The Hidden World of Pathogenic Fungi Human Mycoses

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The Hidden World of Pathogenic FungiHuman Mycoses

• Dr. Salman Elawad
• Biology Instructor
• CVCC

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What Are Fungi?

• Multicellular heterotrophs that obtain their food
  by absorption.
• The feeding body of a fungus, called mycelium, is
  made of slender haploid (n) filaments called
  hyphae.
• Some fungi have a dikaryon stage in which two
  haploid nuclei coexist in a single cell (n n).
• Fungi have cell walls made of chitin and other
  polysaccharides.
• The fungus eventually produces a fruiting body
  that specializes in reproduction.
• Different fungi have different fruiting bodies.

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What Are Fungi?

• Store their excess food as glycogen.
• Have haplontic life cycle (zygotic meiosis).
• Reproduce sexually after two hyphae of opposite
  types fuse.
• Based on type of sexual reproduction, fungi are
  classified into six phyla.
• Asexual reproduction by spores is a common means
  of reproduction
• The scientific study of fungi is called mycology.

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Importance of Fungi

• Primary decomposers that break down dead organic
  matter and recycle nutrients.
• Speed up the cycling of carbon atoms on land by
  degrading lignin to CO2 and cellulose to glucose.
• Excellent candidates for bioremediation, cleaning
  up contaminated soils or waters.
• Metabolic pathways of fungi are used by humans to
  produce food and pharmaceuticals.
• Mycorrhizal fungi provide nutrients for land
  plants.
• Many are edible, and some are delicacies.
• Responsible for billions of dollars of
  agricultural losses annually, and cause many
  human and animal diseases.

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Laurel Wilt

• The Alabama Forestry Commission says two beetles
  trapped in a tree in Mobile County have been
  confirmed as redbay ambrosia beetles.
• Redbay ambrosia beetles (Xyleborus glabratus)
  carry a fungus that causes a destructive disease
  called laurel wilt.
• The fungus (Rafaelea lauricola) moves into redbay
  tree (Persea borbonia) and clogs its vascular
  system, causing it to wilt.
• Redbay is the most susceptible tree, but
  sassafras, camphor, and avocado, among others,
  are also known to succumb from laurel wilt
  disease.
• The fungus is introduced into the host trees by a
  non-native insect such as the redbay beetles.

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Importance of Fungi

• Some produce toxins and carcinogenic and
  hallucinogenic compounds
• Aspergillus flavus produces aflatoxins.
• Fusarium spp. produce vomitoxin.
• Penicillium aurantigriseum produces mycotoxins
  that can cause considerable harms to humans and
  animals.
• Amanita phalloides (the death cap) produces
  toxins responsible for over 90 of human deaths
  from fungus poisonings.
• Amanita muscaria (fly agaric) produces the
  hallucinogenic drugs muscaria and muscimol.
• Coccidiodes posadasii, a soil ascomycete endemic
  in Southwestern US, can cause a fatal infection
  in humans, and has been considered a possible
  bioterrorism threat. Annual infection rate is
  100,000 individuals.
• The chytrid Batrachochytrium dendrobatidis causes
  chytridiomycosis that kills frogs worldwide.

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Importance of Fungi

• Alcohol Beer, wine, Japanese saki, and other
  national drinks.
• Food Bread, cheese, yogurt, soy sauce, fermented
  foods.
• Edible fungi include mushrooms, morels, truffles,
  Coprinus comatus, and many more.
• Pharmaceuticals Antibiotics, cyclosporin,
  fumagillin, etc.
• Aspergillus fumigatus produces fumagillin which
  is used to treat cancer and rheumatoid arthritis
• Fumagillin is also used against the parasitic
  fungus Nosema apis which causes colony collapse
  disorder in the honeybees
• Useful organic acids such as citric and gallic
  acids.
• Gibberellins (plant growth hormones).

