Year : 2014 | Volume
: 25 | Issue : 6 | Page : 1266--1269
Invasive Saccharomyces cerevisiae infection: A friend turning foe?
Unnikrishnan Pillai, Joe Devasahayam, Aparna Narayana Kurup, Alexandre Lacasse
Department of Internal Medicine, St. Mary's HealthCenter, St. Louis, MO, USA
Dr. Unnikrishnan Pillai
Department of Internal Medicine, St. Mary«SQ»s HealthCenter, St. Louis, MO
We report a very rare case of acute pyelonephritis in a 51-year-old female with a history of chronic kidney disease (CKD) and diabetes caused by a normally benign and a well-known human commensal organism, Saccharomyces cerevisiae that is very often prescribed as a probiotic in modern medical practice. The causal role of S. cerevisiae was confirmed by its isolation in blood, urine, stool as well as vaginal swabs thus proving its virulent nature in suitable situations.
|How to cite this article:|
Pillai U, Devasahayam J, Kurup AN, Lacasse A. Invasive Saccharomyces cerevisiae infection: A friend turning foe?.Saudi J Kidney Dis Transpl 2014;25:1266-1269
|How to cite this URL:|
Pillai U, Devasahayam J, Kurup AN, Lacasse A. Invasive Saccharomyces cerevisiae infection: A friend turning foe?. Saudi J Kidney Dis Transpl [serial online] 2014 [cited 2022 Aug 10 ];25:1266-1269
Available from: https://www.sjkdt.org/text.asp?2014/25/6/1266/144265
S. cerevisiae , a non-spore forming yeast, also known as brewer's yeast or baker's yeast, is a common colonizer of the human respiratory, gastrointestinal and urinary tracts and is generally considered as a benign organism. Its role as a clinically important and invasive pathogen is not well known. However, cases have been reported to cause invasive diseases in the setting of chronic underlying diseases like malignancy, HIV/ AIDS or of bone marrow transplantation. , There are very few case reports on invasive S. cerevisiae, and it causing acute pyelonephritis probably has never been reported. Here we report a case of acute pyelonephritis in a 51 year old female with a history of chronic kidney disease (CKD) and diabetes.
Our patient is a 51-year-old African-American female with history of stage 5 chronic kidney disease and diabetes mellitus who presented with a oneweek history of generalized weakness and worsening left flank pain, with fever, chills and burning pain during urination. Her medications included Amlodipine, Thiamine, Folic acid, Metoprolol, Sodium bicarbonate and insulin.
Physical examinations revealed a blood pressure of 140/90 mm Hg, pulse rate of 116/min, respiratory rate of 20/min and temperature of 110.1°F. The patient had hepatomegaly (6 cm) and left costo-vertebral angle tenderness. Pertinent laboratory results included a white blood cell count of 8.5 × 10 3 /μL (reference range 4.5- 10.8 × 10 3 /μL), hemoglobin 8.4 g/dL (reference range 13.5-17.5 g/dL), blood urea nitrogen 62 mg/dL (reference range 9-20 mg/dL), creatinine 4.5 mg/dL (reference range 0.6-1.2 mg/dL) and an estimated glomerular filtration rate of 12. Her baseline blood urea nitrogen and creatinine was 42 mg/dL and 3.0 mg/dL, respectively. Her glycated hemoglobin was 9.8%, indicating suboptimal diabetic control. Rapid HIV test was negative. Renal ultra-sonogram revealed left hydronephrosis with doubtful renal calculi in the left ureter. Computed tomography of the abdomen without contrast was performed, which showed dilated left ureter with significant perinephric and periureteric stranding. There was left hydronephrosis and 5 mm calcification of the left base of the bladder suggestive of distal left ureteric stone. Culture of blood performed on the day of admission grew S. cerevisiae, an unusual pathogen to grow from blood. Her urine culture, stool culture and vaginal swab culture grew significant colony counts of Saccharomyces cerevisiae. Fungus isolated in the blood was sensitive to amphotericin, micafungin and fluconazole. Extensive review of her previous culture reports revealed that she never had any fungemia. The patient was treated with micafungin and her symptoms resolved. Repeat blood culture and urine culture were negative. She was then planned for a surgical removal of renal stone. But, the patient had relief of symptoms and repeat ultrasonogram revealed passage of stone with resolution of hydroureter. Her renal function returned back to her baseline. The patient was discharged home with arrangement for home intravenous antifungal treatment for a full course of 14 days.
S. cerevisiae , also known as brewer's yeast or baker's yeast, is a common colonizer of human mucosal surfaces. Its role as a clinically important and invasive pathogen is not well known. There are very few case reports on invasive S. cerevisiae, and it causing acute pyelonephritis probably has never been reported. S. cerevisiae being a common colonizer and saprophytic contaminant, diagnosis may be often delayed and underestimated with potential lethal consequences.
