Lecture 8 Flashcards
What are the characteristics of mycobacteria?
acid-fast rods, most are slow growers, aerobic, not spore producing
What toxins do mycobacteria produce?
no exotoxins or endotoxins are known or have been identified
What is the typical reservoir of mycobacteria?
human or animal
What type of cell envelope do mycobacteria have?
gram+ -like cell envelope
What covers the cell envelope of mycobacteria?
mycolic acid
What are the characteristics of M. tuberculosis?
long rods in no specific arrangement, very pathogenic to humans, grows slowly at 37ºC body temp, highly resistant to drying
What disease does M. tuberculosis commonly cause?
tuberculosis
What is the reservoir for M. tuberculosis?
human body
What disease does M. bovis cause?
tuburculosis
What is the reservoir for M. bovis?
animals, mostly cows
What disease does M. leprae cause?
Leprosy (hansen’s disease)
What is the reservoir for M. leprae?
human body and armadillo
What disease does M. smegmatis cause?
not pathogenic = none
What is the reservoir for M. smegmatis?
human body = part of human microbiota
What is BCG?
species whos reservoir is artificial culture as it was derived from M. bovis and cultured and attenuated in lab
What temperature does BCG grow at?
37ºC
What temperature does M. bovis grow at?
37ºC
How virulent is M. bovis to humans?
very virulent but rare
What is the BCG vaccine?
works against TB, only 40% effective
Which mycobacteria species led to the development of vaccines?
M. bovis
Who discovered M. tuberculosis?
Robert Koch
What is tuberculosis?
respiratory disease transmitted from person to person
Why is tuberculosis considered to be an old disease?
detected in the remains of bison and Egyptian mummies
Why is tuberculosis a re-emerging disease?
due to traveling and urban-living = easier to spread disease and to antibiotic resistance
Tuburculosis cases/year US?
11,000 new/year
How much of the world population has been infected with tuberculosis?
1/3
What disease has infected more than 1/3 of world population?
H. pylori
Which country has the highest rate of tuberculosis infections?
South Africa
What is the cause of antibiotic resistance in M. tuberculosis?
mycolic acid may prevent some antibiotics penetrating through the cell envelope
How do we study M. tuberculosis?
mouse models and cows
What are the virulence factors of M. tuberculosis?
none have been identified except the ability to live and multiply in macrophages
What are the 2 types of TB infections?
primary infection and post-primary (latent) infection
How is M. tuberculosis transmitted?
inhalation of droplet nuclei that becomes activated when it gets to the lungs
What is droplet nuclei?
bacteria in a dry metabolically-inactive form
What are the stages (events) of tuberculosis?
inhale droplet nuclei of M. tuberculosis »_space; gets to the lungs »_space; uptake by lung macrophages = survive and release unknown virulence factors that cause damage to lungs »_space; M. tuberculosis spreads to other organs and leads to death
What happens when M. tuberculosis spreads to other parts of the body?
can become a disease outside of the respiratory system (ie: nervous system = neural disease) = very rare, stays a respiratory disease
What is one diagnostic test used to confirm active Tb in someone?
x-rays of lungs = shows lung damage
What are 2 things that can happen once someone inhales droplet nuclei of TB?
progressive systemic disease or localized infection in the lungs
What is the Progressive Systemic Disease form of TB?
fast disease becomes systemic throughout body = death quickly || happens in less than 1% people infected
What is the localized infection of the lung form of TB?
M. tuberculosis remains in the lungs and infects lung tissue
What percentage of people who inhale TB but do not become infected and do not have the disease?
91%
What percentage of individuals with the localized infection of the lung form of TB can develop into a progressive systemic disease?
3%
What is the tuberculin skin test?
common diagnostic test to identify the infection
How does the tuberculin skin test work?
take protein extract from M. tuberculosis »_space; inject it under skin »_space; wait 1-3 days to determine if there is a swollen area around site of injection = positive result
What gives a false positive TB test?
have been injected or previously injected with BCG vaccine (not an effective vaccine) = don’t take tuberculin skin test if have been vaccinated with BCG
Why does it take time for the tuberculin skin test to give a positive result?
it is based on immune system = delayed-hypersensitivity and cell-mediated immunity
What does a positive result mean?
either person has been previously exposed to TB or has TB
What are 4 diagnostic tests to identify if a person has M. tuberculosis in their system?
bacterial culture, PCR test, tuberculin skin test, chest c-rays
What are ways to prevent infection of M. tuberculosis?
healthcare workers wear HEPA-filter masks; BCG vaccination
What are 3 kinds of treatments for TB?
antimicrobials (isoniazid, rifampin) and BCG vaccine || treatment takes a long time
What are characteristics of M. leprae?
red rods, don’t grow in lab media, injected into footpads of mice to harvest bacterium; slowest grower of all mycobacteria species
Who discovered M. leprae?
Hansen = Norwegian physician
What is leprosy?
chronic, progressive disease (takes a long time for disease to develop) of skin and peripheral nerves
Is leprosy an old or new world disease?
Old
What percentage of world population have developed natural immunity against leprosy?
95%
What is the cause of the natural immunity against leprosy?
the receptor the pathogen needs to interact with the host cell is absent on the surface of host cells
What are the 6 countries where 90% of the cases happen worldwide?
Tanzania, Nepal, Brazil, India, Madagascar, Mozambique (TN-BIMM)
What is the number of cases of leprosy nationally (US)?
96/year
What is the number of cases of leprosy nationally (US)?
764,000/year
What are the 2 reasons why armadillos important for leprosy?
reservoir for armadillos = pass to humans (zoonotic disease) AND can use armadillos to study M. leprae
What is the mode of transmission of M. leprae?
unknown but assumed zoonotic disease, direct contact, air, soil
What are symptoms of leprosy?
bulb-like lesions on face and extremities
How does leprosy progress?
affects peripheral nervous system = loss of motor functions and destruction of those nerves = lose sense and can easily amputate those parts via small accidents
How can leprosy be treated?
multidrug therapy (MDT) for up to 2 years = very effective; no isolation needed and the patient becomes noninfectious after a few doses
What is the hallmark symptom of Hansen’s disease?
destruction of peripheral nervous system
What can prevent leprosy?
early diagnosis and treatment, BCG provides some protection, further research for a better vaccine
Why is diagnosis for leprosy delayed in the US?
healthcare providers are unaware of leprosy and its symptoms
Does leprosy always have a nerve involvement? If not, what is it?
no = will be considered a minor skin disease
What antibiotics are included in the multi-drug therapy for leprosy?
clofazimine, dapsone, rifampin (CDR)
