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Medical Microbiology > Lecture 7 > Flashcards

Lecture 7 Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

What is the reservoir of bacillus?

A

environment

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2
Q

What are the characteristics of bacillus?

A

gram+, rods can form chains, expression of many toxins = cause different diseases, aerobic (loves O2)

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3
Q

What colony morphology does bacillus form? What is important about this?

A

white fuzzy colonies = unique way to identify bacillus species on BAP plates

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4
Q

Where are the spores located in a bacillus that formed spore?

A

one side of the cell

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5
Q

What does “anthrax” mean and what does it refer to?

A

means “charcoal” referring to the black necrotic wound it causes

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6
Q

What kind of pathogen is B. anthracis?

A

human pathogen

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7
Q

What disease does B. anthracis cause?

A

anthrax

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8
Q

What disease does B. cereus cause?

A

food poisoning (mainly)

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9
Q

What kind of pathogen is B. subtilis?

A

human opportunistic pathogen, part of human microbiota on some individuals

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10
Q

What diseases does B. subtilis cause?

A

eye infection

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11
Q

What kind of pathogen is B. thuringiensis?

A

pathogen for insects

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12
Q

What does B. thuringiensis do to insects and what is beneficial about this to us?

A

produces exotoxins that target specific insect; this bacteria can be used as a bio-pesticide

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13
Q

What are the 3 forms of anthrax diseases due to B. anthracis?

A

cutaneous, inhalation, and GI

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14
Q

What is the most dangerous form of anthrax?

A

cutaneous

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15
Q

What is the most lethal form of anthrax?

A

inhalation

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16
Q

What is the cutaneous form of anthrax?

A

on the skin; happens when there is an opening in the skin (wound) and it gets infected by the pathogen

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17
Q

What is the inhalation form of anthrax?

A

(aka systemic anthrax) breathe in spores –> infect different parts of body

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18
Q

What is cutaneous anthrax characterized by?

A

pustule surrounded by edema

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19
Q

How can cutaneous anthrax be treated? Is this easily treatable?

A

easily treatable with antibiotics

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20
Q

How is one explanation as to why systemic anthrax is most lethal form of anthrax?

A

macrophage cannot digest endospore and when B. anthracis become vegetative = it will divide and multiply and spread to other parts of body

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21
Q

What is GI anthrax form of anthrax?

A

ingesting food (especially meat) with the B. anthracis spore

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22
Q

What is the infectious agent in anthrax that leads to the disease?

A

the endospore

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23
Q

How often does GI anthrax occur in developed countries?

A

very rarely

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24
Q

Which form of anthrax has a high mortality rate?

A

systemic (inhalation)

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25
Q

What is the infection of cutaneous anthrax?

A

necrotizing tissue due to a single exotoxin

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26
Q

What is the mode of infection with the systemic form of anthrax?

A

spore inhaled &raquo_space; lung macrophage takes up spore &raquo_space; spore germinates and divides &raquo_space; bacteria enter bloodstream and cause septic shock

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27
Q

What type of infections does B. cereus cause?

A

most common = GI infections; also can cause eye infections; less common = respiratory infection

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28
Q

Why is anthrax considered a zoonotic disease?

A

if we come into contact with or consume an infected animal

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29
Q

What is the reservoir for anthrax?

A

environment (soil) and infected farm animals

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30
Q

What are the 4 virulence factors of B. anthracis?

A

toxins, capsule, ability to survive in macrophages, and plasmids

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31
Q

What are the 2 toxins B. anthracis produces and what do they cause/lead to?

A

edema toxin = skin infection (cutaneous anthrax) | lethal toxin = systemic anthrax

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32
Q

What is the virulence purpose of the capsule?

A

provides protection to bacteria against host immune system = causes it to not be immunogenic and why the host’s immune system cannot detect the pathogen easily

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33
Q

What are the 2 plasmids B. anthracis posses and what are their functions?

A

pX01 = genes encoding for the exotoxins of anthrax | pX02 = carries the genes for synthesis of capsule

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34
Q

What type of class of toxins do the exotoxins produced from B. anthracis belong to?

A

AB type | both toxins share the same B-subunit; A-subunit varies = bacteria switches between the two

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35
Q

How is B. anthracis able to produce 2 different types of exotoxins?

A

by minimizing the gene products that they need to produce

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36
Q

What is the B-subunit in the B. anthracis exotoxins considered to be? What is the benefit of this?

A

considered to be a protective antigen that can be used in vaccine development; the antigen is used to stimulate the immune system and provide protection from the pathogen and disease

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37
Q

Why is the anthrax vaccine inefficient?

A

lasts short period of time and has serious side effects

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38
Q

What is the mechanism of pathogenesis of the lethal toxin B. anthracis produces? What is the role of the A-subunit?

