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[MT 6320] Clinical Bacteriology Lecture > [2S] UNIT 3.1 Gram (+) Cocci - Staphylococci > Flashcards

[2S] UNIT 3.1 Gram (+) Cocci - Staphylococci Flashcards

1
Q

BACTERIA ACCORDING TO SHAPE

Rod-shaped

A

bacillus/bacilli

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2
Q

Gr(+) or Gr(-) & Shape?

Neisseria and Moraxella

A

Gr(-) cocci

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3
Q

BACTERIA ACCORDING TO SHAPE

Round/Spherical

A

coccus/cocci

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4
Q

Gr(+) or Gr(-) & Shape?

Staphylococcus and streptococcus

A

Gr(+) cocci

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5
Q

Gr(+) or Gr(-) & Shape?

Bacillus & Erysipelothrix

A

Gr(+) bacilli

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6
Q

Gr(+) or Gr(-) & Shape?

most bacilli

A

Gr(-) bacilli

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6
Q

Gr(+) or Gr(-) & Shape?

Listeria & Mycobacterium

A

Gr(+) bacilli

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7
Q

Gr(+) or Gr(-) & Shape?

Enterobacteriaceae & Haemophilus

A

Gr(-) bacilli

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8
Q

Gr(+) or Gr(-) & Shape?

Spirochetes: Treponema, Borrelia, Leptospira

A

Gr(-) spiral

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9
Q

GENERALITIES

grape-like clusters; due to their morphological arrangement when seen under the light microscope

A

Staphylococcus

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10
Q

GENERALITIES

Belong to Family Staphylococcaceae

A

Staphylococcus

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11
Q

GENERALITIES

○ Generally seen as cocci in clusters (most cases)
○ No tetrads

A

Gr (+) Cocci in clusters, in pairs, singly

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12
Q

GENERALITIES

All are Catalase (+) except?

A

S.aureus subsp. anaerobius
and S. saccharolyticus

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13
Q

If tetrads are seen, it might be?

A

micrococcus

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14
Q

GENERALITIES

would detect the enzyme catalase

A

Catalase test

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15
Q

GENERALITIES

Positive result for Catalase Test

A

bubbling of solution or effervescence after addition of 3% hydrogen peroxide

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16
Q

T/F: All staphyloccocus are modified oxidase negative except t S. sciuri, S. lentus, S. vitulus (are modified oxidase positive)

A

T

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17
Q

Modified Oxidase Test is also known as?

A

Microdase Test

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18
Q

Positive result for Modified Oxidase Test

A

blue-purple coloration

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19
Q

All are non-motile and non-spore formers

A

Staphylococcus

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20
Q

T/F: Majority of motile bacteria are bacilli and has no flagella

A

T

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21
Q

T/F: All are halophilic. Growing in high amount of NaCl or salt, at around 7.5%

A

T

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21
Q

T/F: Motility test is commonly done on gram (+)

A

F; gram -

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22
Q

Gaseous Requirement: _________ except Staphylococcus aureus subspecies anaerobius &
Staphylococcus saccharolyticus

A

Aerobic or Facultative Anaerobe

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23
Q

T/F: Staphylococcus are nitrate reducers

A

T

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24
Q

○ Medium sized
■ Pinhead (larger than pinpoint)
○ Raised
○ Creamy with smooth margin
○ Lemon yellow or golden colonies
○ Buttery-looking

A

Staphylococcus

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25
Q

STAPH W/ DISTINCT COLORS

white

A

S. albus

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26
Q

Colonies produced after 18 to 24 hours of incubation are medium sized (4 to 8 mm)

A

Staphylococcus

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27
Q

STAPH W/ DISTINCT COLORS

golden yellow (due to the pigment staphyloxanthin)

A

S. aureus

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28
Q

STAPH W/ DISTINCT COLORS

lemon yellow (more pronounced in Loeffler’s serum slant)

A

S. citreus

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29
Q

Rare strains of _______ are fastidious, requiring carbon dioxide, hemin, or menadione for growth.

A

staphylococci

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30
Q

These so-called small colony variants (SCVs) grow on media containing ______, forming colonies about 1/10 the size of wild-type strains even after 48 hours or more of incubation.

A

blood

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31
Q

an initial test is performed to differentiate Staphylococcus spp.

A

Coagulase Test

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32
Q

T/F: Catalase test is more useful in differentiating
Staphylococcus from Streptococcus

A

T

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33
Q

Usually done after the catalase test (have identified that the organism is Staphylococcus spp.)

