Community-acquired acute pneumonia: B-Animal, or Environmental Exposure: 1- Legionella pneumophila pneumonia: Microscopy: -Gram’s negative rods (in nature) Coccobacillary; (in clinical specimens). -Facultative intracellular parasites. -Rods are motile by monotrichous flagella. Transmission: inhalation of aerosols from contaminated water produced by showers, humidifiers, AC air condition.
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Community-acquired acute pneumonia: B-Animal , or Environmental Exposure:
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Community-acquired acute pneumonia: B-Animal, or Environmental Exposure:
1- Legionella pneumophila pneumonia: Microscopy: -Gram’s negative rods (in nature) Coccobacillary; (in clinical specimens). -Facultative intracellular parasites. -Rods are motile by monotrichous flagella.
Transmission: inhalation of aerosols from contaminated water produced by showers, humidifiers, AC air condition.
Pathogenesis:-Infection of resident alveolar macrophage.-Inhibits phagosome-lysosome fusion.
-Formation of phagosome enveloped by endoplasmic reticulum; formation of replicative rod form; Autophage.-TNF-α, and INF-γ Production; monocytic infiltration of air spaces.-Alveolitis (Consolidation) and micro-abscess formation. -Bronchi are not affected.
Laboratory diagnosis:-Staining of specimens by Gram’s stain and Gimesa stain.-Grown on buffered charcoal yeast extract agar. (Enriched media: L-cysteine, iron, α-ketoglutarate).-Rapid identification: 1-Immunofluorescent microscopy 2-PCR.
Transmission:1-Inhalation of infectious aerosols. 2-Blood sucking arthropods bite; vector (ticks, mites) from animals (rabbit, birds).
Pathogenesis and clinical presentation: -Infection of alveolar macrophage; granuloma of lung: Pneumonic tularemia.
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Pathogenesis and clinical presentation:
-Infection of skin macrophage; ulcerative papule; transmitted to regional lymph nodes; lymphadenitis: Ulceroglandular tularemia ;(the most common presentation).
-Hematogenous dissemination to lung from other sites. (infection of APC of liver, spleen, bone marrow).
Treatment of Tularemia:1- Aminoglycosides: Gentamicin or Streptomycin.2-Ciprofloxacin and doxycycline.
3-Pneumonic Plague: Yersinia pestis infection: Microscopy, virulence, and cultural characteristics: - Gram’s negative coccobacillus. - In sputum: Gram’s negative bipolar-stained bacilli. -Encapsulated: F1, V, and W antigen; Antiphagocytic Ag. -Lipopolysaccharide (LPS) endotoxin. -Plasminogen activator: degrades fibrin.
Transmission: 1-Person-to-person: inhalation of droplets. 2-Vector-borne: insect bite(Fleas) from rodents (Rat).
Treatment of Plague:-Pneumonic plague should be treated within 24 hours of appearance of symptoms, (mortality rate: 100%).-Aminoglycosides: Streptomycin, gentamicin.-Fluoroquinolones and doxycycline.
4-Inhalation anthrax: Woolsorter’s disease: Bacillus anthracis infection: -Caused by Gram’s positive aerobic spore-forming bacilli. -Transmission: inhalation of spores. -Not a true pneumonia. -Alveolar macrophage transfer the spore to mediastinal and peribronchial lymph nodes.
Clinical presentation of inhalation anthrax:-Hemorrhagic Mediastinal lymphadenitis.
-In 50% of inhalation cases; Anthrax meningitis ; extensive
hemorrhage of the leptomeninges; Dark-red “Cardinal’s
cap” appearance on autopsy.
Treatment:
-Only if multiple intravenous antibiotics and passive vaccine
administered prophylactically after spore exposure.
2- Hospital-acquired Pneumonia(Nosocomial):
Pneumonia acquired during or after hospitalization. It occurs at least 72 hour after admission.Who are at Risk?-Patients on mechanical ventilation ( ICU).-Immunocompromised patients. -Other factors: malnutrition, heart and lung diseases.
Causative agents:(Micro-aspiration of Oropharyngeal flora of hospitalized patients):MRSA, Pseudomonas, Enterobacter, Klebsella, Serratia, Acinetobacter (person-to person) and VRE.
2-Fungal granulomatous pneumonia: (Endemic in America): Transmission: Direct contact with birds and bats. A-Coccidioidomycosis. B-Histoplasmosis. C-Blastomycosis. D-Paracoccidioidomycosis.
Coccidioidomycosis: Caused by dimorphic fungi :Coccidioides immitis. Infective stage: Arthrospores generated by septate hyphae.Diagnostic stage: Spherule filled with many endospores.
Fungal Pneumonia in AIDS patients:
1-Pneumocystis Pneumonia: (The most common infection). -Caused by Pneumocystis jiroveci (P.carinii). -Yeast lacking ergosterol in cell membrane. -Can not be treated by Amphotericin. -Encysted forms infects alveoli; exudate; blocks gas exchange.
-Treatment: Sulfamethoxazole and trimethoprim. Cysts of Pneumocystis carinii ; Sliver stain.
2-Cryptococcosis: (The second common cause of Fungal pneumonia in AIDS pat.). -Causative agents: Cryptococcus neoformans. -Yeast transmitted to man from birds (pigeon). -Capsulated microbe. -Meningitis in Immunocompromised host. -Treatment: Fluconazole or amphotericin B.
The Budding capsulated yeast Cryptococcus neoformans as shown in India ink wet mount .