Fungal Infections: Symptoms, Types, And Treatment

Classification Of Fungi

Morphological Classification

Based on the morphological appearance, there are four main groups of fungi.

1. Yeast: They grow as round to oval cells that reproduce by budding, e.g. Cryptococcus neoformans and Saccharomyces
2. Yeast like: They exist as yeasts with pseudohyphae, e.g. Candida
3. Molds: They grow as long branching filaments of 2–10 µm wide called hyphae.
Examples include, Dermatophytes, Aspergillus, Penicillium, Rhizopus and Mucor, etc.
4. Dimorphic fungi: They exist as molds (hyphal form) in the environment at ambient temperature (25°C) and as yeasts in human tissues at body temperature (37°C).
Examples include: Histoplasma capsulatum, Blastomyces dermatitidis, Coccidioides, Paracoccidioides,Penicillium marneffei and Sporothrix schenckii.

Taxonomical Classification

Based on the production of sexual spores, the Kingdom Fungi has been divided into four medically important phyla.

1. Zygomycota: They are lower fungi, produce sexual spores known as zygospores and possess aseptate hyphae, e.g. Rhizopus, Mucor and Absidia
2. Ascomycota: They produce sexual spores known as ascospores and possess septate hyphae,
e.g. Aspergillus
3. Basidiomycota: They produce sexual spores known as basidiospore, Example. Cryptococcus
4. Deuteromycota (Fungi Imperfecti): Sexual state is either absent or unidentified yet,
Example most medically important fungi.

Read And Learn More: Micro Biology And Immunology Notes

Classification of Fungal Diseases

1. Superficial mycoses: Tinea versicolor, Tinea nigra, Piedra and Dermatophytosis
2. Subcutaneous mycoses: Mycetoma, Sporotrichosis, Chromoblastomycosis and Rhinosporidiosis
3. Systemic mycoses: Histoplasmosis, Blastomycosis, Coccidioidomycosis and Paracoccidioidomycosis
4. Opportunistic mycoses: Candidiasis, Cryptococcosis, Zygomycosis, Aspergillosis, Penicilliosis, Pneumocystis and Fusariosis
5. Mycotoxicoses.

Superficial Mycoses

Tinea Versicolor or Pityriasis Versicolor

It is a chronic recurrent condition involving stratum corneum of skin, caused by a lipophilic fungus- Malassezia furfur.

Clinical manifestation: Characterized by scaly patches of hypo to hyperpigmentation of skin of moist humid areas.

• Lesions are noninflammatory and nonpruritic (rarely pruritic)
  Areas rich in sebaceous glands are commonly involved (neck, chest, or upper arms).
• Other manifestations include:
• Seborrheic dermatitis: Also called dandruff in adults and cradle cap in babies.
• Atopic dermatitis, folliculitis (hair follicle infection) and disseminated infection.
• Laboratory diagnosis: Diagnosis is largely made clinically.
  10% KOH mount: Mixture of budding yeasts and short septate hyphae (described as Spaghetti and meat balls appearance)
• SDA culture with olive oil overlay: Fried egg colonies appear
• Urease test is positive
• Wood’s lamp examination: Scaly lesions show golden yellow fluorescence.
• Treatment: Topical lotions like selenium sulfide shampoo, ketoconazole shampoo or cream, terbinafine cream should be used for 2 weeks.

Tinea Nigra

It is characterized by painless, black, non scaly patches present on palm and sole; more commonly in females.
It is caused by a black colored yeast like fungus called Hortaea werneckii.

Piedra

Piedra is characterized by nodule formation on hair shaft (either black or white in color).

1. White Piedra: White nodules are formed on the hair shaft, which are less firmly attached.

• Agent: Trichosporon beigelii
• Identifying feature: T. beigelii is a urease positive, produces creamy white colonies, containing hyaline septate hyphae intervening with rectangular arthrospores.

2. Black Piedra: Black nodule are formed which firmly attach to the hair shaft

• Agent: Piedraia hortae
• Identifying feature: It is a phaeoid fungus; produces reddish brown colonies; containing dark brown thick septate hyphae with ascus containing ascospores.

