|Abstract or Summary
- A Lactobacillus species of human intestinal origin (strain
MLC) used in swine feeding experiments was characterized using
biochemical, genetic and serological techniques and found to be
Lactobacillus lactis. Bottle feeding of the MLC strain in concentrate
form (> 10⁹ cfu/ml) resulted in a reduction in both fecal coliforms
and the incidence of scouring. In one group of pigs which received
concentrate for 54 days, the Lactobacillus to coliform ratio was
1280:1; in the control group the ratio was 2.3:1.
To increase the sample size, a herd of 125 swine was fed concentrates
of Lactobacillus lactis MLC through the drinking water system
using a water proportioner. After 90 days of such treatment,
the coliform counts were reduced by 95%. The scouring incidence in
the treated pigs was 13% as compared to 35% in the control group. However numbers of fecal lactobacilli were not increased.
The influence of Lactobacillus MLC feeding on the bacterial
flora of different parts of gastrointestinal tract was studied. In the
case of scouring pigs, enteropathogenic Escherichia coli (EEC) were
present in larger numbers in the tissue homogenate of different parts
of the tract than in the lumen. The virulence of the EEC found present
was confirmed by experimental infection in pigs. In control, non-scouring
pigs only non-EEC were found in the tissue. In Lactobacillus
MLC-fed pigs, E. coli both in the tissue and lumen was reduced
to low numbers; also, the few E. coli observed were non-enteropathogenic.
Thus by feeding Lactobacillus MLC concentrate, it was
possible to reduce the E. coli to less than 10² /gm There were
higher numbers of lactobacilli in the tissues of Lactobacillus-fed pigs
than in control and scouring pigs. The lactobacilli isolated from
tissue homogenate of the treated animals resembled biochemically
and serologically (fluorescent antibody staining) the Lactobacillus
MLC which was fed.
Histological studies were done to show direct evidence of
colonization in frozen sections of intestine obtained from Lactobacillus
MLC-fed pigs. Gram and toluidine blue-staining revealed
large numbers of Gram-positive bacilli colonizing the surface epithelium
of the villi. On the other hand, control pigs which died of
scouring revealed many EEC colonizing the small intestine. Pigs in groups receiving colostrum and lactobacilli performed very well.
No symptoms of diarrhea was seen and many lactobacilli colonized
throughout the small intestine. Even after the challenge with EEC
serotype 09:K:NM, these two groups of pigs did not show any signs
of disease and very few EEC colonized the intestines even after the
challenge. Pigs not receiving colostrum but only lactobacilli did not
scour before challenge with EEC 09:K:NM and many lactobacilli
colonized the small intestine. However, 72 hours after challenge
these latter animals revealed symptoms of diarrhea and EEC were
seen colonizing the small intestine in addition to lactobacilli.
The possible role of surface antigens in colonization by lactobacilli
was studied. Data revealed that Lactobacillus lactis MLC
and L. salivarius did not have any antigens in common. On the
other hand, Lactobacillus FHS isolated from pig intestine had three
antigens in common with the MLC strain. However, in vivo tests
showed that all three strains colonized the small intestine to the
same degree. This indicated that surface antigens were not involved
in the colonization mechanism.
The ability of Lactobacillus MLC to inhibit a variety of intestinal
pathogens in broth cultures was demonstrated. Organisms
inhibited included E. coli, Staphylococcus aureus, Clostridium perfringens
and Bacterotdes sp. The mechanism of inhibition of S.
aureus and E. coli in milk and broth was examined. These organisms did not grow in cell-free culture supernatants (whey at
pH 4.0) after growth of the Lactobacillus MLC but they grew well in
broth adjusted to pH 4.0 Supernatant from cultures of Lactobacillus
MLC concentrate was found to contain 2-Deoxy-D-glucose in addition
to glucose and galactose. Studies using 2-Deoxy-D-glucose alone
and with glucose and galactose showed that the former was inhibitory
to E. coli, S. aureus and Salmonella typhimurium.
Possible applications of these findings in the animal industry
as a substitute to antibiotics are discussed. A greater use of Lactobacillus
organisms in preventive treatment of intestinal diseases is