Opportunistic Mycoses Part 3 Flashcards
• At risk: acidosis, diabetes mellitus, leukemias, lymphoma, corticosteroid treatment, severe burns, immunodeficiencies, dialysis with iron chelator deferoxamine.
MUCORMYCOSIS
Zygomycosis
MUCORMYCOSIS
Zygomycosis
• Most prevalent:
Rhizopus oryzae
MUCORMYCOSIS
Zygomycosis
• Leading pathogens:
Rhizopus, Rhizomucor, Lichtheimia,
Cunninghamella, Mucor, etc.
• An opportunistic mycosis caused by a number of molds classified in the order Mucorales.
MUCORMYCOSIS
Zygomycosis
MUCORMYCOSIS
Zygomycosis
Major clinical form
: rhinocerebral mucormycosis
• Germination of sporangiospores in the nasal passages and invasion of hyphae into the blood vessels causing thrombosis, infarction, and necrosis
• Invasion: sinuses, eyes, cranial bones, brain
• Edema in involved facial area, a bloody nasal exudate, and orbital cellulitis; thoracic mucormycosis
rhinocerebral mucormycosis
TREATMENT:
• Aggressive surgical debridement
• Rapid administration of amphotericin B
• Control of underlying disease
Many patients survive, but there may be residual effects such as partial facial paralysis or loss of an eye.
MUCORMYCOSIS
Zygomycosis
Direct examination or culture of nasal discharge, tissue, or sputum will reveal:
• BROAD HYPHAE (10-15 um) with UNEVEN THICKNESS, IRREGULAR BRANCHING, &
SPARSE SEPTATIONS.
• Grow rapidly on lab media with abundant cottony colonies.
• Identification is based on the
SPORANGIAL STRUCTURES.
MUCORMYCOSIS
Laboratory diagnosis
Histopathological staining or methenamine silver stain of tissue biopsies shows broad aseptate hyaline hyphae with wide-angle branching
Culture on SDA at 25°C: White cottony woolly colonies with tube filling growth (hence called lid lifters).
MUCORMYCOSIS
- colonies become brown black later, due to sporulation giving rise to salt and pepper appearance
Rhizopus
MUCORMYCOSIS
______ : very slapse; white becoming brownish grey to some tendency to
blackish grey
Sporangiospores - smooth walled, nonseptate, simple or branched, arising from stolons opposite rhizoids usually in groups of three or more.
Rhizopus oryzae (R. arrhizus, R. stolonifer)
.: Associated with rhinocerebral mucormycosis & disseminated disease.
Cottony dirty whilte - mousy brown to gray.
Sporangia intact, rhizoids absent.
Found worldwide.
Mucorspp
Presents as rhinocerebral mucormycosis.
Wooly white - gray to brown colonies.
Dark sporangia fragile and sporangiospores joined by stolons, arching filaments that terminate at the rhizoids.
Found worldwide.
Rhizopus spp
: Presents as rhinocerebral mucormycosis.
White, gray-brown, wooly.
Erect sporangiophores with sporangium.
Smooth, ovoid sporangiospores.
Internodal rhizoids.
Found worldwide.
Lichtheimia spp..
.: Recovered from the sinuses or other organs during disseminated disease.
White to gray molds.
Erect sporangiophores branching vesicles bearing sporangioles.
Found worldwide.
Cunninghamella spp
.: Rarely implicated in human disease but documented in cutaneous infections.
Rapidly growing white to gray colonies.
Sporangiophore with large columella with merosporangia containing stacks of sporangiopores.
Confused with Aspergillus.
Syncephalastrum spp
.: Recovered from almost any source.
Primarily implicated in chronic fungal sinusitis.
Phaeoid rapidly grower, gray-brown-black colonies.
Conidiophores bearing acropetal chains of conidia.
Alternaria spp
.: Infrequent cause of sinusitis or subcutaneous infections.
Often laboratory contaminants.
Phaeoid granular velvety to fluffy brown-olive-black hyphae and conidia.
Branched shieldlike conidia from conidiophores.
Cadosporium spp
: Implicated in chronic sinusitis in immunocompromised patients. Multicelled (3-5), crescent-shaped conidia on sympodial conidiophores. Cottony dirty gray to black colonies.
Curvularia sp.
.: Reported in the brains of patients (with CNS disease).
Associated with problems in indoor air quality.
Numerous perithecia, pineapple shaped, straight/curled hairs/setae.
Pigmented lemon-shaped ascospores. Rapid grower, dirty gray colonies with diffusible red pigment.
Chaetomium sp
• Originally classified as a protozoan
• DNA in close relationship to ascomycetes
• Inhabit the lungs of animals (rats, mice, dogs, cats, ferrets, rabbits)
______- most common in rats
Pneumocystis jirovecii
• P. carinii
• Pneumonia in immunocompromised patients; dissemination rare
• Human disease confined to interstitial plasma cell pneumonitis in malnourished infants & immunosuppressed patients
• are extracellular pathogens, grow only to the surfactant layer hoove the alveolar epithelium
P jirovecii
Diagnosis:
• Specimens: bronchoalveolar lavage, lung biopsy tissue, or induced sputum
PNEUMOCYSTIS PNEUMONIA
• Stains:
Giemsa,
Toluidine blue,
methenamine silver,
calcofluor white
• Specific monoclonal antibody for direct fluorescent examination of specimens
P jirovecii
T or F
• Pneumocystis cannot be cultured.
True
Cell mediated immunity, a dominant role in resistance to disease
• Pneumocystis pneumonia not usually seen until the CD4 lymphocyte count drops below 400/pl.
• Patients are positive for 1,3-B-D-glucan.
Treatment
• Trimethoprim-sulfamethoxazole or
pentamidine isethionate
• No natural reservoir, may be an obligate member of the normal flora
• Unclear mode of transmission; transmission by aerosols may be possible
