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44 Cards in this Set
- Front
- Back
What do most cystic fibrosis patients die from?
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Secondary pathogens:
Pseudomonas pneumoniae |
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Which bacteria are increased following antibiotic therapy?
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C. albicans
Pseudomonas E. coli |
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Following hospitalization, _________ decreases, producing an increase in gram negative bugs.
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fibronectin
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Community acquired pneumonias are generally associated with which gram stain?
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Gram positive
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What are most upper respiratory infections caused by?
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Viruses
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Bacterial causes of acute pharyngitis include which organisms?
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S. pyogenes
H. influenzae C. diphtheriae N. gonorrheae |
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Strep throat is most commonly caused by which organisms?
What are its characteristics? |
Streptococcus pyogenes
Group A β-hemolytic streptococci |
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What are the characteristic features of Group A strep?
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Gram positive cocci, grow in chains
most facultative anaerobes, β-hemolytic catalase negative, non spore-forming |
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What is the most common cause of bacterial tonsillopharyngitis?
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Group A strep
(S. pyogenes) |
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What are the clinical complications/manifestations of Group A Strep?
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Sinusitis, otitis media, meningitis, scarletina, erysipelas, cellulitis
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What are the virulence factors for Group A Strep?
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Capsule (hyaluronic acid)
M protein Hemolysins: streptolysin O and streptolysin S Enzymes SPEs (Strep pyrogenic exotoxins) |
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What is the function of streptolysin O?
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Hemolyzes RBCs
Antigenic, thus used clinically |
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What is the function of streptolysin S?
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Damages membranes of neutrophils, platelets, etc.
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What are the sequelae of Group A Strep infections?
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Rheumatic Heart Disease
Acute Rheumatic Fever Antibodies against Group A carbohydrates react with heart valves |
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What are Aschoff bodies?
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Pathognomonic for Rheumatic Carditis
Nidus of macrophages with adjoining lymphocytes are fibrosis |
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What are the characteristics of H. influenzae?
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Small, non-motile, gram negative
Coccobacilli or pleomorphic bacilli Common colonizers of URT (~50%) |
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Encapsulated type b strains of H. influenza cause which potentially life threatening infections?
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Meningitis and epiglottitis
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Nonencapsulated or nontypable strains of H. influenzae cause which local infections?
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Pharyngitis and otitis media
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What are the virulence factors for H. influenzae?
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Polysaccharide capsule - avoids phagocytosis and complement
Capsule is a polymer of polyribitol phosphate (PRP) IgA protease production Endotoxin (LPS) |
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Which enzyme do many virulent organisms produce?
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IgA protease
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What factors are required for the growth of H. influenzae?
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X factor = hemin
V factor = NAD Chocolate agar (lysed RBCs) |
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At what age range is the incidence of H. influenzae infection the highest?
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6-18 months
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Corynebacterium diphtheriae
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Causes Diphtheria ("leather hide")
Gram positive, catalase positive Non-encapsulated, non-motile, pleomorphic Club-shaped, slender rod Requires potassium tellurite |
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To which bacterium are humans the only reservoir?
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C. diphtheriae
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What is pathognomoic for Corynebacterium infection?
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Bloody tears due to torn corneal pseudomembrane
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What are the virulence factors of Diphtheria?
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Toxin mediated disease of URT
Toxin produced by bacteriophage gene Exotoxin - "A" fragment inactivates elongation factor 2 (EF2) |
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What are some of the organisms that cause sinusitis?
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S. pneumoniae (MCC)
Haemophilus influenzae Moraxella cararrhalis Aspergillus |
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What are the characteristics of Streptococcus pneumoniae?
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Gram positive, lancet-shaped diplococci, catalase negative
α-hemolysis, pathogenic strains encapsulated |
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What are the virulence factors of S. pneumoniae?
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Polysaccharide capsule
Pneumolysin - activates/uses up complement Phosphorylcholine IgA protease |
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What are the characteristics of Moraxella catarrhalis?
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Gram negative diplococci
Aerobic and oxidase + (like Neisseria & Pseudomonas) |
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What are the risk factors for sinusitis?
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URI, dental infection, CFTR mutations, allergies, nasal polyps, smoking in household, structural problems (deviated septum, small ostia)
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What are the risk factors for otitis media?
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young age, viral URIs, low angle of eustachian tube, daycare, bottlefeeding, smoking in household, prematurity, GERD, cleft palate
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What is the most common mechanism for sinusitis and otitis media?
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Usually secondary to a viral URI (rhinovirus, coronavirus, adenovirus)
Mucosal sweeling obstructs outflow tract of sinus/eustachian tube URI impairs mucociliary clearance and overproduction of secretions Negative pressure in middle ear, serous fluid, is an ideal bacterial medium |
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What is the treatment for sinusitis/otitis media?
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"watchful waiting" - due to the fact that most are viral infections
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What are the risk factors for otitis externa?
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excess moisture or cerumen in canal, trauma, foreign bodies, eczema, swimmers/divers, hearing aid use
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What are the clinical symptoms of otitis externa?
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Progressive ear pain (unilateral)
History of exposure to water Purulent discharge Conductive hearing loss |
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What is the most common cause of otitis externa?
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Pseudomonas
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What is the most common of otitis externa due to fungi?
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Aspergillus
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What is the most common cause of malignant otitis externa?
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Pseudomonas
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What are the characteristic features of Bordetella pertussis?
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Gram negative, pleomorphic coccobacilli, strict aerobes
Humans are the only reservoir Causes whooping cough |
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What is the pathophysiologic mechanism of whooping cough?
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B. pertussis bacilli attach to respiratory epithelium via hemagglutinins, A-B toxin causes:
ADP-ribosylation of Gi protein (irreversibly inactivates, thus increasing cAMP) Result: inhibition of phagocytosis of infected ciliated epithelial cells |
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What are the clinical characteristics of whooping cough?
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Tracheobronchitis - leads to paroxysms of cough following by inspiratory whoops, emesis or seizure
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How is a B. pertussis infection diagnosed?
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Strong clinical suspicion
Lymphocytosis on CBC |
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What are the bacterial agents that cause lymphocytosis?
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TB, Brucella, Bordetella
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