Chapter 11: Haemophilus, Bordetella, and Legionella Flashcards Preview

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Flashcards in Chapter 11: Haemophilus, Bordetella, and Legionella Deck (32):

Haemophilus infleunzae

Requires blood-containing medium for growth
Needs Hematin and NAD+ from blood
Obligate human parasite
Transmission: respiratory
Gram-neg rods


What confers virulence in Haemophilus influenzae?

Polysaccharide capsule
- composed of polyribitol ribose phosphate
- 6 types of capsules: B is invasive disease in children (meningitis, epiglottis, and septic arthritis)


Is Haemophilus influenzae the etiologic agent of the flu?

No, the bacterium often attacks the lungs of persons debilitated by a VIRAL influenza infection


Nonencapsulated/nontypeable Haemophilus infleunzae

Can colonize the URT of children and adults
Lack virulent invasiveness: only cause LOCAL infection
Freq cause otitis media in children
Respiratory disease in adults with preexisting lung disease


Who gets frequent infections iwth nontypeable H. Influenzae?

Pts with COPD
Causes COPD exacerbation


Haemophilus influenzae type b causes what diseases?

Meningitis, Acute epiglottitis, Septic arthritis, Sepsis


What is the most serious infection caused by encapsulated Haemophilus influenzae type b?

Main cause of meningitis in young children btwn 6 mts to 3 years (before vaccine)


How does Haemophilus influenzae type b cause meningitis?

Inhalation: invades local LNs and blood-stream
Penetrates into the meninges

When destroyed with antibiotics, lysed bacteria releases LPS lipid A causing violent immune response that destroys neurons


What are the signs of meningits in infants with Haemophilus influenzae type b infection?

Usually do not display classic stiff neck
Non-specific signs: fever, vomiting, altered mental status


Acute epiglottitis

Rapid swelling of the epiglottis, obstructing respiratory tract and esophagus
Follows sore throat and fever
Unable to swallow
Cherry red epiglottis
DO NOT examine larynx ->laryngeal spasm->complete airway obstruction
H. Influenzae type b


Septic arthritis by Haemophilus influenzae type b

MOST COMMON CAUSE of septic arthritis in infants
Single joint
Fever, pain, swelling, decreased mobility of joint
Pleomorphic gram - rods in synovial fluid


Sepsis and Haemophilus influenzae type b

Children 6 mts - 3 yrs
Fever, lethargy, loss of appetite, no localized disease
Invade blood-stream via URT
Absent spleen or non-functioning spleens cant fight off infection: highest risk


What is Haemophilus ducreyi responsible for?

Sexually transmitted disease chancroid
Painful genital ulcer
Unilateral painful swollen inguinal LN rapidly develop
LN become matted and rupture - releasing pus
NO systemic symptoms
Ulcer and Swollen LN coexist


What can Chancroid commonly be confused with? Differential diagnosis?

Syphilis: ulcer painless, LN bilateral and painless, no pus
Herpes (simplex 1/2): Blisters, when burst can look like chancroid, painful. Systemic: fever, myalgias
Lymphogranulom venereum:Chlamydia trach, Painles matted, pus inguinal LN. Primary ulcer disappears before nodes enlarge


H. Ducreyi

Gran-negative cocobacilli
No exotoxins



Slow growing bacteria that cause endocarditis


Cardnerella vaginalis causes what?
What are the clue cells ?

Causes bacterial vaginitis in conjuction with anaerobic vaginal bacteria
S/S: Burning or itching of labia, buring on urination (dysuria), fishy odor

Clue cells: vaginal epithelial cells that contain tiny pleomorphic bacilli within cytoplasm


Bordetella pertussis causes what?

Whooping cough


Describe Bordetella pertussis

Gram - rod
4 major virulence factors:
- Pertussis toxin
- Extra cytoplasmic adenylate cyclase
- Filamentous hemagglutinin
- Tracheal cytotoxin


Pertussis toxin

B subunit
A subunit: activates G reg proteins -> Adenylate cyclase

Exact role?
1. histamine sensitization
2. Increase in insulin synthesis
3. Promotion of lymphocyte production and inhibition of phagocytosis


Extra cytoplasmic adenylate cyclase

Swallowed by host neutrophils, lymphocytes, and monocytes
Internalized AC synthesized cAMP
Results in impaired chemotaxis and impaired generation H2O2 and superoxide
Weakens phagocytosis


Filamentous hemagglutinin (FHA)

Pili rod extending from Bordetella pertussis surface. Helps bind to ciliated epithelial cells of bronchi (Bordetella doesnt invade)


Tracheal cytotoxin

Destroys the ciliated epithelial cells
Results in impaired clearance of bacteria, mucus, and inflammatory exudate
Possibly responsible for violent cough


Whopping cough

Mostly adolescents and aduts
Highly contagious disease
A week-long incubation period
Increase in Lymphocyte count not neutrophils
3 stages of disease: catarrhal stage, paroxysmal stage, and convalescent stage


Catarrhal stage of whooping cough

1-2 weeks
Similar to URTI
Low grade fever, runny nose, sneezing and mild cough
MOST contagious


Paroxysmal stage of whooping cough

Fever subsides
Nonproductive cough bursts
15-25 attacks per day (appear normal btwn events)
During episodes: pts becomes hypoxemic and cyanotic, tongue protrude, eyes bulge, neck veins engorge, vomit
Lasts a month or longer
More severe in young (cough and apnea spells)


Convalescent stage of Whooping cough

Attacks become less frequent over a month
No longer contagious


How to test of whooping cough

Organism will not grow on cotton
Use Ca alginate swab
Culture on medium with potato, blood and glycerol agar = Bordet-Gengou medium


Legionella pneumophila

Aerobic gram-negative rod
Sources: air conditioning systems, cooling towers, whirlpools
Facultative intracellular parasite (for amoebas)
Settles in lower respiratory tract
Cal enter low metabolic state and survive in biofilm


What diseases is Legionella responsible for?

Pontiac fever
Legionnaires' disease


Pontiac fever

Headache, muscle aches, fatigue, followed by fever and chills
Strikes suddenly and completely resolves in less than a week
Legionella pneumophila


Legionnaires' disease

Common cause of CAP
Causes classic lobar consolidative pneumonia similar to pneumococcal pneumonia
Unusual: fever with pulse-temp dissociation (high fever/low HR), sever headache, confusion, myalgia
sometimes rhabdomyolysis (muscle breakdown with increased lvls of serum CPK and myoglobinuria)
Cough, hyponatremia, hypophosphatemia and AST, ALT increase