Dermatophytoses

Dermatophytoses (or tinea or ringworm) is the commonest superficial mycoses infecting keratinized tissues:

1. Trichophyton species: Infect skin, hair and nail
2. Microsporum species: Infect skin and hair
3. Epidermophyton species: Infect skin and nail.

Depending on the usual habitat dermatophytes are classified as follows:

• Anthropophilic species (infect only humans): Most common type of dermatophyte infection in man, produce mild and chronic lesions but respond poorly to treatment.
• Geophilic (soil species) and zoophilic species (infects animals): Produce more acute inflammatory response and severe infections; but they tend to resolve more quickly.

Dermatophytid or ID reaction

Occasionally, hypersensitivity to dermatophyte antigens may occur which leads to appearance of
secondary eruption in sensitized patients because of circulation of allergenic products.

However, these lesions are distinct from the primary ringworm lesions as they occur distal to primary site and fungal culture often turns negative.

Laboratory Diagnosis

Woods lamp examination: Certain dermatophytes fluoresce when the infected lesions are viewed under Woods lamp.

• This is due to presence of pteridine pigment in cell wall.
  It is positive for various Microsporum species and Trichophyton schoenleinii. Negative for other dermatophytes.
• Specimen collection: Skin scrapings, hair plucks (broken or scaly ones) and nail clippings are obtained from the active margin of the lesion and are kept in folded black paper.

Direct examination (10% KOH mount): Reveals thin septate hyaline hyphae with arthroconidia.

Culture on SDA followed by LPCB mount of the colonies: Reveals two types of spores (macroconidia and microconidia), based on which speciation is done.

Other methods of diagnosis

Apart from culture, there are several other methods for identification of dermatophytes:

• Hair perforation test is positive for Trichophyton mentagrophytes and Microsporum canis.
• Urease test: Positive for Trichophyton mentagrophytes
• Dermatophyte test medium and dermatophyte identification medium
• PCR can be used to detect species specific genes (Example. chitin synthase gene)
• Skin test for detecting hypersensitivity to dermatophyte antigen (trichophytin).

Treatment

• Oral terbinafine or itraconazole are the drugs of choice for treatment. Duration of treatment is
  1–2 weeks for skin lesions, 6 weeks for hair infection, 3 months for onychomycosis.
• Alternate: Oral griseofulvin and ketoconazole may be given
• Topical lotion, such as whitfield ointment or tolnaftate can be applied.

Subcutaneous  Mycoses

Mycetoma

Mycetoma is a chronic, slowly progressive granulomatous infection of the skin and subcutaneous tissues.

• Clinically, it is manifested as triad of swelling, discharging sinuses and presence of granules in the discharge.
• Mycetoma (also known as Maduramycosis or Madura foot) is of two types: eumycetoma and actinomycetoma.

Epidemiology

Mycetoma is endemic in Africa, India and the Central and South Americas.

• Overall, actinomycetoma is more common (60%) than eumycetoma (40%) globally.
• Eumycetoma is more common in Africa.
• In India, Rajasthan reports maximum cases of mycetoma per year followed by Tamil Nadu and West Bengal.
• Actinomycetoma predominates in India (65%) except in Rajasthan where eumycetoma is more common.

Laboratory Diagnosis

Direct Examination

Granules are thoroughly washed in sterile saline; crushed between the slides and examined

1. Macroscopic appearance of granules, such as color, size, shape, texture 2.
2. If eumycetoma is suspected: Grains are subjected to KOH mount which reveals hyphae of 2–6 µm
3. If actinomycetoma is suspected: Gram staining which reveals filamentous Gram-positive bacilli (0.5–1 µm wide).
   Modified acid fast stain is performed if Nocardia is suspected as it is partially acid fast.
4. Histopathological staining of the granules:

• Eumycetoma: Reveals granulomatous reaction with palisade arrangement of hyphae in the cement substance
• Actinomycetoma: Shows granulomatous reaction with filamentous bacteria at the margin.

Culture

Granules obtained from deep biopsies are the best specimen for culture. Both fungal (Example. SDA)
and Lowenstein Jensen media (for Nocardia) should be used.

