Mycobacterium Flashcards
What are some general characteristics of mycobacterium?
gram positive rods, non-motile obligate intracellular pathogens, strictly aerobic, can survive in environment for up to a year, highly resistant to killing by host
What is unique about mycobacterium?
unique cell wall with high lipid composition (rough and waxy) that gives ability to resist dehydration, acid/alkaline inactivation, environmental factors, common antibiotics, and disinfectants
When would you expect colonies of mycobacterium to arise on agar plates?
2-6 weeks or longer - VERY SLOW PROCESS
What kind of media is used for mycobacterium?
egg-based media used for isolation (4-8 weeks)
What color do mycobacterium stain with acid-fast stain?
mycobacterium stains red
What stain is used for differential staining of mycobacterium species?
acid-fast stain
Mycobacterium are opportunistic pathogens in __________ patients
AIDS
What are some characteristics of group I mycobacterium?
photochromogens, grow slowly (>7 days to form visible colony), produce yellow pigment when incubated in light
What are some characteristics of group II mycobacterium?
scotochromogens, grow slowly, produce a yellow/orange pigment in the absence of light
What are some characteristics of group III mycobacterium?
non-chromogens, very slow growing, do not produce pigment
What are some characteristics of group IV mycobacterium?
saprophytes, rapid growth (2-4) days to see a visible colony, non-pigmented
What are some diseases associated with mycobacterium?
M. bovis (TB in cattle, humans, and monkeys), M. tuberculosis (TB in humans, parrots, monkeys, elephants), M. avium (TB in birds, poultry, pigs), M. avium subspecies paratuberculosis (Johne’s dz in cattle)
What species of mycobacterium affect humans/are zoonotic?
M. bovis and M. tuberculosis
How is M. bovis transmitted?
respiratory discharges, milk, semen
How is M. tuberculosis transmitted?
respiratory
How is M. avium and M. avium subspecies paratuberculosis transmitted?
shed in feces
What is the pathogenesis of mycobacterium?
entry via oral or respiratory -> macrophages -> local lymph nodes -> lymphatic vessels -> blood -> lungs, liver, spleen -> nodules (collection of macrophages) -> necrosis, caseation -> calcification
What are some virulence factors of mycobacterium?
glycolipids and wax D
Wax D + mycobacterial proteins = ____________________________
delayed hypersensitivity
How do you diagnose mycobacterium?
tuberculin skin testing for cattle, serology, culture, nucleic acid based PCR, gamma interferon test, post-mortem lesions and histology
How do you treat mycoplasma?
rifampin and isoniazid in elephants and bird, BCG vaccine for children and calves (not in US or Canada), food animals are not treated
How do you control mycoplasma?
tuberculin testing and culling of positive reactors, quarantine new additions 60-90 days, disinfect contaminated premises with cresylic compounds
Which one of the following is LEAST accurate with regards to tuberculosis? a) cattle with TB are not treated in the US and Canada b) BCG is a diagnostic reagent used to detect carriers c) parrots can get infection with M. tuberculosis d) acid-fast staining method is useful to visualize mycobacteria e) elephants and exotic birds may be treated with antibiotics
b) BCG is a diagnostic reagent used to detect carriers
What are some general characteristics of Johne’s disease?
associated with M. avium subspecies paratuberculosis (MAP), affects cattle, goats, and sheep worldwide, causes debilitating chronic diarrhea
