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LECOM Microbiology MS1 > Gram Positive Cocci Part 1 (Exam 1) > Flashcards

Gram Positive Cocci Part 1 (Exam 1) Flashcards

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1
Q

What characteristics are shared by all gram-positive cocci

A

all have a spherical shape, no endospores, and are aerobic

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2
Q

How are gram positive cocci differentiated

A

presence of catalase

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3
Q

What is the function of catalase

A

breaks down peroxide into oxygen and water

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4
Q

What are the catalase positive gram positive cocci

A

staphylococcus

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5
Q

What are the catalase negative gram positive cocci

A

streptococcus and enterococcus

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6
Q

What type of structure does staphylococcus have

A

grape like clusters

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7
Q

What type of structure does streptococcus have

A

chains or pairs

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8
Q

What type of infections does staphylococcus have

A

pyogenic infection

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9
Q

What type of infections does streptococcus have

A

pyrogenic infections

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10
Q

What is the difference between pyogenic and pyrogenic infections

A 
pyogenic= pus (neutrophils)
pyrogenic= fever (TNF alpha, IL-1, IL-6)
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11
Q

How will staph appear on gram stain

A

purple cocci in clusters

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12
Q

What are the environmental requirements of staph

A

facultative anaerobes
halophiles
non-motile

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13
Q

What are halophiles

A

salt loving, can grow in high salt concentrations at at 18-40C

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14
Q

What is the catalase reaction results of staph

A

catalase positive

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15
Q

What diseases are associated with Staph aureus

A

Toxin mediated diseases cutaneous diseases

systemic diseases

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16
Q

What are the toxin mediated diseases of staph aureus

A

Scalded skin syndrome
TSS
Food poisoning

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17
Q

What are the cutaneous diseases of staph aureus

A

folliculitis, carbuncles, impetigo, wound infections

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18
Q

What are the systemic diseases of staph aureus

A 
bacteremia
empyema
endocarditis
osteomyelitis
pneumonia
septic arthritis
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19
Q

What diseases are associated with staph epidermidis

A

bacteremia
endocarditis
UTIs
opportunistic infections

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20
Q

How do opportunistic infections of staph epidermidis occur

A

via catheters, shunts, prosthetics

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21
Q

What diseases are associated with staph saprophyticus

A

UTIs; opportunistic infections

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22
Q

Staph saprophyticus UTIs often occur in what population

A

young, newly sexually active women

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23
Q

What are other staph distractors in questions? Be familiar enough to not pick them

A

S. lugdunensis

S haemolyticus

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24
Q

Where are staph found normally

A

oropharynx, GI tract, urogenital tract

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25
Q

Where is S. epidermidis found on everyone

A

the skin

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26
Q

What percent of population carries S. aureus and are healthy

A

15-20%

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27
Q

How is staph transmitted

A

direct contact or fomites

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28
Q

What is staph susceptible to

A

hand washing
disinfectants, antiseptics
high temps

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29
Q

What are the main virulence factors seen in staph

A

capsule
peptidoglycan
teichoic acids

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30
Q

What role does the capsule of staph play in virulence

A

inhibits phagocytosis by PMNs

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31
Q

What role does peptidoglycan play in staph virulence

A

makes cell wall rigid

stimulates cytokine production, activates complement, causes aggregation of PMNs to form an abscess

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32
Q

What role do teichoic acids play in staph virulence

A

major component of cell wall

binds to fibronectin and mediates attachment to mucosal surfaces

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33
Q

What type of immunogen is teichoic acid

A

poor

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34
Q

What will be the gram stain, catalase, and coagulase results of staph aureus

A

gram positive cocci
catalase positive
coagulase positive

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35
Q

What agar is used to culture staph aureus

A

blood agar

mannitol salt agar

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36
Q

What is staph aureus on blood agar

A

beta hemolytic

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37
Q

What are the specific virulence factors associated with staph aureus

A

adhesins
protein A
toxins
enzymes

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38
Q

What do the adhesins do

A

adhere to host matrix proteins: fibronectin, fibrinogen, elastin, collagen

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39
Q

What are the toxin mediated diseases associated with staph aureus

A

scalded skin syndrome/ bulious impetigo
TSS
food poisoning

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40
Q

What are the suppurative infections associated with staph aureus

A

folliculitis, impetigo, furuncles, boils, bacteremia, endocarditis, pneumonia, empyema, osteomyelitis, septic arthritis

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41
Q

What role does protein A play in virulence of S. aureus

A

binds to Fc receptors of IgG to prevent trigger of immune response

forms immune complexes
binds up complement

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42
Q

What virulence factor of S. aureus can be used as identification

A

Protein A, only found on S. aureus

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43
Q

What are the 5 cytolytic toxins of S. aureus

A 
alpha
delta
beta 
gamma
Panton-Valentine (PV) leukocidin
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44
Q