Treatment

Treatment of mycetoma consists of surgical removal of the lesion followed by use of:

• Antifungal agents for eumycetoma (itraconazole or amphotericin B for 8–24 months)
• Antibiotics for actinomycetoma, such as Welsh regimen (amikacin plus cotrimoxazole).

Sporotrichosis

Sporotrichosis or Rose Gardner’s disease is chronic subcutaneous pyogranulomatous disease;
caused by a thermally dimorphic fungus Sporothrix schenckii. Various clinical manifestations have been observed.

• Nodulo-ulcerative lesions (painless) spreading along the lymphatics
• Lymph nodes become enlarged, suppurative and indurated
• Other rare clinical types are osteoarticular type, pulmonary type, disseminated sporotrichosis.

Epidemiology

• Prevalent in tropical countries with high humidity (South Africa and India).
• In India, sporotrichosis is prevalent in sub Himalayan hilly areas (from Himachal Pradesh to Assam).
• Risk factors include people walking bare foot (such as farmers and gardeners).

Laboratory Diagnosis

• Direct Microscopy by H and E staining of tissue sections reveals cigar shaped asteroid bodies.
  It is described as central basophilic yeast cell surrounded by eosinophilic mass,composed of antigen-antibody complexes.
  Such eosinophilic halo is described as Splendore-Hoeppli phenomenon.
• Culture: Specimens are inoculated on SDA and incubated at 25°C and 37°C
• At 25°C: It produces mycelial form, consisting of slender hyphae with conidia arranged in flower like pattern
• At 37°C: It produces yeast form, characterized by moist creamy white colonies.
• Serology: Latex agglutination test detects serum antibodies in patients with extracutaneous form.
• Skin test may demonstrate delayed type of hypersensitivity reaction against sporotrichin antigen.

Treatment

Itraconazole is the DOC, except for disseminated infection (amphotericin B is DOC).

Chromoblastomycosis

Chromoblastomycosis refers to slow-growing chronic subcutaneous lesions caused by group of dematiaceous or phaeoid fungi (i.e. darkly pigmented fungi) that produce a characteristic morphology called sclerotic body.

• Agents: Fonsecaea pedrosoi, Phialophora verrucosa, Cladosporium carrionii and Rhinocladiella aquaspersa.
• Lesions: Verrucose type (most common), crusted, ulcerative and nodular.
• Sclerotic bodies: Thick walled round cells (5–12 µm size) with multiple internal transverse septa.
• They are also called Medlar bodies or muriform cells.
• Treatment consists of surgical removal (cryosurgery or laser therapy) of the lesion followed by antifungals (itraconazole).

Phaeohyphomycosis

Phaeohyphomycosis refers to chronic subcutaneous lesions caused by dematiaceous or phaeoid fungi other than that are described in chromoblastomycosis (i.e. they do not produce sclerotic bodies). They exist in hyphal form. Agents include:

• Alternaria, Bipolaris, Curvularia, Exophiala jeanselmei
• Cladophialophora bantiana (it is neurotrophic, produces brain abscess, affecting frontal lobe).

Rhinosporidiosis

Rhinosporidiosis is a chronic granulomatous disease, characterized by large friable polyps in the nose (MC site), conjunctiva and occasionally in ears, larynx, bronchus and genitalia.

• Agent: It is caused by Rhinosporidium seeberi, recently re-classfied as an Aquatic Protistan Parasite(Mesomycetozoa); previously classified as lower acquatic fungi.
• Source: Stagnant water is the main source of infection. Fungal spores are inhaled while taking bath in ponds and rivers.
• Distribution: Tropical countries especially in Sri Lanka and India (Tamil Nadu, Kerala, Odisha and Andhra Pradesh).
• Diagnosis: Histopathology of polyp reveals spherules (large sporangia containing numerous endospores).
• seeberi has not been cultivated yet.
• It is stained better with mucicarmine stain.

Treatment: Radical surgery with cauterization is the mainstay of treatment. Dapsone has been found to be effective. Recurrence is common.