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Classification of Fungi

• The Kingdom Fungi is divided into six phyla based
  on type of structure in which spores are produced
  sexually.
• Deuteromycota, the imperfect fungi (no sexual
  reproduction observed). Include Microsporidia
  (single celled and parasitic)
• Chytridiomycota, the chytrids (sporophytic
  mycelium)
• Zygomycota, zygomycetes (zygosporangium)
• Glomeromycota, arbuscular mycorrhizal fungi (no
  sexual phase observed)
• Basidiomycota, basidiomycetes or club fungi
  (basidium)
• Ascomycota, ascomycetes or sac fungi (ascus)

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Edible Mushrooms

• Agaricus bisporus White button mushroom
• Basidiocarp showing cap, stipe and gills

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Edible MushroomsAgaricus campestris, common
field mushroom
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Agaricus campestrisCross section of gill showing
basidia with 4 basidiospores each, and sterigmata
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More Edible Mushrooms Morels Truffles
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Truffles, expensive delicaciesTuber magnatum
(white truffles) T. melanosporum (black truffles)
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Coprinus comatus Lawyers capHighly esteemed by
many as eatable, but not with alcohol!
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Amanita muscaria MycotoxicosisFly agaric
contains the hallucinogenic drugs muscaria and
muscimol
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Amanita phalloides MycotoxicosisDeath cap
responsible for over 90 of human deaths from
fungus poisonings.
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Various types of wild mushrooms
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Human Mycoses

• The most common human mycoses include
• Aspergillosis
• Blastomycosis
• Candidiasis
• Chromoblastomycosis
• Coccidioidomycosis
• Cryptococcosis
• Histoplasmosis
• Lobomycosis
• Mycetoma
• Paracoccidioidomycosis
• Phaeohyphomycosis
• Sporotrichosis
• Zygomycosis

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How to Avoid Human Mycoses

• Maintain a strong immune system
• Cleanliness
• Keep your home and office dry and well-ventilated
  
• Avoid infected fruits, vegetables, seeds, and
  other vegetation.
• Use antifungal treatments when infection occurs

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Aspergillosis Aspergillus spp.

• Aspergillus spp. are secondary opportunistic
  pathogens that can cause
• Bronchopulmonary aspergillosis
• Pulmonary aspergilloma
• Invasive aspergillosis
• Colonization of respiratory tract
• Sites involved include lungs, sinuses, and skin.
• Severity and clinical manifestation depends on
  immunologic state of patient
• Aspergillus spp. are found in soil and decaying
  vegetation.

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Mycoses caused by Aspergillus flavus

• Aflatoxins, which are among the most carcinogenic
  compounds known, cause mycotoxicosis.
• Aflatoxins can damage the kidneys and the nervous
  system.
• Some members of the genus Aspergillus can cause
  several human diseases such as aspergillosis,
  ringworm, and athletes foot.

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Aspergillosis Aspergillus pneumonia
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Blastomycosis Blastomyces dermatitidis

• Endemic in Southeastern and South Central states,
  along the Mississippi and Ohio Rivers.
• Affects lungs, skin, bones, and joints.
• Fungus found around streams or rivers with high
  content of soil enriched with organic debris
  and/or rotting wood.
• Infection is caused by inhalation of conidia.
• Forms of blastomycosis
• Asymptomatic
• Acute pulmonary
• Chronic pulmonary
• Skin disease
• Subcutaneous lesions
• Bone and joint infection
• Genitourinary tract infection

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Blastomycosis Blastomyces dermatitidis Lesion
near eye and on nose following dissemination from
lungs
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Blastomycosis Blastomyces dermatitidis
Cutaneous lesion following dissemination from
lungs
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Candidiasis Candida albicans

• Candida are thin-walled small yeasts that
  reproduce by budding.
• Spores found in soil, inanimate objects, food,
  and hospital environment.
• Forms of infection
• Skin and mucosal surfaces
• Mouth and tongue
• Systemic (invasive) candidiasis affects various
  organs
• Bone and joints
• Brain and nerves
• Eye (endophthalmitis)
• Vagina (vulvovaginitis)

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Candidiasis Candida albicans Invasive
candidiasis in young infants
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Oral thrush Candida albicans

• Mouth of normal newborn infants has a low pH
  which may promote proliferation of fungus.
• Infections are usually acquired during birth from
  mothers who had vaginal thrush during pregnancy.
• Clinical symptoms may persist until a balanced
  oral flora is established.

