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30 Cards in this Set
- Front
- Back
What are the basic characterisitics of Haemophilus, Moraxella, and Bordetella
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Small gram negative coccobacilli
Usually require rich media (often blood or its derivatives) for growth |
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What major diseases are caused by Haemophilus, Moraxella, and Bordetella
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Meningitis (Haemophilus influenzae type B)
Epiglottitis (H. influenzae type B) Cellulitis (H. influenzae type B) Pneumonia (H influenzae type B, Moraxella catarrhalis) Chronic otitis media (Moraxella catarrhalis) Acute otitis media (H. influenzae non-encapsulated) Sinusitis (H. influenzae non-encapsulated) Conjunctivis (H. influenzae non-encapsulated Chancroid or soft chancre (H. ducreyi) Whooping cough or pertussis (Bordetella pertussis) |
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In the 1980s, what was the number one cause of bacterial meningitis in children 6 months-5 years
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Haemophilus influenzae. Has decreased because of vaccination
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What are the characteristics of Haemophilus
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Gram negative coccobacilli (curved ends on short rods)
Can be pleomorphic, can appear gram variable Non-motile, non-spore forming Fastidious, requires X (hemin, heat stable) or V (can be replaced by NAD or NADP, heat labile) or both (provided on chocolate agar) Grows best in 5-10% CO2 |
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What are the antigens of Haemophilus influenzae
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Six capsular types, a-f. Strains responsible for systemic disease are primarily capsular type b. Can by typed by Quellung reaction or immunofluorescence
Type b is polyribose-ribitol phosphate (PRP) Antiphagocytic Antibody protective against invasive infections Non-encapsulated forms are normal flora in the URT. Often isolated in otitis media |
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What diseases are caused by typically type B Haemophilus influenzae infections
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Meningitis- unvaccinated toddlers
Epiglottitis- obstructive, cherry red epiglottis, life threatening in unvaccinated children Pneumonia often complicated by empyema. Seen in adults with COPD Bacteremia, cellulitis, septic arthritis |
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What diseases are caused by nontypeable (non encapsulated) Haemophilus influenzae
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Acute otitis media, sinusitis- second only to Streptococcus pneumoniae, may follow viral infection
Exacerbations of COPD Community Acquired Pneumonia Acute respiratory tract infections in 3rd world children Conjunctivitis- outbreaks in daycares Neonatal and maternal sepsis- biotype 4 Bacteremia and invasive infections- in adults with underlying conditions |
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What does meningitis usually result from in Haemophilus influenzae infection
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Hematogenous spread rather than direct penetration of the CNS
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What can predispose to Otitis media or bacteremia caused by Haemophilus influenzae
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Prior nasopharyngeal infection with influenza virus
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Following bloodstream invasion by Haemophilus influenzae type b, the occurrence of meningitis correlates strikingly with what
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The duration and intensity of the bacteremia. Increased incidence of bacteremia in those without proper spleens. Reduced bacteremia incidence after prior administration of specific anti-capsular antibodies or after priming with cross-reactive E.coli
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For lab diagnosis, where can specimens of Haemophilus influenzae be obtained
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Depends on the disease-- CSF, blood, joint aspirate
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How is Haemophilus isolated and identified in the lab
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Gram stain CSF (careful interpretation)
5-10% CO2 Latex agglutination reaction for type b capsule |
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What immune function is important for protection against Haemophilus influenzae
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Phagocytosis. Anti-capsular antibodies act as opsonins that mediate complement-dependent phagocytosis of the organisms. Antibodies plus complement can also lead to bacterial lysis
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Why is it important to vaccinate children between 2 months and 3 years against Haemophilus influenzae
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Their antibody titers are minimal, and disease incidence is high
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How is Haemophilus influenzae treated
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3rd generation Cephalosporin, or ampicillin if susceptible. Childhood meningitis is often treated with both
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How is Haemophilus influenzae infection prevented
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Several different Hib-conjugate vaccines (Hib coupled with diphtheria toxoid)
Rifampin is given to unvaccinated house-hold contacts of Haemophilus influenzae type b-infected young children |
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Besides Haemophilus influenzae, what are some other types of Haemophilus
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H. parainfluenzae- normal URT, 10% in saliva
H. aphrophilus- normal on tooth surfaces; can cause endocarditis or brain abcesses H. aegyptius (Kochs-Weeks bacillus)- acute purulent conjunctivitis or pink eye (contagious) H. influenzae biotype aegyptius type 1 causes Brazilian purpuric fever H. ducreyi |
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What are some signs and symptoms of Haemophilus ducreyi infection
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Causes chancroid or "soft chancre"
Ragged ulcer on genitalia with marked swelling and tenderness Regional lymph nodes often large and tender Associated with poor socioecomonic conditions Increased numbers during wartime |
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Haemophilus ducreyi specimens grow best on what
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Agar enriched with vitamins, amino acids, serum, and blood (Fildes-enriched gonococcal media) in atmosphere of 10% CO2 at 34C
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What are the characteristics of Moraxella
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Gram negative coccobacilli (can be diplococcus)
Oxidase positive Some species require enriched media such as blood or chocolate agar to grow |
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What diseases does Moraxella catarrhalis cause
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Moraxella catarrhalis is normal flora of the URT. It can cause otitis media and pneumonia, particularly in the elderly
It is penicillin resistant due to its Beta lactamase |
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What is the definition of pertussis (whooping cough)
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Acute infectious disease of tracheobronchial tree with characteristic clinical picture. Etiological agent is Bordetella pertussis
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What are the characteristics of Bordetella
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Gram negative, short coccobacilli, pleomorphic, encapsulated when virulent
Requires enriched media that binds fatty acids (Bordet-Gengo Agar (BG) or charcoal agar base (CHB)) |
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What are the three main species of Bordetella
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B. pertussis- humans only
B. parapertussis- May cause pertussis-like disease in humans B. bronchiseptica- dogs |
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What are the main toxins and virulence factors in Bordetella
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Pertussis toxin: causes activation of membrane adenylate cyclase of eucaryotic cell via ADP-ribosylation of the Gi protein
Extracellular adenylate cyclase: Resembles EF of anthrax (calmodulin dependent). Has hemolytic activity Filamentous hemagglutinin and pertactin: adhesive factors Tracheal cytotoxin: Destroys ciliated epithelial cells. Resembles a fragment of the cell wall |
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What are the proposed steps in pathogenesis of Bordetella
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Colonization without invasion of ciliated bronchial epithelia via filamentous hemagglutinin and pertactin
Localized damage with tracheal cytotoxin Impaired host immune response due to extracellular adenylate cyclase (hemolysin) Systemic effects due to pertussis toxin |
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What is the epidemiology of Bordetella?
What are the stages of infection? |
Primarily affects unvaccinated kids under 4
Very contagious Incubation 7-10 days Three stages: Catarrhal (common cold); Paroxysmal (violent coughing); Convalescent (persistent cough) |
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How might adolescents and adults whose natural or acquired immune response to Bordetella pertussis has waned present upon infection
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With a long-standing cough (without a whoop)
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How is pertussis treated
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Just treat the symptoms (may use corticosteroids). Can use erythromycin for the unimmunized
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What is the pertussis (aP) vaccine
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A mixture of purified, inactivated Bordetella pertussis products
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