Evaluation of the Oral, or Subcutaneous, Administration of a Probiotic Based on Lactobacillus for the Reduction of Salmonella Enterica Sorovar Heidelberg in Broilers

Research carried out in our laboratory has proven that the oral administration, or the consumption of FM-B11 (FloraMax^TM) are efficient in the treatment of broilers and turkeys infected with Salmonella (Higgins et al., 2008; Higgins et al., 2010; Vicente et al., 2008). Even though oral via is the most common way of administering probiotics, Sheil et al. (2004) proved that the systemic administration of a probiotic base on Lactobacillus, had an anti-inflammatory effect and diminished colitis and rheumatoid arthritis in rats. Using both via (oral and subcutaneous) the administration of a probiotic made up of Lactobacillus casei, Lactobacillus plantarum, Streptococcus faecalis y Bifidobacterium brevis, Laudanno et al. (2006), proved a significant anti-inflammatory effect, in gastrointestinal lesions in rats, stressing that the beneficial effects of probiotics is not only related to oral administration. The purpose of this study is that of evaluating the effects of oral and subcutaneous administration of the commercial probiotic FM-B11 (live or dead) in the treatment of Salmonella enterica serovar Heidelberg (SH) in one day old broilers.

A sample of Salmonella enterica sorovar Heidelberg (SH), of a poultry origin, resistant to novobiocine (NO) and nalidixic acid (NA) was used as a challenge. FloraMax^TM (FM-B11), a commercial product constituted by eleven bacteria strains, producers of lactic acid, originally isolated in the gastrointestinal tract of broilers, was diluted in powder skimmed milk, for its reconstitution at a concentration of 4 x10⁶ colony forming units (UFC)/ml for oral administration, in a single intake, was administerd. One day old chicks of a commercial incubator were used. Two batteries of cages for bird production were used. Feed and water, without medication, were administered ad libitum, and were formulated surpassing the critical levels of nutrients recommended by the National Research Council (NRC) (1994) of the United States, throughout the experiment. Birds were randomly distributed into two groups and challenged with SH at a concentration of 10⁵ UFC/bird oral via in a single intake of 0.25 ml/ bird and placed in cages (20 birds per cage). One hour after the challenge with SH, birds received the following treatments: oral buffered phosphate saline solution (PBS); FM-B11; live bacteria of FM-B11 by means of a subcutaneous injection (SC); inactivated FM-B11 bacteria by either heat, penicillin or formaldehyde by means of a SC injection. Twenty four hours after treatment, all birds were humanly slaughtered, by means of the inhalation of CO₂. Crop and cecal tonsils were collected aseptically, enriched for isolation and examined for the presence of SH. Ceca were also removed, homogenized, and diluted in a sterile saline solution and seeded in a brilliant green gel (AVB) containing 25 µg/ml of novobiocine (NO) and 20 µg/ml of nalidixic acid (NA) in order to determine the number of UFC of SH.

In this research, all the birds of the control group were SH positive in crop and cecal tonsils. Oral treatment with FM-B11 significantly reduced (P<0.001) the incidence of SH in the crop and cecal tonsils of birds, during a 24 hour period. Furthermore, the SH count in the cecal content, presented a highly significant reduction (3.83 log) (P<0.05) in birds orally treated with FM-B11 in comparison with the non treated controls. The treatment with live bacteria of FM-B11 via SC resulted in 17 of the 20 positive samples (85%) in the crop and cecal tonsils, while the SH count in the cecal content presented a significant reduction (P<0.05) of 1 log in comparison to the control group. The result of the three treatments with inactivated FM-B11 SC administered was similar to the one of the non treated birds, except for the subcutaneous injection of the heat inactivated bacteria, in which, 16 of the 20 birds were positive (80%) to isolation of SH in the cecal tonsils, representing a significant reduction (P<0.05) in comparison to the control group (Table 1). In spite of the endless number of publications related to the efficiency of probiotics in the reduction of intestinal colonization of enteric pathogens, the action mechanisms of probiotics is not yet totally known. By means of animal models for the study of colitis, Rachmilewitz et al. (2002) proved that the sequences of the immunomodulator DNA and its analogs of synthetic oligonucleotides, derived from the bacteria DNA, have immunomodulating and anti-inflammatory effects when administered via SC. Several mechanisms have been described regarding the function of probiotics, amongst them the modulation of the immune system has recently received plenty of attention (Shahani y Ayebo, 1980; Jijon et al., 2004; Ng et al., 2009; Flore et al., 2010). In general terms, we can say that more research is needed in order to elucidate the necessary conditions in which the bacteria of probiotics promote an immune response capable of treating, or preventing enteric infections in the host.

Table Effect of the subcutaneous administration of live and inactivated FM-B11 (SC), in the treatment of Salmonella Heildelberg (SH) infection in broilers, during a 24 hour period

The significant observed reduction of SH in the cecum, after the subcutaneous administration of live bacteria of the FM-B11 probiotic, suggests the existence of an interesting probiotic action mechanism in birds, yet unknown.

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