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MOD Final > Bacteria (Part I) > Flashcards

Bacteria (Part I) Flashcards

1
Q

what are the three methods of transfer of plasmids?

A

direct conjugation, infective viral transduction, or transformation

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2
Q

Why are plasmids significant?

A

they confer various factors and traits to bacteria allowing them additional virulence factors or antibiotic resistance

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3
Q

What are the 4 steps following heat fixing material to slide?

A

1) Crystal violet (primary dye) 2) Iodine (dye trapping agent) 3) Alcohol (decolorizer) 4) Safranin (counterstain)

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4
Q

Why are gram positive bacteria purple?

A

they have a relatively thick cross-linked cell wall made up of peptidoglycan which helps to retain the crystal violet stain

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5
Q

What is the composition of gram negative cell walls?

A

they have thinner cell walls with a high lipid content which is primarily washed away by the alcohol

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6
Q

What gives gram negative bacteria their pink stain?

A

the safranin (the counterstain)

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7
Q

the gram positive bacteria have a thick peptidoglycan wall with embedded what? (2)

A

techoic and lipoteichoic acids

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8
Q

What is used in serologic bacterial identification? (2)

A

techoic and lipoteichoic acids

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9
Q

What do the lipopolysaccharides on the gram negative bacteria cell wall contain?

A

lipid A- which can act as an endotoxin

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10
Q

What are 2 gram stain exceptions?

A

gram variable bacteria and acid fast bacilli

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11
Q

what are 2 examples of gram variable bacteria?

A

clostridium and bacillus species

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12
Q

What is an example of an acid fast bacilli?

A

mycobacterium tuberculosis

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13
Q

What do acid fast bacilli contain and why is this important?

A

they contain mycolic acids, which make it difficult for the gram stain to penetrate the waxy cell wall

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14
Q

How is the acid fast stain different from the gram stain?

A

the acid fast stain has a different primary stain and counter stain the the typical gram stain. It also utilizes an acid decolorizer step

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15
Q

how are cocci bacteria characterized?

A

spherical balls

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16
Q

how can cocci be arranged? (3)

A

in pairs called diplococci, chains called streptococci, or clusters called staphylococci

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17
Q

Some bacilli have unique features such as what?

A

the presence of spores or the presence of club shaped ends

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18
Q

when a bacteria has an ovoid shape in between a rod and a sphere what is it referred to as?

A

coccobacillus

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19
Q

what are the helical shaped bacteria called?

A

spirochete

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20
Q

what are the curvilinear bacteria referred to as?

A

spirilla

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21
Q

Besides gram stains, what else can be used to see spirochetes and spirilla bacteria?

A

silver stain

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22
Q

what are the comma shaped bacteria?

A

vibrio

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23
Q

What are the pros and cons of molecular techniques for microbiology?

A

pros: sensitive and specific cons: expensive

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24
Q

what is serology utilized for?

A

organisms that don’t culture well (fastidious organisms) and for which there is not a good nucleic acid test developed

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25
Q

what is an example of an organism that uses serologic tests for diagnosis?

A

syphilis- from Treponema pallidum

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26
Q

What are the 6 major types of gram positive disease causing bacteria?

A

1) Staphylococcus 2) Streptococcus/Enterococcus 3) Bacillus 4) Clostridium 5) Corynebacterium 6) Listeria

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27
Q

the major gram positive disease causing bacteria consist of two main groups. What are these groups?

A

Cocci and Bacilli

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28
Q

How can the gram positive cocci be further broken down?

A

based on whether the organisms are catalase + or Catalase -

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29
Q

How can the gram positive bacilli be further broken down?

A

based on whether the organism is spore forming or non spore forming

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30
Q

how can the gram positive spore forming bacilli be further broken down?

A

based on whether the organism can grow in oxygen or whether it is anaerobic

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31
Q

how can the gram positive non-spore forming bacilli be further broken down?

A

whether they are club shaped or whether they are motile at 25 degrees C

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32
Q

What is catalase?

