Haemophillus, Legionella, Bordetella, Chlamydia, Mycoplasma Flashcards
What is the morphology of Haemophilus?
Gram negative coccobacilli
Can you grow Haemophilus on blood agar?
No, requires blood factors hemin (X factor) and NAD (V factor) that are released from blood cells by heating.
Need chocolate agar.
What types of diseases does encapsulated v. unencapsulated H. influenze cause?
Unencapsulated: local respiratory infections
Encapsulated: systemic disease (in blood stream)
Which encapsulated H. influenzae type is predominant in invasive disease?
Type b (Hib)
What is the treatment of choice for non-invasive unencapsulated strain H. influenzae infections?
Amoxicillin
Amox-clavulanate for resistant strains
What is the treatment of choice for invasive encapsulated Hib (Type B H. influenzae) infections?
3rd generation cephalosporin
What made the Hib vaccines more successful?
Conjugate! Hib capsule polysaccharide conjugated to protein carrier
What diseases are caused by Moraxella?
Otitis (one of three major bacterial causes)
Sinusitis
Conjunctivitis
What is the treatment for Moraxella?
Amoxicillin/clavulanate
How is Legionella primarily spread?
Aerosols from water systems (NOT person to person)
What differentiates Legionnaire’s disease from other pneumonias?
Very severe, can spread to brain, high mortality but low attack rate
What is the pathogenesis of Legionella?
Multiplies in alveolar macrophages
Forms vacuoles
Dot/Icm type IV secretion system exports vacuole contents into cell
What stains are used for Legionella?
Gimenez and Dieterle
What is the treatment for Legionella?
Azithromycin (or fluoroquinolone)
What population is at risk for Coxiella infection (Q fever)?
People that interact with animals (farmers, ranchers, vets)
What is the treatment for Coxiella?
Doxycycline
What disease does Corynebacterium diphtheriae cause?
Diptheria (acute respiratory infection)
Don’t have in US because of DTP vaccine
What disease does Bordetella pertussis cause?
Pertussis (whooping cough)
How is pertussis spread?
Aerosols, from adults as a reservoir to young children
What are the stages of pertussis?
Catarrhal (cold-like symptoms)
Paroxysmal (severe cough paroxysms, apnea)
Convalescent stage (cough may persist, bacteria absent)
What is the treatment of B. pertussis?
Azithromycin (to prevent further spread but no benefit to patient)
Supportive therapy
How does pertussis toxin (PTX) exert its effect?
ADP-ribosyl transferase that modifies target G proteins
Inhibits the innate immune response
What is the morphology of Legionella?
Gram negative, pleomorphic (long bacilli in media, short coccobacilli in tissue)
What is the morphology of Bordetella?
Gram negative coccobacilli
What is the morphology of Corynebacterium diptheriae?
Gram positive rod
What is the morphology of chalmydia?
Gram negative coccobacilli
What are the two species of Chlamydia infections that usually affect humans?
C. trachomatis
C. pneumoniae
What are the two forms of Chlamydia during its developmental cycle?
EB (elementary body, spore-like form)
RB (reticulate body, metabolically active and multiplies intracellularly by binary fission)
Describe developmental cycle of Chlamydia
- EB (spore-like form, metabolically inactive, dense) is internalized into cell in inclusion membrane
- EB differentiates into RB almost immediately (larger, less dense, metabolically active)
- RB multiplies intraceullularly within the inclusion membrane
- RBs condense back into EBs
- Inclusion exocytosed/cell lysed and progeny EBs go on to infect other cells
What is the main way Chlamydia releases its virulence effector proteins?
Type III secretion system (like molecular syringe that injects virulence factors into infected cell)
What diseases are caused by Chlamydia trachomatis?
Trachoma (Serovars A, B, C) Inclusion conjunctivitis Neonatal pneumonitis (from mother at birth) STI (Serovars D-K)
What sequelae is most commonly linked with Chlamydia pneumoniae?
Atherosclerotic plaques in CVD
What is the treatment of choice for Chlamydia pneumoniae?
Doxycycline or erythromycin
Who is at risk for Chlamydia psittaci?
People that interact with bird feces (pet-store, poultry farm, power line workers)
What is the morphology of Mycoplasma?
Wall-less pleiomorphic bacteria
Fried egg colony morphology
(except M. pneumoniae - mulberry colonies)
What exhibits cold agglutinins?
M. pneumoniae
What disease are M. hominis, M. genitalium and Ureaplasma urealyticum associated with?
STI
What disease are M. fermentans or M. penetrans associated with?
HIV
What toxin does M. pneumoniae produce?
Community Acquired Respiratory Distress Syndrome (CARDS) toxin - an ADP-ribosylating and vacuolating toxin
