Upper/lower Respiratory infections

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Author:
manjinder
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147146
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Upper/lower Respiratory infections
Updated:
2012-04-13 16:19:05
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microbiology
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respiratory bugs
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  1. Moraxella catarrhalis
    • gram - diplococci
    • sinusitis and otitis media
    • normal flora of upper respiratory tract
    • Amoxicillin-clavulanic acid
  2. Haemophilus influenzae nontypeable
    • gram - polymorphic rods; require X (hemin) and V (NAD) factors
    • Sinusitis and otitis media
    • normal flora of nasopharynx
    • pili (adhesion), LPS (inflammation), IgA (mucosal colonization)
    • satellite phenomenon w/ S. aureus, latex agglutination test
    • Rx: amoxicillin
  3. Streptococcus pneumoniae
    • gram + diplococcus lancet-shaped, catalase -, alpha-hemolytic, bile soluble, optochin sensitive
    • Sinusities and otitis media, lobar pneumonia, adult meningitis
    • normal flora of upper respiratory tract
    • polysaccharide capsule (antiphagocytic), IgA protease (colonization), pneumolysin (transmembrane pore-forming toxin)
    • rapid onset fever, productive cough, bloody sputum (rusty sputum), chest pain; sepsis in sickle cell anemia and splenectomy
    • Quellung reaction, latex particle agglutination
    • Rx: Pneumonia: cefotaxime; otitis media: amoxicillin, adult meningitis: ceftriaxone or cefotaxime
    • Prevention: PPSV= 23-valent polysaccharide vaccine (>65 yo); PCV= 7-valent conjugated vaccine (pediatric)
  4. Haemophilus influenzae type-b (Hib)
    • gram - pleomorphic rods, require X (hemin) & V (NAD) factors
    • epiglottitis, pneumonia, meningitis
    • pili (adhesion); LPS (inflammation), IgA (mucosal colonization); capsule type b= poly-ribitolphosphate
    • Culture (chocolate agar), satellite phenomenon w/ S. aureus; latex agglutination test
    • Rx: Cefotaxime
    • Prevention: Hib conjugate vaccine
  5. Klebsiella pneumoniae
    typical
    • Enterobacteriaceae family, gram - rod, capsule, lactose-fermenting colonies on MacConkey agar
    • LPS => fever, inflammation and shock (septicemia) => necrotic destruction of alveolar spaces; abscesses
    • Lobar Pneumonia in patients w/ alcoholism, COPD, diabetes
    • Sudden onset high fever, thick bloody sputum (currant jelly) but not foul-smelling as in anaerobic aspiration pneumonia
    • part of colon and upper respiratory tract normal flora
    • Rx: 3rd generation cephalosporin
  6. Pseudomonas aeruginosa
    typical
    • opportunist gram - rods, oxidase- positive, strict aerobe (nonfermenting)
    • fluorescence under UV light, blue green colonies, fruity aroma- grapelike odor
    • Pneumonia in Cystic fibrosis and immunocompromized patients
    • Pili, capsule, biofilm, LPS, Exotoxin A (ADP ribosylates EF-2 inhibiting protein synthesis)
    • fever, productive cough, weight loss, breathing difficulties and cyanosis
    • Burn patients: cellulitis (blue-green pus) --> septicemia (fever, shock, black, necrotic center, erythematous margin, ecthyma gangrenosum)
    • Chronic granulomatous disease: since Pseudomonas is catalase + recurrence is common in these patients
    • In healthy people causes GI tract colonization (loose stools), hot tub folliculitis (S. aureus is #1 cause), eye ulcers
    • Rx: antipseudomonal penicillin (ticarcillin)+ aminoglycoside (gentamicin)
  7. Streptococcus pyogenes (group A streptococcus)
    • gram + cocci in chains, b-hemolytic, group A antigen, bacitracin sensitive
    • nasopharynx normal flora
    • Pharyngitis: sore throat, fever, erythema + exudate, tender anterior cervical lymph nodes
    • --M-protein (adhesion & antiphagocytic. responsible for acute glomerulonephritis- type III hypersensivity), F-protein (adhesion), hyaluronic acid capsule, streptolysins
    • Scarlet fever: diffuse erythematous rash, "sandpaper" rash, "strawberry" tongue
    • --pyrogenic or erythrogenic (A-C) exotoxins: phage encoded superantigens => scarlet fever, toxic shock syndrome
    • Pyoderma/impetigo: pyogenic skin infection (honey-crusted lesions)
    • Rx: Penicillin to prevent acute rheumatic fever (Type II hypersensitivity)
  8. Corynebacterium diphtheriae
    • gram + club-shaped rods, aerobic