A

an enzyme that breaks down hydrogen peroxide- some bacteria produce it as a defense mechanism to the hydrogen peroxide produced by macrophages and neutrophils

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33
Q

what is the catalase test?

A

a test that shows that a catalase positive organism will reduce hydrogen peroxide which produces bubbles and water when exposed to hydrogen peroxide

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34
Q

What is the main group of catalase + gram positive cocci?

A

staphylococcus

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35
Q

what is the main groups of catalase - gram positive cocci?

A

streptococcus/enterococcus

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36
Q

what are the two main groups of spore-forming gram positive bacilli?

A

bacillus and clostridium

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37
Q

which spore-forming gram positive bacilli is aerobic?

A

bacillus

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38
Q

which spore-forming gram positive bacilli is anerobic?

A

Clostridium

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39
Q

What are the two main groups of non-spore forming gram positive bacilli?

A

Corynebacterium diptheriae and listeria monocytogenes

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40
Q

Which non-spore forming gram positive bacilli is non-motile?

A

corynebacterium

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41
Q

which non-spore forming gram positive bacilli is motile at cooler temperatures below 25-30 degrees C?

A

listeria

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42
Q

what are the three principal pathogens that make up the staphylococcus species?

A

1) Staphylococcus aureus 2) Staphylococcus epidermis 3) staphylococcus saprophyticus

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43
Q

How can the catalase positive staphylococcus group be further broken down/ organized?

A

based on whether the organism is coagulase positive or negative

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44
Q

Which principal pathogen(s) of the staphylococcus species is coagulase positive?

A

Staphylococcus aureus

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45
Q

which principal pathogen(s) of the staphylococcus species is coagulase negative?

A

staphylococcus epidermis and staphylococcus saprophyticus

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46
Q

how does staphylococcus aureus appear on the agar plate?

A

as golden yellow colonies

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47
Q

what is the significance of staphylococcus aureus being coagulase positive?

A

coagulase is a protective protein that activates the fibrin clot (creates a surrounding protective clot)

48
Q

what are the other protective proteins/ virulence factors that staphylococcus aureus has? (4)

A

hemolysins (destroys RBCs), leukocidins (destroy white blood cells), penicillinase (breaks up penicillin), and a protein A which prevents antibody mediated binding

49
Q

What are the 3 tissue destroying proteins/enzymes that staphylococcus aureus produces?

A

hyaluronidase, staphylokinase, and lipase

50
Q

What are the four main diseases that are caused by staphylococcus aureus?

A

pneumonia, superficial skin and underlying soft tissue infections, septic osteomyelitis, endocarditis

51
Q

what are the majority of infections due to staphylococcus aureus in healthy individuals?

A

that of superficial skin and soft tissue infections

52
Q

what are 4 examples of the superficial skin and underlying soft tissue infections that staphylococcus aureus can cause?

A

folliculitis, impetigo, cellulitis, and furuncles/carbuncles

53
Q

what is cellulitis?

A

infection of the subcutaneous tissue just adjacent to the skin which manifests with erythema and tenderness

54
Q

What is the difference between a carbuncle and a furuncle?

A

a carbuncle is the contiguous multiple pus filled cavities; a furuncle is the subcutaneous abscess

55
Q

septic arthritis/ septic osteomyelitis caused by staphylococcus aureus is more prevalent in who?

A

children <12 years and the elderly

56
Q

what are the characteristics of the PNA caused by staphylococcus aureus?

A

necrotizing PNA with high fever and chills, productive cough and lung abscesses seen on chest x-ray; it does not typically occur in the normal healthy patient, but rather it is seen after an initial infection which weakens the body’s defenses (such as as initial viral illness)

57
Q

what is the acute necrotizing endocarditis caused by staphylococcus aureus characterized by?

A

high fever, chills, and weakness

58
Q

who is at risk for developing acute necrotizing endocarditis caused by staphylococcus aureus?

