Bordetella, Haemophilus & Legionella Flashcards Preview

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Flashcards in Bordetella, Haemophilus & Legionella Deck (39):

Bordetella organism type and shape

Gram negative coccobacillus, encapsulated Non-motile fastidious growth requirements


______ is associated with virulent strains of Bordetella



Bordetella stages (3)

Catarrhal - mild fever,cough Paroxysmal - Severe cough, lymphotoxicity results in leukocyte proliferation Convalescent - 45 days, cough is less severe


Bordetella spread and detection

droplet spread (highly contagious) CATARRHAL stage is the most contagious, making it hard to detect before it spreads!


Bordetella epidemiology

mainly kids getting it confers immunity 3 year cycles of incidence


4 reasons for US outbreaks of Bordetella

--Increased reporting (better surveillance) --Increased bacteral Ptx produced by strains --Antigen target of vax has changed --Not enough boosters given


Two virulence factors of Bordetella

Filamentous Hemagglutinin + Ptx Toxin


Filamentous hemagglutinin pathogenicity

  • Allows bacteria to bind to glycoprotein receptor on ciliated epithelial cells
  • **Phagocytosed without MQ activation**
  • Causes ciliary stasis of mucociliary escalator (not able to sweep up bacteria out of URT)
  • Aided by pili, pertactin, and Ptx


Ptx pathogenicity

  • AB5 toxin
  • Contains five B parts that bind to ganglioside specifically present in ciliated cells and phagocytes
  • The A subunit ADP ribosylates an inhibitory G protein
    • Keeps adenyl cyclase ACTIVE (increased cAMP)


What are the other 4 pathogenicity factors for Bordetella (not FH or PTx)

  1. Calmodulin-dependent adenyl cyclase
  2. Dermonecrotic toxin (T3SS)
  3. Tracheal cytotoxin - soluble peptidoglycan
  4. LPS (Lipids A and X)


Bordetella vaccine type and dose


Acellular (onloy surface proteins)

Vax given three times before 1 y.o. (5 times total)

Cocooning strategy for vaccination?


Can antibiotics be used for Bordetella control?


Erythromycin / Azithromycin


*effective only if given in the catarrhal stage


Other bordatella

B. Parapertussis

  • contains cryptic ptx operon that is NOT expressed (less severe)


H. influenzae shape and structure

  • Gram negative
  • Coccobacillus (short)
  • Some have a typable capsule


H. influenzae growth media and appearance

  • the capsulated forms iridescent on BHI agar
  • Chocolate blood agar
  • Satellite colonies on Blood agar + Staph


H. influenzae requires _____ for growth

Heme (factor X)

NAD (Factor V)


How are H. influenzae capsules typed (when they're able to be typed)?

Quellung reaction

  • Types a-f
  • most infectious strains are type B (HiB)


H. influenzae clinical presentation

different in babies, children, and adults!

Fetal = stillbirth if before 24 weeks

Children = Menigitis and Otitis Media (may be primary to meningitis). May cause epitglottitis or conjunctivitis.

Adults = non-typable forms, may cause PNA



The "big three" for acute otitis media

H. influenzae

Strep pneumoniae

Moraxella catarrhalis


Examination sign for epiglottitis

"Thumb sign" on radiograph


H. influenzae is the major cause of ....

community acquired PNA in the US that requires hospitalization


H. influenzae carrier rate, spread, and mortality

  • 75% for non-typable  (only 3% for typable)
  • Spread via droplets
  • HiB meningitis is 90% fatal if not treated in time


H. influenzae pathogenic factors

  1. adhesion pili and proteins (allow uptake and IC growth)
  2. IgA protease
  3. LOS (kinda like Neisseria)
  4. T-cell activation by soluble PG
  5. Poly-Ribosylribitol Phosphate (PRP) Capsule (the main one!)
    1. allows capillary and CNS invasion


H. influenzae vaccine structure

Type B PRP

  • Conjugated to diphtheria toxoid for children older than 15 months
  • Conjugated to other proteins for children under 15 months


Does AOM always require treatment? What agents are used?

No! 80% will resolve on own.

  • Amoxycillin (eardrops)
  • 3rd-gen Cephalosporins can be used,but may cause diarrhea
  • Rifampin is used for prophylaxis for meningitis in epidemic setting (b/c it crosses the BBB!)


Other haemophilus

H. ducreyi

  • Chancroid
  • Ragged soft genital ulcer
  • Spread as STD
    • Contributes to spread of HIV d/t open lesion
  • Africa prevalence
  • Treatment = oral Bactrim or Macrolides


Legionella Organism shape and growth characteristics/media

  • Gram negative Rod
  • Pleomorphic
  • Fastidious growth
    • Requires Iron + Cysteine
    • Needs High humidity
    • Slow growth on buffered charcoal yeast extract


Legionella gram stain

Basic fuchscin must be used as a counterstain, because the unique unbranched fatty acids don't stain well


Legionella clinical presentation (diseases)

(most are ASYMPTOMATIC!)

  1. Pontiac Fever
    1. Highly infectious, mild flu-like disease for 1-2 days
  2. Legionnaires' Disease
    1. Acute PNA
    2. Consolidation and Fibrin deposition in multiple foci, usually in LOWER parts of the lung


Risk factors for Legionnaires disease

elderly (>55)

  • Smoking, emphysema, lung cancer
  • Bronchitis
  • Immunosuppressant drugs


Most common overall bug for community acquired PNA

Strep Pneumo

(H influenzae is only number one for those cases which require hospitalization)


Clinical presentations that favor Dx of legionella

  • Hyperacute
  • Septic shock
  • White cell count >15k
  • Lobar consolidation


Legionella epidemiology

--Distributed in water and soil (city tap water)

--Can invade and parasitize amoeba and flagellated protozoa

--Forms FILM near standing water

  • Cooling towers, shower heads
  • Amoeba can be a reservoir


Legionella transmission

Mechanically aerosolized droplets are inhaled by humans

NOT TRANSMISSIBLE from human > human



Legionella pathogenic factors (4)

  • MQ-specific adhesion pili
  • Types 2 and 4 secretion system
    • T4SS secretes AnkB effector - interferes with microtubule based transport = no formation of phagolysosome
  • Pathogen mediated endocytosis
    • Mq coils one pseudopod around bacterium many times
  • release Blebs of LPS from outer membrane

*grows in macrphages by preventing Phagolysosome fusion (via AnkB)


Legionella detection

Urine antigen test


Legionella control

decontaminate source of droplets with Bleach and Superheating to at least 75 degrees Celsius



____ may cause increased risk for Legionellosis


TNFa blockers


Treatment for Legionnaires disease


  • Erythromycin
  • Azithromycin

Sometimes used in conjunction with fluoroquinolones)