Opportunistic Mycoses

• Opportunistic fungal infections


  Typically identified in a host compromised by some underlying disease process such as lymphoma, leukemia, diabetes mellitus or another defect of the immune system
• Organ transplant patients


  Often placed on treatment with corticosteroids, cytotoxic drugs or other immunosuppressive agents to control rejection of the transplant organ
• Fungi thought to be previously non pathogenic are now recognized as etiologic agents of opportunistic fungal infections

  
• Opportunistic fungal infections


  Acquired during construction, demolition or remodeling of buildings or hospital acquired

  
• Laboratorians must identify and report completely the presence of all fungi recovered
• Opportunistic fungal infections


  • Aspergillosis
  • Fusariosis
  • Geotrichosis
  • Other hyaline septate opportunistic molds
  • Acremonium
  • Penicillum
  • Paecilomyces
  • Scopulariopsis
  • Opportunistic atypical fungus
  • Pneumocystis jiroveci

  
• Aspergillosis


  Caused by Aspergillus spp. capable of causing disseminated infection seen in immunocompromised patients but can also cause: Pulmonary or sinus fungus ball, Allergic bronchopulmonary aspergillosis, External otomycosis, Fungus ball of the external auditory canal, Mycotic keratitis, Onychomycosis, Infection of the nail and surrounding tissue, Sinusitis, Endocarditis, CNSI

  
• Aspergillus


  • Widespread in the environment, Colonizes grain, leaves, soil and living plants, Conidia of aspergilli are easily dispersed into the environment, Humans become infected by inhaling them

  
• Significance of Aspergillus isolate

  Repeated recovery from clinical specimens coming from patient is significant with a compatible clinical picture, Correlation with biopsy results is the best means of establishing the significance of an isolate

  
• Aspergillus culture media


  Most Aspergillus spp. are susceptible to cycloheximide, Culture media must not contain cycloheximide

  
• Aspergillus


  • Most commonly recovered species from immunocompromised patients, Most often seen in clinical laboratory, Rapidly growing mold (2 – 6 days), Fluffy to granular, white to blue-green colony, Mature sporulating colonies most often have a blue-green, powdery appearance, Thermotolerant, able to withstand up to 45°C, Microscopically: septate hyphae and short or long conidiophores with a characteristic "foot cell" at their base, T or L shaped foot cell at the base of the conidiophore, Tip of conidiophore expands into a large, dome-shaped vesicle with bottle-shaped phialides covering the upper half or two thirds of its surface, Long chains of small (2 – 3 µm in diameter), spherical, round walled, green conidia form a columnar mass on the vesicle

  
• Aspergillus flavus


  • Sometimes recovered from immunocompromised patients representing a frequent isolate in the clinical laboratory, More rapidly growing (1 – 5 days), Yellow – green colony, Microscopically: vesicles are globose, phialides are produced directly from the vesicle surface (uniserate) or from a primary row of cells called metulae (biserate), Phialides give rise to shot chains of yellow-orange elliptical or spherical conidia that become roughened on surface with age, Conidiophore are coarsely roughened near the vesicle, Commonly seen in clinical laboratory but its association with clinical disease is limited, Cause of fungus ball and otitis externa

  
• Aspergillus niger


  • Produces mature colonies within 2 – 6 days, Growth begins initially as a yellow colony that soon develops a black, dotted surface as conidia are produced, With age colony becomes jet black and powdery but the reverse remains buff or cream colored, Microscopically: hyphae are hyaline and septate, long conidiophores supporting spherical vesicles giving rise to large metulae and smaller phialides (biserate), from which long chains of brown to black, rough-walled conidia are produced, Entire surface area of vesicle is involved in sporulation, Significant cause of aspergillosis in immunocompromised patients, Frequency of recovery is much lower than the other species

  
• Aspergillus terreus


  • Produces tan colonies that resemble cinnamon, Correct identification is important, Innately resistant to Ampicillin B, Microscopically: vesicles are hemispherical, phialides cover the entire surface and are produced from primary row of metulae (biserate), Phialides produce globose to elliptical conidia arranged in chains, Produce larger cells, aleurioconidia, found on submerged hyphae
• Fusariosis


  Disseminated fusariosis is commonly accompanied by fungemia, Sinusitis, Wound (burn) infection, Allergic fungal sinusitis, Endophthalmitis
• Fusarium is commonly recovered from respiratory tract secretions, skin and other specimens from patients who show no evidence of infection
• Interpretation of Fusarium culture results

  Rests with the clinician and is often assisted with histopathologic results
• Fusarium


  • Colonies grow rapidly within 2 – 5 days, Fluffy to cottony and maybe pink, purple, yellow. green or other colors depending on the species, Microscopically: hyphae are septate and small giving rise to phialides producing either single-celled microconidia, usually borne in gelatinous heads similar to those seen in Acremonium spp. or large multi-celled macroconidia that are sickle or boat-shaped and contain numerous septations, Some cultures commonly produce numerous chlamydoconidia, Cornmeal Agar is used to induce sporulation, Key to identification are based on growth on PDA
• Geotrichosis


  Uncommon cause of infection but has been shown to cause wound infections and oral thrush
• Geotrichum


