ch22

Question 1

fungi

Answer 1

Most fungi exist as saprobes (absorbing
nutrients from dead organisms) and function as the major
decomposers of organic matter in the environment.

Question 2

mycoses transmission

Answer 2

Mycoses are typically acquired via inhalation, trauma,

or ingestion; only very infrequently are fungi spread from person to prson.

Question 3

mycoses transmission exception

Answer 3

One group of fungi that are contagious are dermatophytes, which live on the dead layers of skin and which
may be transmitted between people via fomites (inanimate objects).
Species of the genera Candida and Pneumocystis also appear to be transmitted at least some of
the time by contact among humans.

Question 4

true fungal pathogens

Answer 4

Of all the fungi known to cause disease in humans, only four—
Blastomyces dermatitidis, Coccidioides immitis, Histoplasma capsulatum,
and Paracoccidioides brasiliensis—are considered true
pathogens; that is, they can cause disease in otherwise healthy
individuals.

Question 5

opportunistic fungi

Answer 5

Other fungi, such as the common yeast, Candida
albicans (al´bi@kanz), are opportunistic fungi, which lack genes
for proteins that aid in colonizing body tissues, though they can
take advantage of some weakness in a host’s defenses to become
established and cause disease.

Question 6

Four main factors increase an individual’s risk of experiencing
opportunistic mycoses:

Answer 6

invasive medical procedures, medical therapies, certain disease conditions, and specific lifestyle
factors

Question 7

fungal pathogens and opportunists differ with

respect to geographical distribution:

Answer 7

Whereas the four pathogenic
fungi are endemic to certain regions, primarily in the Americas,
opportunistic fungi are distributed throughout the world.

Question 8

dermatophytes

Answer 8

fungi that normally live on the skin,
nails, and hair—are the only fungi that do not fall comfortably
into either the pathogenic or the opportunistic grouping.
They are considered by some researchers to be “emerging”
pathogens. Dermatophytes can infect all individuals, not just
the immunocompromised, which makes them similar to the
pathogens. They are not, however, intrinsically invasive, being
limited to body surfaces. They also have a tendency to occur in
people with the same predisposing factors that allow access by
opportunistic fungi. For these reasons, dermatophytes will be
discussed as opportunists rather than as pathogens.

Question 9

Fungal diseases are grouped into the following three categories
of clinical manifestations:

Answer 9

• fungal infections
• toxicoses
• allergies

Question 10

fungal infections

Answer 10

the most common mycoses, are
caused by the presence in the body of either true pathogens
or opportunists.

Question 11

toxicoses

Answer 11

Toxicoses (poisonings) are acquired through ingestion, as

occurs when poisonous mushrooms are eaten. rlatively rare

Question 12

allergies

Answer 12

Allergies (hypersensitivity reactions) most commonly result

from the inhalation of fungal spores

Question 13

Microbiologists culture fungi collected from patients on

Answer 13

Sabouraud dextrose agar, a medium that favors fungal growth

over bacterial growth

Question 14

KOH preparations

Answer 14

Potassium hydroxide (KOH) preparations dissolve keratin in skin
cells, leaving only fungal cells for examination

Question 15

GMS stain

Answer 15

Gomori methenamine
silver (GMS) stain is used on tissue sections to stain fungal
cells, black (other cells remain unstained

Question 16

direct immunofluorescence stain

Answer 16

used to detect fungal cells
in tissues; immunological tests are not always
useful for fungi

Question 17

Diagnosis of opportunistic fungal infections is especially

challenging:

Answer 17

When a fungal opportunist infects tissues in which
it is normally not found, it may display abnormal morphology
that complicates identification.
- fungal masses resemble tumors
- symptoms andimaging profiles that resemble TB

Question 18

Mycoses are among the most difficult diseases to heal for two
reasons.

Answer 18

First, fungi generally possess the biochemical ability to
resist T cells during cell-mediated immune responses. Second,
fungi are biochemically similar to human cells, which means
that most fungicides are toxic to human tissues.

Question 19

The majority
of antifungal agents exploit one of the few differences between
human and fungal cells:

Answer 19

instead of cholesterol, the membranes
of fungal cells contain a related molecule, ergosterol. Antifungal
drugs target either ergosterol synthesis or its insertion into fungal
membranes. However, cholesterol and ergosterol are not
sufficiently different to prevent some damage to human tissues
by such antifungal agents

Question 20

Serious side effects associated with

long-term use of almost all antifungal agents include

Answer 20

anemia,
headache, rashes, gastrointestinal upset, and serious liver and
kidney damage.

