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Lecture Flashcards

1
Q

Genus Staphylococcus are grouped under

A

Order Bacillales

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2
Q

General characteristics of staphylococcus

A
  • Catalase (+)
  • Gram (+) cocci
  • Aerobic or Facultative anaerobe
  • Non-motile
  • Non-spore forming
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3
Q

S. aureus Habitat and MOT

A

HABITAT: CSPAN
MOT: Surgical wound, micro-abrasions, person-person, fomites and aerosolized

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4
Q

S.epidermidis Habitat and MOT

A

Habitat: Skin mucous membranes
MOT: implantation of medical devices (shunts, prosthetic devices) and person to person

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5
Q

S. haemolyticus and S. lugdunensis Habitat and MOT

A

Habitat: skin mucous membranes (low)
MOT: same as S. epidermidis

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6
Q

S. saphrophyticus Habitat and MOT

A

Habitat: Skin and genitourinary-tract mucosa
MOT: urinary tract notably in young sexually active females

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7
Q

Micrococcus spp. Kocuria spp. Kytococcus spp. Habitat and MOT

A

Habitat: Skin Mucosa Oropharynx
MOT: Immunocompromised hosts: brain abscess, meningitis, pneumonia, endocarditis

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8
Q

3 types of Nasal Carrier:

A

PIN
Persistent, Intermittent, Non-carriers

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9
Q

has a high prevalent nosocomial transfer from healthcare providers.

A

S. aureus

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10
Q

IMPORTANT VIRULENCE FACTORS FOR S. AUREUS: Structural components

A

Polysaccharide capsule
Peptidoglycan
Teichoic Acid
Protein A

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11
Q

MPORTANT VIRULENCE FACTORS FOR S. AUREUS: Toxins

A

Cytotoxins
Exfoliative toxins
Enterotoxins
Toxic Shock Syndrome toxin-1

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12
Q

MPORTANT VIRULENCE FACTORS FOR S. AUREUS: Enzymes

A

Coagulase
Catalase
Hyaluronidase
Fibrinolysin
Lipases
Nucleases
Penicillinases

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13
Q

Virulence Factor that inhibits phagocytosis

A

Peptidoglycan capsule

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14
Q

Virulence factor that Activates complement, IL-1, Chemotactic to PMNs

A

Peptidoglycan

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15
Q

Virulence factor that Mediate fibronectin binding

A

Teichoic Acid

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16
Q

Virulence factor that has Affinity to the Fc receptor of IgG and complement

A

Protein A

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17
Q

Virulence factor that is Toxic to RBC, WBC, Platelet & hepatocytes

A

Cytotoxin Alpha

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18
Q

Virulence factor that has Sphingomyelinase that catalyzes phospholipids

A

Cytotoxin Beta

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19
Q

Virulence factor that is Toxic to RBC and other mammalian cells

A

Cytotoxin Delta

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20
Q

Virulence factor that is Associated with Panton Valentine Leukocidin

A

Cytotoxin Gamma

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21
Q

Virulence factor that has Pre-formed toxin resulting to gastrointestinal symptoms, Food poisoning within 2-6 hrs after ingestion (pseudomembranous enterocolitis)

A

Heat Stable Enterotoxin (A-E, G-I)

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22
Q

Virulence factor that causes Exfoliative dermatitis and Ritters Disease (Scalded skin syndrome)

A

Exfoliative/Epidermolytic toxins

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23
Q

Virulence factor that causes Fever, desquamation, hypotension and toxic shock syndrome

A

Pyrogenic Exotoxin-C; Enterotoxin F (TSST-1)

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24
Q

Virulence factor that forms fibrin clot

A

Coagulase; clumping factor

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25
Q

Virulence factor that removes fibrin clot

A

Fibrinolysin (Staphylokinase)

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26
Q

Virulence factor: destruction of H202

A

Catalase

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27
Q

Virulence factor: Degradation of hyaluronic acid Cell colonization

A

Hyaluronidase (spreading factor)

