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30 Cards in this Set

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  • Back
What are the basic characterisitics of Haemophilus, Moraxella, and Bordetella
Small gram negative coccobacilli
Usually require rich media (often blood or its derivatives) for growth
What major diseases are caused by Haemophilus, Moraxella, and Bordetella
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)
In the 1980s, what was the number one cause of bacterial meningitis in children 6 months-5 years
Haemophilus influenzae. Has decreased because of vaccination
What are the characteristics of Haemophilus
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
What are the antigens of Haemophilus influenzae
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)
Antibody protective against invasive infections
Non-encapsulated forms are normal flora in the URT. Often isolated in otitis media
What diseases are caused by typically type B Haemophilus influenzae infections
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
What diseases are caused by nontypeable (non encapsulated) Haemophilus influenzae
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
What does meningitis usually result from in Haemophilus influenzae infection
Hematogenous spread rather than direct penetration of the CNS
What can predispose to Otitis media or bacteremia caused by Haemophilus influenzae
Prior nasopharyngeal infection with influenza virus
Following bloodstream invasion by Haemophilus influenzae type b, the occurrence of meningitis correlates strikingly with what
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
For lab diagnosis, where can specimens of Haemophilus influenzae be obtained
Depends on the disease-- CSF, blood, joint aspirate
How is Haemophilus isolated and identified in the lab
Gram stain CSF (careful interpretation)
5-10% CO2
Latex agglutination reaction for type b capsule
What immune function is important for protection against Haemophilus influenzae
Phagocytosis. Anti-capsular antibodies act as opsonins that mediate complement-dependent phagocytosis of the organisms. Antibodies plus complement can also lead to bacterial lysis
Why is it important to vaccinate children between 2 months and 3 years against Haemophilus influenzae
Their antibody titers are minimal, and disease incidence is high
How is Haemophilus influenzae treated
3rd generation Cephalosporin, or ampicillin if susceptible. Childhood meningitis is often treated with both
How is Haemophilus influenzae infection prevented
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
Besides Haemophilus influenzae, what are some other types of Haemophilus
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
What are some signs and symptoms of Haemophilus ducreyi infection
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
Haemophilus ducreyi specimens grow best on what
Agar enriched with vitamins, amino acids, serum, and blood (Fildes-enriched gonococcal media) in atmosphere of 10% CO2 at 34C
What are the characteristics of Moraxella
Gram negative coccobacilli (can be diplococcus)
Oxidase positive
Some species require enriched media such as blood or chocolate agar to grow
What diseases does Moraxella catarrhalis cause
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
What is the definition of pertussis (whooping cough)
Acute infectious disease of tracheobronchial tree with characteristic clinical picture. Etiological agent is Bordetella pertussis
What are the characteristics of Bordetella
Gram negative, short coccobacilli, pleomorphic, encapsulated when virulent
Requires enriched media that binds fatty acids (Bordet-Gengo Agar (BG) or charcoal agar base (CHB))
What are the three main species of Bordetella
B. pertussis- humans only
B. parapertussis- May cause pertussis-like disease in humans
B. bronchiseptica- dogs
What are the main toxins and virulence factors in Bordetella
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
What are the proposed steps in pathogenesis of Bordetella
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
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)
How might adolescents and adults whose natural or acquired immune response to Bordetella pertussis has waned present upon infection
With a long-standing cough (without a whoop)
How is pertussis treated
Just treat the symptoms (may use corticosteroids). Can use erythromycin for the unimmunized
What is the pertussis (aP) vaccine
A mixture of purified, inactivated Bordetella pertussis products