Lecture 10 Flashcards
what are some traits of myobacerium?
- gram positive
- aerobes
- make catalase
- no capsules, flagella, or spores
- grow slowly
what are some general characteristics of myobacterium?
- very slow growing
- protected from lysis once they are phagocytosized
- can grow intracellular
- resistant to detergents and many common antimicrobial drugs
what do all mycobacteria produce?
mycolic acids
true or false: M. tuberculosis produces both exo and endo toxins?
FALSE!!! it doesnt produce any sort of toxin
what is the main virulence factor of M. tuberculosis?
contain complex waxes and cord factor that prevent destruction by lysosomes or macrophages
what are some traits of the cord factor?
- give culture media the corded look
- causes weight loss
- binds cells of M. tuberculosis so they are further resistant to immune system
what are the 3 major human myobacterium infections?
- M. tuberculosis (tuberculosis)
- M. leprae (leprosy)
- M. ulcerans (buruli ulcer)
how is TB transmitted?
- droplets from infected individual
- aerosolization
- skin inoculation
what factors influence how contagious tuberculosis is?
- how close
- how long
- how many infectious droplet nuclei
what are the three groups clinical tuberculosis is divided into?
- primary
- secondary (reactivation or reinfection)
- disseminated
primary tuberculosis infection begins when the bacteria reach what?
the alveoli
what are tubercles?
small, hard nodules formed when macrophages surround and phagocytosize M. tuberculosis
what causes caseous necrosis?
the release of M. tuberculosis when the infected cells within the tubercle in the center die
what is a tuberculous cavity?
when the center of the tubercle liquefies and becomes filled with air
how do granulomas benefit bacteria?
by recruiting macrophages that serve as additional sanctuaries for bacterial growth and population expansion
how do granulomas benefit the host?
represent sites for optimal interactions between pathogen infected antigen presenting cells in close apposition to effector T lymphocytes to allow for immune control of mycobacterial infection
what is the result of granulomas?
a stalemate, establishment and persistence of granulomas
how doe secondary/reactivated tuberculosis occur?
occurs with waning cell mediated immunity
what happens to tubercles in secondary/reactivated tuberculosis?
they expand and drain into the bronchial tubes and upper respiratory tract
how does one get to disseminated TB?
during secondary TB, bacilli disseminate to regional lymph nodes, kidneys, long bones, genital tract, brain and meninges
what are some predisposing factors of TB?
- inadequate nutrition
- debilitation of the immune system
- poor access to medical care
- lung damage
- genetics
how is TB diagnosed?
- in vivo or tuberculin testing
- X rays
- direct identification of acid fast bacilli in specmen
- cultural isolation and biochemical testing
what is the mantoux test?
it is a local intradermal injection of purified protein derivative, look for red bump to form in 48-72 hours, presence of swelling
what are the limitations of TB skin test?
not sensitive (false negatives)
what are IGRA’s?
interferon gamma release assays, they measure ifn gamma response of whole blood cells to TB antigens, whole blood from patient is incubated with TB proteins to detect presence of sensitized WBCs as evidence of prior TB infection
what is a problem of using chest x rays to diagnose TB?
it cannot confirm diagnosis of TB
how are bacteria such as TB considered acid fast?
they hold onto the first dye during an acid fast test and resist the acid wash
why are cultures very useful?
they are used to confirm the diagnosis of TB
what is DOT?
directly observed treatment, refers to a TB control strategy that combines 5 different components
what is XDR tuberculosis?
extensively drug resistance TB, resistant to INH and rifampin and quinolones and injectables