Systemic Mycoses

All the four fungi causing systemic mycoses are dimorphic. Transmission is by inhalation of spores, which then transform into the yeast phase in lungs. Pulmonary manifestation is the MC form.

Histoplasmosis

Histoplasmosis or Darling’s disease is caused by dimorphic fungus Histoplasma              capsulatum.

It has three biovars.

• H. capsulatum var. capsulatum: Causes classical histoplasmosis (most common type)
• H. capsulatum var. duboisii: Causes African histoplasmosis with frequent skin and bone involvement.
• H. capsulatum var. farciminosum: Causes epizootic histoplasmosis (in horses and mules).

Epidemiology

• Histoplasmosis is endemic in USA (Ohio River valley and the lower Mississippi River).
• In India, it is reported frequently from the region of West Bengal along the Ganga River.
• Reservoir: Humid and acidic soil containing bird or bat droppings.
• Transmission: By inhalation of spores (i.e. microconidia) circulating in the air being contaminated with soil.

Clinical Manifestations

• Pulmonary histoplasmosis: It is the most common form.
• Acute form starts as mild flu like illness
• Chronic cavitary histoplasmosis
• Mucocutaneous oral lesion (particularly seen in Indian patients)
• Disseminated histoplasmosis develops if CMI is very low (HIV).

Laboratory Diagnosis

Histopathological staining of specimens reveals tiny oval yeast cells (2–4 µm size) with narrow-based budding within the macrophages and underlying granulomatous response
Culture is the gold standard method of diagnosis: Histoplasma is a dimorphic fungus, hence:

• At 25°C: Produces white mycelial colonies that consist of two types of conidia: Thick tuberculate macroconidia (characteristic) and thin microconidia
• At 37°C: It gets converted into yeast form (creamy white colonies) in special Kelley’s media.

• Antibodies in serum can be detected by CFT and immunodiffusion test.
• Skin test may be done to demonstrate delayed-type hypersensitivity.

Treatment

• Liposomal amphotericin B is the antifungal of choice in acute pulmonary and disseminated histoplasmosis.
• Itraconazole is recommended for chronic cavitary pulmonary histoplasmosis.

Blastomycosis

Blastomycosis (also known as North American blastomycosis or Gilchrist’s disease or Chicago disease) is a fungal infection of humans and other animals, notably dogs and cats, caused by the dimorphic fungus Blastomyces dermatitidis.

Clinical manifestations: Acute pulmonary (MC form). Others include: Skin lesions, osteomyelitis and CNS involvement in AIDS patients (brain abscess)

Epidemiology: Endemic in North America particularly in states bordering the Ohio River and Mississippi River.

Laboratory diagnosis:

• Histopathological staining of the tissue biopsy specimens reveals thick-walled round yeast cells of 8–15 µm size with single broad-based budding (figure of 8 appearance)
• Antibody detection by immunodiffusion test against yeast phase antigens, such as antigen-A, BAD-1 and ASWS antigen (alkali-soluble water soluble)
• Antigen detection assay to detect Blastomyces antigen in urine (more sensitive) and in serum.
• Treatment: Liposomal amphotericin B is the drug of choice. Itraconazole can be given in immunocompetent patients with mild blastomycosis.

Coccidioidomycosis

Coccidioidomycosis (also called desert rheumatism or Valley fever or California fever), is a systemic fungal disease caused by a dimorphic soil dwelling fungus- Coccidioides which has two species, C. immitis and C. posadasii.

Clinical manifestations:

Pulmonary coccidioidomycosis (MC form). Other forms: Skin lesions, erythema nodosum and arthritis in women.
Disseminated infection in males and persons with low CMI (HIV with CD4 count < 250/ µL) are at higher risks.

Common sites for dissemination include skin, bone, joints, soft tissues, and meninges.

Epidemiology: Endemic in certain parts of Arizona, California, New Mexico, Texas, and Northern Mexico.