What is the function of cytolytic toxins of S. aureus

A

membrane damaging toxins: act as perforins

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45
Q

What are the 2 exfoliative toxins of S. aureus

A

A and B

46
Q

What are the 8 enterotoxins of S. aureus

A

A-E, G-I

47
Q

What toxin from S. aureus is associated with toxic shock syndrome

A

TSST-1

48
Q

What toxins of S. aureus are superantigens

A

TSST-1, exfoliative toxin A, enterotoxins

49
Q

Where do superantigens bind

A

to TCR-MHCII groove

50
Q

How will cytolytic toxins of S. aureus affect neutrophils

A

lyse all neutrophils

51
Q

What does lysis of neutrophils lead to

A

release of lysosomal enzymes and damage to tissue

52
Q

Describe the effects of the alpha-gamma cytolytic toxins of S. aureus

A

affect RBCs and other cell types

53
Q

What is the function of the P-V leukocidin in S. aureus

A

pore formation in PMNs

54
Q

What are the heat tolerances of the exfoliative toxins of S. aureus

A

ETA is heat stable

ETB is heat labile

55
Q

What is the function of ETA and ETB

A

serine proteases

56
Q

What do serine proteases do

A

split intercellular bridges (desmosomes) in stratum granulosum epidermis

57
Q

Will there be bacteria or WBCs in affected area of S. aureus skin infections

A

none

58
Q

What are the two diseases associated with exfoliative toxins of S. aureus

A

Staphylococcal scalded skin syndrome and bullous impetigo

59
Q

What is scalded skin syndrome characterized by

A

exfoliative dermatitis

60
Q

Who is scalded skin syndrome commonly seen in

A

neonates and young children

61
Q

What is another name for scalded skin syndrome

A

Ritter’s disease

62
Q

What is the progression of scalded skin syndrome

A

abrupt onset of localized perioral erythema that covers the entire body

large cutaneous blisters form

epithelial desquamation

63
Q

What is bullous impetigo

A

localized form of SSSS

64
Q

What is the symptom of bullous impetigo

A

superficial skin blisters

65
Q

What is different in bullous impetigo than scalded skin syndrome

A

culture positive

66
Q

What type of toxin is responsibel for S. aureus food poisoning

A

enterotoxin

67
Q

What are enterotoxins

A

superantigens that are heat and acid resistant

68
Q

What type of cells are thought to be responsible for the emesis associated with S. aureus food poisoning

A

mast cells

69
Q

What toxin is associated with staphylococcal pseudomembranous enterocolitis

A

Enterotoxin B

70
Q

What can enterotoxin b also cause

A

TSS

71
Q

How can staph aureus lead to TSS

A

enterotoxins enter blood to cause TSS

hypotension: fluid leaves vasculature and enters tissue

72
Q

What cuases the presentation of S. aureus food poisoning

A

sudden onset of diarrhea, vomiting

73
Q

Does heating food kill the toxin

A

no

74
Q

How is S. aureus food poisoning transmitted

A

human carrier with wound infection contaminates food

75
Q

What foods are common for S. aureus food poisoning

A

salted meats
custard filled pastries
potato salad
ice cream

76
Q

What will be the result of Toxic shock syndrome toxin-1 staph aureus

A

cytokine storm leading to hypotension

77
Q

Where are S. aureus that produce TSST-1 found

A

rapidly in hyperabsorbent tampons

78
Q

What are the clinical manifestation of TSS from staph aureus

A

fever
hypotension
diffuse macular erythematous rash

79
Q

What is the function of coagulase in S. aureus

A

converts fibrinogen to fibrin

80
Q

What are the 2 forms of coagulase

A

bound and free

81
Q

What does bound coagulase do

A

converts fibrinogen to insoluble fibrin

82
Q

What does free coagulase do

A

reacts with globulin plasma factor then converts fibrinogen to fibrin

83
Q

What is used to differentiate S. aureus from other staph species

A

coagulase test

84
Q

What is the function of catalase in s aureus

A

breakdown H2O2

85
Q

What is the function of penicillinase in S. aureus

A

breaks down beta lactams

86
Q

What is the pathogenesis of S. aureus

A

production of toxin: no organisms are present at site

direct invasion and destruction of tissue: suppurative infections, organisms are present

87
Q

What factors contribute to the enhanced virulence of Staph aaureus

A

presence of foreign body

congenital diseases

88
Q

Where are S. aureus found in TSS and scalded skin syndrome

A

TSS: toxin in blood, bug not in blood

Scalded skin: bug not found in skin, bug found in mom’s vaginal tract or nose

89
Q

How will S. aureus impetigo present

A

superficial infection

small macule: pus filled vesicle primarily on face and limbs

90
Q

What population is most at risk of impetigo

A

young children

91
Q

What is S. aureus foliculitis

A

pyogenic infection in hair follicles

92
Q

What is folliculitis presentation symptoms

A

follicle base is raised and reddened, contains pus

stye: base of eyelid

93
Q

What is a S. aureus furuncle

A

large, painful, raised nodules

94
Q

What is a s. aureus carbuncle

A

extension of furuncles into subcuaneous tissues and blood; abscess

95
Q

Symptoms of carbuncle

A

fever, chills, bacteria

96
Q

How will s. aureus appear on microscopy

A

gram positive cocci in grape like clusters

97
Q

What agars can be used to culture S. aureus

A

Blood agar

Mannitol salts agar

98
Q

What seriological tests can be used to diagnoses Staph aureus

A

antibodies to teichoic acids

99
Q

What gene encodes for methicillin resistance in S. aureus

A

mecA

100
Q

What does the mecA gene encode

A

mutant PBP

101
Q

How is the mutant PBP different than normalPBP

A

low affinity for beta lactams

102
Q

What does low affinity for beta lactams mean

A

resistance to all penicillins, cephalosporins, carbapenems

103
Q

What chromosome carried the mecA gene

A

staphylococcal cassette chromosome

104
Q

How is mecA gene detected

A

PCR and PFGE

105
Q

How is high level antibiotic resistance acquired in S. aureus

A

van A gene from vancomycin resistant enterococci

106
Q

What antibiotic is used to treat MRSA

A

vancomycin

107
Q

How is staph epidermidis diagnosed

A

novobiocin sensitive, will not grow

108
Q

What disease is associated with S. epidermidis

A

UTI and endocarditis

109
Q

How is staph saprophyticus diagnosed

A

Novobiocin resistant

110
Q

What disease is associated with staph saprophyticus

A

UTI in young, sexually active females

LECOM Microbiology MS1 (22 decks)

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