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28
Q

Breakdown of lipids and nucleic acids

A

Lipases and Nucleases

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29
Q

Virulence factor: Breakdown of B- Lactam AMR

A

Penicillinases

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30
Q

Virulence factor of S. epidermidis

A

Exopolysaccharide “slime” or biofilm; antiphagocytic
Exotoxins: delta toxin

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31
Q

Common Specimens for Diagnosis

A

Abscess (lesion, wound, pustule, ulcer)
Urine (midstream clean catch, catheter collection)
Blood

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32
Q

Initial Plating Medium

A

5% Sheep’s Blood Agar

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33
Q

Special Plating Medium

A

5% Columbia Naladixic Agar

34
Q

Incubation period for isolation from clinical specimen

A

35°C in carbon dioxide (CO2) or ambient air usually occurs within 24 hours of inoculation.

35
Q

o Medium to large colonies (0.3- 1.5 um) o Pin head colonies
o Pigemented creamy- yellow
o Mostly B-hemolytic

A

S. aureus

36
Q

o Small to medum
o Grayish-white colonies
o Slime producing (sticks to agar) o Non-hemolytic

A

S. epidermidis

37
Q

o Large colonies
o White glossy colonies o Butyrous
o Non- hemolytic

A

S. saphrophyticus

38
Q

o B-hemolytic

A

S. haemolyticus & S. lugdunensis

39
Q

o Small to medium
o Non-hemolytic
o Pigmented (white, tan, yellow, orange, pink)

A

Micrococcus spp

40
Q

is a basal nutrient agar that contains peptones derived from casein and meat as well as beef and yeast extracts.

A

Columbia Agar

41
Q

The addition of sheep blood in Columbia Agar allows for the

A

Detection of hemolytic reactions

42
Q

The selective/ inhibitory agent of CAN is the antibiotic _______ quinolone drug similar to Cipro or Levaquin.

A

Naladixic acid

43
Q

used for isolation and differentiation of pathogenic staphylococci, principally Staphylococcus aureus.

A

Mannitol Salt Agar

44
Q

Selective Agent for Mannital Salt Agar

A

7.5% Sodium Chloride (selective for Staphylococcus spp.)

45
Q

Differential Agent for Mannitol Salt Agar

A

Mannitol

46
Q

Indicator for Mannitol Salt Agar

A

Indicator: Phenol Red
▪ Below pH 6.4:YELLOW
▪ pH 7.4–8.4: RED
▪ Above pH 8.4:PINK

47
Q

Incubation time for Mannitol Salt Agar

A

48-72 hours

48
Q

MANNITOL SALT AGAR GROWTH: S. aureus

A

Yellow colonies with yellow halo

49
Q

MANNITOL SALT AGAR GROWTH: CoNS

A

Pink colonies

50
Q

What do you call S. aureus that grows in 75% NaCl or walang NaCl?

A

Halotolerant

51
Q

90% of your MRSA colonies are

A

Mannitol Fermenters.

52
Q

Selective and differential media for the identification of MRSA.

A

CHROMagar

53
Q

These media are becoming more widely used for the direct detection of nasal colonization.

A

CHROMagar

54
Q

Selective agent of CHROMagar

A

Cefoxitin (MRSA is resistant to this antibiotic

55
Q

Indicator of CHROMagar

A

Chromogenic substrates

56
Q

Growth (+) of CHROMagar

A

Mauve-coloredcolony,variety of colored colonies from white to blue to green.

57
Q

Why should gram stain be performed on young cultures?

A

Gram stains should be performed on young cultures, because very old cells may lose its ability to retain crystal violet. When the cells are very old they lose their ability to maintain crystal violet, their characteristic is GRAM VARIABLE.

58
Q

• Gram positive
• Some clusters and some in tetrads (packets of 4)
• Sarcinae (packets of 8)
• “cube-like cocci”

A

Micrococcus spp.