  • On media, initially appears as white to cream-colored, yeast-like colony, Some isolates may appear as white, powdery molds, Microscopically: septate hyphae producing numerous rectangular to cylindrical to barrel-shaped arthroconidia, Arthroconidia do not alternate but are contiguous, in contrast to Coccidiodes immmitis, Blastoconidia are not produced
• Opportunistic atypical fungus Pneumocystis jiroveci


  Also considered as important pathogen in immunocompromised hosts, Associated with disseminated infection, fungemia, subcutaneous lesions and esophagitis

  
• Pneumocystis jiroveci


  • Colonies are rapid growing and may also appear as yeast like when initial growth is observed, Mature colonies become white to gray to rose or reddish-orange, Microscopically: small septate hyphae that produce single, unbranched, tube-like phialides, Phialides give rise to clusters of elliptical, single-celled conidia contained in a gelatinous cluster at the tip of the phialide

  
• Penicillium


  Among the most common organisms recovered in the clinical laboratory, In North America, rarely associated with invasive fungal disease, May be a cause of allergic bronchopulmonary penicilliosis or chronic allergic sinusitis
• Penicillium


  • Colonies are commonly shades of green or blue - green, but pink, white or other colors may be seen, Surface of colonies may be velvety to powdery because of the presence of conidia, Microscopically: hyaline septate hyphae producing brush-like conidiophores (penicilli), Conidiophores produce metulae from which flask-shaped phialides producing chains of conidia arise
• Penicillium marneffei


  Associated with Endophthalmitis, cutaneous infections and arthritis
• Penicillium variotii


  Associated with Endocarditis, fungemia and invasive disease
• Paecilomyces


  • Colonies are velvety, tan to olive brown and somewhat powdery, Microscopically resemble Penicillium spp., Phialides are long, delicate and tapering in contrast to the more blunted phialides of Penicillium spp., Produce numerous chains of small, oval conidia that are easily dislodged, Single phialides producing chains of conidia may also be present
• Scopulariopsis


  Associated with onychomycosis, pulmonary infection, fungus ball and recently a cause of invasive fungal disease in the immunocompromised host, Colonies appear initially as white but later become light brown and powdery, Colonies often resemble those of M. gypseum, Microscopically: resemble large Penicillium organism at first glance because a rudimentary penicillus is produced, Annellophores produce the flask-shaped annellides which support the lemon-shaped conidia in chains, Conidia are large, flat base and rough walled

  
• Pneumocystis jiroveci


  Opportunistic atypical fungus, Causes pneumonia in immunocompromised humans commonly called Pneumocystis carinii pneumonia (PCP), Formerly called Pneumocystis carinii, For rodents, the causative agent for pneumonia is still called Pneumocystis carinii, Thought to be a trypanosome, Precise taxonomic categorization remains challenging, Several factors supported the notion that P. jiroveci was a protozoan parasite because its morphology is similar to that of microbes and protozoa, Clinically responds to antiprotozoal drugs but not to antifungal drugs, Exists as three (3) forms in its life cycle: Trophozoite, Precyst (sporocyte), Cyst (the diagnostic form)

  
• Pneumocystis jiroveci


  • Shown to be a fungus but differs from other fungi in various aspects: Cell membrane contain cholesterol, Flexible - walled trophozoite is susceptible to osmotic disturbances, Contain only one or two copies of the small ribosomal sub unit gene, DNA sequence analysis of the small ribosomal sub unit gene disclosed a greater sequence homology with the fungi rather than with protozoa, Placed Pneumocystis jiroveci in the fungal kingdom somewhere between the Ascomycetes and the Basidiomycetes

  
• Transmission of Pneumocystis jiroveci


  Worldwide distribution, Exact transmission of the disease is still not known, Some speculate person-to-person, Immunocompromised mammals maybe the reservoir transmitted to immunocompromised individuals, Children 2 – 4 years have Ab to P. jiroveci, Vargas et. al showed that pneumocystis DNA was present in 24 of 72 infants as determined from nasopharyngeal specimens and that seroconversion occurred in 85% of infants by 20 months of age

  
• Pneumocystis carinii pneumonia (PCP)


  In 1980's during the onset of HIV, became the most common opportunistic infection among those with HIV or AIDS, The introduction of Highly Active Antiretroviral Therapy (HAART) for patients with HIV reduced the incidence of PCP, PCP still remains a significant medical problem, Numerous patients with HIV do not respond to therapy, Patients do not comply with therapy, Individuals do not know they are infected
• Diagnosis of Pneumocystis jiroveci

  Respiratory specimens from deep portion of the lung such as bronchoalveolar lavage fluid (BALF) are best clinical sample, Diagnosis is currently based on: Clinical presentation, Radiographic studies, Direct and or Pathologic examination of BALF or biopsy material, Stains used: Giemsa, Immunofluorescent, Calcofluor White, Methenamine Silver, Immunofluorescent used as screening tool, Confirmatory method should be performed
• Staining of Pneumocystis jiroveci cysts

  • Gomori's Methenamine Silver Stain, Fresh lung imprint Giemsa stain, Calcofluor White
• Pneumocystis jiroveci detection methods

  Commercial kits for Antigen-Protein Detection available as monoclonal antibodies directed against P. jiroveci, Highly sensitive but expensive, Nucleic Acid amplification had been developed: Real Time Polymerase Chain Reaction (RT PCR), Research settings in molecular biology, Commercial kits are not yet available, Cultivation is very difficult to do. Routine culture methods not performed