Infectious (7)- Gomez Flashcards
Pneumonia =
lung parenchymal inflammation from any cause
Pulmonary Infectious Diseases - general concepts
Respiratory tract involved in infections more often than any other organ system
Most: upper tract viral disease
Lower tract pneumonia major cause of mortality and morbidity
Increased when defense impaired
One type increases chance of second type
* Elevated CRP or procalcitonin favors bacterial over viral pneumonia
Terminal, nosocomial (hospital-acquired) are common
Pneumonia Agents
Bacterial Mycobacterial Fungal Pneumocystis Viral Chemical Physical (radiation)
Pulmonary host defenses
nasal hair, turbinates, mucociliary apparatus, IgA secretion
Saliva, sloughing of epithelial cells, local complement production, interference from resident flora
cough, epiglottic reflexes, sharp-angled branching of airways, mucociliary apparatus, IgG, IgM, IgA
Alveolar lining fluid (surfactant, Ig, complement, fibronectin), Cytokines (IL-1, tumor necrosis factor), alveolar macrophages, polymorphonuclear leukocytes, cell-mediated immunity.
splenectomy? Immunize against
encapsulated bacteria.
Pneumococcus!
Community-acquired acute pneumonia (alveolar exudates)
strep pneumo + diplococci; MOST COMMON, increased risk with splenectomy/ sickle cell; need vaccine)
H. Influenza- #` in COPD
Moraxella- diplococci
Staph aureus G+ cocci (common post viral pneumonia/ influenza)
Legionalla G- rod (macrophages in small bronchioles)
Enterobacteriacaea- klebsiella- G- rod #1 gram neg seen in debilitated, malnourished with bloody thick mucus
- pseudomonas aeruginosa G- coccobacilli (cystic fibrosis and neutropenia*)
Community-acquired atypical pneumonia (patchy or interstitial inflammation
mycoplasma pneumo- spherical to filamentous w/o cell wall (G-) * have cold agglutinins
Chlamydia (pneumoniae, psittaci, trachomatis)
Coxiella burnetti (Q fever)
Viruses
Nosocomial pneumonia
gram neg rods: enterobactericae (klebsiella, serratia marcascens, e coli), and psudomonas
Staph aureus
Aspiration pneumonia (loss of gag or swallowing reflexes or GERD)- types of agents
anaerobic oral flora, admixed with aerobic bacteria
Necrotizing pneumonia and lung abscess
anaerobic bacteria (staph aur, lebsiella, strep pyo, type 3 pneumococcus)
Chronic pneumonia- 4 causative agents
nocardia, actinomyces, mycobacterium tuberculosis (granulomatous) and atypical mycobacteria
Pneumonia in immunocompromised host - 5 particular pathogens +
cytomegalovirus, pneumocystis jirovecii, mycobacterium avium-intracellulare
invasive aspergillosis
invasive candidiasis
“usual” bacterial, viral and fungal organisms
Streptococci
Gram positive cocci in chains
Exception: S. pneumoniae is lancet-shaped diplococcus
Catalase (-)
Lancefield groupings
S. pneumoniae, S pyogenes & S. agalactiae are encapsulated
Group A=S. pyogenes; β hemolysis-#1 cause of bacterial pharyngitis, impetigo. Can later get rheumatic fever, rheumatic valvular disease and post-streptococcal glomerulonephritis.
Also causes necrotizing fasciitis, & toxic shock syndrome (toxin).
Group B neonatal septicemia, meningitis & pneumonia
Group D
S. pneumoniae; α hemolysis-#1 cause of bacterial pneumonia in adults (virulence via capsule), #1 cause of otitis media in children, meningitis in adults
S. viridans species dental caries, subacute endocarditis
Haemophilus
Gram-negative coccobacilli
Capsule is major virulence determinant
Pneumonia, acute epiglottitis, bacteremia, meningitis, septic arthritis, cellulitis, otitis media, purulent pericarditis, endocarditis, arthritis and osteomyelitis
Nonencapsulated strains are (by definition) nontypable
H. influenzae type b - most common cause of bacterial meningitis in children 6 months-2 years
Unencapsulated strains produce ear, sinus and respiratory infections (usually chronic smokers, alcoholics or elderly)
H. ducreyi
h. parainfluenze
H. aegypticus
Moraxella and Kingella
Gram-negative diplococcus
Moraxella catarrhalis
Common – common cold, otitis media and sinusitis
Less common – laryngitis, bronchitis and pneumonia in children and adults chronic lung disease
Staphylococci
Gram positive cocci in clusters
Catalase (+) [H202→H20+02]
S. aureus: coagulase positive (+)
Skin (furuncle=boil, carbuncles, scalded skin syndrome, impetigo) infections, deep abscesses, sepsis, pneumonia, meningitis, acute endocarditis, osteomyelitis, toxic shock syndrome, food poisoning,
Virulence factors
Have developed resistance to penicillins (methicillin) and vancomycin
Legionella
Gram-negative bacilli
are ubiquitous aquatic saprophytes that can live in amoebae and biofilms
Infections are associated with aerosolized water
Legionnaires’ disease (Philadelphia 1976) is a severe lobar pneumonia with non-productive cough, fever, fever which lead to multi-organ disease and death if not treated
Pontiac fever was epidemic flu-like condition (Pontiac, Michigan 1968) with fever, chills, headache and malaise that lasted 2-5 days and resolved
Klebsiella
Gram-negative bacilli
Ferment lactose (reddish on McConkey’s agar)
Encapsulated
Most common cause of nosocomial respiratory tract infections
Hemorrhagic pneumonia with red currant jelly (capsule) colored sputum
Second-most frequent cause of gram-negative bacteremia and urinary tract infections
Capsular types 1 and 2 associated with bacterial pneumonia
K. oxytoca
Causes granuloma inguinale (donovanosis)
Pseudomonas
Gram negative rods
Oxidase-positive
Nonfermentative
Antiphagocytic exopolysaccharide (alginate) slime biofilm Many strains produce pigments (fluorescent pyoverdin and pyocyanin)
Nosocomial infections , opportunistic,
Commonly present in lungs of patients with cystic fibrosis
Hot tub folliculitis (P. aeruginosa)
Dx – culture (often have fruity grape odor and some produce pigments)
Rx – antibiotics (resistance in cystic fibrosis patients)
Mycoplasmataceae
Lack a cell wall around their cell membrane
Believed they originated as Gram positive bacteria but evolutionarily lost cell wall
appear as gram negative (red) on gram staining
Mycoplasma pneumoniae
Causes atypical “walking” pneumonia, acute tracheobronchitis, and bronchiolitis
Associated with cold agglutinin (anti-I IgM) production