Invasiveness of Salmonella Administered Orally to Cold-Exposed Mice

Abstract

Susceptibility to enteric infection with Salmonella was studied in mice housed at different temperatures. The oral doses of S. typhimurium SR-11 and RIA, which caused 50% mortality in animals at 10 C, were about J%0 and M00 of the respective values at 23 C, and that of an avirulent strain of S. enteritidis was also lower in the cold-exposed mice. The frequency of mortality due to Salmonella infection was essentially the same in mice exposed to 34 or 23 C. The divergent responses in the cold and heat probably stem from basic differences in the physiological changes mediated by the two extremes. The pattern and extent of change in weight and rectal temperature were the same among infected mice housed at 10 and 23 C and controls at 10 C, but differed from controls at 23 C. The incidence of Salmonella in samples of liver-spleen, lung, colon, blood, or feces was similar among infected mice housed at 10 and 23 C during a 14-day period of observation. The increased frequency of mortality in cold-exposed infected animals is not due to alterations in invasiveness of the bacteria nor to greater impairment of the thermoregulatory capacity of the mice. It may be attributable, in part at least, to a greater effectiveness of Salmonella toxins as metabolic poisons at low temperatures.

Unstressing intemperate models: how cold stress undermines mouse modeling

“…Studies dating back at least to the 1940s indicate that ambient temperature profoundly alters the course of infection in diverse rodent models. In models of bacterial ( Salmonella typhimurium , Staphylococcus aureus , Klebsiella pneumonia , and Rickettsia typhi ), viral (influenza virus, herpes simplex virus, and rabies virus), and protozoal ( Trypanosoma cruzi ) infection, ambient temperature directly correlates with host responsiveness—lower temperatures leading to impaired immune responses (Moragues and Pinkerton, 1944; Miraglia and Berry, 1962; Previte and Berry, 1962; Underwood et al, 1966; Amrein, 1967; Baetjer, 1968; Previte et al, 1970; Won and Ross, 1971; Bell and Moore, 1974; Jiang et al, 2000; Rice et al, 2005). These effects can be dramatic: in experimental murine typhus, weather-associated changes in ambient laboratory temperature (from 29.4–36.6 to 18.3–22.8°C) shifted mortality rates from 9 to 100% (Moragues and Pinkerton, 1944).…”

Comparative Dynamics of Salmonella Infection After Primary and Secondary Challenge of Mice Exposed to 10 and 23 C

“…The methods used were described in detail in an earlier paper (25). Briefly, Salmonella typhimurium, strain RIA, was grown for 16 to 18 h at 37 C in brain-heart infusion broth (Difco, Detroit, Mich.).…”

“…Samples were assayed qualitatively for the presence of Salmonella. The results were presented in an earlier paper (25). A replicate 3-ml sample was frozen at -50 to -70 C and stored at -25 to -30 C for seven days or less prior to quantitative assay.…”

“…The virulence of Salmonella infections may be enhanced when mice are exposed to low temperature (20,26,33). Although the reasons for the increased pathogenicity are not clear, they are apparently not related to greater invasiveness of the bacteria (25). Depression of cellular and humoral defenses which may occur after acute cold exposure (3,14,16,21,34) might allow an increased proliferation of the bacteria.…”

Can Stress in Farm Animals Increase Food Safety Risk?

“…Early studies (Miraglia and Berry, 1962;Previte et al, 1970Previte et al, , 1973 showed enhanced Salmonella infection (frequency and persistency) in mice exposed to cold temperature. Tannock and Savage (1974) observed that deprivation of food, water, and bedding for 48 hours caused increased intestinal population levels of Salmonella Typhimurium and coliforms, and reduced levels of lactobacilli, in mice.…”