Laboratory diagnosis

• Histopathological staining of sputum or tissue biopsy specimens demonstrates Spherules (large sac like structures filled with endospores)
• Cultures on SDA produces mycelial growth described as-fragmented hyphae consisting of barrel shaped arthrospores with alternate cells distorted (empty cells):
• Coccidioides differ from other dimorphic fungi as it grows as mold at both 25°C and 37°C in usual culture media. It forms spherules at 37°C in certain special culture media only.
• Cultures are highly infectious; require biosafety level-3 precautions
• Serology: Antibodies are detected by immunodiffusion test and CFT.
• Skin test with fungal extracts (coccidioidin or spherulin).
• Treatment: Itraconazole is the DOC (Amphotericin-B is given in diffuse pneumonia).

Paracoccidioidomycosis

Paracoccidioidomycosis (also known as South American blastomycosis, Lutz-Splendore-de Almeida disease) is a systemic disease caused by the dimorphic fungus- Paracoccidioides brasiliensis.

Clinical manifestations: It occurs as two major forms.

• Acute form (or juvenile type): It affects young adults under 30 years age. It is less common variety, but more severe form, manifests as disseminated infection involving multiple viscera and is refractory to treatment.
• Chronic form (or adult form): Common (90%) variety affecting older men, but less severe, manifested as progressive pulmonary disease, skin lesions and cervical lymphadenopathy.
• Epidemiology: Endemic in Brazil and other South American countries.

Laboratory diagnosis:

• Histopathological staining of pus, tissue biopsies or sputum reveals round thick-walled yeasts, with multiple narrow-necked buds attached circumferentially giving rise to Mickey Mouse or pilot wheel appearance.
• Culture on SDA yields mycelial form at 25°C which converts into yeast phase at 37°C.
  Serology: Antibodies are detected by immunodiffusion, and most recently by ELISA (using gp43 antigen).
• Skin test demonstrates delayed type hypersensitivity response against paracoccidioidin antigen.
• Treatment: Itraconazole is the treatment of choice except for the seriously ill patients where Amphotericin B is recommended.

Opportunistic Mycoses

Opportunistic mycoses are caused by a group of fungi, which are normally a part of human anatomical flora (e.g. Candida) or found in nature and frequently isolated as laboratory contaminants (e.g. Aspergillus, Rhizopus and Penicillium).

Candidiasis

• Candidiasis accounts for the most common fungal infection in humans both in HIV and non-HIV-infected people; caused by Candida, a yeast-like fungus that produces pseudohyphae.

Various species of Candida include:

• Candida albicans: The most common and most pathogenic species
• Other rare species are C. tropicalis, C. glabrata, C. krusei, C. parapsilosis, C. dubliniensis, C. kefyr, and C. viswanathii.

Pathogenesis

Predisposing factors that are associated with increased risk of infection with Candida include:

• Physiological state: Extremes of age (infancy, old age), pregnancy
• Low immunity: Patients on steroid or immunosuppressive drugs, post-transplantation, malignancy, HIV
• Patients on broad-spectrum antibiotics suppress the normal flora
• Diabetes mellitus, febrile neutropenia, and zinc or iron deficiency.

Clinical Manifestations

Candida species are a part of the normal flora of the skin and mucosa including gut flora. In the presence of opportunistic conditions, they can cause various infections.

1. Mucosal candidiasis:
Oropharyngeal candidiasis (oral thrush) presents as white, adherent, painless patches in the mouth

• Candidal vulvovaginitis is thin whitish curd-like vaginal discharge Balanitis and balanoposthitis (occurring in uncircumcised males)
• Esophageal candidiasis
• Angular stomatitis and denture stomatitis
• Chronic mucocutaneous candidiasis: Seen in infants with deficient CMI, resistant to treatment.

2. Cutaneous candidiasis:

• Intertrigo, Paronychia, and onychomycosis (fungal infection of the nail)
• Diaper candidiasis in infants, Perianal candidiasis
• Erosion interdigitates blastomycetica, an infection between the digits of the hands or toes
• Generalized disseminated cutaneous candidiasis, is seen in infants.

3. Invasive candidiasis: Results from hematogenous or local spread of the fungi.

Various forms are:

• UTI, pulmonary candidiasis, meningitis, osteomyelitis, and hepatosplenic and disseminated candidiasis
• Septicemia (C. albicans and C. glabrata).
• Ocular: Keratoconjunctivitis and endophthalmitis
• Nosocomial candidiasis (mainly by C. glabrata).

