Haemophilus and Bordetella Flashcards
Cellular characteristics of Haemophilus influenzae?
- Gram (-)
- Non motile
- Non-spore forming
- Only grows on chocolate agar with Factors X and V
- Respiratory droplets
- Two forms - encapsulated and unencapsulated
Characteristics of high pathogenicity strain of H. influenzae?
Polysaccharaide capsule
Which type of H. influenze causes the worse diease?
Type B (Hib)
What is the target of the vaccine for H.influenzae?
The Hib capsule of polyribosyl ribitol phosphate
What is the target of the vaccine in NTHi?
Vaccine does not cover unencapsulated strains
How is H. influenzae similar to N. meningitidis?
Capsule fns in immune evasion
Describe Hib pathogenesis?
- Colonization of resp. mucosa via IgA protease
- Once estab. in resp. mucosa, invades bloodstream
What determines severity of Hib illness?
Magnitude and Duration of bacteremia
When is the peak risk for Hib infection?
6 mo to 1 yr - mother’s Ab wane, child can’t raise strong defense
Describe the NTHi pathogenesis
- NTHi utilizes pili, attachment proteins and IgA protease to invade
What patients are particular susceptible to NTHi?
- Patient’s with CF b/c bug can easily create a biofilm
Disease caused by H. influenzae
- Menigitis
- Cellulitis
- Otitis media and sinusitis
- Epiglottitis - Cherry Red epiglottis
- Septic arthritis
Dx procedure for Hib epitlottitis?
On exam, cherry red epiglottis is seen along with progressive respiratory difficulty, inability to swallow. Once airway secured, lateral neck radiograph is taken
What patients are NTHi associated with?
Neonates and postpartum women
What type of NTHi is particularly virulent?
Biotype 4
Procedure for H. influenzae Dx?
Culture on chocoalte agar with factors X and V; Growth on factor only agar is sufficient for Dx
Tx for H. influenzae meningitis?
Ceftriaxone and in children > 2 mo, add Dexamethasone
Tx for H. influenzae Upper Respiratory infection?
Amoxicillin + clavulanate or trimethoprim+sulfamethoxazole
Primary preventive method for H. influenzae?
Vaccine early!
Cellular characteristics of Bortedella Pertussis?
- Encapsulated
- G (-)
- Human-restricted
Characteristics of Pertussis disease?
- Whooping cough
- Highly contagious
Pathogenesis of B. pertussis?
- Filamentous hemagglutinin pilus attaches bac. to cilia of epithelial cells lining resp. tract
- Pertussis toxin A-B subunit ADP-ribosylator kills ciliated cells, and inhibits chemokine signal transduction = lymphocytosis
- Tracheal cytotoxin - Kills ciliated cells as well
What allows B. pertussis to be so virulent?
- Kills ciliated cells allowing for further bac. growth
- Production of mucopurulosanguineous exudate compromising small airways
- Both allow for paroxysmal cough and spread via many aerosol droplets
Pertussis Px?
- Do bacteremia
- Px good, complications minimal
- Major complication comes from infants deprived of oxygen
Typical presentation of pertussis?
Afebrile, dehydrated, Hx of incomplete/absent vaccination
3 stages of pertussis?
- Catarrhal - Nonspecific upper resp. Syx: Congestion, sneezing, rhinorrea, maximally contagious
- Paroxysmal - Intense coughing: Series of hacking cough, copious mucus production, inspiratory whoop
- Convalescence: Free of bugs but fatigue and chronic cough because bugs killed ciliated cells
How can whoop be absent in adults?
Adult airway is large and may not be as obstructed
Lab tests for B. pertussis?
- Pronounced leukocytosis (70% lymphocytes)
- Bordet-Gengou agar - but bugs are fastidious
Tx for Pertussis?
Macrolides, supportive care b/c of dead ciliated cells
Pertussis management in infants
Supplemental O2, mucus suctioning
Pertussis prevention?
- Acellular vaccine - genetically-inactivated Pertussi toxoid, filamentous hemagglutinin, pertactin, fibriae types 2 and 3 (Used in US)
- Killed vaccine - whole heat-killed, believed risk of encephalopathy
- 10 year boosters needed for either vaccine
Tx for unvaccinated exposed individuals?
Erythromycin
