(incomplete) Haemophilus and Bordetella Flashcards
Explain the meaning of non-typeable H. influenzae.
Typeable = antibodies can recognize the capsule Non-typeable = has no capsule, so anti-capsule Abs cannot recognize it
Explain the role of capsule in Haemophilus infection.
Capsule made of carbohydrates; required for virulence
Antiphagocytic: protects against complement and phagocytosis
Describe clinical syndromes and manifestations of Haemophilus bacteria.
Encapsulated (Typeable)
- -Respiratory tract infections
- -Bacterial meningitis mainly in children <4 years old
Unencapsulated (Non-typeable)
- -Ear aches
- -Respiratory disease
- -Other infections
Likely a secondary invader after flu
Explain the importance of toxins in disease and adhesins in disease.
a
What characteristics of H.i. cause difficulties in diagnosis? Memorize the particular growth conditions needed by H. influenzae.
Facultative anaerobe
NO diagnostic fermentation patterns
Fragile - susceptible to disinfectants and drying
FASTIDIOUS: requires specific growth factors (these are used for diagnosis)
- -Will NOT grow on blood agar -> NOT hemolytic
- —-WILL grow around other bacteria on blood agar b/c they release nutrients
- -Must use CHOCOLATE agar (heated blood, releases nutrients)
- -X factor: hemin (Haemophilus = “heme-loving”)
- -V factor: NAD/NADP
What does “pleomorphic” mean?
The characteristic of having multiple different shapes in a single bacterial culture
List characteristic of H. influenzae.
Small, Gm-, non-motile, non-spore-forming bacillus or coccobacillus (pleiomorphic)
What types of capsules can Haemophilus influenza have? Which is most virulent, and what is different about it?
Include A, B, C, D, E, F
Each type has a capsule with a different sugar composition
Type B = the most virulent
–Contain ribose in capsule (others have hexose)
Epidemiology of Hi/Hib: reservoir, % carriers
Reservoir in nasopharynx of humans only
75% of people carry Hi, but 3-5% carry Hib
–Vaccine usage has reduced levels of carriage
Responsible for 500,000 deaths of children worldwide
Hib: Clinical syndrome
Acquired through aerosol
Starts with nasopharyngitis, can include otitis media or sinusitis
Can invade epithelium and enter bloodstream, progress to bacteremia and meningitis
Can also cause:
- -Epiglotititis/obstructive laryngitis
- -Cellulitis (inflammation of connective tissue)
- -Joint infections
- -Pneumonia
Pathogenesis of Hib:
- Portal into humans
Immunity against Hib:
Capsule (polyribosyl phosphate) linked to proteins (diphtheria toxoid) to enhance T cell memory
Used for 20 years
Extremely successful
Now made with strictly synthetic components
Treatment of Hib infections
Meningitis:
–3rd gen cephalosporins (cefotaxime, ceftriaxone) most common
–Ampicillin with clavulanate (beta-lactamase inhibitor) used
FINISH
Clinical manifestations of non-typeable Hi
Generally restricted to respiratory tract and ear in healthy individuals
Colonization starts in nasopharynx -> damaged epithelia, respiratory mucus
Causes otitis media in children (immune system not as effective, structure of Eustachian tube makes infections more likely)
Conjunctivitis
FINISH
Respiratory disease in pts with underlying respiratory issues
Meningitis in individuals with predisposing factors or in neonates
Pathogenesis of Non-typeable H.i.
Uses MANY different complements of adhesins (don’t need to know them)
Invades via 3 routes: both an extracellular and intracellular pathogen
Is there a vaccine for non-typeable H.i.?
Immunity is strain-specific
Passive immunity is also strain-specific and lasts only a few months
NO vaccine
Treatment of non-typeable H.i.
Amoxicillin for otitis media and sinusitis
Resistant strains treated with amoxicillin + beta-lactamase inhibitor
Persistent infections may be due to biofilm formation or host cell invasion
How is H.i.b diagnosed? (5)
History, age of pt Culture blood and spinal fluid (on chocolate and blood agar; Gm stain spinal fluid sediment) Presence of Type B capsular antigen PCR detection of capsule genes Biochemical tests
H. ducreyi
a
H. aegypticus
a
H. parainfluenzae
a
Characteristics of bordatella pertussis
Smal, Gm- coccobacillus
OBLIGATE aerobe
Causes whooping cough
Epidemiology of Bordetella pertussis
Found only in humans (no animal reservoir)
FINISH
Clinical features of Bordetella pertussis
a
