In vitro evaluation of sodium butyrate on the growth of three Salmonella serovars derived from pigs at a mild acidic pH value

Foodborne zoonotic diseases can be transferred into the food chain at the stage of livestock farming. As an emerging public health challenge, practicable reduction measures in porcine health management for Salmonella are constantly being investigated. This in vitro study aimed to determine the influence of six different sodium butyrate (SB) concentrations (0, 5, 10, 20, 40, and 80 mM) on the growth of three different Salmonella enterica serovars at a constant pH value of 6.0, corresponding to conditions in the pig's hindgut. S. Derby and S. Typhimurium, isolated from a pig farm, and S. Typhimurium DSM 19587, which served as control, were used. Broth microdilution assay was applied to record Salmonella growth in the presence of different SB-concentrations over six different incubation periods (0, 1, 2, 4, 6, and 24 h). Results were quantified in the log colony-forming units (log10 CFU/mL). For 1 h incubation, the addition of SB showed no significant differences in the range of initial Salmonella dose of about 5.7 log10 between concentrations (0–80 mM, 5.26 ± 0.10–5.60 ± 0.07 log10, p > 0.05). After 6 h, for SB addition, the range of Salmonella counts was significantly lower compared to no addition of SB (5–80 mM, p < 0.05), 6.78 ± 0.84–7.90 ± 0.10 log10 for 5 mM, and 7.53 ± 0.04–8.71 ± 0.22 log10 for 0 mM. Moreover, for SB concentrations of 40 and 80 mM, no difference in the range of Salmonella counts over 6 h was obtained (5.23 ± 0.11–5.38 ± 0.05 log10, p > 0.05), and minor Salmonella growth was recorded at the earliest after 24 h incubation. Growth rates for varying SB concentrations and incubation times were confirmed in a similar manner for the three serovars. Obtained results suggest that increasing SB concentrations suppress Salmonella growth for concentrations of 5–20 mM over a 6 h incubation period and for 40 and 80 mM over a 24 h incubation period. When transferring these in vitro findings to the porcine organism, it may be assumed that Salmonella reduction can be achieved by increased butyrate content in the chyme of the large intestine

Epidemiological Study on Salmonella Prevalence in Sow Herds Using Direct and Indirect Detection Methods

In piglet production, the beginning of pork production, Salmonella prevalence requires greater attention as having an impact on the subsequent production steps. The aim of this study was to investigate Salmonella prevalence in three sow herds with attached piglet rearing units. Salmonella prevalence was investigated either directly by boot swabs and feces or indirectly by serum samples taken during gilt integration, the peripartal period, and piglet rearing. Boot swabs and feces were analyzed by real-time PCR and subsequent microbiology. Results indicated that high biosecurity measures in sow husbandry do not necessarily result in a low Salmonella prevalence. Furthermore, the sow herds’ Salmonella prevalence should not be used to infer the situation in the associated piglet rearing. The proportion of positive boot swabs was 10.5, 3.6, and 21.3% for sows (gilts and peripartal) with an inverse situation in piglet rearing with 50.0, 63.3, and 5.8% positive swabs for farms A, B, and C, respectively. Boot swabs are suitable as a direct sampling method to gain an overview of Salmonella prevalence in both sows and piglets. Indirect serum antibody testing can be useful, although it should be evaluated considering age-dependent levels of antibody titres