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BACTERIOLOGY > B1.2 Staphylococcus aureus > Flashcards

B1.2 Staphylococcus aureus Flashcards

1
Q

What is the coagulase status of Staphylococcus aureus?

A

True coagulase-positive

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2
Q

Which species of staphylococci is the most virulent?

A

Staphylococcus aureus.

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3
Q

On which media does Staphylococcus aureus grow well?

A

Nutrient Agar (NA) and Tryptic Soy Broth (TSB).

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4
Q

Describe the appearance of Staphylococcus aureus colonies on solid media

A

Round, smooth, opaque, and butyrous

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5
Q

What is the appearance of Staphylococcus aureus colonies on Blood Agar Plate (BAP)?

A

Golden yellow color and β-hemolytic

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6
Q

What salt concentration is used to cultivate Staphylococcus aureus, and what does this indicate?

A

7.5 to 10% NaCl; indicates halophilic nature

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7
Q

What infections is Staphylococcus aureus responsible for?

A

Skin, wound, and deep tissue infections

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8
Q

What type of teichoic acid is present in the cell wall of Staphylococcus aureus?

A

Ribitol teichoic acid.

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9
Q

Virulence Factors related to staphylococcus aureus

A

Antigenic Structures
Enzymes
Toxins

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10
Q

Antigenic Structures present in S. aureus

A

Teichoic Acid
Peptidoglycan
Protein A
Clumping Factor
Capsular Polysaccharide

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11
Q

What is the role of peptidoglycan in Staphylococcus aureus?

A

Protects from lysis and aids in adherence

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12
Q

What is the unique group-specific antigen in Staphylococcus aureus?

A

Protein A.

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13
Q

Prevents antibody-mediated phagocytosis by competing for the Fc portion of antibodies

A

Protein A

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14
Q

Causes clumping of staphylococci in the presence of plasma

A

clumping factor

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15
Q

What is the role of capsular polysaccharide in Staphylococcus aureus?

A

Protects from phagocytosis

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16
Q

ENZYMES present in S. aureus

A

COAGULASE (STAPHYLOCOAGULASE)

HYALURONIDASE (SPREADING FACTOR)

STAPHYLOKINASE (FIBRINOLYSIN)

LIPASE (Fat-splitting Enzyme)

DEOXYRIBONUCLEASE (DNASE) and PHOSPHATASE

PROTEASE

GELATINASE

β-LACTAMASE

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17
Q

Coagulates fibrinogen in plasma to promote fibrin layer formation around abscesses.

A

coagulase (staphylocoagulase)

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18
Q

Name the two types of coagulase in Staphylococcus aureus

A

Cell-bound (clumping factor) and unbound (free) coagulase

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19
Q

bound to the cell wall and clots human, rabbit or pig plasma

A

Cell-bound Coagulase or Clumping Factor

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20
Q

extracellular enzymes not bound to the cell wall and cause clot formation when bacterial cells are incubated with plasma

A

Unbound or Free Coagulase

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21
Q

Hydrolyzes hyaluronic acid, permitting the spread of infection

A

hyaluronidase

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22
Q

Dissolves fibrin clots (fibrinolysin)

A

staphylokinase

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23
Q

Acts on lipids on the skin surface, aiding in the formation of furuncles, carbuncles, and boils

produced by both coagulase (+) and coagulase (-) staphylococci

A

lipase

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24
Q

Lowers viscosity of exudates and destroys DNA

A

DNase and phosphatase

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25
Q

Which enzyme in Staphylococcus aureus breaks down β-lactam drugs

A

β-Lactamase

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26
Q

TOXINS in S. aureus

A

CYTOLYTIC TOXINS
ENTEROTOXINS
TOXIC SHOCK SYNDROME TOXIN-1(TSST-1)
EXFOLIATIVE TOXIN

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27
Q

CYTOLYTIC TOXINS examples

A

Hemolysins and Leukocidins

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28
Q

4 Types Hemolysins and the leukocidin found in S. aureus

A

α-Hemolysin
β-Hemolysin (Sphingomyelinase C)
δ-Hemolysin
γ-Hemolysin

Staphylococcal Leukocidin/ Panton-Valentine leukocidin

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29
Q

Which hemolysin in Staphylococcus aureus causes severe tissue damage

A

α-Hemolysin

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30
Q

Act as heat-stable exotoxins causing food poisoning

A

enterotoxins

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31
Q

Which toxin is associated with Toxic Shock Syndrome in Staphylococcus aureus?

A

Toxic Shock Syndrome Toxin-1 (TSST-1).