Question 21

The “gold standard” of antifungal agents is

Answer 21

the fungicidal
drug amphotericin B, considered the best drug for treating systemic
mycoses and other fungal infections that do not respond
to other drugs. Unfortunately, it is also one of the more toxic
antifungal agents to humans.

Question 22

azoles

Answer 22

Some major anti-ergosterol alternatives
to amphotericin B are the azole drugs—ketoconazole,
itraconazole, and fluconazole—which are fungistatic (inhibitory)
rather than fungicidal and less toxic to humans.

Question 23

With just a few antifungal drugs being used for long periods
and treating more and more patients, scientists predict that the
drugs should select drug-resistant strains from the fungal population.

Answer 23

Fortunately, this is rarely the case; naturally occurring
resistance, especially against amphotericin B, is extremely rare,
though researchers cannot explain why resistance does not develop
as it does in bacterial populations under similar conditions
of long-term use.

Question 24

Treatment of opportunistic fungal infections in immunocompromised
patients involves

Answer 24

two steps: a high-dose treatment
to eliminate or reduce the number of fungal pathogens, followed
by long-term (usually lifelong) maintenance therapy involving
the administration of antifungal agents to control ongoing infections
and prevent new infections.

Question 25

Three antifungal drugs that do not target ergosterol are

Answer 25

griseofulvin, 5-fluorocytosine, and echinocandins

Question 26

griseofulvin

Answer 26

interferes with microtubule formation and chromosomal
separation in mitosis. Griseofulvin accumulates in the outer epidermal layers of the skin, preventing fungal penetration
and growth. Since these skin cells are scheduled to die as they
move toward the surface, griseofulvin’s toxicity does not permanently
damage humans.

Question 27

5-Fluorocytosine

Answer 27

a nucleoside analog that inhibits RNA

and DNA synthesis

Question 28

echinocandins

Answer 28

inhibit the synthesis of 1,3-d-glucan, which is
a sugar that makes up part of the cell wall of a fungus. This
sugar does not occur in mammals

Question 29

mycoses prevention

Answer 29

Prevention of fungal infections generally entails avoiding
endemic areas and keeping one’s immune system healthy.
Vaccines against fungi have been difficult to develop because
fungal metabolism is similar to our own.

Question 30

systemic mycoses

Answer 30

Systemic mycoses—those fungal infections that spread
throughout the body—result from infections by one of the
four pathogenic fungi: Histoplama, Blastomyces, Coccidioides,
or Paracoccidioides. All are in the fungal division Ascomycota.
These pathogenic fungi are uniformly acquired through inhalation,
and all begin as a generalized pulmonary infection that
then spreads via the blood to the rest of the body. dimorphic

Question 31

dimorphic

Answer 31

the four pathogenic fungi
- In the environment, where the temperature is
typically below 30°C, they appear as mycelial thalli composed
of hyphae, whereas within the body (37°C) they grow as spherical
yeasts

Question 32

Yeast forms

Answer 32

invasive bc they express a variety of enzymes and other proteins that aid
their growth and reproduction in the body. For example, they
are tolerant of higher temperatures and are relatively resistant
to phagocytic killing

Question 33

histoplasmosis organism

Answer 33

histoplasma capsulatum; an
ascomycete and the most common fungal pathogen affecting
humans.

Question 34

histoplasma capsulatum env

Answer 34

found in moist soils containing high levels of
nitrogen, such as from the droppings of bats and birds. Spores
may become airborne and inhaled when soil containing the
fungus is disturbed by wind or by human activities.

Question 35

h capsulatum in the body

Answer 35

H. capsulatum is an intracellular parasite that survives inhalation
and subsequent phagocytosis by macrophages in air
sacs of the lungs. These macrophages then disperse the fungus
beyond the lungs via the blood and lymph. Cell-mediated immunity eventually develops, clearing the organism from
healthy patients

Question 36

histoplasma disease

Answer 36

• 95p asymptomatic

- 5p clinical: chronic pulmonary, chronic cutaneous, systemic, ocular histoplasmosis

Question 37

chronic pulmonary histoplasmosis

Answer 37

characterized by severe
coughing, blood-tinged sputum, night sweats, loss
of appetite, and weight loss. It is often seen in individuals
with preexisting lung disease. It can be mistaken for
tuberculosis

Question 38

chronic cutaneous histoplasmosis

Answer 38

characterized by ulcerative
skin lesions, can follow the spread of infection from the
lungs.

