Other Hyaline Moulds
Beyond Aspergillus, Fusarium, Scedosporium, and Mucorales, a group of hyaline (and some lightly pigmented) environmental moulds cause opportunistic infection, usually in people with neutropenia, transplantation, corticosteroid use, burns, and implanted devices. They are called hyalohyphomycoses, with septate hyaline hyphae in tissue that cannot be separated from Aspergillus by morphology.
The main difficulties are identification, interpretation of a single positive culture (contamination or colonisation versus invasion), and resistance to amphotericin B and azoles. Susceptibility testing and species identification guide therapy.
| Genus and species | Habitat | Typical disease | Susceptibility and therapy |
|---|---|---|---|
| Purpureocillium lilacinum (formerly Paecilomyces lilacinus) | Soil, decaying vegetation, water | Keratitis, endophthalmitis after intraocular lens implantation, cutaneous and subcutaneous infection, sinusitis, catheter infection, fungaemia, and pulmonary infection | Resistant to amphotericin B and echinocandins; usually susceptible to voriconazole, posaconazole, and isavuconazole; terbinafine used in combination |
| Paecilomyces variotii | Soil, food, air; thermophilic | Peritonitis in peritoneal dialysis, catheter infection, endocarditis, and skin infection | Susceptible to amphotericin B, itraconazole, posaconazole, and voriconazole |
| Scopulariopsis brevicaulis and Scopulariopsis gracilis | Soil, plant matter | Onychomycosis, skin infection, and invasive pulmonary and disseminated disease in lung and stem cell transplant | Often resistant to amphotericin B, azoles, and echinocandins; terbinafine active in some; surgery |
| Acremonium complex and Sarocladium kiliense, Sarocladium strictum | Soil, plants | Eumycetoma, keratitis, fungaemia and catheter infection, endocarditis, osteomyelitis; outbreaks from contaminated products | Variable; amphotericin B and voriconazole often active against some species; susceptibility testing needed |
| Trichoderma species (Trichoderma longibrachiatum) | Soil, wood | Peritonitis in peritoneal dialysis, and invasive disease in stem cell transplant | Amphotericin B and echinocandins may be active; azoles variable |
| Penicillium species (non Talaromyces) | Ubiquitous | Keratitis, endophthalmitis, otomycosis, and pulmonary disease in the immunocompromised | Variable; amphotericin B and azoles often active |
| Rasamsonia species | Compost, hot environments | Invasive infection in chronic granulomatous disease | Resistant to amphotericin B in some species; azoles active |
| Metarhizium, Beauveria, Lecanicillium | Soil, insects | Keratitis and invasive disease in the immunocompromised | Variable |
| Geomyces (Pseudogymnoascus), Arthrographis, and others | Soil | Rare skin, nail, and invasive disease | Variable |
| Schizophyllum commune (a basidiomycete mould) | Wood | Allergic bronchopulmonary mycosis, sinusitis, and brain abscess | Voriconazole and amphotericin B active; sequencing is needed |
| Chrysosporium and related genera | Soil, keratin | Skin, nail, and invasive disease | Variable |
| Aspect | Details |
|---|---|
| Specimen | Tissue biopsy, bronchoalveolar lavage, sterile fluids, blood, and corneal material, with direct microscopy (calcofluor white), histology, and culture |
| Interpreting a single isolate | An isolate from a non sterile site such as sputum may be a contaminant; repeated isolation of one organism, a sterile site, or compatible histology establishes disease |
| Culture | Most grow within 2 to 7 days on Sabouraud dextrose agar at 25 to 37 degrees Celsius; identification needs microscopy (phialide shape and conidia), sequencing, and mass spectrometry |
| Molecular identification | Internal transcribed spacer, beta tubulin, translation elongation factor, or large subunit ribosomal DNA sequencing |
| Biomarkers | Galactomannan is negative or variable, and beta D glucan is often positive |
| Susceptibility testing | Reference method; resistance patterns are species specific |
| Element | Details |
|---|---|
| General principles | Identify to species level, test susceptibility, remove infected devices and tissue, reverse immunosuppression, and treat for weeks to months |
| Purpureocillium lilacinum | Voriconazole (standard intravenous or oral dose) or posaconazole or isavuconazole; avoid amphotericin B and echinocandins; keratitis needs topical natamycin or voriconazole, with surgery or removal of the intraocular lens |
| Scopulariopsis | Voriconazole or posaconazole with terbinafine; amphotericin B and surgery; resection of the infected lung; high mortality in invasive disease |
| Acremonium and Sarocladium | Choice by susceptibility, voriconazole or amphotericin B; remove catheters; debridement |
| Trichoderma | Amphotericin B or an echinocandin or voriconazole by testing; remove peritoneal catheters |
| Rasamsonia, Schizophyllum, and others | Voriconazole, posaconazole, or isavuconazole by susceptibility testing |
| Surgery | Debridement and resection of focal disease, drainage of abscesses, and removal of foreign bodies |
| Duration | Several weeks to months, until resolution and immune recovery; secondary prophylaxis with an azole during further immunosuppression |
Doses used in these infections are the usual regimens for invasive mould disease. There is limited evidence for each in these rare infections.
- Voriconazole 6 mg per kg intravenously every 12 hours for 2 doses then 4 mg per kg every 12 hours.
- Posaconazole delayed release tablets 300 mg every 12 hours on day 1 then 300 mg daily.
- Isavuconazonium sulphate 372 mg every 8 hours for 6 doses then 372 mg daily.
- Liposomal amphotericin B 3 to 5 mg per kg daily.
- Terbinafine 250 mg every 12 hours as part of combination therapy.
Outcome is good in localised cutaneous, ocular, and catheter related infection treated promptly with device removal and an active drug. It is poor in invasive and disseminated disease in neutropenic, transplant, and haematological patients, where mortality is 50 to 80 percent or higher and depends on immune recovery.
Prevention includes:
- Air and water control in haematology and transplant units.
- Avoidance of contaminated products (there have been outbreaks from contaminated saline, lidocaine, ophthalmic solutions, and implants).
- Strict aseptic technique during intraocular surgery and peritoneal dialysis.
- Treatment of nail disease before immunosuppression.
