6 Flashcards
What do mycobacteria cause? Why cant gram stain be used?
tuberculosis and leprosy
waxy coat and resistant to disinfectant and it resist decolorization
what special staining method is used?
ZIEHL-NEELSEN
what is mycobacterium tuberculosis
acid fast bacillus causes chronic, slowly progressing, pulmonary infection
what is the first stage of tuberculosis?
Primary tuberculosis
steps for Ziehl neelsen staining
- Ziehl-Neelsen carbol fuchsin to the slide for five minutes while applying heat.
- Follow with a gentle wash with water to cool the slide.
- Acid alcohol is now added to decolorize the slide.
- Wash the slide in water again and counterstain with methylene blue for 1-2 minute
how long does it take to see mycobacterium tuberculosis on a Lowenstein Jensen medium
4-6 weeks
how many people does mycobacterium tuberculosis affect
1.7 billion/year
what happens in primary tuberculosis
- Aerosol inhalation
2.Bacteria multiplication in alveoli
3.Macrophage ingestion of bacilli and formation of 1º complex
4.Foci of infection in lungs (may be spread to kidneys, bones, meninges) - 6 weeks CMI is fully active, infection is stopped
(majority of cases)
6.Some bacilli survive, reactivation several years later
what is the second stage of mycobacterium tuberculosis
- Late reactivation of lesions in lungs, kidneys, bones etc
- 5% of cases; higher in patients with AIDS
3.Chronic infection
immunity in tuberculosis
CMI is most important (T-cells)
-tuberculin solution injected intradermally (wait 48-72 hrs)
-mantoux test
-record diameter >10mm (positive), 5-9 (doubtful), <4mm Negative)
-poisitve dont mean active
What is atypical mycobacteria? it has a higher ______. how does it affect the Mantoux test
Occasionally isolated from patients with chronic pulmonary disease indistinguishable from TB (M. kansassi, M. avium, M. intracellulare)
-resistance to anti-tb drug
-gives doubtful Mantoux test
whats tehe difference between M.marinum and M fortuitum
M. marinum: skin infections
* M. fortuitum: soft tissue abscesses
all atypical mycobacterium infections are typically seen in
the elderly
veterans
immune-comprimised
city people
immune-comprimised
what does mycobacterium leprae cause? how many kinds are there? whats the name?
-leprosy
-2 kinds
tuberculoid leprosy and lepromatous leprosy
is myobacteriumrarely found found in developed countries or undeveloped
developed
what is Tuberculoid leprosy:
visible nerve enlargement,
few erythmatous plaques, few bacilli in infected
tissues, but many lymphocytes and granulomas;
low infectivity
Lepromatous leprosy
no visible nerve
enlargement, many erythromatous nodules, many
bacilli in infected tissue; high infectivity
epidemiology of mycobacterium liprae
not common in North America, mostly seen in Asia and Africa
-between 1-2 million cases currently reported worldwide; only 125 new cases seen in US each
year.
-transmission is primarily human to human through respiratory droplets; in some rare cases
transmission occurs through an animal reservoir (armadillos).
how is the diagnoses for mycobacterium leprae
microscopy is used for the lepromatous diagnosis, but not for the tuberculoid form since so
few bacilli are present; skin testing is used for the tuberculoid form
what are the 3 types of spirochetes
Treponema causing syphilis, yaws, pinta
Leptospira causing leptospirosis
Borrrelia causing relapsing fever, known as Lyme disease
what causes syphillis
T.pallidum
-STI
what is primary syphillis?
Appearance of chancre 3-4 weeks after infection
* Fluid from lesion contains bacteria seen under
dark-field microscopy
Secondary syphilis
- 6 weeks after appearance of chancre
- Generalized or local rash
- Mucosal lesions with many treponemes
Latent syphilis
No symptoms of infection
* Non-transmittable after 4 years
* BUT congenital infection may occur
