Flashcards in Haemophilus, Bordetella, And Legionella Deck (42):
Where is H.influenza found?
How is H.influenza transmitted?
Via respiratory route.
What is the virulence of H.influenza?
1. Capsule: 6 types a-f.
2. Attachment pili
3. IgA1 protease
What is the most virulent capsule type of H.influenza?
What are the toxins of H.influenza?
1. Cytolethal distending toxin (CDT)
What can encapsulated H.influenza (usually type B) cause?
1. Meningitis (3-36 months).
2. Acute epiglottitis
3. Septic arthritis in infants
4. Sepsis (asplenic patients)
What can nonencapsulated H.influenza cause?
1. Otitis media
3. COPD exacerbation and pneumonia
How can we identify H.influenza?
1. Gram stain
2. Chocolate agar - high CO2 environment at 37C.
3. ELISA - Latex particle agglutination
4. Positive Quellung reaction due to its capsule (like S.pneumoniae).
What is important to keep in mind about H.influenza?
It requires two factors for growth (both found in blood).
-X factor: hematin
-V factor: NAD+
How is Haemophilus ducreyi transmitted?
What are the toxins of H.ducreyi?
What can H.ducreyi cause?
What is a chancroid?
Painful genital ulcer, often associated with unilateral swollen lymph nodes that can rupture, releasing pus.
How can we identify H.ducreyi?
Gram stain and culture of ulcer exudate and pus released from swollen lymph node.
What is important to keep in mind about H.ducreyi?
Requires X factor (hematin) only.
How is Gardnerella vaginalis transmitted?
Sexually transmitted disease.
Has Gardnerella vaginalis capsule?
Produce G.vaginalis exotoxins?
What can G.vaginalis cause?
Foul smelling vaginal discharge (with fishy odor), vaginal pruritus, and often dysuria.
How can we diagnose G.vaginalis infection?
Clue cells --> Vaginal epithelial cells that contain tiny pleomorphic gram (-) bacilli within the cytoplasm.
What is important to keep in mind about G.vaginalis?
It does not require X or V factor for growth.
How is Bordetella pertussis transmitted?
Via respiratory route - highly contagious.
What is the virulence of B.pertussis?
3. Filamentous hemagglutinin (FHA): A pili rod that extends from the surface of B.pertussis, enabling the bacteria to bind to ciliated epithelial cells of the bronchi.
What are the toxins of B.pertussis?
1. Pertussis toxin
2. Extracytoplasmic adenylate cyclase
3. Filamentous hemagglutinin
4. Tracheal cytotoxin
What does pertussis toxin do?
Activates G proteins that increase cAMP:
1. Incr. Histamine sensitivity
2. Incr. insulin release
3. Incr. lymphocytes in blood
What does extracytoplasmic adenylate cyclase do?
"Weakens" neutrophils, lymphocytes, and monocytes.
What does filamentous hemagglutinin do?
Allows binding to ciliated epithelial cells.
What does tracheal toxin do?
Kills ciliated epithelial cells.
What can B.pertussis cause?
What happens in the catarrhal phase of whooping cough?
Patient is highly contagious (1-2 weeks).
1. Low grade fever, runny nose and mild cough.
2. Antibiotic susceptible during this stage.
What happens during the paroxysmal phase of whooping cough?
1. Whoop (bursts of non-productive cough)
2. Incr. lymphocytes in blood smear
3. Antibiotics effective during this stage
What is the last stage of whooping cough?
How can we diagnose B.pertussis?
1. Bordet-Gengou media
2. Rapid serology - ELISA
3. Direct fluorescein-labeled antibodies applied to nasopharyngeal specimens for rapid diagnosis
4. PCR detection of bacterial DNA in respiratory secretions
What are the high risk groups for B.pertussis infection?
1. Infants less than one year old.
2. Adults (as immunity acquired from vaccines wears off).
Where is Legionella pneumophila found?
Ubiquitous in man and natural water environments.
1. Air conditioners
2. Cooling towers
What is the virulence of L.pneumophila?
1. Facultative intracellular parasite
2. Cu-Zn superoxide dysmutase and catalase-peroxidase protects from macrophage.
3. Pili and flagella promote attachment and invasion.
4. Secretion of protein toxins like RNAase, phospholipase A, and phospholipase C.
What is the toxin of L.pneunophila?
Cytotoxin: kills hamster ovary cells.
What can L.pneumophila cause?
1. Pontiac fever
2. Legionnaires' disease
What happens in pontiac fever?
3. Muscle aches and fatigue
4. Self-limiting - recovery in a week is very common
What happens in Legionnaires' disease?
3. Non-productive cough
How can we diagnose L.pneumophila?
1. Culture on buffered charcoal yeast extract (L-cysteine is a critical ingredient).
2. Serology (IFA and ELISA)
3. Urinary antigen test - detects only L.pneumophila serogroup 1 (90% of cases).