Download MBBS (Bachelor of Medicine, Bachelor of Surgery) General Medicine 2022 PPT 11 Fungal Infections Lecture Notes
Infectious diseases
4/5th Semester Classes on Infectious Diseases, 8-9AM, Tuesdays (LT-1)
Topics
1
Approach to Infectious Diseases and their prevention
2
Antibiotic stewardship practices
3
Community-Acquired Infections
4
Health Care?Associated Infections
5
Gram-Positive Bacteria (part-1)
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Gram-Positive Bacteria (part-2)
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Gram-Negative Bacteria (part-1)
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Gram-Negative Bacteria (part-2)
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Spirochetal Diseases
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Diseases Caused by Atypical/Miscel aneous Bacterial Infections
11
Revision-cum-exam on bacteria (Must to know type)
12
Infections Due to DNA Viruses
1
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Infections Due to RNA Viruses (part 1)
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Infections Due to RNA Viruses (part 2)
15
HIV/AIDS ? part 1
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HIV/AIDS ? part 2
17
Fungal Infections
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Parasitic Infections (part 1)
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Parasitic Infections (part 2)
20
Revision-cum-exam on Virus, Fungal, and Parasite (Must to know type)
Fungi as Infectious Agents
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? Fungi are the most common plant pathogens
? Of the 100,000 fungal species, only 300 have been
linked to disease in animals
? Most striking adaptation to survival and growth in the
human host is the ability to switch from hyphal cells to
yeast cells (Thermal dimorphism ? grow as molds at
30?C and as yeasts at 37?C)
? True fungal pathogens are distributed in a
predictable geographical pattern - climate, soil
? The growth of the fungi generally involves two phases;
vegetative (mold/yeast) and reproductive (asexual
(spore) /sex)
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Classification - by both anatomic location
and epidemiology
? Superficial infections and Cutaneous
infections (Dermatophycoses)
? Subcutaneous infections involve the dermis,
subcutaneous tissues and muscle
? Systemic infections
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Pathogenesis
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? Mycotic disease is often a consequence of predisposing factors
? Only the dermatophytes and Candida are communicable from human to human
? The other agents are acquired from the environment
? Portal of entry
? primary mycoses ? respiratory portal; inhaled spores
? subcutaneous - inoculated skin; trauma
? cutaneous and superficial ? contamination of skin surface
? Virulence factors ? thermal dimorphism, toxin production, capsules and adhesion
factors, hydrolytic enzymes, inflammatory stimulants
? The role of humoral defenses is somewhat controversial, but cell mediated one has
predominant role
? Three distinct tissue responses;
? Chronic inflammation (scarring, accumulation of lymphocytes)
? Granulomatous inflammation
? Acute suppurative inflammation
Diagnosis
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? Definitive Diagnosis ? histopathologic identification of the
fungus invading tissue and accompanying evidence of an
inflammatory response
? Laboratory identification require
? Microscopic examination of stained specimens (KOH mount
& PAS/Silver staining) - Most laboratories now use calcofluor white staining coupled with
fluorescent microscopy
? Culturing in selective and enriched media (Sabouraud's
dextrose agar)
? Specific biochemical (GM/B-glucan) and serological
tests
Control/treatment
? Sanitary: Control by sanitary means is difficult, but the incidence of
communicable disease can be reduced by good hygiene
? Immunological: No vaccines are currently available
? Chemotherapeutic
? Many antifungals are available but some are very toxic to the host and
must be used with caution
? Topical powders and creams often contain tolnaftate or azole derivatives
(miconazole, clotrimazole, econazole)
? and are useful against superficial dermatophytes.