A

targets and kills macrophages where the A-subunit (lethal factor) acts as a protease

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39
Q

What are 2 ways anthrax can be diagnosed?

A

culture from infected tissues and PCR

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40
Q

What is the antibiotic that cutaneous anthrax is treated with?

A

Cipro = quinolone

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41
Q

Can we treat systemic anthrax with antibiotics? Why or why not?

A

No because the mortality rate is very high

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42
Q

What does “heat-labile” mean?

A

inactivated or altered molecule at hot temperatures

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43
Q

What are the two types of enterotoxins B. cereus can produce?

A

heat-stable and heat labile

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44
Q

What enzymes mediate tissue destruction during infection with B. cereus?

A

cytotoxic enzymes such as phospholipase C and cereolysin

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45
Q

What are the 4 types of people that are at risk of infection of B. cereus

A

those that ingest contaminated food, have penetrating injuries, receive intravenous injections, immunocompromised patients

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46
Q

What are the 2 forms of GI infections due to B. cereus?

A

emetic and diarrheal

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47
Q

Which form of GI infection due to B. cereus is caused by a heat-labile enterotoxin?

A

emetic form (vomiting)

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48
Q

Which form of GI infection due to B. cereus is caused by a heat-stable enterotoxin?

A

diarrheal form

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49
Q

What dictates which form of GI infection due to B. cereus that someone will get?

A

depends on which kind of food gets infected

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50
Q

What kind of food would the contamination lead to an emetic form of GI infection due to B. cereus?

A

rice

51
Q

What kind of food would the contamination lead to a diarrheal form of GI infection due to B. cereus?

A

meat and vegetables

52
Q

What are the characteristics of Clostridia?

A

anaerobic (NO O2), gram+ rods, produce endospores, produce many different toxins, unable to reduce sulfate to sulfite

53
Q

Where are clostridia species usually found?

A

environments or intestines of animals

54
Q

Compare the size of clostridia to e. coli

A

clostridia is larger than e. coli

55
Q

What are the 4 common species of clostridia that will we be learning about?

A

C. difficile, C. perfringens, C. botulinum, C. tetani

56
Q

What is the reservoir for C. difficile?

A

human colon

57
Q

What is significant of C. difficile?

A

difficult to treat with antibiotics; it is one of the 3 superbugs

58
Q

What diseases does C. difficile cause?

A

intestinal disorders

59
Q

What can be a cause of infection due to C. difficile

A

use of antibiotics

60
Q

What is the reservoir for C. perfringens?

A

soil and intestines of animals

61
Q

What diseases does C. perfringens cause?

A

food poisoning and wound infections

62
Q

What is the reservoir for C. botulinum?

A

soil and meat

63
Q

What disease does C. botulinum cause?

A

botulism

64
Q

What is the reservoir for C. tetani?

A

soil and intestines of humans and animals

65
Q

What disease do C. tetani cause?

A

tetanus

66
Q

What are the 3 reasons why clostridia are able to cause many different diseases?

A

1) spores allow them to survive in difficult/extreme environments | 2) rapid growth in a nutrient-rich O2-deprived environment means no sharing of nutrients | 3) can produce many different types of toxins (ie: enterotoxin and neurotoxins)

67
Q

What does PMC stand for and which bacterium causes it?

A

pseudomembranous colitis due to C. difficile

68
Q

What is pseudomembranous colitis and what causes it?

A

inflammatory disease of colon caused by antibiotics

69
Q

How does taking antibiotics cause PMC?

A

kills other microbes present in the GI microbiota and takes over area

70
Q

What percentage of normal individuals have C. difficile as part of their microbiota?

A

less than 5%

71
Q

What induces C. difficile to grow and produce exotoxins? Which specific “inducers” mediate this?

A

antibiotics especially ampicillin and clindamycin

72
Q

What immediately happens once C. difficile produces its exotoxins?

A

causes diarrhea &raquo_space; ulceration of colon &raquo_space; death if not treated

73
Q

What are the exotoxins that C. difficile produce?

A

exotoxins A and B

74
Q

What is the mode of transmission of C. difficile?

A

via spores

75
Q

What are the 3 virulence factors of C. difficile?

A

exotoxins A and B and some adhesins

76
Q

How do we diagnose/detect C. difficile in an infected individual?

A

run ELISA assay on a fecal sample to detect toxin A

77
Q

Which antibiotics kill C. difficile?

A

vancomycin and metronidazole

78
Q

What are some treatment methods to treat C. difficile infections?

A

stop taking antibiotics causing problem, early diagnosis, take probiotics

79
Q

What are 3 prevention methods against PMC?

