MICROBIOLOGY ASSIGNMENT.docx1HGWUYGYETYDGNBK

TABLE OF CONTENT
1. INTRODUCTION
2. Blastomycoses
3. Coccidiodomycoses
4. Paracoccidiodomycoses
5. Histoplasmosis
6. Summary

1. Introduction
• Systemic mycoses are fungal diseases that may affect internal organs and
may disseminate to multiple sites of the body
• sometimes known as deep mycoses.
• They are difficult to eradicate and many patients with deep mycoses die in
spite of extensive medical care especially when the central nervous system
is involved.
• Systemic mycoses occur in three disease forms:
• acute self limited pulmonary (asymptomatic to severe)
• chronic (pulmonary or disseminated)
disseminated
• Since many fungi that cause superficial or cutaneous mycoses are
skin parasites by nature, the source of infection is usually humans or
animals.
• The disease is transmitted directly from an infected person to a
susceptible host.
• The agents of subcutaneous and systemic mycoses, however, are
normally saprophytic fungi growing in the soil.
These fungi do not need human or animal hosts for survival because the primary
source of infection is soil
• Humans acquire these mycoses only when the spores of the soil
organisms are either inhaled or introduced in to the body through a break
in the skin.
• The systemic fungi include
• Blastomyces dermatitis (blastomycosis),
• Coccidioides immitis (coccidioidomycosis),
• Histoplasma capsulatum (Histoplasmosis),
• Paracoccidioides brasiliensis (paracoccidioidomycosis).

• These various systemic mycoses and their respective etiologic agents will
be considered separately despite their similarities.
2. Blastomycosis
Definition
• Blastomycosis refers to the disease caused by the endemic, saprophytic,
dimorphic fungus Blastomyces dermatitidis.
• It grows at room temperature as a white or tan mold but grows within the
host or at 37
0
c as budding, round yeast like cells.
• The fungus can be identified on the bases of its appearance, its
dimorphism the small spores borne as hyphae of the mold form, or the
results of nucleic hybridization.
Geographic Distribution:
• The disease is endemic in South Eastern and South Central states of North
America, along the Mississippi and Ohio Rivers.
• Source of infection:
• Outbreaks have been associated with occupational or recreational
activities around streams or rivers with high content of moist soil enriched
with organic debris and/ or rotting wood.
Pathogenesis and clinical picture
• Blast mycosis is acquired via inhalation of the conidia, which transforms in
to the yeast form once in the lungs.
• After 30 to 45 days an acute pulmonary disease indistinguishable from a
bacterial pneumonia may occur.
• However, at least 50% of primary infections are asymptomatic.
• Inmost cases the disease manifest during a
chronic and indolent phase that may affect the
lungs, the skin, the bones, the genitourinary
tract and other reticuloendothelial system.

Fig. Cutaneous blastomycosis. (Courtesy of Dr M. James,Royal Berkshire
Hospital, Reading, UK.)
• A few patients have acute, self-limited pneumonia; fever productive cough,
myalgia, and malaise are common and are usually resolve within a month.
• The infection has three forms:
 Acute pulmonary blastomycosis, even though it may resolve with out
treatment; however treatment is often used.
 Chronic pulmonary blastomycosis usually has granulomatous
lesions in the upper lobe often misdiagnosed as carcinoma.
• Disseminated blastomycosis is a progressive disease that follows hematogenous
spread from unresolving pulmonary lesions by macrophages to remote sites, most
commonly skin and bones.
Laboratory Diagnosis
Direct Examination
• Clinical material, such as prostate fluid, or tissue, is examined in 10% KOH.
• It reveals the characteristic yeast form of B. dermatitidis.
• The fungus usually occurs as thick- walled, globose yeast that measures 8-
15µm in diameter.
• Each blastoconidium is attached to the parent cell by broad base.
• Owing to their size, the yeasts of B. dermatitidis could be confused with C
immitis or C. neoformans under some circumstances.
Culture and identification
• Culture is performed in the laboratory onto sabouraud glucose agar, brain
heart infusion agar, yeast extract- phosphate agar, and a medium with
cycloheximide, and then incubated.
• The culture should be kept 4 weeks (7-28 days) before discarding as
negative:
Colonial appearance

