CHAPTER 59

• Mucorales:

  • Produce large, ribbonlike hyphae with occasional septa
  • Saclike fruiting structures produce spherical, yellow or brown spores
  • Sporangiphores connected by stolons, which attach at contact points with rootlike structures (rhizoids) anchoring the organism to the agar surface
• Mucorales are less common than aspergilli but can cause morbidity and mortality in immunocompromised patients, especially those with diabetes mellitus
• Mucorales are commonly found in decaying vegetable matter, old bread, and soil, and are generally acquired through inhalation or ingestion of spores or percutaneous routes
• Mucormycosis, caused by Mucorales, presents a great risk for uncontrolled diabetes mellitus, transplant patients, and individuals undergoing prolonged corticosteroid, antibiotic, or cytotoxic therapy
• Infections caused by Mucorales can involve various organs, with the rhinocerebral form being one of the most common presentations, affecting nasal mucosa, palate, sinuses, orbit, face, and brain
• Laboratory Diagnosis for Mucorales:

  • Blood cultures are not appropriate for diagnosis
  • Deep lesions or tissues and sterile sites should be collected rapidly and aseptically
  • Diagnosis for rhinocerebral forms of infection should include nasal discharge or scrapings, sinus aspirate, and tissue specimen from vascularized tissue
• Direct detection methods for Mucorales include stains like calcofluor white and potassium hydroxide preparation, antigen-protein testing is not used for diagnosis, and molecular methods like nucleic acid testing and PCR amplification can be performed
• Cultivation of Mucorales:

  • High concentration of carbohydrates inhibits the production of asexual fruiting bodies
  • Recommended media include potato dextrose, 2% malt, and cerry decoction agar
  • Colonies resemble cotton candy, and hyphae can grow rapidly, lifting the lid of the agar plate
• Mucor spp. have sporangiophores that are singularly produced or branched with a round sporangium at the tip filled with sporangiospores, while Rhizopus spp. have unbranched sporangiophores with rhizoids appearing opposite the point where the stolon arises
• Entomophthorales:

  • Newly created phylum Entophythoromycota contains over 250 species worldwide
  • Primarily present in soil, decaying vegetable material, and animal feces
  • Infections associated with Conidiobolus spp. are found in various regions including Africa, Madagascar, India, China, and Japan
• Basidiobolomycosis, caused by Basidiobolus ranarum, primarily affects subcutaneous tissue, while Conidiobolus spp. infections are localized around the nose and face, often due to inhalation of spores or inoculation after trauma
• Laboratory Diagnosis for Entomophthorales:

  • Splendore-Hoeppli phenomenon is highly indicative of entomophthoromycosis
  • Molecular methods like single PCR have been developed for the diagnosis of Basidiobolus entomophthoromycosis
  • Cultivation of tissue samples should be sliced to minced and incubated at specific temperatures for different species
• Identification of Basidiobolus ranarum involves slightly yellow pigmented colonies with radial folds and aseptate mycelia, while Conidiobolus spp. are fast-growing fungi producing hyaline, radially folded colonies
• Dermatophytes:

