1
Approach to Infectious Diseases and their prevention
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Antibiotic stewardship practices
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3Community-Acquired Infections
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Health Care?Associated Infections
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Gram-Positive Bacteria (part-1)6
Gram-Positive Bacteria (part-2)
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Gram-Negative Bacteria (part-1)
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8Gram-Negative Bacteria (part-2)
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Spirochetal Diseases
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Diseases Caused by Atypical/Miscel aneous Bacterial Infections11
Revision-cum-exam on bacteria (Must to know type)
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12
Infections Due to DNA Viruses
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113
Infections Due to RNA Viruses (part 1)
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14
Infections Due to RNA Viruses (part 2)
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15HIV/AIDS ? part 1
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HIV/AIDS ? part 2
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Fungal Infections18
Parasitic Infections (part 1)
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19
Parasitic Infections (part 2)
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20Revision-cum-exam on Virus, Fungal, and Parasite (Must to know type)
Fungi as Infectious Agents
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2
? Fungi are the most common plant pathogens
? Of the 100,000 fungal species, only 300 have been
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linked to disease in animals
? Most striking adaptation to survival and growth in the
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human host is the ability to switch from hyphal cells toyeast cells (Thermal dimorphism ? grow as molds at
30?C and as yeasts at 37?C)
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? True fungal pathogens are distributed in a
predictable geographical pattern - climate, soil
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? 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
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and epidemiology
? Superficial infections and Cutaneous
infections (Dermatophycoses)
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? Subcutaneous infections involve the dermis,
subcutaneous tissues and muscle
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? Systemic infections6
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Pathogenesis
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8? 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
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? Portal of entry? primary mycoses ? respiratory portal; inhaled spores
? subcutaneous - inoculated skin; trauma
? cutaneous and superficial ? contamination of skin surface
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? Virulence factors ? thermal dimorphism, toxin production, capsules and adhesion
factors, hydrolytic enzymes, inflammatory stimulants
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? The role of humoral defenses is somewhat controversial, but cell mediated one haspredominant role
? Three distinct tissue responses;
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? Chronic inflammation (scarring, accumulation of lymphocytes)
? Granulomatous inflammation
? Acute suppurative inflammation
Diagnosis
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? Definitive Diagnosis ? histopathologic identification of the
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fungus invading tissue and accompanying evidence of aninflammatory response
? Laboratory identification require
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? Microscopic examination of stained specimens (KOH mount
& PAS/Silver staining) - Most laboratories now use calcofluor white staining coupled with
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fluorescent microscopy? Culturing in selective and enriched media (Sabouraud's
dextrose agar)
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? Specific biochemical (GM/B-glucan) and serological
tests
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Control/treatment? Sanitary: Control by sanitary means is difficult, but the incidence of
communicable disease can be reduced by good hygiene
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? Immunological: No vaccines are currently available
? Chemotherapeutic
? Many antifungals are available but some are very toxic to the host and
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must be used with caution
? Topical powders and creams often contain tolnaftate or azole derivatives
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(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,
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Voriconazole, Itraconazole, Candins, etc
Histoplasmosis: Ohio Valley Fever
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? Distributed worldwide, most prevalent in eastern and
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central regions of US? Most prevalent endemic mycosis
? Grows in moist soil high in nitrogen content (Bird
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dropings)? The clinical spectrum ranges from asymptomatic
infection to life-threatening illness
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? The attack rate and severity of the disease depend on
? The intensity of exposure,
? The immune status of the exposed individual,
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? The underlying lung architecture of the host12
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Blastomyces dermatitidis: Blastomycosis14
? Dimorphic like Histoplasma but causes systemic
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pyogranulomatous infection
? Inhaled 10-100 conidia convert to yeasts and multiply in
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lungs? Most commonly presents as acute or chronic
pneumonia that has been refractory to therapy with
