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Journal of Clinical Microbiology, November 2003, p. 5340-5343, Vol. 41, No. 11
0095-1137/03/$08.00+0 DOI: 10.1128/JCM.41.11.5340-5343.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Outbreak of Saccharomyces cerevisiae Subtype boulardii Fungemia in Patients Neighboring Those Treated with a Probiotic Preparation of the Organism
Marco Cassone,1* Pietro Serra,1 Francesca Mondello,2 Antonietta Girolamo,2 Sandro Scafetti,3 Eleonora Pistella,1 and Mario Venditti1
III Clinica Medica, Dipartimento di Medicina Clinica, Università degli Studi di Roma "La Sapienza,",1
Dipartimento di Malattie infettive, parassitarie ed immunomediate, Istituto Superiore di Sanità,2
Reparto di Rianimazione e Terapia Intensiva, Ospedale "Sandro Pertini," Rome, Italy3
Received 4 February 2003/
Returned for modification 26 April 2003/
Accepted 7 August 2003

ABSTRACT
We report an outbreak of
Saccharomyces cerevisiae subtype
boulardii fungemia among three intensive care unit roommates of patients
receiving lyophilized preparations of this fungus. The fungemia
was probably due to central venous catheter contamination and
resolved after fluconazole treatment. The need for stringent
application of proper hygiene when using a probiotic preparation
of this organism is emphasized.

