The effect of probiotics on shortening episodes of acute infectious
diarrhea has been well-documented. Enterococcus faecium ,
Streptococcus faecium SF68 and certain lactobacillus strains have
proven efficacy. A metaanalysis of previously published randomized,
controlled studies of lactobacillus therapy reveals that the duration
of diarrhea in hospitalized children is shortened by an average of 0.7
days. Similarly a randomized, placebo-controlled trial in a cohort of
nonhospitalized children attending day-care centers also reduced the
mean duration of diarrhea. The underlying mechanism by which
probiotics produce their clinical effect is likely multifactorial and
has led to much speculation. Some theorize that lactobacilli enhance
the expression and elaboration of intestinal mucins. These
glycoproteins appear to be protective during intestinal infections.
However, protective qualities may be overcome by mucinase-producing
bacteria. Others hypothesize that rotavirus causes biphasic diarrhea,
the first osmotic and the second due to overgrowth of urease-producing
bacteria; probiotics prevent bacterial overgrowth.
In studies of the immunomodulating effects of probiotics, 49 children
with acute rotavirus diarrhea were randomized to receive Lactobacillus
GG (LGG), Lactobacillus casei subsp. rhamnosus ( Lactophilus ) or a
combination of Streptococcus thermophilus and Lactobacillus delbruckii
(Yalacta). Mean duration of diarrhea was 1.8 days for children in the
LGG group, 2.8 in the Lactophilus group and 2.6 in the Yalacta group.
Only LGG significantly increased the number of rotavirus-specific
IgA-secreting cells and serum IgA level in the convalescent stage.
This and similar studies suggest that the humoral immune system is
significant in the effect of probiotics. However, enhanced humoral
response does not fully explain the clinical effect of probiotics as
evidenced by a study comparing the efficacy of heat-inactivated LGG
against viable bacteria in the treatment of rotaviral diarrhea.
Reduction in the duration of diarrhea was the same for both groups,
but significantly fewer infants receiving the heat-inactivated strains
had detectable IgA responses.
