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Medical Microbiology > Lecture 8 > Flashcards

Lecture 8 Flashcards

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USMLE® Step 1 flashcards Biology 101 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
Q

Tuburculosis cases/year US?

A

11,000 new/year

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26
Q

How much of the world population has been infected with tuberculosis?

A

1/3

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27
Q

What disease has infected more than 1/3 of world population?

A

H. pylori

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28
Q

Which country has the highest rate of tuberculosis infections?

A

South Africa

29
Q

What is the cause of antibiotic resistance in M. tuberculosis?

A

mycolic acid may prevent some antibiotics penetrating through the cell envelope

30
Q

How do we study M. tuberculosis?

A

mouse models and cows

31
Q

What are the virulence factors of M. tuberculosis?

A

none have been identified except the ability to live and multiply in macrophages

32
Q

What are the 2 types of TB infections?

A

primary infection and post-primary (latent) infection

33
Q

How is M. tuberculosis transmitted?

A

inhalation of droplet nuclei that becomes activated when it gets to the lungs

34
Q

What is droplet nuclei?

A

bacteria in a dry metabolically-inactive form

35
Q

What are the stages (events) of tuberculosis?

A

inhale droplet nuclei of M. tuberculosis &raquo_space; gets to the lungs &raquo_space; uptake by lung macrophages = survive and release unknown virulence factors that cause damage to lungs &raquo_space; M. tuberculosis spreads to other organs and leads to death

36
Q

What happens when M. tuberculosis spreads to other parts of the body?

A

can become a disease outside of the respiratory system (ie: nervous system = neural disease) = very rare, stays a respiratory disease

37
Q

What is one diagnostic test used to confirm active Tb in someone?

A

x-rays of lungs = shows lung damage

38
Q

What are 2 things that can happen once someone inhales droplet nuclei of TB?

A

progressive systemic disease or localized infection in the lungs

39
Q

What is the Progressive Systemic Disease form of TB?

A

fast disease becomes systemic throughout body = death quickly || happens in less than 1% people infected

40
Q

What is the localized infection of the lung form of TB?

A

M. tuberculosis remains in the lungs and infects lung tissue

41
Q

What percentage of people who inhale TB but do not become infected and do not have the disease?

A

91%

42
Q

What percentage of individuals with the localized infection of the lung form of TB can develop into a progressive systemic disease?

A

3%

43
Q

What is the tuberculin skin test?

A

common diagnostic test to identify the infection

44
Q

How does the tuberculin skin test work?

A

take protein extract from M. tuberculosis &raquo_space; inject it under skin &raquo_space; wait 1-3 days to determine if there is a swollen area around site of injection = positive result

45
Q

What gives a false positive TB test?

A

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
Q

Why does it take time for the tuberculin skin test to give a positive result?

A

it is based on immune system = delayed-hypersensitivity and cell-mediated immunity

47
Q

What does a positive result mean?

A

either person has been previously exposed to TB or has TB

48
Q

What are 4 diagnostic tests to identify if a person has M. tuberculosis in their system?

A

bacterial culture, PCR test, tuberculin skin test, chest c-rays

49
Q

What are ways to prevent infection of M. tuberculosis?

A

healthcare workers wear HEPA-filter masks; BCG vaccination

50
Q

What are 3 kinds of treatments for TB?

A

antimicrobials (isoniazid, rifampin) and BCG vaccine || treatment takes a long time

51
Q

What are characteristics of M. leprae?

A

red rods, don’t grow in lab media, injected into footpads of mice to harvest bacterium; slowest grower of all mycobacteria species

52
Q

Who discovered M. leprae?

A

Hansen = Norwegian physician

53
Q

What is leprosy?

A

chronic, progressive disease (takes a long time for disease to develop) of skin and peripheral nerves

54
Q

Is leprosy an old or new world disease?

A

Old

55
Q

What percentage of world population have developed natural immunity against leprosy?

A

95%

56
Q

What is the cause of the natural immunity against leprosy?

A

the receptor the pathogen needs to interact with the host cell is absent on the surface of host cells

57
Q

What are the 6 countries where 90% of the cases happen worldwide?

A

Tanzania, Nepal, Brazil, India, Madagascar, Mozambique (TN-BIMM)

58
Q

What is the number of cases of leprosy nationally (US)?

A

96/year

59
Q

What is the number of cases of leprosy nationally (US)?

A

764,000/year

60
Q

What are the 2 reasons why armadillos important for leprosy?

A

reservoir for armadillos = pass to humans (zoonotic disease) AND can use armadillos to study M. leprae

61
Q

What is the mode of transmission of M. leprae?

A

unknown but assumed zoonotic disease, direct contact, air, soil

62
Q

What are symptoms of leprosy?

A

bulb-like lesions on face and extremities

63
Q

How does leprosy progress?

A

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
Q

How can leprosy be treated?

A

multidrug therapy (MDT) for up to 2 years = very effective; no isolation needed and the patient becomes noninfectious after a few doses

65
Q

What is the hallmark symptom of Hansen’s disease?

A

destruction of peripheral nervous system

66
Q

What can prevent leprosy?

A

early diagnosis and treatment, BCG provides some protection, further research for a better vaccine

67
Q

Why is diagnosis for leprosy delayed in the US?

A

healthcare providers are unaware of leprosy and its symptoms

68
Q

Does leprosy always have a nerve involvement? If not, what is it?

A

no = will be considered a minor skin disease

69
Q

What antibiotics are included in the multi-drug therapy for leprosy?

A

clofazimine, dapsone, rifampin (CDR)

Medical Microbiology (20 decks)

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