Question 39

systemic histoplasmosis

Answer 39

can also follow if infection spreads
from the lungs, but it is usually seen only in AIDS patients.
This syndrome, characterized by enlargement of the spleen
and liver, can be rapid, severe, and fatal.

Question 40

ocular histoplasmosis

Answer 40

a type I hypersensitivity reaction
against Histoplasma in the eye; it is characterized by inflammation
and redness.

Question 41

histoplasmosis diagnosis

Answer 41

Diagnosis of histoplasmosis is based on the identification
of the distinctive budding yeast in KOH- or GMS-prepared
samples of skin scrapings, sputum, cerebrospinal fluid, or various
tissues. The diagnosis is confirmed by the observation of
dimorphism in cultures grown from such samples. Cultured
H. capsulatum produces distinctively spiny spores that are
also diagnostic

Question 42

blastomycoses organism

Answer 42

caused by another ascomycete,

Blastomyces dermatitidis

Question 43

Blastomyces dermatitidis env

Answer 43

B. dermatitidis normally
grows and sporulates in cool, damp soil rich in organic
material, such as decaying vegetation and animal wastes. In
humans, both recreational and occupational exposure occurs
when fungal spores in soil become airborne and are inhaled.
A relatively small inoculum can produce disease.

Question 44

most common manifestation

of Blastomyces infection

Answer 44

Pulmonary blastomycosis is the most common manifestation
of Blastomyces infection. After spores enter the lungs,
they convert to yeast forms and multiply. Initial pulmonary
lesions are asymptomatic in most individuals. If symptoms
do develop, they are vague and include muscle aches,
cough, fever, chills, malaise, and weight loss. Purulent (pusfilled)
lesions develop and expand as the yeasts multiply,
resulting in death of tissues and cavity formation. In otherwise healthy people, pulmonary
blastomycosis typically resolves successfully, although
it may become chronic.

Question 45

types of blastomycosis

Answer 45

pulmonary, cutaneous, osteoarticular

Question 46

cutaneous blastomycosis

Answer 46

The fungus can spread beyond the lungs. Cutaneous blastomycosis
occurs in 60% to 70% of cases and consists of generally
painless lesions on the face and upper body (Figure 22.6). The
lesions can be raised and wartlike, or they may be craterlike if
tissue death occurs.

Question 47

osteoarticular blastomycosis

Answer 47

In roughly 30% of cases, the fungus spreads
to the spine, pelvis, cranium, ribs, long bones, or subcutaneous
tissues surrounding joints, a condition called osteoarticular2
blastomycosis

Question 48

Coccidioidomycosis organism

Answer 48

caused by

ascomycete Coccidioides immitis

Question 49

c immitis cycle

Answer 49

In the warm and dry summer and fall months, particularly
in drought cycles, C. immitis grows as a mycelium and produces
sturdy chains of asexual spores called arthroconidia. When mature,
arthroconidia germinate into new mycelia in the environment,
but if inhaled, arthroconidia germinate in the lungs to produce
a parasitic form called a spherule. As each
spherule matures, it enlarges and generates a large number of
spores via multiple cleavages, until it ruptures and releases the
spores into the surrounding tissue. Each spore then forms a new spherule to continue the cycle of division and release. This type
of growth accounts for the seriousness of Coccidioides infection.

Question 50

coccidioidomycosis symptoms

Answer 50

The major manifestation of coccidioidomycosis is pulmonary.
About 60% of patients experience either no symptoms or
mild, unremarkable symptoms that go unnoticed and typically resolve on their own. Other patients develop more severe infections
characterized by fever, cough, chest pain, difficulty breathing,
coughing up or spitting blood, headache, night sweats,
weight loss, and pneumonia; in some individuals a diffuse rash
may appear on the trunk.
- in those
who are severely immunocompromised, C. immitis spreads
from the lungs to various other sites. Invasion of the central
nervous system (CNS) may result in meningitis, headache,
nausea, and emotional disturbance. Infection can also spread
to the bones, joints, and painless subcutaneous tissues

Question 51

paracoccidioidomycosis organism

Answer 51

Another ascomycete, Paracoccidioides brasiliensis

Question 52

what is paracoccidioidomycosis

Answer 52

a chronic fungal disease similar to
blastomycosis and coccidioidomycosis.
- Because this fungus is far more
geographically limited than the other true fungal pathogens,
paracoccidioidomycosis is not a common disease.

