. The first report of S. heidelberg from animals in the United States was in 1954 (14). In 1964, 483 isolations of S. heidelberg were reported in this country from nonhuman sources. Over 90% of these came from fowl, eggs, and egg products (15). The organism has also been recovered from many domestic animals, monkeys, and turtles.

When a live broth culture of Salmonella heidelberg was given orally to turkeys, both 19S gamma-1-macroglobulins and 7S gamma2-immunoglobulins were synthesized. The 7S antibody was not affected by 2-mercaptoethanol (2ME) treatment. Fractionation of the turkey serum on DEAE cellulose column and assaying the antibody activity by indirect hemmagglutination (IHA) test showed that 19S antibodies were produced longer in turkeys than were 7S, and were susceptible to 2ME. Heat-killed suspensions of S. heidelberg injected intravenously produced 19S antibodies, and no 2ME-resistant titers were detected by the IHA test even during early infection, because no flagellar antigens were present. The IHA test detected both 7S and 19S antibodies, the 19S class being detected over long periods while tube agglutination remained negative.