• Mycelia phase: on sabouraud glucose agar, colony first white, waxy, yeast like and
later cottony with white aerial mycelium; turns tan to brown with age.
• Yeast phase: on brain heart infusion agar, colony cream to tan, waxy and wrinkled;
inhibited chloramphenicol or cyclohexmide.
Microscopic appearance
• Mycelia phase: delicate, septate hyphae with round or pyriform conidia borne singly
on conidiophores or directly on hyphae.
• Yeast phase: thick-walled large yeast cells with single bud on a broad base
Fig.(a) Giemsa stain of Blastomyces dermatitidis showing broad-based budding yeast.
(b)
(b)Blastomyces dermatitidis mould phase
Serologic Tests
Immunodifussion test: antigen - yeast culture filtrate
• Serologic tests for specific antibodies against yeast-phase antigen A using
immunodiffusion technique is of some diagnostic value but more
importantly serves as indicator of the effect of therapy; antibodies
disappear a few months after successful treatment.
• However anti-A antibody appears after infection is not known.
• The specificity of the ‘K’ antigen remains to be determined.
• Complement Fixation test: antigen – yeast form
• Titers of 1:8 to 1: 16 ---------- suggestive of active infection
• Titers of 1:32 or greater ------ indicative of the infection

Note; cross-reaction occurs in patients having coccidiodomycosis or
histoplasmosis ; however titers are usually lower
Skin Tests
• Skin tests with blastomycin are usually of no diagnostic value because the
test is often falsely negative or falsely positive due to cross reactivity with
other pathogenic fungi, such as Histoplasma capsulatum
5.2. Coccidioidomycosis (Desert fever, valley fever,
San Joaquin fever
Definition
• Coccidioidomycosisis, which is caused by C. immitis, is also referred to as
valleys fever or San Joaquin fever because of the geographic distribution
of C. immitis and the associated area of occurrence of this disease.
• It is seen often in the San Joaquin valley of California that it has gained the
common name of “valley fever or San Joaquin Fever”.
• The organism reproduces in a host tissue by forming small endospores within mature
spherules.
• After rupture of spherule, the released endospores enlarge and repeat the cycle.
• The agent has two forms, growing as a white fluffy mold on most culture media but as
a non-budding spherical form (a spherule) in host tissue or under special condition.
Epidemiology
 Geographic Distribution: Coccidioidomycosis is endemic in the
semi-arid region of Central America, Southwestern U.S.A., small
portion of South America, Mexico, which offer the unique climate
essential for the growth, and dissemination of C. immitis.
 Although the geographical distribution is well defined, cases of
coccidioidomycosis may be seen in any part of the world because of
the case of travel.
 Source of infection:

 The infective fungal spore is found in the soil.
Patients with a history of exposure to soil acquire the disease by inhalation of wind borne
arthrospores from dust generated when contaminated soil is agitated
• The usual course of primary pneumonia is complete healing, although an
area of pnuemonitis (detected on radiographs) may heal by formation of a
coin like lesions called a coccidioidoma.
• Less commonly, a single thin-walled cavity remains as a chronic sequela in
areas of consolidation.
• A chronic, progressive, granulomatous disease occurs in less than 1% of
those infected, especially immuno suppressed individuals; this is
granulomatous less resemble the tubercles of tuberculosis and cavitations
may occur.
• The infection may disseminate to different parts of the body, including bones, viscera,
and the CNS;
• however, the gastrointestinal tract is remarkably resistant to infection
• The acute and most common forms of the disease resemble influenza.
• Approximately 60% of the cases remain asymptomatic and self-limiting.
• The initial symptoms of pulmonary infection consist of cough, fever, and malaise.
• One to two weeks later, about 3 to 5% of patients develop complications attributable
to a hypersensitivity reaction, the most frequent being skin lesions (erythema) or joint
symptoms (desert rheumatism).
• The symptoms of a chronic thin-walled cavity include cough or hemoptysis in half of
cases; the other half is asymptomatic.
• Chronic pulmonary coccidiodomycosis cause cough, sputum production, variable
degree of fever, and weight loss
Direct Examination

• Sputum, lung biopsy, pus from lesions and other clinical specimens can be
examined microscopically by means of a KOH wet mount slide preparation,
which reveals characteristic spherules.
• It appears as large non-budding, thick-walled spherical cells of various
sizes (2 to 5µm in diameter) containing small endospores or granular
material.
(a) (b)
(C)
(a . Coccidioidomycosis tissue section. Spherules of various sizes are stained black with GMS. In the
top left-hand part of the slide
(b) Coccidioides immitis spherule
(c) Coccidioides immitis mould phase
Colonial appearance
• Mycelia phase: Culturing on Sabouraud’s glucose agar, mature colonies
may appear with 3 to 5 days of incubation.
• C. immitis often appear as delicate, some portion of the colony will exhibit
aerial hyphae, where as others will have the hyphae adherent to the agar
surface.

