haemophilus, bordetella Flashcards
shape of haemophilus
small, bacilli or coccobacilli
haemophilus motile?
no
haemophilus gram + or -
-
how is haemophilus categorized?
1) encapsulated - meningitis in young children
2) unencapsulated - ear aches, resp disease
what is the function of the capsule in HIB and other encapsulated haemophilus strains?
- made of carbohydrates
- required for virulence and is antiphagocytic
- basis for serotyping
what are the encapsulated haemophilus serotypes?
a, b, c, d, e, f
what is the most important encapsulated haemophilus serotype and why?
b - has ribose instead of hexose in polysaccharide structure
what is the most common clinical syndrome for haemophilus?
nasopharyngitis with accompanying otitis media. invasion of epithelium, bacteremia, involvement of meninges
how does haemophilus enter the body?
resp tract, between children
when are children most susceptible to haemophilus?
after passive immunity wears off, 6-12 months of age with risk up to 5 years
vaccine for haemophilus?
yes - capsular against type b. linked to diphtheria toxoid for increased T cells and memory
encapsulated haemophilus treatment
- third generation cephalosporin is used immediately because of increased resistance to ampicillin.
- augmentin - ampicillin+clavulanate - b-lactamase inhibitor to render ampicillin resistant strains sensitive to antibiotic. if b-lactamase negative, drop clavulanate
location of non-capsule haemophilus
restricted to resp tract and ear
clinical manifestations of non-capsuler haemophilus
- second most common cause of otitis after S pneumoniae
- conjunctivitis
- resp infections if underlying rest issues
- meningitis - usually a predisposing factor
non-encapsulated haemophilus treatment
- amoxicillin with or without b-lactamase inhibitor
diagnosis of haemophilus
- requires growth factors X and V
- preparation of chocolate agar releases both X and V from red blood cells
- encapsulated colonies are smooth
- suspected meningitis - blood and CSF taken
other haemophilus pathogens
1) ducreyi - emerging STD - genital chancre
2) aegypticus - purulent conjunctivitis
3) parainfluezae - pharyngitis and endocarditis, part of natural flora
major disease associated with bordetella
whooping cough
bordetella gram + or -?
-
shape of bordetella
small coccobacilli
bordetella incubation period
7-10 days
two stages or bordetella
1) catarrhal stage - runny nose, sneezing, low grade fever, mild cough
2) paroxysmal stage - bursts of coughing, high pitched whoop, cyanosis,
how does bordetella infect?
- water droplets
- ciliated epithelia in trachea and nasopharynx
- adherence
- multiplication and toxin production
four bordetella toxins
1) pertussis toxin - ribosylation of inhibitory G protein of adenylate cyclase, increased accumulation cAMP
2) adenylate cyclase toxin - cAMP from ATP, affects leukocytes
3) dermonecrotic toxin - vascular smooth muscle contraction, ischemic necrosis of lung tissue
4) tracheal cytotoxin - inhibits DNA synth, kills tracheal epithelial cells
Main test for diagnosis of bordetella?
gram stain nasopharyngeal swab, direct anti-body test, culture on B-G
drug of choice for bordetella?
erythromycin
