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BACTERIOLGY > Lecture | Staphylococcus > Flashcards

Lecture | Staphylococcus Flashcards

1
Q

Greek term that means “bunches of grapes”

A

Staphle

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2
Q

gram positive cocci, so round, that may appear in singles, in pairs, in clusters, or even in tetrads.

A

Staphylococcus spp.

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3
Q

non-motile and non spore forming

A

Staphylococcus spp.

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4
Q

When it comes to growing of Staphylococcus spp. in culture, they can be considered as

A

aerobic or facultatively anaerobic

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5
Q

means you have to grow them in an environment without oxygen.

A

obligate anaerobes

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6
Q

In culture, colonies are produced after how many hours

A

18-24 hours of incubation.

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7
Q

appearance of Staphylococcus spp.

A

medium size, cream colored, white, or rarely light gold and buttery looking especially Staphylococcus aureus.

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8
Q

Common isolates in the clinical laboratory and are responsible for several suppurative infections.

A

Staphylococci

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9
Q

term of infection by pus-producing organism

A

suppurative infection

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10
Q

most virulent species of staphylococci

A

S. aureus

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11
Q

S. aureus is present among the indigenous flora of the

A

skin, eye, upper respiratory tract, gastrointestinal tract, urethra, and frequently in our vagina.

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12
Q

infections are frequently acquired when colonizing strains gain access to a normally sterile site as a result of

A

trauma or abrasion to the skin or mucosal surface

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13
Q

S. aureus is the most common cause of

A

Spinal epidural abscess, suppurative intracranial, septic arthritis, and osteomyelitis.

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14
Q

infection especially in pre-pubertal children.

A

septic arthritis

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15
Q

may be recovered from brain abscesses, typically following trauma.

A

suppurative intracranial phlebitis

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16
Q

It causes various cutaneous infections and purulent abscesses.

A

S. aureus

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17
Q

skin and soft tissue infections can be superficial, such as

A

impetigo or cellulitis.

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18
Q

Cutaneous infections can progress to deeper abscesses, such as

A

carbuncles

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19
Q

Cutaneous infections can progress to deeper abscesses and involve other organ systems and produce

A

bacteremia and septicemia.

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20
Q

cause of infective endocarditis

A

S.aureus

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21
Q

S.aureus is a common cause of toxin-induced diseases, such as

A

food poisoning

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22
Q

What is SSS

A

scalded skin syndrome

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23
Q

What is TSS

A

toxic shock syndrome

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24
Q

“protein A” has sites that is able to bind the

A

FC portion of IgG.

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25
Q

Protein A protects the organism from

A

opsonization and phagocytosis of neutrophils

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26
Q

Coagulase is an enzyme that can even lead to

A

fibrin formation around the bacteria

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27
Q

an enzyme around the bacteria that protect the bacteria from phagocytosis

A

Coagulase

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28
Q

Coagulase helps this to disrupt the beta lactam portion of the molecule rendering the antibiotic useless against this organism

A

penicillinase or beta-lactamase

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29
Q

4 Types of Hemolysin

A
  1. Alpha toxins
  2. Beta toxins
  3. Delta toxins
  4. Gamma toxins
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30
Q

able to destroy or hemolysed your red blood cells, neutrophils, macrophages, and platelet.

A

Hemolysin

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31
Q

disrupts smooth muscle in blood vessels

A

Alpha toxins

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32
Q

toxic to erythrocytes, leukocytes, hepatocytes, and platelets

A

Alpha toxins

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33
Q

acts on sphingomyelin in the plasma membrane of erythrocytes

A

Beta toxins

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34
Q

Beta toxins is also called

A

sphingomyelinase C or “hot-cold” lysin

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35
Q

“hot-cold” feature associated with Beta toxin is seen as enhanced hemolytic activity on

A

incubation at 37° C and subsequent exposure to cold (4° C)

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36
Q

Beta toxins is exhibited in this test

A

Christie, Atkins, and Munch-Petersen (CAMP) test

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37
Q

performed in the laboratory to identify group B streptococci.