A

Coagulase Test

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34
Q

CONS OR COPS

Staphylococcus aureus

A
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35
Q

CONS OR COPS

S. intermedius (associated with animal infections)

A

COP

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36
Q

CONS OR COPS

S. aureus subspecies anaerobius

A

COPS

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37
Q

CONS OR COPS

S. delphini

A

COPS

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37
Q

CONS OR COPS

S. epidermidis, S. haemolyticus

A

CONS - Novobiocin Susceptible

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37
Q

CONS OR COPS

S. lutrae

A

COPS

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38
Q

CONS

After testing the isolate for the antibiotic novobiocin, if they would have a _____
zone of inhibition, they would be novobiocin susceptible.

A

clear

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39
Q

CONS OR COPS

S. saprophyticus, S. xylosus

A

CONS - Novobiocin Resistant

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39
Q

No or little zone of inhibition after testing
it with the antibiotic novobiocin.

A

CONS - Novobiocin Resistant

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40
Q

Primary reservoir

A

Human nares particularly S. aureus

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41
Q

GENERALITIES

Belong to Family Micrococcaceae

A
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41
Q

GENERALITIES

Gram (+) cocci in clusters; in tetrads (in fours)

A
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42
Q

GENERALITIES

Usually normal flora and associated with skin lesions and more commonly isolated among immunocompromised
patients

A
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43
Q

GENERALITIES

Less medically relevant than Staphylococcus but may be easy confused as Staphylococcus

A
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43
Q

GENERALITIES

May be found in the environment (ubiquitous in nature)

A
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44
Q

MICROCOCCI

■ Negative in catalase test
■ Found in air, dust, and hospital equipments

A

Aerococcus

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44
Q

MICROCOCCI

■ Isolated in the middle ear of the infected patient
■ Commensal organisms

A

Alloiococcus otitis

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45
Q

Staph vs Micrococcus

Catalase test

A

Both positive

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46
Q

MICROCOCCI
■ emerging pathogen (UTI, endocarditis)
■ Capsulated gram (+) cocci
■ Emerging pathogen

A

Rothia mucilaginosa / Stomatococcus mucilaginosus

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47
Q

Staph vs Micrococcus

Aerobic growth

A

Both yes

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47
Q

Staph vs Micrococcus

Glucose Utilization

A

Staph: Fermentative
Micro: Oxidative / Nonsaccharolytic

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48
Q

Staph vs Micrococcus

Anaerobic growth

A

Staph

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49
Q

Staph vs Micrococcus

Benzidine

A

S : Negative
M : Positive

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49
Q

Staph vs Micrococcus

Lysostaphin (>/=200 g/L) (Resistance)

A

S : Susceptible
M : Resistant

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49
Q

Staph vs Micrococcus

Modified Oxidase/ Microdase

A

S : Negative except for S.
sciuri, S. lentus, S. vitulus
M : Positive

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50
Q

Staph vs Micrococcus

Bacitracin/Taxo A Disk
(Resistance) (0.04 unit)

A

S : Susceptible
M : Resistant

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50
Q

Staph vs Micrococcus

Production of Acid from
Glycerol in the Presence of Erythromycin

A

S : Positive
M : Negative

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51
Q

Staph vs Micrococcus

Lysosome

A

S : Resistant
M : Susceptible

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52
Q

Staph vs Micrococcus

Growth on furoxone-tween 80-oil red o agar

A

S : Negative
M : Allow growth of micrococcus

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53
Q

CLINICALLY SIGNIFICANT STAPHYLOCOCCI : Coag +/-

Staphylococcus aureus

A

Coag +

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54
Q

CLINICALLY SIGNIFICANT STAPHYLOCOCCI : Coag +/-

● Staphylococcus epidermidis
● Staphylococcus lugdunensis
● Staphylococcus saprophyticus

A

Coag -

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55
Q

Staph vs Micrococcus

○ S. warneri
○ S. capitis
○ S. hominis
○ S. schleiferi
○ S. haemolyticus

A

Less common but implicated as opportunistic pathogens

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56
Q

Most clinically significant staph

A

S. aureus

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56
Q

Can be recovered from almost any clinical specimen
○ Normally found in the human nares
○ Found in swabs

A

S. aureus

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57
Q

Can cause acne, sty, celulities & folliculitis

A

S. aureus

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57
Q

Can cause toxic shock syndrome, scalded skin syncrome, food poisoning, impetigo, and furuncles and carbuncles

A

S. aureus

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58
Q

STAPHYLOCOCCUS AUREUS

■ Systemic illness that can lead to hypotension
■ Certain groups of people would have a higher
risk, particularly females who use tampons.