    • A-B exotoxin from prophage: ADP ribosylation of EF-2 => blocks protein synthesis => cell death => necrosis; diffusion of toxin via blood => damages heart and nervous system
    • sore throat, gray exudate, thick pseudomembrane (bleeds easily) => obstruction and suffocation; bull neck; cardiac dysfunction, laryngeal nerve palsy
    • culture: selective tellurite medium black colonies arranged in V or L shapes (chinese letters); Elek test for toxin production (see precipitin lines for toxin producing diphtheriae; no precipitin line for normal flora)
    • Rx: antitoxin serum therapy + penicillin, erythromycin
    • Prevention: toxoid vaccine (DTaP, Tdap)
  9. Bordetella pertussis
    • gram - coccobacilli, fastidious
    • pertussis (whooping cough)
    • infects tracheobronchial epithelium
    • Fha (fliamentous hemagglutinin) + Ptx (pertussis toxin) immobilize cilia
    • tracheal cytotoxins kill ciliated cells
    • Ptx (A-B toxin, ADP-ribosylation of G-protein => inc cAMP) leads to inc in mucus secretio and edema
    • Catarrhal stage: non specific cold symptoms, highly contagious
    • Paroxysmal stage: paroxysmal cough with inspiratory whoop, mucus production, vomiting
    • Convalescent stage: gradual recovery; complicaitons: seizure, neuro damage...
    • Culture charcoal blood agar
    • Rx:erythromycin, azithromycin or clarithromycin
    • prevention: DTaP- acellular, just using Ptx
  10. Mycoplasma pneumoniae
    Atypical
    • no cell wall, sterols in membrane
    • Atypical/walking pneumonia
    • P1 adhesin (adherence to respiratory epithelial cells) --> inhibits ciliary action and protection; damage via toxic metabolic products
    • ligth fever, headache, malaise, persistent hacking cough (dry or little sputum); on X-ray patchy infiltrate= bronchopneumonia
    • Cold agglutinins
    • Rx: azithromycin or clarithromycin
  11. Chlamydophilia pneumoniae
    Atypical
    • small obligate intracellular pathogen; 2 stages: elementary body (EB) and reticulate body (RB); no peptidoglycan layer in cell wall
    • pneumonia or bronchitis: gradual onset of cough, malaise, little or no fever, dry cough
    • Rx: Macrolides
  12. Chlamydophila psittaci
    • small obligate intracellular pathogen; 2 stages: elementary body (EB) and reticulate body (RB); no peptidoglycan layer in cell wall
    • inhalation of dried secretions from infected birds
    • pneumonia associated w/ hepatitis
    • Rx: doxycycline or tetracycline
  13. Legionella pneumophila
    atypical
    • fresh water organisms, gram - facultative intracellular pathogen, biofilms
    • elderly, smokers, immunocompromised patients
    • replication inside the phagosome; lysis of phagocytes => lung damage and inflammatory response
    • fever, chills, non-productive cough, chest pain
    • BCYE agar (buffered charcoal yeast extract)
    • Rx: macrolides
    • Prevention: disinfection of water systems
  14. Mycobacterium tuberculosis
    • Acid-fast rods, slow growth, facultative intracellular
    • survival & growth in alveolar macrophages: cell wall components (Mycolic acid, lipids & LAM); development of reactive inflammatory focus --> tissue necrosis- damage due to host response --> Granuloma formation (Ghon Complex); Dissemination to local LN --> possible distribution to other tissues
    • Active TB: chronic cough, weight loss, night sweats, bloody sputum....skin test, X-ray and sputum all positive
    • Latent TB: no symptoms...skin test positive, X-ray and sputum negative
    • Reactivation TB: possible dissemination
    • Ziehl-Neelsen stain (acid fast)
    • Rx:
    • Latent: isoniazid
    • Active: isoniazid + rifampin + pyrazinamide + ethambutol for 2 months then isoniazide + rifampin for 4-6 months
  15. Bacillus anthracis
    • gram (+) rod single, paired or long serpentine chains (box car chains); spore forming, polypeptide capsule
    • inhalation of spores from animal hair and wool
    • bioterrorist anthrax
    • PA + EF= edema toxin; PA + LF= lethal toxin
    • inhalatin of anthrax spores --> germinate and replicate in alveolar macrophages --> transport to mediastinal LN --> mediastinal hemorrhagic lymphadenitis
    • fever, chills, cough, malaise, headache, rapidly worsening course of fever, edema and massive enlargement of mediastinal LN, respiratory distress, cyanosis, and shock
    • Rx: fluoroquinolones (ciprofloxacin); if not treated death w/in 3 days of initial symptoms
  16. Coccidioides immitis
    True pathogen, dimorphic, endemic
    • environment: hyphae, tissue: spherules filled w/ endospores
    • Valley fever
