Probiotics and Parasitic Infections
Probiotics, while not as powerful as traditional antimicrobials, can be helpful in the prevention and treatment of parasitic infections, especially when combined with antimicrobials.
- Parasites and mutualists
- Entamoeba histolytica and Giardia lamblia
- Trichomoniasis and Candidiasis
- References and further reading:
Parasites and mutualists
Parasitic infections stem from non-bacterial organisms that live in us or on us, including protozoa, and do us harm. In contrast, mutualists are organisms that live in us or on us and do us good, improving our health or protecting us from harmful organisms. Mutualistic organisms, when ingested as part of the diet, are known as "probiotics".
One of the most important categories of mutualistic microorganisms is that of the natural intestinal bacteria. According to Dr. Elisabeth Bik of the Stanford University School of Medicine (1), the colon is colonized by more than a trillion organisms per gram of intestinal contents; the number of bacterial cells inside us is actually higher than the number of our own cells! The vast majority of these fall within four phyla (major groups) of bacteria: Firmicutes (including Lactobacillus), Bacteroidetes, Actinobacteria, and Proteobacteria (including the familiar E. coli) (1). Bacteria commonly ingested in probiotic foods include lactobacilli (found in yogurt) and bifidobacteria. In addition, Saccharomyces (yeast, a fungus) is another beneficial microorganism used as a probiotic.
Entamoeba histolytica and Giardia lamblia
Entamoeba histolytica is a severely invasive amoeba that causes bloody diarrhea, among other symptoms. This parasite infects over 50 million people each year, and causes 100,000 deaths (2). In a study comparing the efficacy of the antimicrobial metronidazole alone vs. together with the probiotic yeast Saccharomyces boulardii, researchers found that, while both treatments were effective, the addition of S. boulardii decreased the duration of bloody diarrhea and enhanced the elimination of E. histolytica cysts (3). In addition, S. boulardii has been found to be helpful in the elimination of Giardia lamblia, another protozoan parasite that causes diarrhea and other intestinal symptoms (4). The probiotic bacterium Lactobacillus casei has also been used to treat Giardia infection. Treatment with L. casei reduced both the severity and the duration of giardiasis in malnourished mice (5).
Trichomoniasis and Candidiasis
Trichomoniasis, a sexually transmitted parasitic disease, is caused by Trichomonas vaginalis, a flagellate protozoan (6). The effects of probiotics, particularly Lactobacillus, on Trichomoniasis are currently being investigated. Preliminary results from some studies show that there may be a small beneficial effect of Lactobacillus on Trichomonas infection. One study found a small but significant positive effect, with high levels of Lactobacillus associated with lower rates of Trichomonas infection in women with greater than a high school education (7). In addition, Lactobacillus may be helpful in the prevention of Candidiasis (infection with yeast organisms of the genus Candida) in women with HIV (8).
Malaria, caused by parasites of the genus Plasmodium, is the most important of the parasitic diseases worldwide, in terms of morbidity and mortality, with hundreds of millions of clinical episodes and up to one million deaths, according to WHO 2008 data (9). In a study of Lactobaciilus casei and Plasmodium chabaudi, a malarial parasite of mice, a subspecies of this probiotic bacterium, Lactobacillus casei ssp. rhamnosus, was found to enhance resistance to P. chabaudi; the infection took longer to become symptomatic, the number of parasites was reduced, and the viability (ability to survive) of parasites recovered from the spleen of infected mice was lowered (10).
While not as strong a treatment option as antimicrobials, probiotics may be helpful in the prevention and treatment of parasitic infections, especially when combined with antimicrobials.
References and further reading:
1. Bik EM. (2009) Composition and function of the human-associated microbiota. Nutrition Reviews: 67:S164–S171.
2. Bercu TE, Petri WA, Behm JW, 2007. Amebic colitis: new insights into pathogenesis and treatment. Curr Gastroenterol Rep 9: 429–433
3. Dinleyici EC, Eren M, Yargic ZA, Dogan N, Vandenplas Y. Clinical efficacy of Saccharomyces boulardii and metronidazole compared to metronidazole alone in children with acute bloody diarrhea caused by amebiasis: a prospective, randomized, open label study. Am J Trop Med Hyg. 2009 Jun;80(6):953-5.
4. Bercu TE, Petri WA, Behm JW, 2007. Amebic colitis: new insights into pathogenesis and treatment. Curr Gastroenterol Rep 9: 429–433
5. Shukla G, Sidhu RK. Lactobacillus casei as a probiotic in malnourished Giardia lamblia-infected mice: a biochemical and histopathological study. Can J Microbiol. 2011 Feb;57(2):127-35.
6. CDC. http://www.dpd.cdc.gov/dpdx/HTML/Frames/S-Z/Trichomoniasis/body_Trichomoniasis_page1.htm#Causal%20Agent
7. Torok MR, Miller WC, Hobbs MM, Macdonald PD, Leone PA, Schwebke JR, Sena AC. The association between Trichomonas vaginalis infection and level of vaginal lactobacilli, in nonpregnant women. J Infect Dis. 2007 Oct 1;196(7):1102-7.
8. Williams AB, Yu C, Tashima K, Burgess J, Danvers K. Evaluation of two self-care treatments for prevention of vaginal candidiasis in women with HIV. J Assoc Nurses AIDS Care. 2001 Jul-Aug;12(4):51-7.
9. CDC. http://www.cdc.gov/malaria/about/facts.html
10. Martínez-Gómez F, Ixta-Rodríguez O, Aguilar-Figueroa B, Hernández-Cruz R, Monroy-Ostria A. Lactobaciilus casei ssp. rhamnosus enhances non specific protection against Plasmodium chabaudi AS in mice. Salud Publica Mex. 2006 Nov-Dec;48(6):498-503.