4. Allergic candidiasis include:

Candidid: Vesicular lesions in the web space of hands, similar to that of dermatophytid reaction (both conditions are together called ‘ID’ reaction)
Other allergic reactions include Gastritis, irritable bowel syndrome, and eczema.

 

Laboratory Diagnosis

• Direct microscopy: Gram-positive oval budding yeast cells (4–6 µm size) with pseudohyphae.
• Culture on SDA: Colonies are described as creamy white, smooth, and pasty with a typical yeasty odor.
• Tests for species identification:
• Germ tube test: It is also called the Reynolds Braude phenomenon, a specific test for C. albicans.
• It is differentiated from pseudohyphae as there is no constriction at the origin
• Though the test is specific for C. albicans, it may also be positive for C. dubliniensis.
• Dalmau plate culture on Cornmeal agar C. albicans produces thick-walled chlamydospores.
• CHROM agar: Different Candida species produce different colored colonies on CHROM agar.
• Growth at 45°C: It differentiates C. albicans (grows well) from C. dubliniensis (does not grow at 45°C).
• Sugar fermentation test and sugar assimilation test.

Immunodiagnosis:

• Antibody detection: Against cell wall mannan antigen.
• Antigen detection: Cell wall mannan and cytoplasmic antigens can be detected by

Elisa

• Enzyme detection: Specific for Candida such as enolase, aspartate proteinase, etc.
• Test for metabolites specific for Candida such as mannitol, and arabinitol can be detected.
• G test is done for the detection of α1-3 glucan

Treatment

• The antifungal drugs recommended depends upon the type of candidiasis:
• Cutaneous candidiasis or oral thrush–drug of choice is topical azole
• Esophageal and vulvovaginal candidiasis–drug of choice is oral fluconazole
• Disseminated candidiasis- drug of choice is Amphotericin B
• C. glabrata and C. krusei exhibit intrinsic resistance to azoles and are refractory to treatment with azoles.

Cryptococcosis

Cryptococcus has two species, C. neoformans and C. gattii, and four serotypes A, B, C, and D.
C. neoformans occurs in two varieties – Cryptococcus neoformans var. grubii and
Cryptococcus neoformans var. neoformans; which correlate with serotypes A and D, respectively.
C. gattii is antigenically diverse and corresponds to serotypes B and C.
Most laboratories do not routinely distinguish between the types, and report all isolates simply as C. neoformans.

• CNS spread: The unique feature of Cryptococcus is its ability to cross the blood-brain barrier which occurs by yeast cells either migrate directly across the endothelium or are carried inside the macrophages as a ‘Trojan horse’.
• Virulence factors of Cryptococcus that favor invasion and spread of infection include:
• Polysaccharide capsule.
• Ability to make melanin by producing phenyl oxidase enzyme.
• Production of other enzymes, such as phospholipase and urease.

Risk factors: Individuals at high risk for cryptococcosis include:

• Patients with advanced HIV infection with CD4 T-cell counts < 200/µL is the most
• important risk factor for C. neoformans. However, C. gattii is not associated with HIV.
• It usually causes infection in immunocompetent individuals.
• Patients with hematologic malignancies.
• Transplant recipients.
• Patients on immunosuppressive or steroid therapy.

Clinical Manifestation

• Various clinical manifestations of cryptococcosis include:
• Pulmonary cryptococcosis is the first and the most common presentation
• Chronic meningitis
• Skin lesions are commonly seen with C. neoformans var. neoformans (serotype D)
• Osteolytic bone lesions.

Epidemiology

Geographical distribution: C. neoformans var. grubii (serotype A) strains are found worldwide, but C. neoformans var. neoformans is common in Europe.

Habitat: C. neoformans is frequently found in soils contaminated with avian excreta and pigeon droppings. In contrast, C. gattii inhabits in eucalyptus tree.

Laboratory Diagnosis

Direct detection methods:

Negative staining by modified India ink stain and nigrosin stain to demonstrate the capsule which appears as refractile delineated clear space surrounding the round budding yeast cells against black ground. Sensitivity is 60–70%.