59
Q

• Gram positive
• Cocci in clusters or in group
• Grape-like structure

A

Staphylococcus spp.

60
Q

BIOCHEMICAL TEST: This test differentiates catalase-positive micrococcal and staphylococcal species from catalase-negative streptococcal species.

A

Catalase

61
Q

Bicohemical Test Principle: Aerobic and facultative anaerobic organisms
produce two toxins during normal metabolism

A

hydrogen peroxide (H2O2) and superoxide radical (O22)

62
Q

is capable of converting hydrogen peroxide to water and oxygen.

A

Catalase

63
Q

(+) result of catalase

A

Effervescence

64
Q

Catalase Limitation

A

Enterococci and Hemoglobin (from blood agar)
Psudoperoxidase reacts with your hydrogen peroxide goving false positive reaction

65
Q

Catalase quality control

A

o Positive: Staphylococcus aureus (ATCC 25923)
o Negative: Streptococcus pyogenes (ATCC 19615)

66
Q

This test differentiates micrococci from staphylococci

A

Oxidation – Fermentation Test

67
Q

Oxidation-Fermentation Test Principle: __________will be fermented or oxidized by the isolate based on the color manifestation in the medium.

A

Glucose

68
Q

Indicator of Oxidation – Fermentation Test

A

Bromothymol blue

69
Q

Closed Tube: yellow
Open tube: yellow
Interpretation:

A

Fermenter (Staphylococci spp.)

70
Q

Closed Tube: green
Open tube: yellow
Interpretation:

A

Oxidizer (Micrococcus spp.)

71
Q

Oxidation – Fermentation Test

Yellow pH
Green pH

A

6.0
7.1

72
Q

The microdase test is a rapid method to differentiate Staphylococcus from Micrococcus spp. by detection of the enzyme oxidase.

A

Microdase (Modified Oxidase) Test

73
Q

Microdase (Modified Oxidase) Test Principle: In the presence of atmospheric oxygen, the oxidase enzyme reacts with the oxidase reagent _______to form the colored compound, indophenol).

A

tetramethyl-paraphylene diamine hydrochloride with dimethylsulfoxide and cytochrome C

74
Q

Microdase (Modified Oxidase) Test
(+) result
(-) result

A

(+) Result:
o Blue to Purple-Blue color (Micrococcus spp.)

(-) Result:
o Colorless (Staphylococcus spp.)

75
Q

Microdase (Modified Oxidase) Test Limitation: Staphylococci should yield a negative color
change, except for:

A

S. sciuri S. lentus S. vitulus

76
Q

Microdase (Modified Oxidase) Test Quality Control:

A

o Positive: Micrococcus leteus (ATCC10240)
o Negative: Staphylococcus aurerus (ATCC25923)

77
Q

Used to distinguish:
▪ Staphylococcus aureus (+) from other Staphylococcus spp, (-),
▪ Moraxella catarrhalis (+) from Neisseria spp.

A

DNAse Test

78
Q

Used to distinguish:
▪ Staphylococcus aureus (+) from other Staphylococcus spp, (-),
▪ Moraxella catarrhalis (+) from Neisseria spp.

A

DNAse Test

79
Q

DNAse test principle: An enzyme catalyzes hydrolysis of DNA into small fragments (1. _______) or single nucleotide called deoxyribonuclease or 2. ______. One formulation for Dnase Agar consists of peptides from 3. _____ and 4. ________ and 5. ______. After incubation, 6._______ is added. Intact DNA will form cloudy ppt while oligonucleotide will produce clearing around the growth.

A
  1. oligonucleotides
  2. DNase
  3. soybean
  4. casein
  5. DNA
  6. 1N HCl
80
Q

DNase Test: Result

A

o (+)
▪ Clearing on the medium (Staphylococcus aureus)

o (-)
▪ Cloudy ppt (Staphylococcus spp.)

81
Q

The test is used to differentiate Staphylococcus aureus (+) from coagulase-negative staphylococci (-).

A

Coagulase Test

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