? Sporotrichosis may be treated using potassium iodide or AMB
? Systemic infections are general y treated by AMB , 5- FC, Fluconazole,
Voriconazole, Itraconazole, Candins, etc
Histoplasmosis: Ohio Valley Fever
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? Distributed worldwide, most prevalent in eastern and
central regions of US
? Most prevalent endemic mycosis
? Grows in moist soil high in nitrogen content (Bird
dropings)
? The clinical spectrum ranges from asymptomatic
infection to life-threatening illness
? The attack rate and severity of the disease depend on
? The intensity of exposure,
? The immune status of the exposed individual,
? The underlying lung architecture of the host
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Blastomyces dermatitidis: Blastomycosis
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? Dimorphic like Histoplasma but causes systemic
pyogranulomatous infection
? Inhaled 10-100 conidia convert to yeasts and multiply in
lungs
? Most commonly presents as acute or chronic
pneumonia that has been refractory to therapy with
antibacterial drugs
? Hematogenous dissemination to skin, bones, and the
genitourinary system is common
Sporothrix schencki - Sporotrichosis (rose
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-gardener's disease)
? Very common saprobic fungus that decomposes plant matter in soil
? Infects appendages and lungs
? Lymphocutaneous variety occurs when contaminated plant matter penetrates the
skin and the pathogen forms a nodule, then spreads to nearby lymph nodes
Chromoblastomycosis
17
? A progressive subcutaneous mycosis characterized by highly visible verrucous lesions
? Etiologic agents are soil saprobes with dark-pigmented mycelia and spores
? Fonsecaea pedrosoi, Phialophora verrucosa, Cladosporium carrionii
Mycetoma
? When soil microbes are accidentally implanted into the skin
? Progressive, tumorlike disease of the hand or foot due to chronic fungal infection;
may lead to loss of body part
? Caused by Pseudallescheria or Madurella
Cutaneous Mycoses - Infections strictly confined to keratinized
epidermis (skin, hair, nails) are cal ed dermatophytoses- ringworm and tinea
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? Ringworm of scalp (tinea capitis)
? Ringworm of beard (tinea barbae)
? Ringworm of body (tinea corporis)
? Ringworm of groin (tinea cruris)
? Ringworm of foot and hand (tinea pedis and tinea manuum)
? Ringworm of nails (tinea unguium)
? Tinea versicolor ? caused by Malassezia furfur
? White piedra ? caused by Trichosporon beigelii; whitish or colored masses develop
scalp, pubic, or axillary hair
? Black piedra ? caused by Piedraia hortae; dark-brown to black gritty nodules, mainly
on scalp hairs
Candidiasis
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? Budding cells may form both elongate pseudohyphae
and true hyphae
? Forms off-white, pasty colony with a yeasty odor
? Normal flora of oral cavity, genitalia, large intestine or
skin of 20% of humans
? Account for 80% of nosocomial fungal infections
? Account for 30% of deaths from nosocomial infections
Cryptococcosis - Cryptococcus neoformans
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? A widespread encapsulated budding yeast that
inhabits soil around pigeon roosts
? Infection of lungs leads to cough, fever, and lung
nodules
? Cryptococcosis should be included in the differential
diagnosis when any patient presents with findings
suggestive of chronic meningitis
Pneumocystis (carinii) jiroveci
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? A smal , unicel ular fungus that causes pneumonia (PCP)
? The organism was discovered in rodents in 1906 and was initial y
believed to be a protozoan
? Because Pneumocystis cannot be cultured, our understanding of
its biology has been limited
? Presents as acute or subacute pneumonia that may initial y be
characterized by a vague sense of dyspnea alone but that
subsequently manifests as fever and nonproductive cough with
progressive shortness of breath ultimately resulting in respiratory
failure and death
? Extrapulmonary manifestations of PCP are rare but can include
involvement of almost any organ, most notably lymph nodes,
spleen, and liver
Aspergillosis
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? 600 species, 8 involved in human disease; A. fumigatus
most commonly
? Infection usually occurs in lungs ? spores germinate in
lungs and form fungal balls; can colonize sinuses, ear
canals, eyelids, and conjunctiva
? Invasive aspergillosis can produce necrotic
pneumonia, and infection of brain, heart, and other
organs
? The primary risk factors for invasive aspergillosis are
profound neutropenia and glucocorticoid use
Mucormycosis (Previously Zygomycosis)
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? Genera most often involved are Rhizopus, Absidia, and
Mucor, Cunninghamella
? Rhizopus oryzae is by far the most common cause of
infection (not mucor)
? Usually harmless air contaminants invade the
membranes of the nose, eyes, heart, and brain of
people with diabetes and malnutrition, with severe
consequences
? Infection primarily in patients with diabetes or defects
in phagocytic function (e.g., those associated with
neutropenia or glucocorticoid treatment) or Patients
with elevated levels of free iron
? Divided into at least six clinical categories:
? Rhino-orbital-cerebral,
? Pulmonary,
? Cutaneous,
? Gastrointestinal,
? Disseminated,
? Miscellaneous
? The successful treatment of mucormycosis requires
four steps:
(1) early diagnosis;
(2) reversal of underlying predisposing risk factors, if
possible;
(3) surgical debridement;
(4) prompt antifungal therapy
Fungal Al ergies and Intoxications
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Fungal spores are common sources of atopic allergies
? Seasonal allergies and asthma
?
farmer's lung, teapicker's lung, bark stripper's disease
? Fungal toxins lead to mycotoxicoses usually caused by
eating poisonous or hallucinogenic mushrooms.
?
aflatoxin toxic and carcinogenic; grains, corn peanuts; lethal to poultry and livestock
? Stachybotrys chartarum ? sick building syndrome;
severe hematologic and neurological damage
Thank you
This post was last modified on 05 April 2022