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Medical Microbiology > Lecture 8 > Flashcards

Lecture 8 Flashcards

1
Q

What are the characteristics of mycobacteria?

A

acid-fast rods, most are slow growers, aerobic, not spore producing

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2
Q

What toxins do mycobacteria produce?

A

no exotoxins or endotoxins are known or have been identified

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3
Q

What is the typical reservoir of mycobacteria?

A

human or animal

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4
Q

What type of cell envelope do mycobacteria have?

A

gram+ -like cell envelope

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5
Q

What covers the cell envelope of mycobacteria?

A

mycolic acid

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6
Q

What are the characteristics of M. tuberculosis?

A

long rods in no specific arrangement, very pathogenic to humans, grows slowly at 37ºC body temp, highly resistant to drying

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7
Q

What disease does M. tuberculosis commonly cause?

A

tuberculosis

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8
Q

What is the reservoir for M. tuberculosis?

A

human body

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9
Q

What disease does M. bovis cause?

A

tuburculosis

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10
Q

What is the reservoir for M. bovis?

A

animals, mostly cows

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11
Q

What disease does M. leprae cause?

A

Leprosy (hansen’s disease)

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12
Q

What is the reservoir for M. leprae?

A

human body and armadillo

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13
Q

What disease does M. smegmatis cause?

A

not pathogenic = none

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14
Q

What is the reservoir for M. smegmatis?

A

human body = part of human microbiota

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15
Q

What is BCG?

A

species whos reservoir is artificial culture as it was derived from M. bovis and cultured and attenuated in lab

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16
Q

What temperature does BCG grow at?

A

37ºC

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17
Q

What temperature does M. bovis grow at?

A

37ºC

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18
Q

How virulent is M. bovis to humans?

A

very virulent but rare

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19
Q

What is the BCG vaccine?

A

works against TB, only 40% effective

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20
Q

Which mycobacteria species led to the development of vaccines?

A

M. bovis

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21
Q

Who discovered M. tuberculosis?

A

Robert Koch

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22
Q

What is tuberculosis?

A

respiratory disease transmitted from person to person

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23
Q

Why is tuberculosis considered to be an old disease?

A

detected in the remains of bison and Egyptian mummies

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24
Q

Why is tuberculosis a re-emerging disease?

A

due to traveling and urban-living = easier to spread disease and to antibiotic resistance

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25
Tuburculosis cases/year US?
11,000 new/year
26
How much of the world population has been infected with tuberculosis?
1/3
27
What disease has infected more than 1/3 of world population?
H. pylori
28
Which country has the highest rate of tuberculosis infections?
South Africa
29
What is the cause of antibiotic resistance in M. tuberculosis?
mycolic acid may prevent some antibiotics penetrating through the cell envelope
30
How do we study M. tuberculosis?
mouse models and cows
31
What are the virulence factors of M. tuberculosis?
none have been identified except the ability to live and multiply in macrophages
32
What are the 2 types of TB infections?
primary infection and post-primary (latent) infection
33
How is M. tuberculosis transmitted?
inhalation of droplet nuclei that becomes activated when it gets to the lungs
34
What is droplet nuclei?
bacteria in a dry metabolically-inactive form
35
What are the stages (events) of tuberculosis?
inhale droplet nuclei of M. tuberculosis >> gets to the lungs >> uptake by lung macrophages = survive and release unknown virulence factors that cause damage to lungs >> M. tuberculosis spreads to other organs and leads to death
36
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
37
What is one diagnostic test used to confirm active Tb in someone?
x-rays of lungs = shows lung damage
38
What are 2 things that can happen once someone inhales droplet nuclei of TB?
progressive systemic disease or localized infection in the lungs
39
What is the Progressive Systemic Disease form of TB?
fast disease becomes systemic throughout body = death quickly || happens in less than 1% people infected
40
What is the localized infection of the lung form of TB?
M. tuberculosis remains in the lungs and infects lung tissue
41
What percentage of people who inhale TB but do not become infected and do not have the disease?
91%
42
What percentage of individuals with the localized infection of the lung form of TB can develop into a progressive systemic disease?
3%
43
What is the tuberculin skin test?
common diagnostic test to identify the infection
44
How does the tuberculin skin test work?
take protein extract from M. tuberculosis >> inject it under skin >> wait 1-3 days to determine if there is a swollen area around site of injection = positive result
45
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
46
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
47
What does a positive result mean?
either person has been previously exposed to TB or has TB
48
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
49
What are ways to prevent infection of M. tuberculosis?
healthcare workers wear HEPA-filter masks; BCG vaccination
50
What are 3 kinds of treatments for TB?
antimicrobials (isoniazid, rifampin) and BCG vaccine || treatment takes a long time
51
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
52
Who discovered M. leprae?
Hansen = Norwegian physician
53
What is leprosy?
chronic, progressive disease (takes a long time for disease to develop) of skin and peripheral nerves
54
Is leprosy an old or new world disease?
Old
55
What percentage of world population have developed natural immunity against leprosy?
95%
56
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
57
What are the 6 countries where 90% of the cases happen worldwide?
Tanzania, Nepal, Brazil, India, Madagascar, Mozambique (TN-BIMM)
58
What is the number of cases of leprosy nationally (US)?
96/year
59
What is the number of cases of leprosy nationally (US)?
764,000/year
60
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
61
What is the mode of transmission of M. leprae?
unknown but assumed zoonotic disease, direct contact, air, soil
62
What are symptoms of leprosy?
bulb-like lesions on face and extremities
63
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
64
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
65
What is the hallmark symptom of Hansen's disease?
destruction of peripheral nervous system
66
What can prevent leprosy?
early diagnosis and treatment, BCG provides some protection, further research for a better vaccine
67
Why is diagnosis for leprosy delayed in the US?
healthcare providers are unaware of leprosy and its symptoms
68
Does leprosy always have a nerve involvement? If not, what is it?
no = will be considered a minor skin disease
69
What antibiotics are included in the multi-drug therapy for leprosy?
clofazimine, dapsone, rifampin (CDR)

Medical Microbiology (20 decks)

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