A

Christie, Atkins, and Munch-Petersen (CAMP) test

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38
Q

bacterias capable of producing delta toxin

A

S.aureus, S. epidermidis, and S. haemolyticus

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39
Q

toxin that is cytolytic to erythrocytes and demonstrates nonspecific membrane toxicity to other mammalian cells.

A

Delta toxins

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40
Q

produced by all strains of S. aureus

A

Gamma toxins

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41
Q

Gamma toxins function in association with PVL. pvl stands for?

A

PantonValentine leukocidin

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42
Q

an exotoxin lethal to polymorphonuclear leukocytes.

A

PVL

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43
Q

PVL has been implicated as contributing to the invasiveness of the organism by

A
  1. suppressing phagocytosis
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44
Q

associated with severe cutaneous infections and necrotizing pneumonia.

A

PVL

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45
Q

Spreading factor; Permits bacteria to spread through connective tissues

A

Hyaluronidase

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46
Q

breaks down the proteoglycans in our connective tissue

A

Hyaluronidase

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47
Q

lyses the formed-fibrin clots

A

Staphylokinase

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48
Q

similar to streptokinase produced by Streptococcus

A

Staphylokinase

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49
Q

Able to degrade fats and oils that are often accumulated the surface of our body

A

Lipase

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50
Q

degradation of fats and oil facilitates the ability of S. aureus to colonize especially in our

A

sebaceous glands

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51
Q

Destroys protein

A

Protease

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52
Q

Exotoxin TSST-1 is also known as

A

pyrogenic exotoxin C

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53
Q

Responsible for the Toxic shock syndrome

A

Exotoxin TSST-1

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54
Q

illness most common in women 15-25 years of age who use tampons during menstruation

A

Toxic shock syndrome

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55
Q

cause of the majority of staphylococcal food poisoning cases

A

Enterotoxins A-E

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56
Q

cause the epidermal layer of the skin to slough off

A

Exfoliative Toxins

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57
Q

known to cause staphylococcal SSS (Skin Scald Syndrome)

A

Exfoliative Toxins

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58
Q

Most significant Exfoliative Toxins

A

epidermolytic toxin A & B

59
Q

Associated with our community acquired methicilin-resistant Staphylococcus aureus

A

Panton-Valentine leukocidin toxin

60
Q

cause fever, desquamation, hypotension, and could even lead to bacterial shock and death

A

exotoxin-TSST 1 or the pyrogenic exotoxin C

61
Q

common source of hospital-acquired infections

A

S. epidermis

62
Q

contaminant in improperly collected blood culture specimens

A

S. epidermis

63
Q

less virulent than S.aureus and are opportunistic pathogens.

A

S.epidermis

64
Q

cause of UTIs; Prosthetic valve endocarditis

A

S.epidermis

65
Q

commonly isolated CoNS. It has been reported in wounds, bacteremia, endocarditis, and UTIs

A

S.haemolyticus

66
Q

Usually involve implantation of medical devices; infection can even resemble S.aureus infection

A

S. lugdunensis

67
Q

Identification of this bacteria is important because this particular genus is resistant to oxacillin

A

S. lugdunensis

68
Q

associated with UTIs in young sexually active females; it is the second most common cause, after E. coli

A

S. saprophyticus

69
Q

they are both community-associated and hospital acquired infections.

A

S. lugdunensis and S. aureus

70
Q

organism is more virulent than other is known to contain the gene mecA

A

S. lugdunensis

71
Q

gene which encodes oxacillin resistance.

A

gene mecA

72
Q

also display resistance to your vancomycin.

A

S.haemolyticus

73
Q

Opportunistic Pathogens

A
  1. S. Warneri
  2. S. Capitis
  3. S.simulans
  4. S. Hominis
  5. S. Schleiferi
74
Q

3 Modes of Transmission

A
  1. Endogenous strain
  2. Direct contact
  3. Indirect contact
75
Q

MOT: sterile site by traumatic introduction

A

Endogenous strain

76
Q

MOT: person-to- person, fomites

A

Direct contact

77
Q

MOT: aerosolized

A

Indirect contact

78
Q

Laboratory dx: Specimen

A

No special considerations

79
Q

Laboratory dx: Microscopy

A

Gram positive cocci

80
Q

used to eliminate contamination by gram-negative organisms in heavily contaminated specimens such as feces.