CASE REPORTS
Outbreak cases. (i) Case 1.
Case 1 involved a 34-year-old man hospitalized for hypoxia after
head and thoracic trauma. He was placed on enteral nutrition,
with insertion of a central venous catheter (CVC), and broad-spectrum
antibiotic therapy was administered. On day 42 after admission
(5 November 2000), he developed a fever, which was unsuccessfully
treated with teicoplanin and imipenem. Multiple blood cultures
yielded
Saccharomyces cerevisiae. The fever and fungemia subsided
under treatment with fluconazole at 400 mg/day. The CVC was
removed 3 weeks after initiation of fluconazole treatment. The
infectious episode resolved, but no catheter culture was performed.
(ii) Case 2.
Case 2 involved a 48-year-old man hospitalized for rupture of a cerebral aneurysm and fever. He was given enteral nutrition, and a CVC was inserted. Teicoplanin alone and then teicoplanin and meropenem were administered. On day 14 (10 November 2000), one blood culture yielded S. cerevisiae. On day 19, the CVC was removed and fluconazole therapy (400 mg/day) was immediately started. No catheter culture was performed. The fever subsided within 48 h of the initiation of fluconazole treatment.
(iii) Case 3.
Case 3 involved a 75-year-old woman admitted for acute myocardial infarction. She was given enteral nutrition, and a CVC was inserted. She was treated with various antibiotic regimens for several febrile episodes. On day 56 (10 April 2001), a blood culture yielded S. cerevisiae. The CVC was removed, leading to immediate defervescence. The CVC tip was positive for S. cerevisiae. Fluconazole therapy (400 mg/day) was started 2 days later and administered for 2 weeks.
None of the three patients described above received any probiotic treatment.
Case 4 (incomplete report).
A 35-year-old woman with multiple traumas who had been hospitalized in the intensive care unit (ICU) at the same time as patients 1 and 2 had blood cultures positive for S. cerevisiae. Unfortunately, her medical record was sequestered for forensic purposes and whether she had received probiotic treatment or not could not be determined. This patient improved and was transferred to the orthopedic division, from which she was discharged 2 months later.
The outbreak setting was an eight-bed ICU in a 400-bed secondary-care hospital in Rome, Italy. During the year preceding the outbreak, about 20% of the ICU patients were hospitalized for emergency surgery, 12% were hospitalized for elective surgery, 18% were hospitalized for trauma, and 50% were hospitalized for medical diseases. The mean (± standard deviation) age of patients was 66 ± 16 years, the mean ICU hospitalization time was 17 ± 18 days, and the mortality rate was 25%.
The ICU consists of a large room with the beds arranged in a semicircle, two small single-patient rooms, and the nurse's room, where drugs, medical records, and computer equipment are kept. There are four sinks in the patient rooms (two in the large one and one each in the small ones). All of these rooms have direct, independent access to the corridor.
A probiotic preparation labeled Codex (Zambon Farmaceutici, Vicenza, Italy) and declared to contain 250 mg of lyophilized Saccharomyces boulardii (see below for correct taxonomy) had been in use at the ICU since 1999. It was usually administered by a nurse wearing standard latex gloves, who opened the package containing the probiotic powder and dissolve it close to a sink located approximately 3 m from the nearest bed in the six-patient room. For administration of the probiotic preparation, the full content of the package was directly poured into the cylinder of a 50-ml syringe to which 30 ml of saline solution was added. The probiotic suspension was finally administered via the enteral nutrition tube.
In October 2000 (just before the outbreak), the probiotic preparation had been administered to four patients but not to the three patients involved in the outbreak (cases 1 to 3) reported in this study. After the first two cases of fungemia occurred, the probiotic preparation was not used further for 3 months. Importantly, the third case of fungemia was diagnosed about 1 month after reintroduction of the probiotic preparation into prophylactic regimens. Consequently, the probiotic preparation was no longer used.
The microorganism was initially identified by growth on Sabouraud chloramphenicol agar and by an automated biochemical identification panel (API Italia). A karyotype obtained by pulsed-field gel electrophoresis, which was performed in accordance with the protocol of Petersen et al. (11), provided a comparison between the two available isolates from the patients and the yeast contained in a package of the probiotic preparation that had been stored in the ICU's pharmacy. All of the yeast isolates were identical (Fig. 1), thus confirming both the exact identification as S. cerevisiae and the clonal relationship of the clinical isolates with the probiotic agent.
In recent years, invasive fungal infections due to new or unusual
agents have been frequently reported worldwide. This is currently
considered to be a consequence of an increase in the population
at risk for chronic or debilitating diseases, increased use
of immunosuppressive drugs or broad spectrum antibiotics, as
well as parenteral nutrition, and use of CVCs. Freeze-dried
preparations labeled
S. boulardii are used in several countries
as a biotherapeutic agent to prevent antibiotic-induced diarrhea
in ICU patients (
2). This treatment has also been proposed for
Crohn's disease and other inflammatory bowel conditions (
5).
Overall, it is considered to be safe and well tolerated (
8).
Although
S. boulardii is, according to official taxonomic definitions,
simply a subtype of the species
S. cerevisiae, we will consider
here only the fully described cases of fungemia that have been
attributed to this subtype and not all cases of
S. cerevisiae fungemia. Fungemia caused by
S. cerevisiae subtype
boulardii should not be considered rare. To our knowledge, 24 well-described
clinical cases have been reported in the literature (
1,
3,
4,
6,
7,
9,
10,
13-
16) (Table
1). In a further report, 12 (93%)
of 13
S. cerevisiae blood isolates collected in five hospitals
over a 2-year period were retrospectively subtyped as
S. cerevisiae subtype
boulardii, and their etiologic role in fungemias was
demonstrated by a genotypic comparison with commercial preparations
labeled
S. boulardii (
12). Moreover, single cases, especially
in patients receiving oral therapy, are unlikely to be published.
Importantly, fungemia by
S. cerevisiae subtype
boulardii can
occur in patients who are not treated with a probiotic preparation
of this organism when they share a room with treated patients
(Table
1 and Fig.
2), as a result of airborne or interpersonal
colonization. It has been demonstrated that after a package
of freeze-dried yeast is opened, viable cells persist on room
surfaces after 2 h at a 1-m distance and may persist on the
bare hands of operators even after vigorous hand washing (
6).
Two studies have so far reported a case of fungemia in a patient
not receiving
S. cerevisiae subtype
boulardii therapy (
7,
10).
However, our study is the first one describing multiple contemporary
cases of
S. cerevisiae subtype
boulardii fungemia in patients
in the same ward who did not receive a probiotic preparation
of this organism as biotherapeutic treatment.
Contamination of a CVC insertion site is likely to be one of
the main mechanisms of
S. cerevisiae subtype
boulardii fungemia,
as suggested by Hennequin et al. (
6). In our study, the role
of CVCs in the pathogenesis of the infection has been demonstrated
by CVC tip culture (in one of our patients), and it is also
probable in the other two cases since neither patient was orally
administered the probiotic preparation. Fungemias are not limited
to immunocompromised patients (Fig.
2), and for this reason,
S. cerevisiae subtype
boulardii should be considered a potentially
dangerous microorganism. Although no case of death clearly attributable
to fungemia due to this yeast has been reported, two studies
documented septic shock in the presence of positive blood cultures
that yielded
S. cerevisiae subtype
boulardii as a single isolate
(
6,
10). In one case, fungemia developed despite prophylactic
antifungal treatment (
3). In several additional cases, this
microorganism was the only cause of fever in debilitated patients
in which the metabolic stress caused by fever could have contributed
to a downward prognostic shift unless prompt therapy was instituted.
Four patients (three of whom were treated with antifungal agents)
died, but death was not attributed to fungemia (
7,
14) (Table
1). All of the other cases described in the literature and the
three patients described here as well had a rapid response,
even if they were immunocompromised, after suspension of treatment
with the probiotic preparation, CVC removal, and/or antifungal
therapy. These observations, taken together, underscore the
prognostic importance of the rapid diagnosis of fungemia.
Decreased susceptibility to fluconazole was reported in some strains of S. cerevisiae subtype boulardii (6), although this did not lead to therapeutic failure. However, none of the patients reported in the literature had any intravascular devices, such as prosthetic valves or aorto-bifemoral grafts, that could be contaminated during fungemia and could be potential factors of increased risk of fungemia and therapeutic failure.
In conclusion, we describe the largest outbreak of S. cerevisiae subtype boulardii fungemia involving patients not receiving biotherapy with the fungus. A review of the literature showed that (i) fungemias can occur in immunocompetent patients and may contribute to morbidity and mortality in immunocompromised patients, (ii) enteral translocation of ingested microorganisms and CVC insertion site contamination are the main portals of entry into the bloodstream, (iii) prevention of CVC-related fungemias can be achieved by simple prophylactic measures, and (iv) fluconazole and amphotericin B are effective therapeutic options; CVC removal alone was also effective in some cases.
Finally, our study emphasizes the risk of infection if the package containing the lyophilized fungal preparation is opened in a patient's room and without proper infection control precautions, such as changing gloves before administration of the probiotic preparation and careful hand washing.

FOOTNOTES
* Corresponding author. Mailing address: Department of Molecular Biology, University of Siena, Policlinico "Le Scotte," lotto 5, piano 1, Viale Bracci, 53100 Siena, Italy. Phone: 390577233373. Fax: 390577233334. E-mail:
mcassone{at}libero.it.


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Journal of Clinical Microbiology, November 2003, p. 5340-5343, Vol. 41, No. 11
0095-1137/03/$08.00+0 DOI: 10.1128/JCM.41.11.5340-5343.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
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