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Bloodborne
Pathogens
COURSE 2 | MODULE 4
Introduction to Fungi
Introduction
Introduction
Fungi is a general term used to encompass the diverse morphologic forms of
yeasts and molds. Originally classified as primitive plants without chlorophyll,
the fungi are placed in the kingdom Fungi.
Cause of Disease
Fungi share with bacteria the important ability to break down complex organic
substances of almost every type (cellulose) and are essential to the recycling of
carbon and other elements in the cycle of life. Fungi are important as foods and
to the fermentation process in the development of substances of industrial and
medical importance, including alcohol, antibiotics, other drugs, and foods.
Classification of Fungi
Glossary
Relatively few types of fungus are pathogenic for humans, whereas most plant
diseases are caused by fungi.
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Aspergillus niger
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Bloodborne Pathogens
COURSE 2 | MODULE 4
Cause of Disease
Introduction to
Fungi
Introduction
Cause
ofDisease
Disease
Cause of
Some fungi can cause serious diseases in humans, several of which may be
fatal if untreated. These include aspergillosis, candidiasis, coccidioidomycosis,
cryptococcosis, histoplasmosis, mycetomas, and paracoccidioidomycosis.
Furthermore, persons with immunodeficiencies are particularly susceptible to
disease by genera such as Aspergillus, Candida, Cryptoccocus, Histoplasma, and
Pneumocystis. Other fungi can attack eyes, nails, hair, and especially skin, the socalled dermatophytic and keratinophilic fungi, and cause local infections such as
ringworm and athlete’s foot. Fungal spores are also a cause of allergies, and fungi
from different taxonomic groups can evoke allergic reactions.
Microscopic image (100-fold magnification)
of Aspergillus nigar, grown on Sabouraud
agar medium.
Classification of Fungi
Glossary
Review
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Histoplasma capsulatum
(or Ajellomyces capsulatum)
causes Histoplasmosis which
mainly affects lungs.
A mycosis is a fungal infection.
Mycoses are common, and a variety of environmental and physiological conditions
can contribute to the development of fungal diseases. Inhalation of fungal spores
or localized colonization of the skin may initiate persistent infections; therefore,
mycoses often start in the lungs or on the skin.
At Risk
People are at risk of fungal infections when they are taking strong antibiotics for a
long period of time because antibiotics kill not only damaging bacteria, but healthy
bacteria as well. This alters the balance of microorganisms in the mouth, vagina,
intestines and other places in the body, and results in an overgrowth of fungus.
Individuals with weakened immune systems are also at risk of developing fungal
infections. This is the case of people with HIV/AIDS, people under steroid
treatments, and people taking chemotherapy. People with diabetes also tend to
develop fungal infections. Very young and very old people, also, are groups at risk.
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Bloodborne Pathogens
COURSE 2 | MODULE 4
Classification of Fungi
Introduction to
Fungi
Introduction
Cause of Disease
Classification of Fungi
Classification
of Fungi
Mycoses are classified according to the tissue levels initially colonized.
Superficial mycoses
Superficial mycoses are limited to the outermost layers of the skin and hair. An
example of such a fungal infection is Tinea versicolor, a fungus infection that
commonly affects the skin of young people, especially the chest, back, and upper
arms and legs. Tinea versicolor is caused by a fungus that lives in the skin of
some adults. It does not usually affect the face. This fungus produces spots that
are either lighter than the skin or a reddish-brown. This fungus exists in two forms,
one of them causing visible spots. Factors that can cause the fungus to become
more visible include high humidity, as well as immune or hormone abnormalities.
However, almost all people with this very common condition are healthy.
Cutaneous mycoses
Glossary
Review
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Cutaneous mycoses extend deeper into the epidermis, and also include invasive
hair and nail diseases. These diseases are restricted to the keratinized layers of
the skin, hair, and nails. Unlike the superficial mycoses, host immune responses
may be evoked, resulting in pathologic changes expressed in the deeper layers
of the skin. The organisms that cause these diseases are called dermatophytes.
The resulting diseases are often called ringworm (even though there is no worm
involved) or tinea. Cutaneous mycoses are caused by Microsporum, Trichophyton,
and Epidermophyton fungi, which together comprise 41 species.
Ringworm appears as red patches
which are often redder around the
outside with normal skin tone in the
center.
One common disease is the athlete’s
foot which most commonly affects men
and children before puberty. It is divided
in three categories: chronic interdigital
athlete’s foot, chronic scaly athlete’s
foot, and acute vesicular athlete’s foot.
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Bloodborne Pathogens
COURSE 2 | MODULE 4
Classification of Fungi (continued)
Introduction to
Subcutaneous mycoses
Introduction
Subcutaneous mycoses involve the dermis, subcutaneous tissues, muscle, and
fascia. These infections are chronic and can be initiated by piercing trauma to the
skin, which allows the fungi to enter. These infections are difficult to treat and may
require surgical interventions such as debridement.