  • Cause infections involving superficial areas of the body like hair, skin, and nails
• Dermatophytes are fast-growing fungi that produce hyaline, radially folded colonies
• Dermatophytes initially appear waxy and become powdery when mycelia begin to develop
• Dermatophytes produce infections (dermatomycoses) involving the superficial areas of the body like hair, skin, and nails
• Principal etiologic agents of dermatomycoses include Trichophyton, Microsporum, and Epidermophyton
• Trichophyton is capable of invading hair, skin, and nails, while Microsporum spp. involves only hair and skin, and Epidermophyton spp. involves only skin and nails
• Tinea, Latin for "worm" or "ringworm," is the most common fungal infection of humans, with variations like tinea corporis, tinea cruris (jock itch), tinea capitis, tinea barbae, tinea unguium, and tinea pedis (athlete's foot)
• Trichophyton spp. are widely distributed and are the most important and common causes of infections of the feet and nails, responsible for tinea corporis, tinea capitis, tinea unguium, and tinea barbae
• Direct detection methods for dermatophytes include stains like calcofluor white or potassium hydroxide preparations, and cultivation on cornmeal agar or potato dextrose agar to induce sporulation
• Trichophyton spp. are characterized by smooth, club-shaped, thin-walled macroconidia with three to eight septa, with T. rubrum being slow-growing and T. mentagrophytes rapidly growing
• Microsporum spp. are recognized by the presence of large, spindle-shaped, echinulate, rough-walled macroconidia with thick walls containing four or more septa
• Epidermophyton spp., like E. floccosum, are slow-growing and are common causes of tinea cruris and pedis
• Opportunistic mycoses are tissue-invasive fungal infections that occur almost exclusively in immunocompromised patients, including Aspergillus spp. which colonize grains, leaves, soil, and living plants
• Aspergillus spp. are capable of causing disseminated infections and a wide variety of infections like pulmonary or sinus fungus ball, allergic bronchopulmonary aspergillosis, mycotic keratitis, onychomycosis, sinusitis, endocarditis, and CNS infection
• Direct detection methods for Aspergillus spp. include antigen-protein assays like galactomannan assay and beta-D-glucan assay, and cultivation methods susceptible to cycloheximide
• Aspergillus fumigatus is the most commonly recovered species from immunocompromised patients, characterized by fluffy to granular, white to blue-green colonies
• Fusarium spp. grow rapidly, with fluffy to cottony colonies of various colors, and Geotrichum candidum initially appears as a white to cream-colored, yeastlike colony
• Penicillium spp. are commonly shades of green or blue-green, while Talaromyces marneffei is a particularly virulent species
• Systemic mycoses involve internal organs of the body and include dimorphic fungi like Blastomyces spp., Coccidioides spp., Emmonsia spp., Histoplasma capsulatum, and Paracoccidioides brasiliensis
• Histoplasma capsulatum:

  • Associated with activities dispersing aerosolized conidia or small hyphal fragments
  • Acquired through inhalation of these infective structures from the environment
  • Most commonly produces a chronic, granulomatous infection that is primary and invades the reticuloendothelial system
  • Approximately 95% of cases are asymptomatic and self-limited
  • Chronic pulmonary infections occur
• Paracoccidioides brasiliensis:

  • Most commonly found in South America, with highest prevalences in Brazil, Venezuela, and Colombia
  • Has a pulmonary origin
  • Acquired by inhalation of the organism from the environment
  • Produces a chronic granulomatous infection that begins as a primary pulmonary infection
  • Lesions are characteristically ulcerative, with a serpiginous (snakelike) active border and a crusted surface
• Talaromyces marneffei:

  • Associated with the bamboo rat and the Vietnamese bamboo rat
  • An emerging pathogen that commonly infects immunosuppressed individuals
  • Causes either a focal cutaneous or mucocutaneous infection, or a progressive disseminated and commonly fatal infection
• Sporothrix spp.:

  • Acquired through trauma usually to the hand, arm, or leg
  • Commonly known as rose gardener’s disease
  • Pulmonary sporotrichosis rarely occurs as a result of inhalation of spores
  • Primary lesion begins as a small, nonhealing ulcer, often of the index finger or the back of the hand
  • Subcutaneous nodules ulcerate to form a chronic infection
• Blastomyces spp.:

  • Commonly produce an acute or chronic suppurative and granulomatous infection
  • May spread and involve secondary sites of infection in the lungs, long bones, soft tissue, and skin
• Coccidioides spp.:

  • Approximately 60% of patients with coccidioidomycosis are asymptomatic and have self-limited respiratory tract infections
• Emmonsia spp.:

  • Nonreplicating Emmonsia spp., most notably E. crescens, produces 25 to 400 um adiaspores in vitro on brain-heart infusion (BHI) agar incubated at 37°C
  • Severity of the disease depends on the immunologic status of the patient as well as the inoculum size
• Laboratory Diagnosis - Direct Detection Methods:

  • Stains for different fungi:
  • Histoplasma capsulatum: may be detected in Wright- or Giemsa-stained specimens of bone marrow
  • Paracoccidioides brasiliensis: large, round or oval, multiple budding yeast cells (8-40 mm in diameter) are usually recognized in sputum
  • Talaromyces marneffei: small, yeastlike cells that have internal cross-walls
  • Sporothrix spp.: direct examination usually has little diagnostic value