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Ch. 10: Haemophilus, Bordetella and Legionella


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How do you treat gardnerella vaginalis (formerly haemophilus vaginalis)?
How can you tell gardnerella vaginalis from candida or trichomonas?
clue cells: vaginal epithelial cells w/ tiny pleomorphic bacilli within the cytoplasm
What causes bacterial vaginitis in conjunction with anaerobic vaginal bacteria?
gardnerella vaginalis
How do you treat chancroid?
erythromycin or trimethoprim/sulfamethoxazole
What are 3 differentials when ruling our chancroid?
1. syphilis (treponema pallidum); 2. herpes (simplex virus 1 & 2); 3. lymphogranuloma venereum (LGV: chlamydia trachomatis)
What causes chancroid? What are the signs?
1. haemophilus ducreyi; 2. painful genital ulcer, unilateral painful inguinal lymph nodes
What type of vaccine is used against h. influenza?
combo of H. influenza capsule + diphteria toxin (diphteria toxin activates T-lymphocytes)
What are 3 gram - rods acquired through the respiratory tract?
haemophilus influenza, bordetella pertussis, legionella pneumophila
What diseases are caused by h. influenzae?
1. meningitis; 2. acute epiglottitis; 3. septic arthritis; 4. sepsis
What makes the h. influenza virulent?
1. b capsule (polysaccharide); 2. kids aged 6mos to 3yrs don't make antibodies against the b capsule
In what medium does h.influenza grow?
blood-containing medium; needs hematin and NAD+
Who is susceptible to h. influenza infection?
people weakened by viral lung infection, people without spleen
What is the mechanism of bordetella pertussis? What disease does it cause?
1. attaches to ciliated epithelial cells of trachea and bronchi; 2. whoopinig cough
What are the 4 exotoxin weapons of bordetella pertussis?
1. pertussis toxin A + B (Bind and Action); 2. extra cytoplasmic adenylate cyclase; 3. filamentous hemagglutinin (FHA); 4. tracheal cytotoxin
What is the role of adenylate cyclase & cAMP in bordetella pertussis?
AC increases cAMP, leading to impaired chemotaxis, impaired generation of H202 and superoxide, leading to decreased phagocytosis and bacterial clearance
What does the FHA (filamentous hemagglutinin) in bordetella pertussis do?
allows binding to ciliated epithelial cells of bronchi
What does the tracheal cytotoxin in b. pertussis do?
helps destroy the ciliated epithelial cells
Is whooping cough contagious?
What are the 3 stages of whooping cough?
1. catarrhal stage; 2. paroxysmal stage; 3. convalescent stage
How do you culture suspected b. pertussis?
1. calcium alginate swab; 2. grow on Bordet-Gengou medium (potato + blood agar)
What is the treatment for whooping cough?
primarily supportive therapy; erythromycin in the predromal or catarrhal stage to prevent the disease
What is the vaccine against whooping cough?
part of the DPT vaccine (diphteria, pertussis, tetanus); made of pertussis toxin, FHA, adenylate cyclase
Where do you find legionella pneumophilia?
in natural and manmade water environments
What is the main mechanism of legionella pneumophilia?
intracellular parasite that settles in the lower resp tract and taken in by macrophages; inhibits phagosome-lysosome fusion
What are 2 diseases caused by legionella pneumophilia?
1. pontiac fever (mild flu-like symptoms); 2. Legionnaires' disease (pneumonia in people 50+ years, esp. with smokers)
What is the treatment of legionella pneumophila infection?

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