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32
Q

What does exfoliative toxin cause in Staphylococcus aureus infections

A

Staphylococcal Scalded Skin Syndrome (Ritter’s disease) and bullous impetigo

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33
Q

damage RBC, platelets and macrophages and cause severe tissue damage
Predominant hemolysin

A

α-Hemolysin

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34
Q

acts on sphingomyelin in the plasma membrane of RBC

A

β-Hemolysin (Sphingomyelinase C)

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35
Q

aka“hot-cold” lysine : enhanced hemolytic activity on incubation at 37° C (heat labile) and subsequent exposure to cold (4° C)

A

β-Hemolysin (Sphingomyelinase C)

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36
Q

exhibited in the CAMP test
lethal and dermonecrotic

A

β-Hemolysin (Sphingomyelinase C)

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37
Q

less toxic to cells than either α-hemolysin or β-hemolysin
produced by all S. aureus strain that cause RBC injury in culture and produce edematous lesions

A

δ-Hemolysin

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38
Q

associated with Panton-Valentine leukocidin (PVL)

A

γ-Hemolysin

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39
Q

exotoxin lethal to polymorphonuclear leukocytes
Pore forming exotoxin that suppress phagocytosis and associated with severe cutaneous infections and necrotizing pneumonia
associated with community-acquired staphylococcal infections

A

Staphylococcal Leukocidin/ Panton-Valentine leukocidin

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40
Q

heat-stable exotoxin: 100° C for 30 minutes
resistant to hydrolysis by gastric and jejunal enzymes
act as neurotoxins that stimulate vomiting through the vagus nerve

A

ENTEROTOXINS

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41
Q

Enterotoxins are produced by _____% of S. aureus isolates

A

30% to 50%

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42
Q

Enterotoxins A, B, and D causes

A

Staphylococcal food poisoning

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43
Q

Enterotoxins B and C and sometimes G and I causes

A

TSS

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44
Q

Enterotoxin B causes

A

Staphylococcal Pseudomembranous Enterocolitis (contaminated milk products)

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45
Q

TOXIC SHOCK SYNDROME TOXIN-1(TSST-1) is also known as

A

ENTEROTOXIN F or PYROGENIC EXOTOXIN C

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46
Q

menstruating-associated TSS= TSS associated with tampon use
chromosomal-mediated toxin
SUPERANTIGEN stimulating T-cell proliferation and production of a large amount of cytokines

A

TOXIC SHOCK SYNDROME TOXIN-1(TSST-1)

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47
Q

TOXIC SHOCK SYNDROME TOXIN-1(TSST-1) low concentrations=

higher concentrations=

A

low concentrations= leakage by endothelial cells;

higher concentrations= cytotoxic

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48
Q

EXFOLIATIVE TOXIN aka

A

EPIDERMOLYTIC TOXIN A and B or EXFOLIATIN
serotypes A and B

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49
Q

Serine protease that divides the intrcellular bridges of the epidermis and causes excessive sloughing of the epidermis (stratum granulosum)

causes STAPHYLOCOCCAL SCALDED SKIN SYNDROME referred to as RITTER’S DISEASE

implicated in BULLOUS IMPETIGO

A

EXFOLIATIVE TOXIN

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50
Q

RELATED INFECTIONS AND DISEASES S. aureus

A

Cutaneous Infections
Toxic Shock Syndrome
Food Poisoning
Staphylococcal Bacteremia
Staphylococcal Osteomyelitis
Staphylococcal Pneumonia
Septic Arthritis
Acute Bacterial Endocarditis
UTI

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51
Q

Cutaneous Infections caused by S. aureus

A

Folliculitis
Furuncles (Boils)
Carbuncles
Bullous Impetigo
Scalded Skin Syndrome
Toxic Epidermal Necrolysis (TEN)

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52
Q

mild inflammation of a hair follicle or oil gland; infected area is raised and red

A

Folliculitis

53
Q

focal suppurative lesions which has resulted from an infection (folliculitis) that extend into subcutaneous tissue; large, raised, superficial abscesses

A

Furuncles (Boils)

54
Q

larger, more invasive lesions develop from multiple furuncles, which can progress into deeper tissues; present with fever and chills, indicating systemic infection

A

Carbuncles

55
Q

 larger pustules surrounded by a small zone of erythema
highly contagious infection that spread by direct contact, fomites, or autoinoculation

A

Bullous Impetigo

56
Q

superficial cutaneous infection commonly seen in newborns and young children characterized by the formation of encrusted pustules surrounded by red border

A

Impetigo

57
Q

bullous exfoliative dermatitis that occurs primarily in newborns and previously healthy young children