A

Toxic Shock Syndrome

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59
Q

STAPHYLOCOCCUS AUREUS

Skin infections affecting the hair follicles

A

Furuncles and carbuncles

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60
Q

STAPHYLOCOCCUS AUREUS

Affect infants or neonates

A

Scalded Skin Syndrome

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61
Q

STAPHYLOCOCCUS AUREUS

more deep seated affecting the hair follicles

A

Furuncles

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62
Q

Also an important cause of nosocomial and opportunistic infections

A

S. aureus

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62
Q

STAPHYLOCOCCUS AUREUS

shallow, affectes nearby or adjacent hair follicles

A

Carbuncles

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63
Q

PROTEIN DETERMINANTS

○ Present on the cell surface
○ Cell wall component
○ Prevent opsonization
○ Binds to antibodies (IgG)

A

Protein A

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64
Q

PROTEIN DETERMINANTS

Antiphagocytic

A

Protein A

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65
Q

PROTEIN DETERMINANTS

Endotoxin like activity

A

Peptidoglycan and Teichoic Acids

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65
Q

PROTEIN DETERMINANTS

Protein A will bind to what antibody?

A

IgG

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66
Q

PROTEIN DETERMINANTS

Activates complement, Interleukin 1
■ Activation of complement can lead to inflammation
■ Interleukin 1 can trigger fever

A

Peptidoglycan and Teichoic Acids

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66
Q

3 Protein Determinants of S. aureus

A

Protein A
Capsular Polysaccharide
Peptidoglycan & Teichoic Acids

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67
Q

PROTEIN DETERMINANTS

Chemotactic factor for PMN

A

Peptidoglycan and Teichoic Acids

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68
Q

S. AUREUS - VIRULENCE FACTORS

affects the smooth muscle of the blood vessels

A

Alpha hemolysin

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69
Q

S. AUREUS - VIRULENCE FACTORS

■ Heat-labile (destroyed by heat)
■ Type of sphingomyelinase
■ Hot-cold lysin

A

Beta hemolysin

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69
Q

S. AUREUS - VIRULENCE FACTORS

Lyses red blood cells

A

Hemolysins (alpha, beta, gamma and delta)

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70
Q

S. AUREUS - VIRULENCE FACTORS

■ Less toxic
■ Associated to Panton Valentine Factor

A

Gamma

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71
Q

S. AUREUS - VIRULENCE FACTORS

Toxic to red blood cells and other mammalian cells

A

Delta

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72
Q

S. AUREUS - VIRULENCE FACTORS

○ Penicillin binding protein
○ Binds to penicillin making the organism resistant
○ Often studied among Methicillin-resistant
Staphylococcus aureus (MRSA)

A

PBP2

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72
Q

S. AUREUS - VIRULENCE FACTORS

Leukocidin (destroys WBC)

A

Panton Valentine Factor

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73
Q

S. AUREUS - VIRULENCE FACTORS

○ The one we detect in coagulase test
○ Significant in the identification process of the
organism
○ Clots fibrinogen

A

Staphylocoagulase

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74
Q

S. AUREUS - VIRULENCE FACTORS

○ Superantigen
■ Can cause T cells to proliferate
■ Induce cytokine release
● Cytokine - an important cell secretion in inflammation

A

TSST-1

75
Q

S. AUREUS - VIRULENCE FACTORS

○ Causes almost all cases of menstruating TSS
○ Formerly called Enterotoxin F

A

TSST-1

76
Q

S. AUREUS - VIRULENCE FACTORS

○ Cause staphylococcal food poisoning, diarrhea,
vomiting but the disease is self limiting
○ Heat-stable toxins

A

Enterotoxins

77
Q

S. AUREUS - VIRULENCE FACTORS

○ Epidermolytic toxin that can cause sloughing off of the skin
○ Implicated in Scalded Skin Syndrome (SSS), Ritter-Lyell Disease or Dermatitis Exfoliativa
○ Also implicated in Bullous Impetigo

A

Exfoliative Toxin

78
Q

S. AUREUS - VIRULENCE FACTORS

extracellular toxins that affect RBCs and WBCS

A

Cytolytic Toxins

79
Q

S. AUREUS - VIRULENCE FACTORS

Group?

