Introduction: The Pink Enemy
In 2014, a 28-year-old man with Hodgkin's lymphoma died after a relentless battle against fungal meningitis. The culprit? A yeast called Rhodotorula mucilaginosa, identified only after 40 days of investigation 4 . This case symbolizes a paradox of modern medicine: a microorganism once considered harmless, common in soils and oceans, has transformed into a silent threat in hospitals. With mortality rates reaching 46% in central nervous system infections and 15% in fungemia, Rhodotorula species emerge as opportunistic pathogens in immunocompromised patients, challenging diagnostics and therapies 2 5 .
Key Fact
Rhodotorula infections have mortality rates up to 46% in CNS infections and 15% in bloodstream infections, particularly affecting immunocompromised patients.
1. What is Rhodotorula?
Rhodotorula spp. belong to basidiomycetes, a group of spore-producing fungi. Their colonies display a coral or salmon pink color due to the production of carotenoids like β-carotene 8 . Three species stand out clinically:
R. mucilaginosa
Accounts for 70% of human cases
R. glutinis
7% of reported cases
R. minuta
Rare clinical cases
Their resistance to adverse conditions explains their ubiquity: found in soil, water, fruits, and even toothbrushes 7 . In the human body, they colonize skin, nails, and the gastrointestinal tract, behaving as commensals until immunity fails.
Figure 1: Rhodotorula mucilaginosa colonies showing characteristic pink color (Source: Science Photo Library)
2. Why an Emerging Pathogen?
The rise of Rhodotorula is intrinsically linked to medical advances:
Venous and dialysis catheters serve as "bridges" for infections. Rhodotorula biofilms adhere to plastic, forming barriers against antifungals 6 .
Patients with cancer, diabetes or undergoing chemotherapy are vulnerable. A Brazilian study with 243 chronic renal patients showed oral colonization by R. mucilaginosa in 12% of cases 6 .
As they are intrinsically resistant to fluconazole, they prosper when this drug eliminates competing fungi 7 .
Critical Data: 80% of invasive infections occur in patients with prolonged venous catheters .
3. Clinical Manifestations: Beyond Fungemia
Although fungemia is the most common presentation (60% of cases), Rhodotorula causes serious infections in multiple organs:
| Infection Site | Reported Cases | Risk Factors |
|---|---|---|
| Blood (Fungemia) | ~60% | Venous catheter, parenteral nutrition |
| Nervous System | 13 cases (46% mortality) | Lymphoma, chemotherapy |
| Peritoneum | 10 cases (CAPD) | Peritoneal dialysis, antibiotic therapy |
| Liver (Biloma) | Single case | Liver trauma, percutaneous drainage |
Emblematic case: A 31-year-old patient with grade IV liver injury post-accident developed a biloma infected by R. mucilaginosa. The infection persisted despite drainage and fluconazole, requiring hemihepatectomy and amphotericin B 1 .
Figure 2: Distribution of Rhodotorula infection sites based on reported cases
4. The Diagnostic Challenge: Delays and Pitfalls
Identifying Rhodotorula requires combined methods:
Culture
Grows in 48-72h on Sabouraud agar, forming pink colonies.
MALDI-TOF
Rapid confirmation by mass spectrometry.
PCR-ITS
Sequencing of the ITS region for species differentiation 6 .
Common Problems:
- Sample contamination (present on hospital surfaces)
- Confusion with Cryptococcus (both are encapsulated yeasts)
- Prolonged time for molecular identification (up to 4 weeks) 4
5. Antifungal Resistance: A Therapeutic Maze
Rhodotorula exhibits an intrinsic resistance profile that limits options:
| Antifungal | MIC (μg/mL) | Status |
|---|---|---|
| Amphotericin B | 0.25–0.5 | Active |
| Fluconazole | 32–128 | Resistant |
| Voriconazole | 0.015–2 | Variable |
| Echinocandins | >8 | Resistant |
| Flucytosine | 0.06 | Active |
Figure 3: Antifungal susceptibility profile of Rhodotorula spp.
Standard Treatment:
- Immediate removal of infected catheters
- Liposomal amphotericin B (3–5 mg/kg/day) for ≥2 weeks
- Flucytosine in combination for CNS infections 4