A

an IV drug abuser using dirty needles

59
Q

what valve is the first to be infected/ most commonly affected by acute necrotizing endocarditis caused by staphylococcus aureus?

A

the tricuspid valve

60
Q

what is one major problem that is associated with staphylococcus aureus?

A

these infections are increasingly resistant to multiple antibiotics

61
Q

What are 3 examples of staphylococcus aureus toxin mediated diseases?

A

Gastroenteritis, scalded skin syndrome, and TSS

62
Q

what happens when staphylococcus aureus contaminates food?

A

it creates a preformed enterotoxin

63
Q

what does the preformed enterotoxin cause?

A

12-24 hours of nausea, vomiting, diarrhea, and abdominal pain

64
Q

what causes scalded skin syndrome (be specific)?

A

exfoliative toxin A and B

65
Q

who is at higher risk of scalded skin syndrome (caused by staphylococcus aureus exfoliative toxin A and B)?

A

children and infants

66
Q

What foods are at risk of being contaminated with staphylococcus aureus?

A

foods that are not cooked after handling, such as sandwiches, sliced meats, puddings and pastries

67
Q

What can be seen in patients with scalded skin syndrome before the skin manifestations occur?

A

fever, irritability, and poor feeding

68
Q

What causes TSS (be specific)?

A

the TSST-1 toxin (this is a superantigen)

69
Q

what does the TSST-1 toxin cause the release of?

A

TNF and IL-1

70
Q

what are the signs/ symptoms/ clinical presentations of TSS? (3)

A

1) gastroenteritis symptoms (fever, nausea, vomiting, watery diarrhea) 2) diffuse rash (involves the palms and soles) 3) shock, hypotension, and death

71
Q

Where could staphylococcus epidermidis be found normally?

A

it is normal skin flora

72
Q

what is the key virulence factor that staphylococcus epidermidis has?

A

the creation of a biofilm

73
Q

what is a biofilm?

A

an extracellular polysaccharide matrix which adheres to the foreign device substrate and forms a scaffold in which the organism exists

74
Q

What types of infections do staphylococcus epidermidis cause? (1 general term and 2 big examples)

A

nosocomial infections: prosthetic components (like heart valves) and catheters

75
Q

after penetration through the skin, what happens to staphylococcus epidermidis?

A

it finds its way into the blood stream where it can cause a subacute endocarditis

76
Q

what is the difference between the endocarditis that is caused by staphylococcus aureus and the endocarditis that is caused by staphylococcus epidermidis?

A

unlike the endocarditis seen with staphylococcus aureus, which is a necrotizing endocarditis with a high fever, staphylococcus epidermidis subacute endocarditis presents with a low grade fever

77
Q

why are multiple positive blood cultures for staphylococcus epidermidis typically necessary to prove infection?

A

since it is frequently an incidental contaminating organism to a standard blood culture

78
Q

What does staphylococcus saprophyticus cause?

A

it is a common cause of community acquired urinary tract infections

79
Q

Who is more at risk for a urinary tract infection caused by staphylococcus saprophyticus?

A

sexually active young women “honeymoon cystitis”

80
Q

How can the streptococci be further organized?

A

based on their colony growth pattern on standard blood agar plate–> beta hemolytic, alpha hemolytic, and gamma hemolytic

81
Q

what is beta hemolytic?

A

complete hemolysis

82
Q

what is alpha hemolytic?

A

partial hemolysis

83
Q

what is gamma hemolytic?

A

no hemolysis

84
Q

how do alpha-hemolytic species appear?

A

the surrounding colony appears green to the partial breakdown

85
Q

once we have group the beta-hemolytic organisms together, how can they further be organized/ separated?

A

based on their sensitivity to bacitracin

86
Q

what are the 2 broad groups of beta-hemolytic streptococcus organisms?

A

streptococcus pyogenes and streptococcus agalactiae

87
Q

What are the 2 broad groups of alpha hemolytic streptococcus organisms?

A

streptococcus pneumoniae and viridans strep

88
Q

what are the 2 broad groups of gamma-hemolytic streptococcus organisms?