A

good hygiene, stop using antibiotics that cause PMC, early diagnosis

80
Q

What are the characteristics of C. perfringens?

A

large rods (size depends on nutrient availability and species); non-motile, spores-rarely, hemolytic

81
Q

What disease does C. perfringens most commonly cause?

A

food poisoning

82
Q

What are the 3 common bacteria that cause food poisoning (in order)?

A

Campylobacter jejuni; Salmonella; C. perfringens

83
Q

What kind of disease is food poisoning due to C. perfringens considered to be?

A

self-limiting disease

84
Q

What does self-limiting disease mean?

A

disease goes away in short time because immune system is able to resolve the infection

85
Q

How many cases/year does food poisoning occur due to C. perfringens?

A

250,000

86
Q

What are some symptoms of food poisoning due to C. perfringens?

A

watery diarrhea with no fever

87
Q

What is the most common contaminated food that causes food poisoning due to C. perfringens?

A

meat, poultry, fish

88
Q

What causes diarrhea and cramps from food poisoning due to C. perfringens?

A

enterotoxins

89
Q

What diagnostic test is used for food poisoning due to C. perfringens?

A

ELISA detects presence of enterotoxin in fecal sample

90
Q

What another disease can C. perfringens cause? What can it lead to?

A

soft-tissue infections due to wounds &raquo_space; can lead to gangrene

91
Q

What toxin does C. perfringens produce to cause gangrene?

A

alpha toxin = causes gas gangrene

92
Q

What is the treatment for wound infections due to C. perfringens?

A

antibiotics, antitoxin, and exposing wound to oxygen

93
Q

What is an antitoxin?

A

antibody that targets and neutralizes the toxin

94
Q

How would exposing the wound infected from C. perfringens to oxygen treat the infection?

A

C. perfringens is anaerobic = cannot live in presence of O2

95
Q

What are some characteristics of C. botulinum?

A

large rods, does not form chains, can produce spores

96
Q

What is botulism?

A

severe food poisoning by a toxin

97
Q

What is the botulinum toxin?

A

a neurotoxin

98
Q

How many types of botulinum toxin are there?

A

8 types depending on source of infection

99
Q

Which botulinum toxins are commonly present in human cases?

A

A, B and sometimes E

100
Q

What is the LD50 of the botulinum toxin?

A

0.4 kg

101
Q

What is the result of botulism if not treated promptly?

A

paralysis in 2 days

102
Q

What are the 4 types of botulism?

A

“classic”/foodborne | infant botulism | wound botulism | inhalation botulism

103
Q

What is the “classic” or foodborne botulism?

A

consuming infected food = infects GI system

104
Q

What are the symptoms of classic botulism?

A

blurred vision fixed dilated pupils, dry mouth, constipation, abdominal pain, no fever

105
Q

How can classic botulism be prevented?

A

proper food preparation, no honey for infants

106
Q

What is wound botulism?

A

opening on skin leads to infection in skin area

107
Q

What is inhalation botulism?

A

due to bioweapon (inhale spores) = very rease

108
Q

What is infant botulism?

A

due to consumption of honey (may have contained spores)

109
Q

Which type of botulism is more common in the US?

A

infant botulism

110
Q

What can cause death in classic botulism?

A

respiratory paralysis due to botulinum toxin

111
Q

What are 3 types of treatment for classic botulism?

A

antitoxin, antibiotics, ventilatory support

112
Q

For the antitoxin treatment of classic botulism, how will an antibody against the toxin be produced?

A

inject toxin into large animal (ie horses) and extract serum

113
Q

Is there a vaccine available to treat botulism?

A

no

114
Q

What are the characteristics of C. tetani?

A

large rods, motile, anaerobic, extremely toxic to oxygen toxicity

115
Q

What causes tetanus? What type of life-event is usually associated with this disease?

A

traumatic wounds where C. tetani spores will invade and germinate = release toxin and get into bloodstream

116
Q

What is the mortality rate of tetanus?

A

30-50%

117
Q

What is the tetanus toxin? What does it cause?

A

neurotoxin causes paralysis

118
Q

How do we diagnose for tetanus?

A

clinical symptoms

119
Q

What treatments are available to treat tetanus?

A

antitoxin

120
Q

How can one prevent tetanus?

A

vaccine (tetanus toxoid, part of DPT vaccine)

121
Q

How many cases of tetanus are in the US?

A

low, less than 40 cases/year

122
Q

What are the early signs of tetanus infection?

A

drooling, back spasms, irritability, sweat

123
Q

How many doses does one need of the DPT vaccine and how often is the booster dose?

A

5 doses (as a child) and booster dose every 10 years

Medical Microbiology (20 decks)

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