Question 53

paracoccidioidomycosis organism env

Answer 53

Paracoccidioides brasiliensis is found

in cool, damp soil

Question 54

paracoccidioidomycosis symtptoms

Answer 54

Infections range from asymptomatic to systemic, and disease
first becomes apparent as a pulmonary form that is slow
to develop but manifests as chronic cough, fever, night sweats,
malaise, and weight loss. The fungus almost always spreads,
producing a chronic inflammatory disease of mucous membranes.
Painful ulcerated lesions of the gums, tongue, lips,
and palate progressively worsen over the course of weeks to
months

Question 55

paracoccidioidomycosis diagnosis

Answer 55

KOH or GMS preparations of tissue samples reveal yeast
cells with multiple buds in a “steering wheel” formation that is
diagnostic for this organism

Question 56

Opportunistic mycoses do not typically affect healthy humans

because

Answer 56

the fungi involved lack genes for virulence factors that

make them actively invasive.

Question 57

Even though any fungus can become an opportunist, five genera of fungi are routinely encountered:

Answer 57

Pneumocystis,

Candida, Aspergillus, Cryptococcus, and Mucor.

Question 58

Opportunistic infections present a formidable challenge to

clinicians.

Answer 58

Because they appear only when their hosts are weakened,
they often display “odd” clinical signatures; that is, their
symptoms are often atypical, or they occur in individuals not
residing in endemic areas for a particular fungus.

Question 59

PCP organism

Answer 59

Pneumocystis pneumonia; ascomycete Pneumocystis pneumonia
- formerly known as P. carinii n classified as protozoan (reclassified as a fungus based on rRNA nucleotide sequences
and biochemistry. Its morphological and developmental characteristics,
however, still resemble those of protozoa more than
those of fungi.)
- Because P. jiroveci is an obligate parasite and cannot
survive on its own in the environment, transmission most
likely occurs through inhalation

Question 60

PCP how widespread

Answer 60

Prior to the AIDS epidemic,
disease caused by Pneumocystis was extremely rare. Now, the disease is almost diagnostic
for AIDS.
- P. jiroveci is distributed worldwide in humans; based on
serological confirmation of antibodies, the majority of healthy
children (75%) have been exposed to the fungus by the age of
five

Question 61

PCP symptoms

Answer 61

Once the fungus enters the lungs of an AIDS patient, it multiplies
rapidly, extensively colonizing the lungs because the patient’s
defenses are impaired. Widespread inflammation, fever,
difficulty in breathing, and a nonproductive cough are characteristic.
If left untreated, PCP involves more and more lung tissue
until death occurs.

Question 62

PCP opportunistic aspect

Answer 62

In immunocompetent people, infection is asymptomatic,
and generally clearance of the fungus from the body is followed
by lasting immunity

Question 63

candidiasis organism

Answer 63

any opportunistic fungal infection
or disease caused by various species of the genus Candida (dimorphic ascomycetes)—
most commonly Candida albicans

Question 64

candida env

Answer 64

common members of the
microbiota of the skin and mucous membranes; for example,
the digestive tracts of 40% to 80% of all healthy individuals harbor
Candida species.

Question 65

candidiasis diagnosis

Answer 65

Physicians diagnose candidiasis on the basis of signs and
demonstration of clusters of budding yeasts (see Figure 22.1b)
and pseudohyphae, which are series of buds remaining attached
to the parent cell and appearing as a filamentous hypha

Question 66

candidiasis in immunocompetent patients

Answer 66

In immunocompetent patients for whom excessive friction
and body moisture in skin folds or preexisting diseases
are the reasons for fungal colonization, resolution involves
treating these underlying problems in addition to administering
topical antifungal agents

Question 67

candidiasis opportunistic aspect

Answer 67

• It is Candida that causes vaginal
  yeast infections, as the fungus grows prolifically when
  normal bacterial microbiota are inhibited due to changes in
  vaginal pH or use of antibacterial drugs
• Systemic disease is seen almost universally in immunocompromised
  individuals

Question 68

thrush

Answer 68

oral candidiasis

Question 69

aspergillosis organism

Answer 69

not a single disease but instead
a term for several diseases resulting from the inhalation of spores
of fungi in the genus Aspergillus

Question 70

aspergillosis organism env

Answer 70

Aspergillus is found in soil, food, compost, agricultural
buildings, and air vents of homes and offices worldwide.
- Because the fungi are so common in the environment,
little can be done to prevent exposure to the spores.