Gram staining may show Gram-positive round budding yeast cells.

Other stains: Mucicarmine stain Masson-Fontana stain, Alcian blue stain.

Capsular antigen detection from CSF or serum by latex agglutination test is rapid and sensitive (95%).

• Confirmation of Cryptococcus species is made by:
• Culture on SDA: Colonies appear as mucoid creamy white yeast-like colonies
• Niger seed agar and bird seed agar is used to demonstrate melanin production
• Growth at 37°C, urease test positive
• Assimilation of inositol and nitrate and mouse pathogenicity test positive.

Treatment

Treatment depends upon the type of cryptococcosis.

Cryptococcosis without CNS involvement: Fluconazole is the drug of choice.
HIV-infected patients with CNS involvement Induction phase for two weeks (Amphotericin-B ± flucytosine) followed by lifelong maintenance therapy with fluconazole.

Zygomycosis

Zygomycosis or mucormycosis represents a group of life-threatening infections caused by aseptate fungi belonging to the phylum Zygomycota.

Examples include Rhizopus, Mucor, and Absidia.

• Predisposing factors: Agents of mucormycosis require iron as a growth factor. Hence conditions with increased iron load are at higher risk of developing invasive mucormycosis, such as:
• Diabetic ketoacidosis (DKA) is the most important risk factor
• End-stage renal disease
• Patients taking iron therapy or deferoxamine (iron chelator)
• Defects in phagocytic functions (For Example. neutropenia or steroid therapy).

Clinical Manifestations

Agents of mucormycosis are angioinvasive in nature. There are six types of clinical presentations:

1. Rhinocerebral mucormycosis: MC form; presents as orbital cellulitis, proptosis, and vision loss.
2. Pulmonary mucormycosis is the second MC form, that occurs in patients with leukemia.
3. Cutaneous mucormycosis.
4. Gastrointestinal mucormycosis, such as necrotizing enterocolitis; is seen commonly in premature neonates.
5. Disseminated mucormycosis: The brain is the most common site of dissemination.
6. Miscellaneous forms may involve any body site, including bones, trachea kidneys, etc.

Laboratory Diagnosis

Histopathological staining of tissue biopsies shows broad aseptate hyaline hyphae with wide-angle branching
Culture on SDA at 25°C reveals cottony woolly colonies which are initially white, later become brown-black due to sporulation giving rise to a salt and pepper appearance

• Microscopic appearance: LPCB mount of the colonies reveals broad aseptate hyaline hyphae, from which sporangiophore arise which ends at sporangium containing numerous sporangiospores
• Rhizoid: Some species bear a unique root-like growth called rhizoid which provides an initial clue for the identification of the fungus.

Treatment

Amphotericin B deoxycholate remains the drug of choice for all forms of mucormycosis except the mild localized skin lesions in immunocompetent patients, which can be removed surgically.

Aspergillosis

Aspergillus species are widely distributed on decaying plants, producing chains of conidia.

Clinical Manifestations

Clinical manifestations of aspergillosis depend on the site of involvement. The incubation period varies from 2 to 90 days.

1. Pulmonary aspergillosis (MC form): Various forms include Allergic bronchopulmonary aspergillosis (ABPA), Asthma, Extrinsic allergic alveolitis, Aspergilloma (fungal ball), and Chronic cavitary pulmonary aspergillosis

2. Invasive sinusitis: Invasive sinusitis, chronic granulomatous sinusitis, maxillary fungal ball and allergic fungal sinusitis
3. Ocular aspergillosis: Keratitis and endophthalmitis
4. Ear infection: Otitis externa
5. Others: Endocarditis, brain abscess, skin lesions and onychomycosis.

Clinical manifestations also depend on the species involved:

• A. fumigatus accounts for most of the cases of acute pulmonary and allergic aspergillosis.
• A. flavus is more common in hospitals and causes more sinus, skin, and ocular infections than
• A. fumigatus.
• A. niger can cause invasive infection but more commonly colonizes the respiratory tract and causes otitis externa.

