Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2001
Publication Date: 8/1/2001
Citation: Cray, P.J., Ladely, S.R., Bailey, J.S., Stern, N.J. 2001.Colonization of broiler chicks by salmonella typhimurium definitive phage type 104. Journal of Food Protection. 64: (11) P. 1698-1704.
Interpretive Summary: Salmonella typhimurium DT104 first emerged in the UK in the 1980's and is associated with an increase in morbidity and mortality in both humans and animals. It has also been isolated in the US and is now recognized globally. It is characterized by resistance to 5 antimicrobials and has a tendency to acquire additional resistance attributes, especially to the newer drugs which are available to treat both humans and animals. Because Salmonella can be transmitted through the food chain, we infected broiler chicks with different strains of DT104 to see if it caused clinical illness in the birds or persisted in the poultry environment through production. Chicks that were exposed to DT104 did not demonstrate any clinical signs of illness at the dose of bacteria they were exposed to. However, DT104 did appear to persist for a longer period of time than a strain of DT104 which was less resistant. We also observed that colonization with other Salmonella serotypes at hatch, which is often observed in poultry production, had no effect on outcompeteing the DT104 strain, in fact the opposite was observed. These data indicate that once DT104 appears in the poultry production arena it may persist in the environment and become the predominant strain in the poultry house. This suggest that intervention measures may be warranted to prevent introduction of DT104 into broiler production facilities.
Technical Abstract: Colonization and shedding of Salmonella typhimurium DT104 was studied in broiler chickens in two trials. In trial 1, 180 day-of-hatch chicks (n=60/group) were challenged with 106 CFU DT104 (wild type isolate from poultry), or were commingled with a seeder chick challenged with 106 CFU DT104. A control group was not exposed to DT104. The level of Salmonella spp. shedding in feces did not differ among groups while colonization of DT104 remained constant at high levels in the challenged group, increased over time in the seeder group and was not recovered from the control chicks. In Trial 2, 360 day-of-hatch chicks (n=120/group) were divided into three groups. Chicks in the susceptible group were commingled with two seeder chicks which were orally challenged with 107 CFU/bird of a pan-sensitive strain ofDT104. Chicks in the resistant group were commingled with two seeder chicks which were orally challenged with 107 CFU/bird DT104 from Trial 1. A control group was not exposed to DT104. The percentage of chicks colonized with susceptible DT104 declined over the course of the trial, while recovery of the resistant DT104 persisted. DT104 was not recovered from the control chicks. For both trials, co-colonization with hatchery derived salmonellae did not affect outcome. Additionally, no apparent effect on morbidity or mortality was observed. Introduction of DT104 by commingling may induce colonization resulting in persistent high levels of shedding in flocks.