Direct feeding of microencapsulated bacteriophages to reduce Salmonella colonization in pigs

Anthea C Saez, Purdue University

Abstract

Salmonella shedding often increases in pigs following transportation and/or lairage. We previously showed that administering anti-Salmonella bacteriophages to pigs by gavage significantly reduced Salmonella colonization when the pigs were exposed to a Salmonella-contaminated holding pen. We aimed to increase the efficacy of our phage treatment by expanding its host range, improving the microencapsulation technique and delivering the treatment via feed. The newly developed phage cocktail effectively lysed not only Salmonella Typhimurium but also serovars Enteriditis and Kentucky. In addition, the new microencapsulation technique produced phages that were stable at 4°C and 22°C for up to two weeks (mean titer: 8.9 log10 PFU/mL). In live animal experiments, pigs (n = 21) were randomly placed into three groups: feed, gavage, and control. The feed group was direct-fed a microencapsulated phage cocktail daily for five days. On the fifth day, the gavage group received the same phage cocktail by gavage, while control pigs received a mock treatment containing no phage. All pigs were then orally challenged with Salmonella serovar Typhimurium. Fecal swab samples were collected every two hours. At six hours post-challenge, all pigs were euthanized, and ileal and cecal contents and mesenteric lymph nodes were collected and analyzed for the challenge organism. Pigs in the feed group were less likely to shed Salmonella Typhimurium at 2 h (38.1%) and 4 h (42.9%) post-challenge compared to pigs in both the gavage (2 h: 71.4%; 4 h: 81.1%) and control (2 h: 71.4%; 4 h: 85.7%) groups (P < 0.05). Likewise, concentrations of Salmonella Typhimurium in ileal (2.0 log10 CFU/mL [contents]) and cecal (2.7 log 10 CFU/mL) contents from feed pigs were lower than ileal (3.0 log 10 CFU/mL) and cecal (3.7 log10 CFU/mL) contents from control pigs. High concentrations of anti-Salmonella phages were detected in ileal and cecal contents from both feed and gavage pigs (feed ileal: 1.4 x106; feed cecal 8.5x106; gavage ileal 2.0 x104; gavage cecal: 2.2 x103). It was concluded that direct feeding of microencapsulated phages is a practical and effective means of reducing Salmonella colonization and shedding in pigs.

Degree

M.S.

Advisors

Ebner, Purdue University.

Subject Area

Microbiology|Animal sciences

COinS