Probiotic use in the critically ill.

Probiotics are "live microbes which when administered in adequate amounts confer a health benefit to the host" (FAO/WHO joint group). Their potential role in bio-ecological modification of pathological internal milieu of the critically ill is under evaluation. Probiotics are available as single microbial strain (e.g., Bacillus clausii, Lactobacillus) or as a mix of multiple strains of Lactobacillus (acidophilus, sporogenes, lactis, reuteri RC-14, GG, and L. plantarum 299v), Bifidobacterium (bifidum, longum, infantis), Streptococcus (thermophillus, lactis, fecalis), Saccharomyces boulardii etc. Lactobacilli and Bifidobacteria are gram-positive, anaerobic, lactic acid bacteria. These are normal inhabitant of human gut and colonize the colon better than others. Critical illness and its treatment create hostile environment in the gut and alters the micro flora favoring growth of pathogens. Therapy with probiotics is an effort to reduce or eliminate potential pathogens and toxins, to release nutrients, antioxidants, growth factors and coagulation factors, to stimulate gut motility and to modulate innate and adaptive immune defense mechanisms via the normalization of altered gut flora. Scientific evidence shows that use of probiotics is effective in prevention and therapy of antibiotic associated diarrhea. However, available probiotics strains in currently used doses do not provide much needed early benefits, and need long-term administration to have clinically beneficial effects (viz, a reduction in rate of infection, severe sepsis, ICU stay, ventilation days and mortality) in critically ill surgical and trauma patients. Possibly, available strains do not adhere to intestinal mucosa early, or may require higher dose than what is used. Gap exists in our knowledge regarding mechanisms of action of different probiotics, most effective strains--single or multiple, cost effectiveness, risk-benefit potential, optimum dose, frequency and duration of treatment etc. More information is needed on safety profile of probiotics in immunocompromised state of the critically ill in view of rare reports of fungemia and sepsis and a trend toward possible increase in nosocomial infection. At present, despite theoretical potential benefits, available evidence is not conclusive to recommend probiotics for routine use in the critically ill.