A

enterococci and nonenterococcus

89
Q

What is another name for the streptococcus pyogenes group?

A

group A streptococcus

90
Q

what is the most common disease caused by streptococcus pyogenes?

A

streptococcal pharyngitis

91
Q

How does strep throat present?

A

with an exudative white purulent infection of the palatine tonsils; high fever and lymphadenopathy can occur

92
Q

what are the virulence factors associated with streptococcus pyogenes? (2)

A

M protein and streptolysins

93
Q

what is the effect of the virulent factor M protein?

A

it inhibits activation of complement

94
Q

what is the effect of the virulent factor streptolysins?

A

they destroy RBCs (beta-hemolytic)

95
Q

why is it important to adequately treat a streptococcus pyogenes infection?

A

subsequent immune response can lead to rheumatic fever or post-strep glomerulonephritis

96
Q

besides streptococcal pharyngitis, what other diseases can streptococcus pyogenes cause? (7)

A

scarlet fever, erysipelas, necrotizing faciitis, impetigo, cellulitis, rheumatic fever, and post-strep glomerulonephritis

97
Q

what specifically causes scarlet fever?

A

the pyrogenic (erythrogenic) exotoxin of streptococcus pyogenes

98
Q

how does scarlet fever present?

A

fever, an erythematous rough “sandpaper” rash on trunk and neck (spares the face), an erythematous “strawberry” tongue

99
Q

Who is most susceptible to getting scarlet fever caused by streptococcus pyogenes?

A

school aged children

100
Q

scarlet fever typically occurs in association with what?

A

pharyngitis

101
Q

how does erysipelas caused by streptococcus pyogens present?

A

as a sunburn like appearance often involving the face, warm to the touch, sharp demarcation

102
Q

what does erysipelas infection involve?

A

the upper dermis and superficial lymphatics

103
Q

what is the peak incidence of erysipelas caused by streptococcus pyogenes?

A

age 60-80

104
Q

how does necrotizing fasciitis present?

A

as a purplish discoloration which is very painful; rapidly progressive

105
Q

streptococcus pyogens can cause many of the same infections as staphylococcus aureus including what? (2)

A

impetigo and cellulitis

106
Q

what is rheumatic fever?

A

a multisystem inflammatory disorder following group A streptococcus pharyngitis

107
Q

what causes rheumatic fever?

A

antibodies and CD4+ T cell reaction against M streptococcal antigen following streptococcal pharyngitis

108
Q

what are 6 common signs and symptoms of acute rheumatic fever?

A

1) fever (101 or above), 2) migratory polyarthritis (large joints) 3) pancarditis (pericarditis, mitral valvulitis) 4) subcutaneous nodules 5) erythema marginatum 6) Sydenham chorea

109
Q

what is erythema marginatum?

A

curved, ring shaped macular rash

110
Q

what is syndham chorea?

A

hopping, halting, gait, asymmetric jerking, grimacing

111
Q

what causes post-streptococcal glomerulonephritis?

A

it is immune complex mediated–> antibody-antigen complex (strep antigen), deposit in the glomerular basement membrane; it is caused by group A streptococcus pharyngitis or skin infection

112
Q

who is at risk for post-strep glomerulonephritis and how does it present?

A

children; edema, hypertension, hematuria, and proteinuria

113
Q

how can acute rheumatic fever and post-strep glomerulonephritis be diagnosed?

A

with detection of certain post streptococcal antibodies in the proper clinical context- namely detection of antibodies to streptolysin O and DNAse B

114
Q

Where does streptococcus agalactiae colonize?

A

vagina

115
Q

what can streptococcus agalactiae result in?

A

neonatal meningitis, PNA, and sepsis; maternal sepsis can also occur

116
Q

when does antepartum screening for streptococcus agalactiae occur?

A

during pregnancy during 3rd trimester (36-37 weeks)

117
Q

what is the number one cause of neonatal meningitis?

A

streptococcus agalactiae

MOD Final (11 decks)

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