Deep Mycoses (Fungal Infection)
Deep mycoses,
also known as systemic mycoses or invasive fungal infections, are caused by
fungi that have the ability to invade and disseminate within deeper tissues
and organs, including the bloodstream. Unlike superficial mycoses, which
primarily affect the outer layers of the skin, hair, and nails, deep mycoses
can involve internal organs and often pose a more serious clinical
challenge. These infections typically occur in immunocompromised individuals or
those with underlying medical conditions make them susceptible to fungal
colonization and invasion.
Different Infections and their Treatment
1. Histoplasmosis: Histoplasma capsulatum is the
causative agent of histoplasmosis, a fungal infection endemic to certain
regions, particularly in North and Central America. It is a dimorphic fungus
means it grows as mold in environment and as yeast in tissues. Inhalation of
airborne fungal spores from soil enriched with bird or bat droppings,
chicken houses, bat inhabiting caves initiates infection. The yeast is engulfed
by macrophages but it survived by producing alkaline substances (ammonia and
bicarbonates) that increases the pH to inactivate the degradative enzymes of
macrophages. Most infections remain asymptomatic but infection may spread to
lungs primarily, where it can cause a spectrum of manifestations ranging from
asymptomatic or mild respiratory illness to severe pneumonia with respiratory
failure. Dissemination to other organs, including the liver, spleen, and bone
marrow, may occur in infants and immunocompromised individuals (AIDS, Cancer
patients undergoing chemotherapy).
Culture
test on SDA (Sabouraud’s dextrose agar) shows hyphal (mold) growth at 37 degree
centigrade but Yeast at 25 degree centigrade.
Treatment is not required if patient remain Asymptomatic
but in progressive lung, liver or meningeal infections oral itraconazole,
amphotericin B or fluconazole may be given only under the supervision of expert
doctor.
2. Coccidioidomycosis: Coccidioides spp., including Coccidioides
immitis and Coccidioides posadasii, are dimorphic fungi endemic to
arid regions of the southwestern United States, Mexico, and parts of Central
and South America. Inhalation of airborne arthroconidia initiates infection,
leading to primary pulmonary coccidioidomycosis characterized by flu-like
symptoms, cough, and chest pain. Most people develop cell mediated immunity to
inhibit the growth of fungus but if this immunity suppressed by any disease or
drug, the infection can disseminate to extrapulmonary sites, including the
skin, bones, joints, and central nervous system, resulting in severe and
potentially life-threatening complications.
Diagnosis can be done microscopically of tissue
specimen where spherules of fungus can be seen. Culture test on SDA
(Sabouraud’s dextrose agar) shows hyphal (mold) growth with arthrospores at 25 degree
centigrade. Serologically can be determined by detection of IgM and IgG
after 2 weeks of infection.
Treatment is not required in Asymptomatic patients but in
progressive lung or meningeal infections oral itraconazole, amphotericin B or
fluconazole may be given only under the supervision of expert doctor.
3. Blastomycosis: Blastomyces dermatitidis is the
etiologic agent of blastomycosis, another dimorphic fungus endemic to regions
with moist soil enriched with decaying organic matter in the United States and
parts of Africa. Inhalation of fungal conidia (spores) initiates infection,
which typically manifests as pulmonary disease with symptoms resembling
pneumonia. Dissemination to extrapulmonary sites, including the skin, bones,
and central nervous system, can occur, particularly in immunocompromised
individuals or those with underlying lung disease.
Diagnoses can be done by direct microscopy of tissue
sample in which budding yeast can be seen. Culture test of the specimen on SDA
shows growth of Hyphae with pear shaped conidia.
Treatment involve oral itraconazole or amphotericin B under
the supervision of healthcare provider.
4. Cryptococcosis: Cryptococcus neoformans and Cryptococcus
gattii are encapsulated yeast-like fungi found in the environment,
particularly in bird excreta and soil contaminated with bird droppings.
Inhalation of fungal spores or desiccated yeast cells can lead to pulmonary
cryptococcosis, which may be asymptomatic or present with mild respiratory
symptoms. Spread to the central nervous system, causing cryptococcal meningitis
(gelatinous mass of fungi grows in meninges), is a common and serious
complication, particularly in individuals with HIV/AIDS or other forms of
immunosuppression.
5. Aspergillosis: Aspergillus fumigatus and other spp. of
Aspergillus ubiquitous molds found in the environment, can cause a spectrum of
clinical manifestations collectively known as aspergillosis. Inhalation of
airborne conidia can lead to pulmonary disease, ranging from allergic aspergillosis,
sinusitis, asthma to invasive pulmonary aspergillosis, particularly in
immunocompromised individuals or patients with neutropenia (decrease in number
of neutrophils) due to any disease. Infection spread by germination of conidia into
hyphae which invades tissues. Dissemination to extrapulmonary sites, including
the central nervous system, heart, and blood vessels, can occur in severe
cases.
Lab
diagnosis can be done by culturing the fungus
on SDA or by direct microscopy where fruiting bodies and septate hyphae can be
observed.
Management
of deep mycoses involves antifungal therapy, with the choice of agent and
duration of treatment guided by the severity of infection, underlying host
factors, and causative organism. Agents such as amphotericin B, azoles (e.g.,
fluconazole, voriconazole), and echinocandins (e.g., caspofungin, micafungin)
are commonly used for treatment, with combination therapy or surgical
intervention considered in refractory or complicated cases. Adjunctive
measures, including optimization of host immune function and management of
underlying comorbidities, are essential for comprehensive management and
prevention of recurrence.
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