    • inhalation of dust, no human to human transmission
    • Granulomatous inflammatory reaction
    • immunocompromised: from self limiting flulike illness to severe pulmonary infections (similar to tuberculosis) and disseminated infections
    • Rx:
    • Mild to moderate disease: Azole derivatives
    • Severe or disseminated disease: amphotericin B followed by azole
  17. Histoplasma capsulatum
    true pathogens, dimorphic, endemic
    • intracellular budding yeasts in reticuloendothelial cells
    • soil contaminated by bird or bat feces
    • Eastern US- ohio mississippi river valley
    • inhalation of dust, no human to human transmission
    • Granulomatous inflammatory reaction
    • immunocompromised: from self limiting flulike illness to severe pulmonary infections (similar to tuberculosis) and disseminated infections- to mucocutaneous sites
    • lesions tend to calcify as they heal
    • Rx:
    • Mild to moderate disease: Azole derivatives
    • Severe or disseminated disease: amphotericin B followed by azole
  18. Blastomyces dermatitidis
    true pathogens, dimorphic, endemic
    • enviro: hyphe, tissue: single broadbased budding yeasts
    • soil w/ decaying organic material
    • Eastern US
    • inhalation of dust, no human to human transmission
    • Granulomatous inflammatory reaction
    • from self limiting flulike illness to severe pulmonary infections (similar to tuberculosis) and disseminated infections to skin as implied by the name
    • Rx:
    • Mild to moderate disease: azole derivatives
    • Severe or disseminated disease: amphotericin B followed by azole
  19. Paracoccidioides brasiliensis
    true pathogens, dimorphic, endemic
    • Budding Yeasts with pilot wheel morphology
    • Soil- south america
    • inhalation of dust, no human to human transmission
    • Granulomatous inflammatory reaction
    • from self limiting flulike illness to severe pulmonary infections (similar to tuberculosis) and disseminated infections
    • Rx:
    • Mild to moderate disease: azole derivatives
    • Severe or disseminated disease: amphotericin B followed by azole
  20. Cryptococcus neoformans
    opportunistic, monomorphic
    • encapsulated yeast
    • soil enriched w/ pigeon droppings
    • inhalation from environment, no human to human trasmission
    • Predisposing conditions: AIDS patients (meningitis), patients w/ immune deficiencies or diabetes
    • disseminate from lungs to CNS
    • detect capsular antigen in CSF by latex particle agglutination, india ink, Urease positive yeast
    • Rx: amphotericine B + flucytosine until afebrile and culture negative, then fluconazole
  21. Aspergillus fumigatus & flavus
    opportunistic, monomorphic
    • filamentous fungus (mold); septate hyphae w/ 45 deg angle
    • inhalation from environment
    • AIDS, immune deficiencies, diabetes
    • angioinvasive fungi
    • Diseases:
    • - allergic bronchopulmonary aspergillosis (asthma and CF): common in farmers. causes fungus ball in preformed cavities from previous infections. Surgically removed to reduce coughing
    • - invasive aspergillosis: invades tissues causing MI, hemorrhage, pneumonia, meningitis, cellulitis in burn patients may disseminate
    • Rx: amphotericine B + surgical removal of local infection
  22. Mucor and Rhizopus spp.
    • Nonseptate filamentous fungi
    • Rhinocerebral infection
    • characterized by paranasal swelling, necrotic tissues, hemorrhagic exudates from nose and eyes, and mental lethargy
    • occurs in ketoacidotic diabetic and leukemic patients
    • these fungi penetrate w/out respect to anatomical barriers, progressing rapidly from sinuses into the brain tissue
    • Diagnosis: KOH, broad ribbon-like nonseptate hyphae with 90 deg angles, black necrotic eschar on face
    • Rx: Amphotericin B. high fatality rate because of rapid growth and invasion
  23. Pneumocystis jiroveci
    opportunistic, monomorphic
    • Single-celled eukaryotic microorganism
    • Life cycle= trophozoites, cyst
    • No ergosterol in the cell membrane
    • AIDS, immune deficiencies, diabetes
    • pneumocystosis attaches to and kills Type I pneumocytes, causing excess replication of type II pneumocytes and damage to alveolar epithelium. serum leaks into alveoli, producing an exudate w/ a foamy or honeycomb appearance on H & E stain,
    • Diagnosis: silver stained cysts in tissue, X-ray: patchy infiltrate (ground-glass appearance)
    • Rx: TMP-SMZ

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