• It must only be carried out in a mycology laboratory with facilities for the
safe handling of cultures.
• The arthroconidia produced by C. immitis molds are highly infectious.
• Yeast phase: on brain heart infusion test have similar appearance to
mycelia phase.
• Mycelia phase: coarse, septate, branched hyphae that produce thick-
walled, barel-shaped, rectangular arthroconidia that alternates with empty
disjucture cells.
• Yeast phase: large, round, thick-walled spherules with endospores as
observed in tissue and direct examination. Not true yeast.
Serologic tests
 Serologic testing on spaced serum specimens is highly valuable for the
diagnosis and prognosis of coccidioidomycosis.
Tube precipitin
• Tube precipitin is the most sensitive test result, which becomes positive 1
to 3 weeks after onset of infection, with about 80% of cases positive by 2
weeks but the test usually reverts to negative by 6 months after onset of
infection.
Latex particle agglutination
• antigen - coccidiodin
• Latex particle agglutination and immunodiffusion tests are other serologic
tests used as screening tools in endemic areas and can detect 93% of
cases.
• It is slightly more sensitive than tube precipitin, but with 6% to 10% false
positive results.
Complement fixation tests
• Antigen - coccidiodin

• Complement fixation tests are also widely used, especially for spinal fluid
specimens for confirmation and quantification of serum antibody detected
by screening tests.
• In the CSF specimen it detects more than 90% of active
coccidioidomycosis infection, whereas the tube precipitin test is not
reliable on spinal fluid.
• Titer of 1:2 to 1: 4 ------- active infection; low titers should be followed by
repeat testing at 2 to 3 weeks intervals.
• Titer of > 1:16 ---------- usually indicates active infection.
• Titer of 1:32 or higher--- usually reflects disseminated disease; a continuing
rise in titer above 1:32 signifies progressing infection and poor prognosis.
Note: Cross-reaction occurs in patients with histoplasmosis and negative
reaction result occurs in patient with pulmonary lesions.
Skin Tests
• Skin test is used to screen a population for individuals who are infected
with a pathogen but who have not developed clinical symptoms.
• It is very useful, being equally as sensitive as serologic tests.
• Skin test does not produce an antibody response that would interfere with
the other tests.
• Generally skin tests are available for the diagnosis of coccidioidomycosis,
using occidioidin; an antigen derived from C. immitis.
3. Paracoccidioidomycosis(paracoccidi-oidl
granuloma, Lutz-splendore-almeida’s disease)
Definition
• Paracoccidioidomycosis formerly called South American blastomycosis,
which is a chronic granulomatous systemic mycosis caused by a
saprophytic P. brasiliensis.
• A dimorphic fungus, P. brasiliensis grows as budding yeast in tissue but
may grow as either yeast or a mold on culture medium.
Epidemiology

• Geographic Distribution
• Paracoccidioidomycosis is found in Brazil and also in the other South American
countries,
• Central America and Mexico, but its extreme indolence may delay its recognition until
many years after the patient has left the endemic area.
• Source of infection: The exact mechanism by which paracoccidioidomycosis is
acquired is unclear; however, it is speculated that is the origin is pulmonary which is
acquired by inhalation of organisms from the environment.
• The infection begins as primary pulmonary infection. It is often asymptomatic and
then disseminates to produce ulcerative lesions of the mucous membrane.
• Ulcerative lesions are commonly present in the nasal and oral mucous, gingival, and
less commonly in the conjunctiva.
• Lesion occurs most commonly on the face is associated with Oral membrane
infection.
• The lesions are characteristically ulcerative, with serpinous active border and a
crusted surface.
• Pulmonary infection is seen most often, and progressive chronic pulmonary infection
is found in approximately 50% of the cases.
• Dissemination to other anatomic site, including the lymphatic system, spleen,
intestine, liver, brain meninges, and adrenal glands occur in some patients
Common signs include indurated ulcers of mouth, oropharynx, larynx, and nose; enlarged and
draining lymph nodes;lesions of the skin and genitalia; and productive cough, weight loss,
and some times fever
• Diagnosis rests on microscopic, examination of specimens for multiple budding yeast
forms, serologic tests, and culture with or without antibacterial agents.
Direct Examination

