Bacteriology II Flashcards
What are the general characteristics of atypical bacteria? (6)
- Difficult to culture
- Unusual cell wall/absence of cell wall
- Specific/unusual cellular staining properties
- Usually small size
- Most replicate intracellularly
- Slow growth
What are common clinical examples of atypical bacteria?
- Mycobacterium tuberculosis
- Chlamydia
- Mycoplasma
The growth speed of mycobacteria is generally [higher/lower] than that of other bacteria
(Much) lower
What makes mycobacteria difficult to stain?
Specialized cell wall with a waxy lipid layer
What is the advantage of the specialized cell wall to mycobacteria?
They are resistant to killing by phagocytes
What is a common comorbidity found in TB patients?
HIV
How many cases of TB are cleared by the innate immune system?
~70%
What happens when TB infections are not cleared by the innate immune system?
Formation of a Ghon complex -> granulomatous inflammation encasing the infection site
Where does the majority of TB-associated granulomas occur?
Lungs
How many % of TB infections become latent?
~10%
How many of the granulomatous laesions TB will break down? What happens if they do?
1-3% of granulomas (=0,3-1% of all TB infections) will break down, resulting in dissemination of TB through the body
How many % of TB cases immediately disseminate?
~3%
What causes reactivation of latent TB?
Impairment of the cellular immune system due to various stressors (stress, malnutrition, malignancy, HIV, old age, immunosuppression, diabetes, etc.)
What are two important virulence factors of Mycobacterium tuberculosis?
- Nuog-gene
- hip1-gene
What does the nuog gene of TB do? (2)
- Delays migration of DCs to the lungs
- Inhibits apoptosis of infected neutrophils
What does the hip1 gene of TB do? (3)
- Inhibits inflammasome-dependent macrophage proinflammatory responses
- Impairs CD40-mediated costimulatory responses of DCs
- Restricts Th17 polarization during infection
What is the treatment of tuberculosis? How long does this treatment have to be given?
Antibiotics, usually 2 months intensive + 4 months continuation
Which compounds are the current first line treatment for TB? (2)
- Rifampicin
- Isonazid
What are the 3 main factors contributing to TB drug resistance?
- Not completing the complete treatment regimen
- Pharmacokinetic population variablity (=dosage too low)
- Granuloma variation (size, composition, etc.)
What is the TB vaccine? What is it based on?
BCG, derived from live Mycobacterium bovis
What is the disadvantage of the BCG vaccination?
May hide infection when testing for TB
Which chlamydia species form a danger to humans?
- C. trachomatis
- C. pneumoniae
- C. pstittaci
What is C. psittaci associated with?
Birds, mainly parrots
What are the general characteristics of Chlamydia bacteria? (4)
- Obligate intracellular parasitic bacteria
- Gram-
- Cannot synthesize ATP -> requires host ATP
- Unique biphasic life cycle
What are the two phases in the biphasic life cycle of chlamydia?
- Elementary bodies -> resistant to harsh environmental conditions
- Reticulate bodies -> non-infectious, intracellularly replicating form
Which two biological variants of Chlamydia trachomatis can be distinguished? Which cell types do they infect?
- Trachoma -> eye and urogenital epithelial cells
- Lymphogranuloma venereum -> macrophages
Which of the two biological variants of Chlamydia trachomatis can lead to invasive tissue infections?
Lymphogranuloma venereum
What is a major complication of chronic/recurrent C. trachomatis eye infections?
Blindness (leading preventable cause of blindness worldwide)
Where are eye infections with C. trachomatis often found?
Children in rural areas of Africa
How are eye infections of C. trachomatis spread? (2)
- Discharge from the eyes
- Flies
Where are lymphogranuloma venereum infections often found?
Genital area
What is the disadvantage of lymphogranuloma venereum infections?
They are often asymptomatic -> high transmission
What are complications of lymphogranuloma venereum? (3)
- Ectopic pregnancy
- Pelvic inflammatory disease (PID)
- Sterility
Which bacterium is frequently found in co-infection with lymphogranuloma venereum?
N. gonorrhoea