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Mechanisms of Action  |  Safety

Medical Uses of Probiotics

Diarrheal Disease

Acute gastroenteritis, more commonly referred to as acute diarrhea, is a disorder that probiotics have been used to alleviate. Marchand and Vandenplas discuss at least ten double-blind, randomized, prospective acute diarrheal studies, five of which used Lactobacillus rhamnosum strain GG (LGG) [1]. Other studies included L. acidophilus, Enterococcus faecium (E. faecium), and combination of Streptococcus thermophilus (S. thermophilus), L. acidophilus, and L. delbreuchii SSP bulgarius.

LGG has been shown to shorten the duration of rotavirus diarrhea in studies conducted in a number of different countries [2], [3], [4], [5], [6], [7], [8]. Administration of L. reuteri has also been shown to decrease the duration of rotavirus induced diarrhea [9] and Bifidobacterium bifidum (B. bifidum) has been shown to prevent rotavirus induced diarrhea [10]. LGG has also been shown to lower the rate of diarrhea among Finnish travelers visiting Turkey [11]. A randomized study performed with American travelers given either placebo or LGG [12] showed that the subjects who took the placebo had a 7.4% per day risk of developing diarrhea and the travelers who ingested LGG daily had a 3.9% per day risk of developing diarrhea. This translated into a 47% protection rate.

There have been two studies evaluating the effect of L. acidophilus treatment alone on preventing traveler’s diarrhea (TD) and one study with L. fermentatum. These studies have involved a total of 702 subjects and none of these studies showed a significant effect on the clinical outcome [1]. A traveler’s diarrhea prevention study involving 94 patients treated with a combination of L. acidophilus, L. delbrueckii, SSP bulgarius, B. bifidum, and S. thermophilus showed the treatment gave a significantly positive protection rate [13]. These studies demonstrate the probiotic preparation is important in evaluating the clinical outcome for specific treatment.

There have been a number of studies designed to determine if probiotics can prevent antibiotic associated diarrhea. Two studies in which patients were given L. delbrueckii, SSP bulgarius, plus L. acidophilus to prevent amoxicillin or ampicillin associated diarrhea were negative [14], [15]. A third reported a significant preventive effect for antibiotic associated diarrhea in children fed LGG [16]. The results of the studies with probiotics and prevention of antibiotic diarrhea again point to the fact that the type of probiotic used, the antibiotics studied and the nature of the patient population can all influence the clinical outcome.

LGG has been shown to stop episodes of relapsing diarrhea caused by a toxin produced by clostridium difficile (C. difficile). Antibiotic use has been shown to allow for the growth of C. difficile in the intestinal tract. In a study involving 32 patients treated with LGG daily for relapsing C. difficile induced diarrhea, 84% were cured after two weeks of treatment. An additional three patients were cured upon retreatment with LGG resulting in a 94% cure rate among those patients [17].

Critical Thinking Questions:

1. What are the agents that cause gastroenteritis?
2. What mechanisms would explain the usefulness of probiotics in treating gastroenteritis?
3. Is there evidence for probiotic treatment of gastroenteritis?
4. What are the advantages and disadvantages for the use of probiotics compared to other treatments?
   

Allergic Responses

Allergic reactions resulting in asthma, allergic rhinitis, and atopic eczema have increased in economically developed nations. There have been a series of papers showing that the probiotic Lactobacillus rhamnosum strain GG (LGG) can prevent atopic eczema in infants [5], [18]. It has been proposed that the antiallergenic mechanism of action involves hydrolysis of Casein proteins, T-helper-1-type immunity, suppression of T-helper-2-induced allergic inflammation and induction of oral tolerance, and IgA production.

Majamma and Isolauri [5] studied thirty-one infants who were divided into a placebo group fed hydrolyzed whey formula and treatment group fed the same formula plus LGG. After one month there was a significant decrease in the extent and intensity of atopic eczema (dermatitis). A recent study [18] has shown that when LGG was given prenatally to women with a family history of atopic eczema or asthma and postnatally to their infants for six months, at two years of age the children given the probiotic had a 50% reduction in atopic eczema. This was a double-blind randomized trial. This study indicates that probiotics can be useful in treating early childhood allergic reactions. Critical Thinking Questions:

1. Why are allergic conditions on the increase?
2. What are the immunological responses that cause allergic reactions?
3. What are the common agents that modify allergic responses, and what are the most common mechanisms of action?
4. What may be the differences between probiotics and other allergy treatments?

Lactose Intolerance

Oral ingestion of the disaccharide lactose can cause severe intestinal distress with accompanying symptoms of flatulence, bloating, and abdominal pain in individuals with low levels of intestinal lactase. Kim and Gilliland [19] found that feeding fermented milk to individuals suffering from lactose-intolerance had a lower level of hydrogen in their breath when compared to the breath levels for subjects fed unfermented milk. High hydrogen levels in the breath is a marker for bacterial metabolism of lactose in the large bowel and indicates that lactose was not metabolized in the small intestine. Kolars et al. [20] compared lactose digestion for lactose deficient subjects fed yogurt or milk and these investigators found that yogurt consumption enhances lactose digestion. These favorable results have been attributed to b-galactosidase (lactase) levels in the probiotic bacteria.

Critical Thinking Questions:

1. What is the cause for lactose intolerance?
2. Do probiotics act by altering food composition and/or intestinal digestion?
3. Will the use of probiotics significantly increase the ability of people to consume dairy products?

Vaccine Adjuvant

Many vaccines do not elicit a maximal immunological response. Therefore, there is a need for adjuvants that enhance immunity. Isolauri et al. [21] tested Lactobacillus rhamnosum strain GG(LGG) as an adjuvant to an oral vaccine against rotavirus in children. The researchers noted an increase of rotavirus-specific IgM-secreting cells in the group receiving LGG compared to a group given placebo eight days postvaccination. LGG also increased IgA and IgM seroconversion when assayed in paired sera measured prior to vaccination and 30 days postvaccination. This study points to another interesting potential health benefit of probiotics.

Critical Thinking Questions:

1. Why are adjuvants often required for vaccines?
2. How could probiotics improve vaccine?
3. What vaccines may be improved by probiotics?