A

Scalded Skin Syndrome

58
Q

localized skin lesion SSS:

A

few blisters,
pemphigus neonatorum,
Ritter disease

59
Q

generalized form of SSS:

A

cutaneous erythema, profuse peeling of the epidermis

60
Q

clinical manifestation with multiple causes; symptoms are due to hypersensitivity reaction

A

Toxic Epidermal Necrolysis (TEN)

61
Q

rare but potentially fatal, multisystem disease characterized by sudden onset of fever, chills, vomiting, diarrhea, muscle aches, and rash, which can quickly progress to hypotension and shock

A

Toxic Shock Syndrome

62
Q

Food Poisoning caused by

A

Enterotoxins A (78%), D (38%), and B (10%)

63
Q

intoxication resulting from ingestion of a toxin formed outside the body

symptoms appear rapidly (2 to 8 hours after ingestion) and resolve within 24 to 48 hours: nausea, vomiting, abdominal pain, and severe cramping, diarrhea

A

Food Poisoning

64
Q

perfuse and watery diarrhea due to water and electrolyte loss

A

FOOD POISONING

65
Q
  • Food won’t appear or taste tainted
  • Death: Intoxication rather than infection
  • Reheating the food – kills the bacteria, but not
    inactivate the heat stable toxin
A

FOOD POISONING

66
Q

ENTEROCOLITIS caused by

A

Enterotoxin A and (leukocidins) LukE
and LukP

67
Q

leads to secondary pneumonia and endocarditis observed among IV drug users

A

Staphylococcal Bacteremia

68
Q

secondary to bacteremia

A

Staphylococcal Osteomyelitis

69
Q

secondary to influenza virus infection
multiple abscesses and focal lesions in the pulmonary parenchyma

A

Staphylococcal Pneumonia

70
Q

frequent in children and occur in patients with a history of rheumatoid arthritis or IV drug abuse

A

Septic Arthritis

71
Q

JOINT INFECTIONS/SEPTIC ARTHRITIS found in

Both Adults and Neonates/Children

A

S. aureus
S. agalactiae
S. pyogenes
Enterobacteriaceae

72
Q

JOINT INFECTIONS/SEPTIC ARTHRITIS found in

Neonates/Children
only

A

H. influenzae type b (Hib)
Kingella kingae

73
Q

JOINT INFECTIONS/SEPTIC ARTHRITIS found in

Sexually Active

A

N. gonorrhoea

74
Q

Specimen of choice for testing S. aureus

A

Pus,
Purulent Fluids,
Sputum,
Urine,
Blood

75
Q

Gram Stain results of S. aureus

A

Gram(+) cocci in irregular clusters

76
Q

Culture Media used for S. aureus

A

BAP, PEA, MSA, CNA, Chapman Stone Agar, Vogel-Johnson Medium

Columbia Colistin–Nalidixic acid (CNA)

MSA and PEA

CHROM Agar

77
Q

media used for purulent exudates

A

Columbia Colistin–Nalidixic acid (CNA)

78
Q

Media used for heavily contaminated specimen

A

MSA and PEA

79
Q

Media used for selective-differential for MRSA

A

CHROM Agar

80
Q

Biochemical Tests used for S. aureus

A

Catalase Test
Coagulase Test
Mannitol Fermentaion Test
Growth on Tellurite Glycine Agar
Polymyxin B Sensitivity
Lysostaphin Sensitivity Test (2ug/ml)
Voges-Proskauer (VP) Test
Deoxyribonuclease (Dnase) Test
Pyrrolidonyl Arylamidase (PYR) Test
Rapid Methods of Identification
Molecular Methods

81
Q

What reagent is used in the aerobic catalase test?

A

3% H2O2

82
Q

What reagent is used in the anaerobic catalase test?

A

15% H2O2

83
Q

What is the catalase reaction result for Staphylococcus?

A

Catalase positive

84
Q

What is the catalase reaction result for Streptococcus?

A

Catalase negative

85
Q

best single criterion of recognition and pathogenicity of S. aureus

A

Coagulase Test

86
Q

What reagent is used in the coagulase test?

A

Rabbit plasma with EDTA

87
Q

Methods for coagulase test

A

Slide Method
Tube Method

88
Q

rapid screening test
detects cell-bound coagulase or clumping factor

Other Slide Coagualse Positive: S. lugdunensis and S. schleiferi

A

Slide Method

89
Q

sensitive but definitive; confirm all slide negative results
detects extracellular or free coagulase

A

Tube Method

90
Q

What does the slide coagulase test detect?

A

Cell-bound coagulase (clumping factor)

91
Q

Which species are slide coagulase positive besides S. aureus?