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Candidiasis Candida albicansOral thrush. White
material consists of budding yeast cells and
pseudohyphae
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Candidiasis Candida albicans Mucocutaneous
candidiasis showing lesions on hands
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Candidiasis Candida albicans Candidiasis of the
penis and groin
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Chromoblatomycosis

• Caused by
• Cladophialophora carrionii
• Phialophora verrucosa
• Fonsencaea pedrosoi
• Chronic localized infection of skin and
  subcutaneous tissue
• Affects hands, arms, and feet
• Remains localized with extensive keloid formation
• After many years, lesions may resemble the head
  of cauliflower

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Chromoblastomycosis Phialophora verrucosa
Chronic foot infection
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Chromoblastomycosis Fonsencaea pedrosoi
Verrucose form and chronic nodular lesions on
foot and leg
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Coccidioidomycosis Coccidiodes immitis

• Also known as the Valley Fever.
• Found only in the Western Hemisphere.
• In the US, endemic areas include Southern
  Arizona, Central California, Southern New Mexico,
  and West Texas.
• Outbreaks occur following dust storms,
  earthquakes, and earth excavation where dispersal
  of conidia is favored.
• Acquired by inhalation of conidia. Once in lungs,
  conidia transform into spherical cells called
  spherules.
• Causes pulmonary syndrome, diffuse pneumonia, and
  skin rash and lesions.
• Acute respiration infection occurs 7 21 days
  after infection.

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Coccidioidomycosis Coccidioides immitis Nose
lesion and multiple skin lesions resulted from
dissemination of fungus from lungs
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Coccidioidomycosis Coccidioides immitis Chronic
cutaneous infection showing lesions on face,
neck, and chin
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Coccidioidomycosis Coccidioides immitis
Extension of pulmonary infection showing a large
superficial ulcerated plaque
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Cryptococcosis Cryptococcus neoformans

• Primary infection may remain localized into lungs
  or disseminate throughout body.
• Cryptococcal meningitis can occur once fungus
  reaches CNS tissue.
• Primary pulmonary infections are usually
  asymptomatic.
• Prostate may be a reservoir for relapse.
• Infects lungs, central nervous system, and skin.
• Considered opportunistic infection as it affects
  mainly immunosuppressed individuals.
• AIDS, cancer, organ transplant, and diabetes are
  risk factors.

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Cryptococcosis Cryptococcus neoformans
Ulcerated perianal skin lesion
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Entomophthoromycosis

• Caused by Entomophthorales, a family in the
  phylum Zygomycota
• Basidiobolus ranarum
• Coccidiodes coronatus
• Disease associated with acidotic diabetics,
  malnourished children, and severely burned
  patients.
• Also seen with leukemia, lymphoma, AIDS, and use
  of immunosuppressive drugs such as
  corticosteroids.
• Infection typically involves the
  rhino-facial-cranial area, lungs,
  gastrointestinal tract, and skin
• Rhinocerebral disease in acidotic patients
  usually results in death

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Entomophthoromycosis Basidiobolus ranarum
Subcutaneous lesions involving entire thigh and
buttock
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Entomophthoromycosis Basidiobolus ranarum
Ulcerated subcutaneous lesions on abdomen of
young boy
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Entomophthoromycosis Coccidioides coronatus
Massive swelling and distortion of subcutaneous
tissue of nasal and perioral regions, with a
large polypoid protrusion on the inner aspect of
lower lip
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Lobomycosis Lacazia loboi

• Fungus also called Loba loboi and Blastomyces
  loboi
• Causes keloid lesions on face, ear, leg, and arm
• Endemic in rural regions of South and Central
  America, especially the Amazon Valley of Brazil

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Lobomycosis Lacazia loboi Keloid lesions on leg