It is a non-spore forming yeast, belonging to the family Saccharomycetaceae. Its nomenclature is derived from Latinized Greek meaning sugar mould, i.e. "Saccharo" meaning sugar and "myces" meaning mould or fungus. Cerevisiae comes from the latin word meaning "beer". S. cerevisiae is a single celled eukaryotic organism with a short generation time (doubling time 1.25-2 h) at 30°C (86°F) and can be easily cultured.  It has also been used as a probiotic. This organism is also used widely in the commercial setting for brewing beer and for providing CO 2 for underwater aquatic plants by "CO 2 injection by yeast technique." S. cerevisiae does not produce toxins that are harmful to humans or animals. However, it is capable of producing what are known as "killer toxins" that are fatal to other yeasts. S. cerevisiae is used in food and beverage preparation facilities to control the contamination of fermentation production areas by other kinds of yeasts. Heat-killed Saccharomyces cerevisiae (HKY) used as a vaccine protects mice against systemic aspergillosis and coccidioidomycosis. 
S. cerevisiae is a common colonizer of the human respiratory, gastrointestinal and urinary tracts and is generally considered as a benign organism. However, cases have been reported to cause invasive diseases in the setting of chronic underlying diseases like malignancy, HIV/AIDS or of bone marrow transplantation. , The evidences are in favor of the increased vulnerability of the host rather than the increased virulence of the pathogen in causing invasive disease. Pathogenic strains of S. cerevisiae exhibit the ability to grow at 42°C, produce proteinase and are capable of pseudohyphal growth. S. cerevisiae is often isolated with other forms of yeast, and it is rarely isolated as a single pathogen in yeast-induced vaginitis. One report on three cases of invasive S. cerevisiae infection causing pneumonia, liver abscess and sepsis indicates that pathogenic isolates of this yeast are capable of tissue invasion and dissemination. There are limited cases showing an association of this yeast and ingestion of vitamins and brewer's yeast. S. boulardii, used commonly as a biotherapeutic agent for chronic and recurrent diarrhea, is a strain of S. cerevisiae that has been implicated in a few cases of fungemia. S. boulardii analysis has revealed moderate virulence levels when tested in murine models of systemic infection. Hence, caution is recommended when using this yeast to control this condition in severely ill or immunocompromised hosts. There are case reports of S. cerevisiae affecting newborns, where there is a mention of horizontal transmission of the disease from the primarily affected newborn that developed fungemia secondary to treatment with S. boulardii.
Although very rare, S. cerevisiae can cause invasive infections like pyelonephritis in immune-competent patients also, as in our case. There have been case descriptions of infection in patients with an indwelling catheter, prosthetic valves  and in bone marrow transplant patients.  In our patient, the presence of the renal stone could have caused obstruction of the urinary flow and hence had become a nidus for this organism, further confounded by a "semi-immunocompromised" state due to advanced chronic kidney disease and poorly controlled diabetes mellitus. With our patient having definite clinical and radiologic evidence of acute pyelonephritis, isolates of S. cerevisiae were found in literally all the bodily secretions; hence, proving that this normally benign organism could turn dangerously virulent in suitable conditions.
Diagnosing Saccharomyces infection is difficult as it is a normal flora in the human body. Isolating S. cerevisiae from the part of the body where it is normally colonized does not add much to clinical suspicion when the clinical symptoms and signs are subtle. However, the decision to attribute a causal role to S. cerevisiae is easier when the organism is isolated from a normally sterile body site, and the patient should be treated for an invasive fungal infection. There is no commercially available serological test for Saccharomyces. However, S. cerevisiae readily grows in blood cultures and on Sabouraud dextrose media.
Saccharomyces are susceptible to most anti-fungal drugs, including amphotericin B, 5-flucytosine, ketoconazole, fluconazole, itraconazole, voriconazole, posaconazole and isavuconazole, ,, although resistance to azoles have been reported.  However, most Saccharomyces isolates have higher minimum inhibitory concentrations (MIC) to most antifungal drugs than does Candida albicans. Patients would generally require a full two week course of medical treatment. Because the use of probiotic agents is widely prevalent in modern day practice, physicians need to be cognizant about this potential complication.
Even in people who have no prior exposure to probiotic agents, in the setting of impaired immune response, S. cerevisiae can cause invasive disease. In our patient, the fact that she had advanced chronic kidney disease and obstructive uropathy may have predisposed her to have invasive infection. Although this disease could be fatal, appropriate suspicion for this organism in susceptible persons, early recognition and treatment with anti-fungal medicines can cure the infection.
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