Saccharomyces boulardii, a non-pathogenic yeast very commonly used in the bakery industry, is also used as probiotic therapy in a variety of conditions. Its use has been increasing rapidly, even in very small children [1]. Probiotic treatment with S. boulardii is reported to cause invasive fungemia by the related subtype S. cerevisiae. This is found particularly in premature infants and those with underlying immunocompromised state or with chronic debilitating conditions.

A 3½-month-old male infant was admitted with history of watery diarrhea for three days. The child had three episodes of respiratory tract infection since one month of age, which had been treated with oral antibiotics. In order to prevent antibiotic-associated diarrhea, the baby had also been prescribed probiotic preparation containing S.boulardii 250 mg twice daily for the 10 days during each episodes. The baby was born at term gestation by Cesarean section and his birth weight was 2.7 kg. He was the first baby born to non-consanguineous parents. His weight on admission was 3.9 kg (<3rd percentile). For unspecified reasons, the baby had not received any vaccines since birth. During the current admission, the child was malnourished and dehydrated. He had intermittent fever (up to 102°F), and erythematous macular skin rashes over the trunk and limbs. The liver was enlarged, there was no splenomegaly. There were few discrete palpable lymph nodes in the cervical region (<1 cm). Blood investigations revealed hemoglobulin of 11.4 g/dL and total WBC count of 3400 with 74% neutrophils. The C-reactive protein was mildly raised; liver and renal function tests were normal. Malarial parasite and dengue antigen tests were negative. The urine culture was sterile. Chest X-ray revealed prominent bronchovascular markings on either side, with a barely discernible thymic shadow. The blood culture grew the fungus S.cerevisiae, sensitive to Amphotericin B and Caspofungin. The parents shifted the baby to another hospital for financial reason where he was treated with a two week course of intravenous Amphotericin B. Immunological work-up performed during this period revealed combined T and B cell deficiency (Table I). The parents declined any further genetic tests, and got the infant discharged against medical advice. They did not come for follow-up.

TABLE I	Immunological Tests for T cell and B Cell  Function in the Patient with S. cerevisiae Sepsis

Invasive fungal sepsis by the normally non-pathogenic strains of S. cerevisiae following therapy with S. boulardii is being reported increasingly. S. boulardii strains are asporogenous strains of S. cerevisiae, and hence should not be regarded as a different species [2].

S. cerevesiae is responsible for 0.1-3.6% of all fungemia; the incidence having been on the rise since the introduction of S. boulardii as probiotic in 1991 [3]. Most cases of S. cerevisiae fungemia, have been described in infants [4]. All such infants have underlying conditions such as prematurity, acute leukemia, congenital malformations, burns, abdominal surgery, severe neutropenia or permanent central venous catheters [1,5].

S. boulardii in a dose of 250-750 mg/day typically for 5-7 days is recommended treatment in addition to rehydration therapy in acute gastroenteritis has been shown to be effective in prevention of antibiotic-associated diarrhea [6]. The safety profile of probiotic preparations are generally considered satisfactory but caution must be exercised when prescribing them to patients with suspected compromise of the immune status. If underlying immunodeficiency is missed or overlooked, this seemingly harmless medication may have devastating consequences.

6. Szajewska H, Canani R, Guarino A, Hojsak I, Indrio F, Kolacek S, et al. Probiotics for the prevention of antibiotic-associated diarrhea in children. J Pediatr Gastroenterol Nutr. 2016;62:495-506.