MICR_041813 haemo_bordetella Flashcards Preview

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What are some characteristics of haemophilus influenza (Hi)?

gram (-) bacillus or coccobacillus, non-motile, non-spore forming, can be either encapsulated (typeable) or unencapsulated (non-typeable)


What does encapsulated (typeable) haemophilus influenza cause?

acute meningitis in young children


What does UNencapsulated (non-typeable) haemophilus influenza cause?

ear aches + respiratory disease; predominant form in population


What is the critical virulent component of encapsulated (typeable) haemophilus influenza?

capsule - required for virulence because it confers anti-phagocytic properties


There are 6 serotypes of encapsulated (typeable) haemophilus influenza. What's the difference between them? Which one is the most virulent?

Types a-f. Type B has a ribose, while the rest has hexose. Type B is the most virulent one.


What is the most common cause of meningitis in children under 4 y.o. up until the 90s?

type B encapsulated haemophilus influenza; reduction due to antibiotics and vaccines


What kinds of symptoms can encapsulated haemophilus influenza cause? (5)

1) nasopharyngitis w. otitis media or sinusitis, 2) epiglottis + obstructive laryngitis, 3) cellulitis (rash), 4) pyarthrosis (pus in joint), 5) pneumonia


What is the mechanism of pathogenesis of encapsulated haemophilus influenza?

aerosol droplets are inhaled, leading to respiratory tract colonization


What are 3 virulence factors that encapsulated haemophilus influenza produce?

1) IgA protease - aids in immune evasion. 2) LPS - induces ciliary stasis. 3) capsule - antiphagocytic properties


What are the 3 types of immunity can be developed against encapsulated haemophilus influenza?

1) passive immunity (0-4mo.), 2) acquired immunity (3-4yo), 3) vaccine


When is the most susceptible age to encapsulated haemophilus influenza?



What is the vaccine against encapsulated haemophilus influenza?

conjugated capsular vaccine: capsule protein (PRP) linked to diphtheria toxoid to increase dependence of T cells/memory and to increase immunogenicity


How would you treat encapsulated haemophilus influenza?

Ampicillin, 3rd generation cephalosporin (cefotaxime, ceftrixone), Augmentin (ampicillin + clavulanate)


What are some complications of encapsulated haemophilus influenza?

residual neurological damage, which can be reduced by incorporating corticosteroid into the treatment regime to reduce inflammation


Where does UNencapsulated (non-typeable) haemophilus influenza usually infect?

generally respiratory tract and ear, but can also cause conjunctivitis or meningitis (usually in patients with predisposing factors, such as trauma, sinusitis, CSF leak)


What are the virulence factors that UNencapsulated haemophilus influenza produce? (2)

1) adhesion molecules (Hap, HMW1/2, Hia, Hsf), 2) biofilm, which confers antibiotic resistance


T/F UNencapsulated haemophilus influenza is an intracellular pathogen.

False. It is an intracellular AND extracellular pathogen


What are the 3 routes that UNencapsulated haemophilus influenza use to invade cells?

1) macropinocytosis, 2) paracytosis (between tight junctions), 3) LPS-platelet activating factor


What are the 3 types of immunity can be developed against UNencapsulated haemophilus influenza?

1) passive immunity (0-4mo.), 2) adults are susceptible to infection; not sure if long-term immunity develops b.c. of strain variation, 3) NO vaccine


How would you treat UNencapsulated haemophilus influenza? (3)

1) amoxicillin, 2) amoxicillin w. b-lactamase inhibitor (clavulanate), 3) ceftriaxone


T/F UNencapsulated haemophilus influenza is an obligate anaerobe.

False. It's a facultative anaerobe


Why are UNencapsulated haemophilus influenza considered "fragile"?

it is susceptible to disinfectants and drying


T/F encapsulated haemophilus influenza can spontaneously convert to UNencapsulated haemophilus influenza.



Why is UNencapsulated haemophilus influenza considered a fastidious pathogen?

it requires growth factors X (hemin) and V (NAD or NADP) to grow.


What type of medium would be appropriate for UNencapsulated haemophilus influenza? Inappropriate?

appropriate: CHOCOLATE AGAR, because the heating causes RBCs to release X, V via actions of staphylococci and streptococci. Inappropriate: BLOOD AGAR because it lacks factors X, and V


How would you diagnose UNencapsulated haemophilus influenza?

1) blood + CSF culture - gram stain followed by growth on chocolate agar. 2) immunofluorescence - detect type B capsular antigen in spinal fluid. 3) biochemical tests


What vaccine is available for UNencapsulated haemophilus influenza?

conjugate vaccine of H1b polysaccharide and carrier protein


What does bordetella pertussis cause?

whooping cough


What are some characteristics of bordetella pertussis?

gram (-) coccobacillus, obligate aerobe


What are the hosts of bordetella pertussis?

humans only