Question 71

aspergillosis manifestation

Answer 71

Although
exposure to Aspergillus most commonly causes only allergies, more
serious diseases can occur, and aspergillosis is a growing problem
for AIDS patients.
- can be opportunistic pathogens
of almost all body tissues
- 3 clinical pulmonary diseases: hypersensitivity, noninvasive, acute invasive pulmonary aspergillosis

Question 72

Hypersensitivity aspergillosis

Answer 72

manifests as asthma or other
allergic symptoms and results most commonly from inhalation
of Aspergillus spores. Symptoms may be mild and
result in no damage, or they may become chronic, with recurrent
episodes leading to permanent damage.

Question 73

nonivasive aspergillosis

Answer 73

ball-like masses of fungal
hyphae—can form in the cavities resulting from a previous
case of pulmonary tuberculosis. Most cases are asymptomatic,
though coughing of blood-tinged sputum may occur.

Question 74

Acute invasive pulmonary aspergillosis

Answer 74

more serious. Signs
and symptoms, which include fever, cough, and pain, may
present as pneumonia. Death of lung tissue can lead to significant
respiratory impairment.

Question 75

Aspergillus also causes

Answer 75

nonpulmonary disease when aspergillomas
form in paranasal sinuses, ear canals, eyelids (Figure 22.14),
the conjunctivas, eye sockets, or brain

Question 76

cryptococcosis organism

Answer 76

A basidiomycete, Cryptococcus neoformans
- C neoformans gattii
- C. neoformans neoformans is found
worldwide and infects mainly AIDS patients. Approximately
50% of all cryptococcal infections reported each year are due to
strain neoformans.

Question 77

cryptocossosis transmission

Answer 77

Human infections follow the inhalation of spores or dried

yeast in aerosols from the droppings of birds.

Question 78

The pathogenesis of Cryptococcus is enhanced by several characteristics
of this fungus:

Answer 78

the presence of a phagocytosis-resistant
capsule surrounding the yeast form; the ability of the yeast to produce
melanin, which further inhibits phagocytosis; and the organism’s
predilection for the central nervous system (CNS), which is
isolated from the immune system by the so-called blood-brain barrier.
Cryptococcal infections also tend to appear in terminal AIDS
patients when little immune function remains.

Question 79

list of cryptococcoses

Answer 79

• primary pulmonary cryptococcosis
• cryptococcal meningitisi
• cryptococcoma
• cutaneous cryptococcosis

Question 80

Primary pulmonary cryptococcosis

Answer 80

is asymptomatic in most individuals,
although some individuals experience a low-grade fever,
cough, and mild chest pain

Question 81

Cryptococcal meningitis

Answer 81

the most common clinical form of
cryptococcal infection, follows dissemination of the fungus to
the CNS. Symptoms develop slowly and include headache, dizziness,
drowsiness, irritability, confusion, nausea, vomiting, and
neck stiffness. In late stages of the disease, loss of vision and
coma occur. Acute onset of rapidly fatal cryptococcal meningitis
occurs in individuals with widespread infection

Question 82

cryptococcoma

Answer 82

a very rare condition
in which solid fungal masses form in the cerebral hemispheres,
cerebellum, or (rarely) in the spinal cord. The symptoms of this
condition, which can be mistaken for cerebral tumors, are similar
to those of cryptococcal meningitis but also include motor
and neurological impairment.

Question 83

Cutaneous cryptococcosis

Answer 83

Primary infections
manifest as ulcerated skin lesions or as inflammation of subcutaneous
tissues. Infection may resolve on its own, but patients should
be monitored for infection spreading to the CNS. Secondary
cutaneous lesions occur following spread of Cryptococcus to other
areas of the body. In AIDS patients, cutaneous cryptococcosis is the
second most common manifestation of Cryptococcus infection (after
meningitis). Lesions are common on the head and neck.

Question 84

zygomycoses organisms

Answer 84

various genera of fungi classified in the division

Zygomycota, especially Mucor (sometimes rhizopus, absidia)

Question 85

zygomycoses organism env

Answer 85

extremely common in soil, on decaying

organic matter, or as contaminants that cause food spoilage

Question 86

zygomycoses oopportuistic aspect

Answer 86

Zygomycoses are commonly seen in patients with uncontrolled
diabetes, in people who inject illegal drugs, in some
cancer patients, and in some patients receiving antimicrobial
agents.