Laboratory Diagnosis

• Direct examination: Reveals narrow septate hyaline hyphae with acute angle branching
• Culture on SDA followed by colonies subjected to LPCB mount (see table)
• Antigen detection: ELISA detecting galactomannan antigen
• Antibody detection: Useful for chronic invasive aspergillosis and aspergilloma, where the culture is usually negative
• In allergic syndromes, such as ABPA and severe asthma, specific serum IgE levels are elevated
• Detection of metabolites, such as α1-3 glucan (by G test) or mannitol.

Treatment

Following are the first-line treatments recommended in different forms of aspergillosis:

• For invasive aspergillosis: Voriconazole is the drug of choice.
• For ABPA: Itraconazole is the drug of choice.
• For single aspergilloma: Surgery is indicated.
• For chronic pulmonary aspergillosis: Itraconazole or voriconazole is the drug of choice.
• For prophylaxis, posaconazole is indicated.

Penicilliosis

Penicillium species are usually found in the environment and as laboratory contaminants.

Rarely infects humans.

• Common manifestations: Endophthalmitis, otomycosis, onychomycosis, and allergic pneumonitis
• Microscopy: Reveals hyaline thin septate hyphae, vesicles are absent, and conidia arranged as brush border appearance.
• Penicillium marneffei
• Penicillium marneffei is a thermally dimorphic fungus that causes opportunistic infection in HIV-infected patients.
  • Systemic infection mimicking that of disseminated histoplasmosis
  • Skin lesions: Warty lesions mimicking that of Molluscum contagiosum are seen.
  • It is endemic in SE Asian countries including Thailand, Vietnam, and India (Manipur).
  • P. marneffei is found mostly in rural areas and bamboo rats are the reservoirs of infection

Lab Diagnosis:

Direct Microscopy: Shows oval or elliptical yeast cells with central septation, which indicates that these cells divide by transverse fission rather than budding

• Culture: P. marneffei being dimorphic; produces yeast-like colonies at 37°C and mold form at 25°C. The mold form has a characteristic brick-red pigment.
• Treatment: AIDS patients with severe penicilliosis are treated with amphotericin B till the condition improves followed by maintenance therapy with itraconazole for 12 weeks. In mild
• penicilliosis, itraconazole is recommended for 12 weeks.
• Pneumocystis Pneumonia (PCP)
• Pneumocystis is classified under fungus based on nucleic acid sequence studies:
• Exist in two forms: In the environment cysts are found, whereas in human tissues both cysts and trophozoites are found.
  Cysts are inhaled, carried to the lungs, and transformed into the trophozoite stage which induces an inflammatory response that leads to the recruitment of plasma cells resulting in the formation of frothy exudate filling the alveoli. Hence, PcP is also called plasma cell pneumonia.

Laboratory Diagnosis:

Gomori’s methenamine silver (GMS) staining is the method of choice to demonstrate the cysts of P. jirovecii. The cysts resemble black-colored crushed ping-pong balls, against the green background.

• Pneumocystis is not cultivable and there is no serological test available.
• Treatment: Cotrimoxazole is the DOC for Pneumocystis pneumonia. It is given for 14 days in non-HIV patients and 21 days in patients with HIV. It is also the recommended drug for primary and secondary prophylaxis in patients with HIV.

Fusariosis

Fusarium is a saprophyte; that rarely causes human infections.

• In immunocompetent individuals, they cause: Keratitis in contact lens wearers and Onychomycosis
• In immunocompromised patients: They are angioinvasive and cause pulmonary and sinus infections.
• In neutropenic patients and with hematologic malignancies: Disseminated fusariosis occurs with frequent skin lesions.

• Lab Diagnosis: LPCB mount of the colony reveals hyaline septate hyphae bearing round microconidia, sickle-shaped large macroconidia and chlamydospores.
• Treatment: Liposomal amphotericin B, voriconazole or posaconazole are recommended.

Mycotoxicoses

Mycotic poisoning can be classified into two varieties:
1. Mycotoxicosis: Occurs following consumption of food contaminated by toxins liberated by certain fungi
2. Mycetism: Refers to the toxic effects produced by eating poisonous fleshy fungi (e.g.mushrooms).