Fungi
Systemic mycoses due to primary pathogens
Cause of Disease
Classification
of Fungi
Classification of Fungi
(continued)
Glossary
Review
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Systemic mycoses due to primary pathogens originate primarily in the lungs and
may spread to many organ systems. Organisms that cause systemic mycoses are
inherently virulent. Generally, primary pathogens that cause systemic mycoses
are dimorphic.
Systemic mycoses due to opportunistic pathogens
Systemic mycoses due to opportunistic pathogens are infections of patients
with immune deficiencies who would otherwise not be infected. An example of
an opportunistic pathogen is a form of fungal meningitis called cryptococcal
meningitis. Patients treated for cancer or chronic illnesses where treatments and/
or the disease itself compromise the patient’s immune system are particularly
vulnerable. Most common in AIDS patients, cryptococcal fungal meningitis cases
have increased globally during the past decade. National health data estimates the
incidence to be approximately 1,500 cases annually in the U.S. Other examples of
opportunistic mycoses include Candidiasis, Cryptococcosis and Aspergillosis.
In October 2012, an outbreak of fungal
meningitis was reported in the United States.
The U.S. Centers for Disease Control and
Prevention (CDC) traced the outbreak to
contaminated medication used for epidural
steroid injections. The U.S. Food and Drug
Administration (FDA) examined foreign
materials from unopened vials under
microscope and found fungal matter. The
fungus was found in the cerebrospinal fluid
of several patients, which confirmed that the
fungus caused the meningitis. A black mold
called Exserohilum rostratum was found in the
majority of the cases identified.
Exserohilum rostratum
Treatment
•
•
•
Antifungal drugs are used to treat mycoses.
Depending on the nature of the infection, a topical or systemic agent may be used.
Yeast infections in the vagina, caused by candida albicans, can be treated with
medicated suppositories such as tioconazole and pessaries whereas skin yeast
infections are treated with medicated ointments.
Prevention
•
•
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Keeping the skin clean and dry, as well as maintaining good hygiene is important.
Because fungal infections are contagious, it is important to consider isolation
procedures and extremely important to use gloves and clean hands after
patient care.
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Bloodborne Pathogens
COURSE 2 | MODULE 4
Glossary
Introduction to
Fungi
Athlete’s foot (noun) \ ath-leet z\ foot\
Also known as ringworm of the foot or tinea pedis, is a fungal infection of the skin
that causes scaling, flaking, and itching of affected areas
Introduction
Debridement (noun) \ dih-breed-muhnt\
The medical removal of dead, damaged or infected tissue to improve the healing
potential of the remaining healthy tissue
Cause of Disease
Dimorphism (noun) \ dahy-mawr-fiz-uhm\
Switching between two cell-types
Classification of Fungi
Epidermis (noun) \ ep-i-dur-mis\
Composed of the outermost layers of cells in the skin; ‘epi’ in Greek means ‘over’
or ‘upon’, which together with ‘dermis’ forms the cutis
Glossary
Glossary
Fungal meningitis (noun) \ fuhng-guh l\ men-in-jahy-tis\
Refers to meningitis caused by a fungal infection
Review
Meningitis (noun) \ men-in-jahy-tis\
An inflamation of the protective membranes covering the brain and spinal cord,
known collectively as the meninges
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Steroid (noun) \ ster-oid\
Any of a large number of hormonal substances with a similar basic chemical
structure, produced mainly in the adrenal cortex and gonads. Steroids are
chemically related to sterols
Click on the glossary term to return.
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Bloodborne Pathogens
COURSE 2 | MODULE 4
Review
Introduction to
Fungi
• Fungi is a general term used to encompass the diverse morphologic forms of
yeasts and molds.
• Some fungi can cause serious diseases in humans, several of which may
Introduction
be fatal if untreated. Furthermore, persons with immunodeficiencies are
particularly susceptible to fungal disease.
• Other fungi can attack eyes, nails, hair, and especially skin, and cause local
Cause of Disease
infections such as ringworm and athlete’s foot.
• Fungal spores are also a cause of allergies, and can evoke allergic reactions.
Classification of Fungi
Glossary
Review
Review
• People are at risk of fungal infections when they are taking strong antibiotics
for a long period of time because antibiotics kill not only damaging bacteria,
but healthy bacteria as well. This alters the balance of microorganisms in
the mouth, vagina, intestines and other places in the body, and results in an
overgrowth of fungus.
• Antifungal drugs are used to treat fungi. Depending on the nature of the
infection, a topical ointment, suppository or systemic agent may be used.
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Bloodborne Pathogens
COURSE 2 | MODULE 4
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Introduction to
Fungi
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