Question 87

Rhinocerebral zygomycosis

Answer 87

begins with infection of the nasal
sinuses following inhalation of spores. The fungus spreads
to the mouth and nose, producing macroscopic cottonlike
growths. Mucor can subsequently invade blood vessels,
where it produces fibrous clots, causes tissue death, and
subsequently invades the brain, which is fatal within days,
even with treatment.

Question 88

pulmonary zygomycosis

Answer 88

follows inhalation of spores (as from
moldy foods). The fungus kills lung tissue, resulting in the
formation of cavities.

Question 89

gastrointestinal zygomycosis

Answer 89

involves ulcers in the intestinal tract

Question 90

Cutaneous zygomycosis

Answer 90

results from the introduction of
fungi through the skin after trauma (such as burns or needle
punctures). Lesions range from pustules and ulcers to
abscesses and dead patches of skin.

Question 91

Over the course of the past decade,

several new fungal opportunists have been identified

Answer 91

Fusarium spp. and Penicillium marneffei, which are ascomycetes,
and Trichosporon beigelii, which is a basidiomycete.

Question 92

fusarium spp

Answer 92

cause respiratory distress,
disseminated infections, and fungemia (fungi in the bloodstream).
These species also produce toxins that can accumulate
to dangerous levels when ingested in food. Fusarium spp. are
resistant to most antifungal agents.

Question 93

penicillium marneffei

Answer 93

a dimorphic,

invasive fungus that causes pulmonary disease upon inhalation.

Question 94

trichosporon beigelii

Answer 94

When Trichosporon beigelii enters
an AIDS patient through the lungs, the gastrointestinal tract, or
catheters, it causes a drug-resistant systemic disease that is typically
fatal.

Question 95

Superficial, Cutaneous,

and Subcutaneous Mycoses

Answer 95

localized
at sites at or near the surface of the body. They are the most commonly
reported fungal diseases. All are opportunistic infections,
but unlike those we have just discussed, they can be acquired both
through environmental exposure and more frequently via personto-person
contact. Most of these fungi are not life threatening, but
they often cause chronic, recurring infections and diseases.

Question 96

Superficial, Cutaneous,

and Subcutaneous Mycoses

Answer 96

localized
at sites at or near the surface of the body. They are the most commonly
reported fungal diseases. All are opportunistic infections,
but unlike those we have just discussed, they can be acquired both
through environmental exposure and more frequently via personto-person
contact. Most of these fungi are not life threatening, but
they often cause chronic, recurring infections and diseases.

Question 97

superficial mycoses

Answer 97

Superficial mycoses are the most common fungal infections.
They are confined to the outer, dead layers of the skin, nails, or
hair, all of which are composed of dead cells filled with a protein
called keratin—the primary food of these fungi. In AIDS patients,
superficial mycoses can spread to cover significant areas
of skin or become systemic.

Question 98

ringworms

Answer 98

dermatophytoses were called ringworms because
dermatophytes produce circular, scaly patches that resemble
a worm lying just below the surface of the skin.

Question 99

dermatophytes

Answer 99

Dermatophytes use keratin as a nutrient
source and thus colonize only dead tissue. The fungi may
provoke cell-mediated immune responses, which can damage
living tissues. Dermatophytes are among the few contagious
fungi; that is, fungi that spread from person to person. Spores
and bits of hyphae are constantly shed from infected individuals,
making recurrent infections common.

Question 100

dermatophytoses organisms

Answer 100

3 genera of ascomycetes r responsiblefor most:

1. trichophyton spp
2. epidermophyto floccosum
3. microsporum spp

Question 101

athletes foot

Answer 101

tinea pedis 
- Red, raised lesions on and
around the toes and soles of the
feet; webbing between the toes
is heavily infected

Question 102

jock itch

Answer 102

tinea cruris
- Red, raised lesions on and
around the groin and buttocks

Question 103

tinea unguium

Answer 103

onychomycosis
- superficial white: patches or pits on the nail surface
- invasive: yellowing
and thickening of the distal
nail plate, often leading to loss
of the nail