• The yeast appears large, round to oval measuring 10-40µm in diameter are usually
recognized in direct wet mount microsocopic examination of sputum, mucousal
biopsy, and other exudates.
• large, round to oval, thick-walled yeast cells with multiple buds, which attach to
mother cells by narrow constrictions; resemble a “ ship’s wheel” will be seen under
microscope.
 Colonial appearance
 Colonies of P. brasiliensis grows very slowly (21 to 28 days) on culture and has
wrinkled and moist appearance
Mycelia phase: on Sabouraud glucose agar, white, leathery colony; turns tan-brown with age;
short aerial mycelium.
Yeast phase: on blood agar, cream to tan, moist, wrinkled colony; turns waxy with age
 Mycelial phase: small, septate, branched hypha with intercalary and terminal
chlamydoconidia; few periform micoconidia.
 Yeast phase: large, round to oval, thick-walled yeast cells with multiple buds, which
attach to mother cells by narrow constrictions; resemble a “ ship’s wheel”.
Serologic Tests
• The immuno-diffusion test for specific antibodies is highly valuable for diagnosis,
prognosis and disappears with regression.
• It is also valuable for identifying the fungus.
4. Histoplasmosis (Darling ‘s disease, Reticuloendotheliosis,
Reticulo-enthelial cytomycosis)
• Histoplasmosis is the most common type of systemic fungal infection caused by
Histoplasma capsulatum (classic or small form) and Histoplasma duboissi (African or
large form).

• Histoplasma capsulatum is a dimorphic fungus that grows as a mold in nature or on
sabourauds agar at room temperature.
• Hyphae bear both large and small spores, which are used for identification.
• Samuel Darling, who discovered H. capsulatum in around 1900, so-named the
organism because he mistook it for a capsulated animal parasite.
• Since it is now known to be a non- capsulated saprophytic soil fungus, its present
name is obviously inappropriate. Histoplasmosis, caused by H. capsulatum, shared
many characteristics with coccidioidomycosis.
• Both diseases extend over a spectrum from acute self-limited to chronic,
granulomatous infection, and both are endemic in man. However, histoplasmosis
occurs worldwide.
Epidemiology
• Geographic Distribution
• Histoplasma capsulatum
• infection occurs in many parts of the world,
• notably in the USA along the Mississippi river, and in many areas along the East cost
• It is common in areas with optimal growth conditions like accumulation of bird or bat
droppings enrich the soil with nutrient (eg. Nitrogen) that encourages the growth of H.
capsulatum.
• Histoplasma duboissi
• It occurs in tropical Africa.
• It is often referred to as large cell histoplasmosis because the intracellular yeast forms
are three to four times larger than H. capsulatum.
Source of infection
• Histoplasmosis is acquired via inhalation of the infective units from the environment;
particularly soil enriched by dropping of certain birds and bats that are deposited in
the lungs.

• Infection begins with small primary focus of lung infection much like the early lesions
of tuberculosis.
• The causative agents are ingested by alveolar macrophage in the lung.
• These macrophages carry the fungi to nearby lymph nodes, usually the hilar nodes.
• The fungi multiply within the node tissue and ultimately are released into a
circulating blood, from which they go on to seed other organs or destroyed by the
body defenses.
• The initial lung infection is usually in apparent.
• Clinical disease develops in some 5% of those infected.
• The majority of the infections are either asymptomatic or mild, and the diagnosis is
elusive cough fever, malaise, and chest X-ray findings of hilar adenopathy with or with
out one or more areas of pneumonitis is typical features.
• Chronic pulmonary histoplasmosis is characterized by a gradual onset (over weeks or
months) of increasing productive cough, weight loss and some times night sweats.
• Acute disseminated histoplasmosis may be mistaken milary tuberculosis.
• Common findings include fever, hepatosplenomegaly, lymphadenopathy, Jaundice,
anemia leukocytopenia and thrombocytopenia
• In such individuals the infection may occur either as an acute disease, as a chronic
cavitary disease or as a severe blood born disseminated disease
• Acute pulmonary histoplasmosis ranges from asymptomatic to a severe self-limiting
disease in which symptoms resemble a mild cold
• Chronic pulmonary histoplasmosis is the outcome of the continued progression of the
initial infection or the result of reactivation of an old quiescent lesion; cavitation is
frequent.
The disease resembles chronic pulmonary tuberculosis clinically
• Disseminated Histoplasmosis is commonly a generalized disease of the
reticuloendothelial system that presents lesions in almost every organ of the body.
• It is rare, occurring mostly in individuals with patients of depressed cellular immune
response (e.g. Patients with AIDS, T-cell defects, or lymphoma)