A

Phenylethyl alcohol (PEA) or Columbia colistin-nalidixic acid (CNA)

81
Q

Staphylococcus aureus growing on Sheep Blood Agar would produce

A

beta-hemolytic, creamy, buttery-looking colonies.

82
Q

name “aureus” has something to do with the production of the

A

Staphyloxanthin or golden yellow pigment

83
Q

a coagulase positive organism.

A

Staphylococcus aureus

84
Q

coagulase negative staphylococci

A

S.epidermis & S.saprophyticus
(non-staphylococcus aureus organisms)

85
Q

mannitol sugar agar contains a high concentration of salt with a percentage of

A

7.5%-10%

86
Q

phenol red as the pH indicator

A

Mannitol Salt Agar

87
Q

makes the medium selective for Staphylococcus

A

high NaCl concentration (7.5%) in MSA

88
Q

incorporation of this distinguishes S. aureus from most CoNS (Coagulase negative staphy)

A

mannitol and phenol red

89
Q

S. aureus ferments mannitol and produces a

A

yellow halo

90
Q

S. aureus ferments mannitol and produces a yellow halo as a result of

A

acid production altering the pH

91
Q

CHROMagar is for the identification of

A

methicillinresistant Staphylococcus aureus (MRSA)

92
Q

CHROMagar for the identification of methicillinresistant Staphylococcus aureus (MRSA) isolates through

A

selective and differential formation of mauve-colored colonies

93
Q

grow on media containing blood, orming colonies about one tenth the size even after 48 hours or more of incubation

A

small colony variants (SCVs)

94
Q

appear as small, pinpoint, nonhemolytic, and nonpigmented colonies on blood agar.

A

small colony variants of S. aureus

95
Q

Catalase Test is used to differentiate

A

Catalase positive Micrococcus & Staphyloccocus from Catalase negative Streptococcus

96
Q

Catalase is an enzyme that converts the hydrogen peroxide into?

A

oxygen and water

97
Q

positive result of Catalase test

A

presence of bubbles (effervescence)

98
Q

this bacteria is coagulase positive both in slide and tube test

A

S.aureus

99
Q

Bound coagulase, or “clumping factor” is performed on

A

Slide Test

100
Q

Free coagulase or staphylocoagulase is performed on

A

Tube Test

101
Q

formerly referred to as cell-bound coagulase and causes agglutination

A

Clumping factor

102
Q

directly converts fibrinogen to fibrin

A

Clumping factor

103
Q

resembles thrombin and indirectly converts fibrinogen to fibrin

A

coagulase-CRF complex

104
Q

positive result of slide coagulase test

A

clumping/agglutination within 30 seconds

105
Q

positive result of tube coagulase test

A

clot formation

106
Q

a negative result of slide test should always be followed up by

A

a tube coagulase test.

107
Q

an extracellular molecule that causes a clot to form when bacterial cells are incubated with plasma.

A

Staphylocoagulase

108
Q

Staphylocoagulase reacts with a thermostable, thrombin-like molecule called

A

coagulase- reacting factor (CRF)

109
Q

In Tube coagulase test, look for clot formation after

A

4 hours of incubation at 37° C

110
Q

If no clot appears fter 4 hours of incubation at 37° C during Tube coagulase test, what should be done

A

tube should be left at room temperature and checked the next day.

111
Q

Fibrinolysin activity is enhanced at

A

37° C.

112
Q

organisms that may present false positive result in slide test

A

S.Lugdugensis and S.schleiferi

113
Q

organisms that may present false positive result in Tube Test

A

S.Intermedius and S.hyicus

114
Q

Testing for pyrrolidonyl arylamidase activity can be used to differentiate S. aureus (negative) from

A

S. lugdunensis, S. intermedius, and S. schleiferi (positive).

115
Q

It is hydrolyzed to L-pyrrolidone and β-
naphthylamine, which combines with p- dimethylaminocinnamaldehyde to form a red compound.