Question 104

tinea corporis

Answer 104

Red, raised, ringlike lesions occurring

on various skin surfaces

Question 105

tinea capitis

Answer 105

ectothrix invasion, endothrix invasion, favus

Question 106

ectothrix invasion

Answer 106

fungus
develops arthroconidia on the
outside of the hair shafts,
destroying the cuticle

Question 107

endothrix invasion

Answer 107

fungus develops
arthroconidia inside the
hair shaft without destruction

Question 108

favus

Answer 108

crusts form on the scalp,

with associated hair loss

Question 109

pityriasis organism

Answer 109

the dimorphic basidiomycete malassezia furfur

Question 110

m furfur env

Answer 110

a normal member of the microbiota of the skin of
humans worldwide. It feeds on the skin’s oil and causes common,
chronic superficial infections.

Question 111

pityriasis symptoms

Answer 111

characterized by depigmented or hyperpigmented patches of
scaly skin resulting from fungal interference with melanin production
(Figure 22.16). This condition typically occurs on the
trunk, shoulders, and arms, and rarely on the face and neck.

Question 112

sub, cutaneous mycoses

Answer 112

The fungi involved in cutaneous and subcutaneous mycoses are
common soil saprobes (organisms that live on dead organisms),
but the diseases they produce are not as common as superficial
mycoses because infection requires traumatic introduction
of fungi through the dead outer layers of skin into the deeper,
living tissue. Most lesions remain localized just below the skin,
though infections may rarely become systemic.

Question 113

chromoblastomycosis, phaeohyphomycosis orgaisms

Answer 113

caused by dark-pigmented
ascomycetes. Despite the worldwide occurrence of the relevant fungi,
the overall incidence of infection is relatively low. People who
work daily in the soil with bare feet are at risk if they incur foot
wounds. prevention by wearing shoes

Question 114

chromoblastomycosis symptoms

Answer 114

Initially, chromoblastomycosis uniformly presents as small,
scaly, itchy, but painless lesions on the skin surface resulting
from fungal growth in subcutaneous tissues near the site of
inoculation. Over the course of years and decades, the lesions
progressively worsen, becoming large, flat to thick, tough, and
wartlike. They become tumorlike and extensive if not treated
(Figure 22.17). Inflammation, fibrosis, and abscess formation
occur in surrounding tissues. The fungus can spread throughout
the body

Question 115

Phaeohyphomycoses

Answer 115

more variable in presentation, involving
colonization of the nasal passages and sinuses in allergy
sufferers and AIDS patients or of the brains of AIDS patients.
Fortunately, brain infection is the rarest form of phaeohyphomycosis
and occurs only in the severely immunocompromised

Question 116

Phaeohyphomycoses vs chromoblastomycosis

Answer 116

key distinguishing
feature between the two diseases: the microscopic morphology
of the fungal cells within tissues. Tissue sections from
chromoblastomycosis cases contain golden brown sclerotic bodies
that are distinctive and distinguishable from budding yeast
forms (Figure 22.18a), whereas tissues from phaeohyphomycosis
cases contain brown-pigmented hyphae.

Question 117

mycetomas organisms

Answer 117

caused by fungi of several genera in the division Ascomycota. The cases
that occur in the United States are almost always caused by
Pseudallescheria or Exophiala

Question 118

mycetoma organism env

Answer 118

Mycetoma-producing fungi live in the soil and are introduced
into humans via wounds caused by twigs, thorns, or
leaves contaminated with fungi. As with chromoblastomycosis
and phaeohyphomycosis, those who work barefoot in soil
are most at risk, and wearing protective shoes or clothing can
greatly reduce incidence.

Question 119

mycetoma symptoms

Answer 119

Infection begins near the site of inoculation with the formation
of small, hard, subsurface nodules that slowly worsen and
spread as time passes. Local swelling occurs, and ulcerated lesions
begin to produce pus. Infected areas release an oily fluid
containing fungal “granules” (spores and fungal elements). The
fungi spread to more tissues, destroying bone and causing permanent
deformity.

Question 120

sporotrichosis organism

Answer 120

dimorphic ascomycte sporothrix schenckii

Question 121

sporotrichosis organism env

Answer 121

S. schenckii resides in the soil and is most commonly introduced by thorn pricks or wood splinters. Avid gardeners, farmers, and
artisans who work with natural plant materials have the highest
incidence of sporotrichosis.

