Abstract
This study aimed to investigate the protective effects of Bacillus amyloliquefaciens (BA40) against Clostridium perfringens (C. perfringens) infection in mice. Bacillus subtilis PB6 was utilized as a positive control to compare the protective effects of BA40. In general, a total of 24 5-week-old male C57BL/6 mice were randomly divided into four groups, with six mice each. The BA40 and PB6 groups were orally dosed with resuspension bacteria (1 × 109 CFU/ml) once a day, from day 1 to 13, respectively. In the control and infected groups, the mice were orally pre-treated with phosphate-buffered saline (PBS) (200 μl/day). The mice in the infected groups, PB6 + infected group and BA40 + infected group, were orally challenged with C. perfringens type A (1 × 109 CFU/ml) on day 11, whereas the control group was orally dosed with PBS (200 μl/day). The results showed that the BA40 group ameliorated intestinal structure damage caused by the C. perfringens infection. Furthermore, the inflammatory responses detected in the infected groups which include the concentrations of IL-1β, TNF-α, IL-6, and immunoglobulin G (IgG) in the serum and secretory immunoglobulin (SigA) in the colon, and nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) activity in the jejunum, were also alleviated (P < 0.05) by BA40 treatment. Similarly, cytokines were also detected by quantitative PCR (qPCR) in the messenger RNA (mRNA) levels, and the results were consistent with the enzyme-linked immunosorbent assay (ELISA) kits. Additionally, in the infected group, the mRNA expression of Bax and p53 was increasing and the Bcl-2 expression was decreasing, which was reversed by BA40 and PB6 treatment (P < 0.05). Moreover, the intestinal microbiota imbalance induced by the C. perfringens infection was restored by the BA40 pre-treatment, especially by improving the relative abundance of Verrucomicrobiota (P < 0.05) and decreasing the relative abundance of Bacteroidetes (P < 0.05) in the phyla level, and the infected group increased the relative abundance of some pathogens, such as Bacteroides and Staphylococcus (P < 0.05) in the genus level. The gut microbiota alterations in the BA40 group also influenced the metabolic pathways, and the results were also compared. The purine metabolism, 2-oxocarboxylic acid metabolism, and starch and sucrose metabolism were significantly changed (P < 0.05). In conclusion, our results demonstrated that BA40 can effectively protect mice from C. perfringens infection.
Highlights
Clostridium perfringens, an opportunistic pathogen that can cause diarrhea and fever in animals and humans, can be found in raw meat and poultry, in the intestines of animals, and the environment [1]
After being challenged with C. perfringens (ATCC13124), the body weight (BW) of the infected group was significantly reduced from day 11 to 13, but the BW of the control group and BA40 + infected group had the same trends and almost had no change at all
Principal component analysis (PCA) (Figure 7C) was performed and the results show that the four groups were all resolved and distinct, and the BA40 treatment group recovered the microbiota damaged by the C. perfringens infection
Summary
Clostridium perfringens, an opportunistic pathogen that can cause diarrhea and fever in animals and humans, can be found in raw meat and poultry, in the intestines of animals, and the environment [1]. Outbreaks tend to happen in some places that serve large groups of people, such as hospitals, school cafeterias, prisons, because there are various sources of infection, including meat, poultry, and other foods cooked at an unsafe temperature [2]. Clostridium perfringens outbreaks occur most often in November and December, which are linked to commonly served food such as turkey and roast beef. There is an urgent and imminent need to develop novel antimicrobial alternatives to reduce the incidence of C. perfringens infection while maintaining human health
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