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
How is Johne’s disease transmitted?
pathogens enter when an infected but healthy looking animal is introduced to the herd, calves ingest contaminated feed, milk of infected cows, or infected feces
T/F: cattle in infected herds of Johne’s disease can be clinically ill, asymptomatic shedders, or infected but neither ill or shedding
TRUE
When do clinical signs of Johne’s disease appear?
after 2 years of age
What is the pathogenesis of Johne’s disease?
ingestion -> penetrates mucosa of colon -> phagocytosed -> multiple in intraepithelial macrophages -> granulomatous reaction -> chronic inflammatory response -> thickening of intestinal mucosa -> impaired intestinal function and leakage of plasma protein -> clinical signs
What are the clinical signs of Johne’s disease?
diarrhea, rapid weight loss with normal appetite, intermandibular edema
Where is the incidence of Johne’s disease higher?
northern dairy states such as MN, WI, MI, OH, PA, and NY
How do you diagnose Johne’s disease?
fecal smear and culture followed by PCR, immunological tests (ELISA), Johnin skin test, microscopy
What diagnostics are most recommended for Johne’s disease?
culture and ELISA
How do you control Johne’s disease?
remove all clinical cases/cull positive animals, regularly test herds every 6-12 mo by fecal culture and ELISA, prevent infection via feces with calcium oxide/lime, separate newborn calves
T/F: antibiotics are used as treatment for Johne’s disease
false - there is no treatment
What does the eradication program of tuberculosis enforce?
milk pasteurization, slaughter of animals positive for TB skin test
How is tuberculosis transmitted?
via aerosol, coughing by humans or animals with active infection, gastrointestinal endoscopy equipment (poor disinfection), contaminated unpasteurized milk
How do you diagnose tuberculosis in humans?
tuberculin skin test, radiographs, culture, serum analysis
How do you treat tuberculosis?
combination therapy using anti-TB drugs (i.e. rifampin)
What species acts as a carrier of Mycobacterium leprae that causes human leprosy (Hansen’s disease)?
armadillo
What are some general characteristics of Mycobacterium lepraemurium?
causes feline leprosy, NOT zoonotic, transmitted by infected rats, treated by surgical removal of nodules
What can atypical (saprophytic) mycobacterium cause?
skin nodules in cattle, lesions in turtles
Which one of the following statements is FALSE with regard to Johne’s disease? a) it affects cattle, sheep, and goats b) clinical signs are severe in calves c) the causative organisms can be cultured d) ELISA for antibodies can be used for diagnosis e) the causative agent is an acid-fast bacterium, and stains pink
b) clinical signs are severe in calves