Question 122

sporotrichosis symptoms

Answer 122

a subcutaneous infection usually limited to the arms or legs. Sporotrichosis initially appears as painless, nodular lesions that
form around the site of inoculation. With time, these lesions produce
a pus-filled discharge, but they remain localized and do not
spread. If the fungus enters the lymphatic system from a primary
lesion, it gives rise to secondary lesions on the skin surface along
the course of lymphatic vessels (Figure 22.20). The fungus remains
restricted to subcutaneous tissues and does not enter the blood.

Question 123

mycotoxins

Answer 123

fungal toxins. low molcular weight metabolites that can harm humans and animals that ingest them,
causing toxicosis

Question 124

fungal allergens

Answer 124

Fungal allergens are usually proteins or
glycoproteins that elicit hypersensitivity reactions in sensitive
people who contact them.

Question 125

Mycotoxicosis

Answer 125

caused by eating mycotoxins; the fungus itself is not present.

Question 126

Mycetismus

Answer 126

is mushroom poisoning resulting

from eating the fungus.

Question 127

mycotins env

Answer 127

Fungi produce mycotoxins during their normal metabolic activities.
People most commonly consume mycotoxins in grains
or vegetables that have become contaminated with fungi. Up to 25% of the world’s food
supply is contaminated with mycotoxins, but only 20 of the 300
or so known toxins are ever present at dangerous levels.
- Longterm
ingestion of mycotoxins can cause liver and kidney damage,
gastrointestinal or gynecological disturbances, or cancers;
each mycotoxin produces a specific clinical manifestation.

Question 128

aflatoxins organism

Answer 128

ascomycete Aspergillus

Question 129

aflatoxins

Answer 129

the best-known mycotoxins. Aflatoxins are fatal to
many vertebrates and are carcinogenic at low levels when consumed
continually. Aflatoxins cause liver damage and liver cancer
throughout the world

Question 130

aflatoxins env

Answer 130

aflatoxicosis is most prevalent in the tropics,
where mycotoxins are more common because of subsistence
farming, poor food-storage conditions, and warm, moist conditions
that foster the growth of Aspergillus in harvested foods

Question 131

useful mycotoxins

Answer 131

Among them are
ergot alkaloids, produced by some strains of another ascomycete,
Claviceps purpurea

Question 132

ergometrine

Answer 132

used to stimulate labor contractions and is used to
constrict the mother’s blood vessels after birth (when she is at
risk of bleeding excessively)

Question 133

ergotamine

Answer 133

used to treat migraine headaches.

Question 134

mushrooms

Answer 134

the spore-bearing structures of certain basidiomycetes

Question 135

must mushrooms arent toxic, though some

Answer 135

produce extremely dangerous
poisons capable of causing neurological dysfunction or
hallucinations, organ damage, or even death.

Question 136

toadstools

Answer 136

poisonous mushrooms

Question 137

myctismus treatment

Answer 137

Treatment involves inducing vomiting followed by oral
administration of activated charcoal to absorb toxins. Severe
mushroom poisoning may necessitate a liver transplant.

Question 138

deadliest mushroom toxin

Answer 138

produced by the “death
cap” mushroom, Amanita phalloides. The death cap contains two related polypeptide
toxins: phalloidin, which irreversibly binds actin within cells,
disrupting cell structure, and alpha-amanitin, which inhibits
mRNA synthesis. Both toxins cause liver damage.

Question 139

hallucinogenic mycotoxins

Answer 139

Psilocybe cubensis produces hallucinogenic
psilocybin, and Amanita muscaria produces
two hallucinogenic toxins—ibotenic acid and muscimol. These
toxins may also cause convulsions in children.

Question 140

Fungal allergens

typically cause

Answer 140

type I hypersensitivities in which immunoglobulin
E binds the allergen, triggering responses such as asthma,
eczema, hay fever, and watery eyes and nose.

Question 141

Fungal allergens

typically cause

Answer 141

type I hypersensitivities in which immunoglobulin
E binds the allergen, triggering responses such as asthma,
eczema, hay fever, and watery eyes and nose.

Question 142

type III hypersensitivities

Answer 142

Less frequently, type III hypersensitivities result from
chronic inhalation of particular fungal allergens. In these cases,
allergens that have penetrated deep into the lungs encounter complementary antibodies and form immune complexes in the
alveoli that lead to inflammation, fibrosis, and in some cases
death. Type III fungal hypersensitivities are associated with certain
occupations, such as farming, in which workers are constantly
exposed to fungal spores in moldy vegetation.