A

S. lugdunensis and S. schleiferi

92
Q

What does the tube coagulase test detect?

A

Extracellular (free) coagulase

93
Q

Name other tube coagulase-positive species besides S. aureus

A

S. hyicus,
S. intermedius,
S. lutrae,
S. delphini, and
S. schleiferi subsp. coagulans

94
Q

At what temperature should the tube coagulase test be incubated initially?

A

35°C–37°C

95
Q

How long should the tube coagulase test be incubated before reading the result?

A

1-4 hours

96
Q

During a coagulase test, if no clot forms after 4 hours what should you do

A

reincubate at room temperature for additional 20 hours

97
Q

What is the significance of reading the tube coagulase test result within 4 hours?

A

To prevent false negatives due to fibrinolysin activity

98
Q

Coagulase plasma is not suitable with

A

Citrate

99
Q

These species use citrate and release calcium forming clot in the absence of coagulase causing a false positive result for Coagulase test

A

Pseudomonas and Enterococci

100
Q

What medium is used for the mannitol fermentation test?

A

Mannitol Salt Agar (MSA)

101
Q

S. aureus can ferment mannitol and can tolerate high salt concentrations of what percent

A

(7.5-10%)

102
Q

What is the pH indicator used in the mannitol fermentation test

A

Phenol Red

103
Q

What is the positive result for mannitol fermentation on MSA?

A

Yellow-colored colonies with a yellow halo

104
Q

What colonies does S. aureus produce on tellurite glycine agar?

A

Jet-black colonies

105
Q

What is the reaction of S. aureus to polymyxin B?

A

Resistant

106
Q

What is the reaction of other staphylococci to polymyxin B?

A

Susceptible

107
Q

What is the reaction of S. aureus in the lysostaphin sensitivity test?

A

Sensitive

108
Q

What is the reaction of micrococci in the lysostaphin sensitivity test?

A

Resistant

109
Q

What is the culture medium for the Voges-Proskauer (VP) test?

A

VP broth with 5% glucose

110
Q

used to differentiate S. aureus (+) from S. intermedius (-)

A

Voges-Proskauer (VP) Test

111
Q

What reagents are used in the Voges-Proskauer (VP) test?

A

α-naphthol and KOH

112
Q

Name VP-positive species besides S. aureus

A

S. lugdunensis, S. haemolyticus, and S. schleiferi

113
Q

What culture medium is used in the DNase test?

A

DNA-methyl green agar

114
Q

What is the DNase result for S. aureus?

A

DNase positive

115
Q

What substrate is used in the PYR test?

A

Pyroglutamyl-β-naphthylamide (PYR)

(Lpyrrolidonyl-β-naphthylamide; PYR)

116
Q

differentiates coagulase(+) staphylococci by slide method

A

Pyrrolidonyl Arylamidase (PYR) Test

117
Q

What reagent is used in the PYR test?

A

p-dimethylaminocinnamaldehyde

118
Q

What is the end product of the PYR test?

A

L-pyrrolidone and β-naphthylamine

119
Q

What is the positive result for the PYR test?

A

Cherry red color

120
Q

Name PYR-positive species

A

S. lugdunensis,
S. intermedius,
S. schleiferi,
S. haemolyticus

121
Q

Rapid Methods of Identification

A

Particle Agglutination Test
Staphyloslide use sensitized sheep RBC
Staphaurex
BACTiStaph
Staphylochrome
Sero-STAT
Bacto Staph Latex
Accu-Staph
Hemostaph
Staphylatex

122
Q

plasma-coated carrier particles (latex)
plasma detects both clumping factor (with fibrinogen) and protein A in the cell wall of S. aureus (with IgG)

A

Staphylatex

123
Q

What does plasma-coated carrier particles in rapid tests detect?

A

Clumping factor (fibrinogen) and Protein A (IgG)

124
Q

Molecular Methods used in the detection of S. aureus

A

Real-time PCR
Qualitative Nucleic Acid Hybridization
Assays

125
Q

What molecular method is used to detect MRSA and MSSA?

A

Real-time PCR

126
Q

staphylococci from prepared smears in
blood cultures
identification of mecA gene

A

Qualitative Nucleic Acid Hybridization
Assays

127
Q

What gene is identified by molecular methods in S. aureus?

A

mecA gene

128
Q

What specimen is used for molecular testing for S. aureus?

A

Anterior nares swabs

129
Q

Advantage of Qualitative Nucleic Acid Hybridization Assays

A

rapid detection test for MRSA

BACTERIOLOGY (26 decks)

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