• In children younger than age one year who appear to have reticuloendothelial defect
(fulminant disease of child hood)
Direct Examination
• The direct microscopic examination of respiratory tract specimens is usually
unsatisfactory for the detection of H.capsulatum and H. duboissi.
• The organism however may be detected when examining wrigght’s or Giemsa-
stained specimen of bone marrow or peripheral blood.
The yeast can be seen in the cytoplasm of endothelial and mononuclear cells
• H. capsulatum is found intracellular with in mononuclear cells as small, rounded oval
yeast cells 1 to 4 µm in diameter.
• They require differentiation from the amastigotes of leishmania donovani, which can
also be found in mononuclear cells.
• H. duboissi appear as large, round to oval cells measuring 7-15µm in diameter.
• The cells may appear nucleated.
(a) Histoplasma capsulatum mould
phase
showing tuberculate macroconidia
(b) Giemsa stain of Histoplasma
Capsulatum
Culture

• Histoplasma can be easily cultured from clinical specimens. It is usually considered to
be a slow growing mold and commonly requires 2 to 4 or more weeks for colonies to
appear at 250
c to 300
c
Colonial appearance
• Mycelia phase: on sabouraud’s glucose agar the colonial morphology produces
mycelial growth with characteristic warty conidia when cultured at room
temperature.
• Yeast phase: on brain heart infusion agar small microconidia and characteristic large,
round, spiny macroconidia are produced.
• At 370
C on certain media it is possible to induce the yeast phase of this dimorphic
fungus.
Mycelia phase:
 Septate hyphae with round to periform microconidia on short branchs or directly on
hyphal stalk; later large, round thick-walled, knobby tuberculate macroconidia forms.
Mycelia phase:
• small budding round to oval yeast cells.
Serologic Tests
Complement fixation test (CFT):
antigen – histoplasmin or its yeast form.
• Complement fixation is the most commonly used diagnostic and prognostic test in
histoplasmosis.
• Specific CF antibodies arise in 90% of patients 2 to 4 weeks following initial infection.
• A titer of 1:8 to 1:16 highly suspicios of infection.
• A titer of 1:32 or greater indicative of active infection. by about 9 months.
• In patients with an established diagnosis, titers of 1:16 are considered suspicious, and
1:32 or above and persist for a few weeks indicate progressive disease.

• Latex agglutination;
• antige - Histiplasmin.
• The test is unreliable;may cause false positive and false negative teste may be
observed.any positive test should be confirmed by the CFT test.
• Skin test
• Histoplasma skin tests are usually contraindicated in histoplasmosis, first because of
extensive cross- reactivity with other fungal pathogens and, more importantly,
because skin tests alter the level of humoral antibodies important in serologic
diagnosis.
5.Summary
 Systemic mycoses are caused by specific fungi that thrive in particular
environments. The pathogens include *Histoplasma capsulatum*,
*Coccidioides spp.*, and *Blastomyces dermatitidis*.
 Infections arise from environmental sources such as soil enriched with
organic matter or dust storms.
 These fungi exist in two forms: a mold form found in the environment and a
yeast form in human tissues.

 Each mycosis has distinct characteristics, including its causative agent,
clinical presentation, and potential for dissemination, making them unique
in terms of diagnosis and treatment.
6. References
• Murry Medical microbiology 5th
edn.
• Sherris Medical microbiology an introuction to infection.
• Jawetz, Melnick, & Adelberg's Medical Microbiology, 24th Edition.

MICROBIOLOGY ASSIGNMENT.docx1HGWUYGYETYDGNBK

More Related Content

Similar to MICROBIOLOGY ASSIGNMENT.docx1HGWUYGYETYDGNBK

Recently uploaded

MICROBIOLOGY ASSIGNMENT.docx1HGWUYGYETYDGNBK