A

substrate pyroglutamylβ-naphthylamide (L-pyrrolidonyl- β-naphthylamide)

116
Q

Bright red precipitate

A

PYR Test

117
Q

Voges- Proskauer positive result

A
  1. formation of acetoin from glucose or pyruvate
  2. Red color = S. aeurus
118
Q

a test to determine whether an organism that is inoculated in the plate is susceptible to 5-ug novobiocin disk.

A

Novobiocin Susceptibility Test

119
Q

this organism is resistant to novobiocin and lack of a Zone of inhibition.

A

S. saprophyticus

120
Q

In Microdase test, Staphylococcus epidermidis screening plate may show resistance to

A

Bacithracin (Taxo A) and furazolidone (Fx)

121
Q

a modified oxidase test, detects your Cytochrome C; and used for differentiating Micrococcus spp. from Staphylococcus spp.

A

Microdase Test

122
Q

In Microdase Test, Micrococcus spp. turn color ? within how how many mins

A

blue within 2 minutes.

123
Q

bacteria is positive for both the 2-hour PYR and ornithine decarboxylase tests.

A

S. lugdunensis

124
Q

kits use plasma-coated carrier particles

A

latex.

125
Q

detect both clumping factor (with fibrinogen) and protein A

A

latex kit

126
Q

kits that detect both clumping factor (with fibrinogen) and protein A and contain antibodies that bind capsular antigens 5 and 8, or other surface molecules.

A

Third-generation agglutination kits

127
Q

These kits often have a higher specificity and sensitivity than the traditional plasma slide test and are quicker than the tube coagulase test.

A

latex kit

128
Q

more sensitive, they are generally less specific.

A

Third-generation agglutination kits

129
Q

Using Third-generation agglutination kits, False-positive results can occur with

A

S. saprophyticus, S. hominis, and S. haemolyticus.

130
Q

mediated by the mecA gene, which encodes an altered penicillin-binding protein, PBP-2a

A

B-Lactamase

131
Q

The mainstay of antistaphylococcal therapy is the use

A

methicillin, naficillin, and oxacillin

132
Q

due to the gene mecA which is carried on a mobile cassette known as SCCmec

A

MRSA

133
Q

using cefoxitin disk, MRSA zone of inhibition is

A

> 22 mm is reported as susceptible

134
Q

using cefoxitin disk with zone sizes that is less or equal (</= 21 mm) is reported as ? and it is most probably a?

A

oxacillin resistant , MRSA

135
Q

To screen isolates of S.aureus for oxacillin resistance, we use

A

Mueller Hinton agar supplemented with 4% sodium chloride and containing your 6 ug/ml of oxacillin inoculated unto a cotton swab and incubated 24 hours at 35C

136
Q

gold standard for MRSA detection

A

Molecular nucelic acid probes or pCR amplification

137
Q

Macrolide Resistance

A
  1. Clindamycin
  2. Efflux pump, MRSA
  3. Methylase enzyme that alters the ribosomal binding site.
  4. D-zone test
138
Q

useful when discrepant macrolide test results are obtained (e.g., erythromycin resistant and clindamycin susceptible).

A

modified double disk diffusion test (D-zone test)

139
Q

to determine the organism’s susceptibility to Clindamycin, what is used?

A

modified Kirby-Bauer test or D zone test

140
Q

most commonly used cell wall–active agent that retains activity and is an alternative drug of choice for the treatment of infections with resistant strains

A

Vancomycin

141
Q

Any clinical isolates that are identified as oxacillin-resistant S. aureus or coagulase-negative staphylococci and been found to be resistant to

A

vancomycin

142
Q

resistant to vancomycin should be considered resistant to all other

A

beta-lactam antibiotics.

143
Q

Alternatives for vancomycin

A

Linezolid & Daptomycin

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