Potentials of probiotics B. subtilis RX7 and B. methylotrophicus C14 strains as an alternative to antibiotics in Salmonella challenged weaning pigs

Abstract Text: Due to therapeutic use of antimicrobials, the emergence of antibiotic resistant strains in animals is a threat to human and animal health. Probiotics has been considered as one of the alternative to antibiotics.  The objective of this experiment was to evaluate the potential of locally isolated probiotics in a Salmonella challenge model. A total of 40 pigs were used for Salmonella Typhimurium challenge model in a 6-wk trial. Pigs were randomly allotted to four experimental diets according to their initial BW (9.21 ± 1.1 kg) and sex (10 pigs per treatment; 5 barrows and 5 gilts) to evaluate blood profiles and fecal microflora after 12 hr of challenge on d-21 of the experiment. Dietary treatments consisted of: CON; corn soybean meal based basal diet (without antibiotics and not challenged), SC; basal diet + oral Salmonella Typhimurium challenge once in day 21 of experiment, T1; SC + 0.1% of 1x10⁹cfu/g Bacillus subtilis RX7 and T2; SC + 0.1% of 1x10⁹cfu/g Bacillus methylotrophicus C14. Salmonella Typhimurium was administered orally once at day 21 at the dosage of 1ml which contained 1x10¹¹ cfu/mL Salmonella Typhimurium. Orthogonal contrasts were used to test the following :(i) the overall effect of different treatment versus control (CON vs. SC, T1, T2) and ii) overall effect of 2 strains of Bacillus supplementation in challenged animals versus Salmonella challenge without probiotics supplementation (SC vs. T1, T2). After 12 hours of Salmonella challenge, the RBC, IgG and IgM, concentration were reduced (P < 0.05) whereas WBC and cortisol concentration increased (P < 0.05) in SC, T1 and T2 compared with non-challenged pigs. However, the concentration of RBC (6.34 x 10⁶/µL vs 6.77 x 10⁶/µL, 6.88 x 10⁶/µL), lymphocyte (21.0% vs 29.8%, 30.97%), IgG (197.4 mg/dL vs 246.9 mg/dL, 268.4 mg/dL) and IgM (24.2 mg/dL vs 26.9 mg/dL, 27.7 mg/dL) were reduced (P < 0.05) in SC compared to T1 and T2 whereas haptoglobin (39.2 mg/dL vs 34.5 mg/dL, 35.3 mg/dL) and cortisol (4.41 µg/dL vs 3.78 µg/dL, 3.82 µg/dL) were increased (P < 0.05)  in SC compared to T1 and T2. The supplementation of probiotics increased (P < 0.05) fecal Lactobacillus counts (7.49, 7.46 vs 7.39 log 10 cfu/g) and decreased (P < 0.05) Salmonella counts (3.57, 3.69 vs 3.87 log 10 cfu/g) in piglets after 12 hours of challenge. Thus, the locally isolated Bacillus strain has a potentiality of being used as probiotics.

Keywords: B. subtilis, B. methylotrophicus, Salmonella Typhimurium