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antibacterial drugs
? Hematogenous dissemination to skin, bones, and the
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genitourinary system is commonSporothrix schencki - Sporotrichosis (rose
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16-gardener's disease)
? Very common saprobic fungus that decomposes plant matter in soil
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? 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
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Chromoblastomycosis
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? 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
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? 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
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? Caused by Pseudallescheria or MadurellaCutaneous 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)
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? Ringworm of body (tinea corporis)? Ringworm of groin (tinea cruris)
? Ringworm of foot and hand (tinea pedis and tinea manuum)
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? Ringworm of nails (tinea unguium)
? Tinea versicolor ? caused by Malassezia furfur
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? White piedra ? caused by Trichosporon beigelii; whitish or colored masses developscalp, pubic, or axillary hair
? Black piedra ? caused by Piedraia hortae; dark-brown to black gritty nodules, mainly
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on scalp hairs
Candidiasis
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? Budding cells may form both elongate pseudohyphae
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and true hyphae? Forms off-white, pasty colony with a yeasty odor
? Normal flora of oral cavity, genitalia, large intestine or
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skin of 20% of humans
? Account for 80% of nosocomial fungal infections
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? Account for 30% of deaths from nosocomial infectionsCryptococcosis - Cryptococcus neoformans
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24? A widespread encapsulated budding yeast that
inhabits soil around pigeon roosts
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? Infection of lungs leads to cough, fever, and lung
nodules
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? Cryptococcosis should be included in the differentialdiagnosis when any patient presents with findings
suggestive of chronic meningitis
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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
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? Because Pneumocystis cannot be cultured, our understanding of
its biology has been limited
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? Presents as acute or subacute pneumonia that may initial y becharacterized by a vague sense of dyspnea alone but that
subsequently manifests as fever and nonproductive cough with
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progressive shortness of breath ultimately resulting in respiratory
failure and death
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? Extrapulmonary manifestations of PCP are rare but can includeinvolvement of almost any organ, most notably lymph nodes,
spleen, and liver
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Aspergillosis
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? 600 species, 8 involved in human disease; A. fumigatus
most commonly
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? Infection usually occurs in lungs ? spores germinate inlungs and form fungal balls; can colonize sinuses, ear
canals, eyelids, and conjunctiva
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? Invasive aspergillosis can produce necrotic
pneumonia, and infection of brain, heart, and other
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organs? The primary risk factors for invasive aspergillosis are
profound neutropenia and glucocorticoid use
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Mucormycosis (Previously Zygomycosis)
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? Genera most often involved are Rhizopus, Absidia, and
Mucor, Cunninghamella
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? Rhizopus oryzae is by far the most common cause ofinfection (not mucor)
? Usually harmless air contaminants invade the
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membranes of the nose, eyes, heart, and brain of
people with diabetes and malnutrition, with severe
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consequences? Infection primarily in patients with diabetes or defects
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in phagocytic function (e.g., those associated withneutropenia or glucocorticoid treatment) or Patients
with elevated levels of free iron
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? Divided into at least six clinical categories:
? Rhino-orbital-cerebral,
? Pulmonary,
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? Cutaneous,? Gastrointestinal,
? Disseminated,
? Miscellaneous
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? The successful treatment of mucormycosis requiresfour steps:
(1) early diagnosis;
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(2) reversal of underlying predisposing risk factors, ifpossible;
(3) surgical debridement;
(4) prompt antifungal therapy
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Fungal Al ergies and Intoxications33
Fungal spores are common sources of atopic allergies
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? Seasonal allergies and asthma?
farmer's lung, teapicker's lung, bark stripper's disease
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? Fungal toxins lead to mycotoxicoses usually caused by
eating poisonous or hallucinogenic mushrooms.
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?aflatoxin toxic and carcinogenic; grains, corn peanuts; lethal to poultry and livestock
? Stachybotrys chartarum ? sick building syndrome;
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severe hematologic and neurological damage
Thank you
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