Toxic Shock Syndrome

A

BCGI

79
Q

S. AUREUS - VIRULENCE FACTORS

Group?

Staphylococcal Food Poisoning

A

ABD

79
Q

S. AUREUS - VIRULENCE FACTORS

Group?

Staphylococcal pseudomembranous enterocolitis

A

B

80
Q

S. AUREUS - VIRULENCE FACTORS

Group?

Also known as Toxic shock syndrome toxin 1 (TSST-1) / Pyrogenic Exotoxin C

A

F

81
Q

S. AUREUS - VIRULENCE FACTORS

(cell free or bound); localization of abscess
■ Virulence marker
■ Used for diagnostic purposes

A

ENZYME: Staphylocoagulase

82
Q

4 other factors (enzyme not related to pathogenicity)

A

● Penicillinase
● Catalase
● Thermonuclease
● Gelatinase

83
Q

ASSOCIATED INFECTIONS

Exfoliative dermatitis that occurs among newborns
and previously healthy young children; also seen
among adults with chronic renal failure

A

SSS: Scalded Skin Syndrome

84
Q

ASSOCIATED INFECTIONS

○ Multisystemic disease
○ 2 Categories: Menstruating Associated and Nonmenstruating associated
○ S/S: sudden onset of fever, chills, vomiting, diarrhea, muscle pain, rashes, can progress to hypotension and
shock

A

Toxic Shock Syndrome

85
Q

ASSOCIATED INFECTIONS

has multiple causes; maybe
due to a hypersensitivity reaction; very similar initial
presentation to that of SSS

A

Toxic Epidermal Necrolysis

85
Q

ASSOCIATED INFECTIONS

○ Lesions may be localized or generalized
○ Cutaneous erythema followed by peeling of skin

A

SSS: Scalded Skin Syndrome

86
Q

ASSOCIATED INFECTIONS

○ Involves the ingestion of a preformed enterotoxin from food that is improperly stored
○ S/S: appear rapidly (incubation period: 2-8 hrs);
nausea, vomiting, diarrhea, abdominal pain

A

Staphylococcal Food Poisoning

87
Q

ASSOCIATED INFECTIONS

Most common enterotoxin causing food poisoning

A

Enterotoxin A

88
Q

Most common staph for osteomyelitis

A

S. aureus

89
Q

OTHER INFECTIONS

Has been known to occur
secondary to influenza virus infection

A

Staphylococcal pneumonia

90
Q

OTHER INFECTIONS

Develops as a contiguous, lower respiratory tract infection or a complication of bacteremia, is characterized by
multiple abscesses and focal lesions in the pulmonary parenchyma

A

Staphylococcal pneumonia

91
Q

OTHER INFECTIONS

○ Observed among intravenous drug users.
○ The organisms gain entrance to the bloodstream via contaminated needles or from a focal lesion present
on the skin or in the respiratory or genitourinary tract

A

Staphylococcal bacteremia

92
Q

OTHER INFECTIONS

○ Occurs as a manifestation secondary to bacteremia.
○ Inflammation of the bone

A

Staphylococcal osteomyelitis

93
Q

OTHER INFECTIONS

○ Affecting the heart
○ For those who have undergone heart surgery

A

Endocarditis

94
Q

Usually a normal inhabitant of the skin (predominant
normal flora) but is a
common source of hospital-acquired infections and
often a contaminant in improperly collected blood
culture specimens

A

S. epidermidis

95
Q

● Can cause opportunistic infections (associated with
endocarditis)
● Most common cause of prosthetic valve endocarditis and wound infection

A

S. epidermidis

96
Q

Able to colonize prosthetic devices or surgical devices if
not properly disinfected

A

S. epidermidis

97
Q

T/F: S. epidermidis is coagulase (-)

A

T

98
Q

2nd most common cause of UTIs

A

S. saprophyticus

99
Q

○ This species adheres more effectively to the epithelial cells lining the urogenital tract than other CoNS
○ Rarely found on other mucous membranes or skin
surfaces

A

S. saprophyticus

100
Q

T/F: S. saprophyticus is coag -

A

T

101
Q

Associated with pyelonephritis and cystitis in young women and in older men using catheters

A

S. saprophyticus

102
Q

Colony counts may be <100,000 CFU/mL but is still
significant to be considered as a cause of UTI

A

S. saprophyticus

103
Q

T/F: UTI: colony count should be 100,000 or more but if it is less than 100,000, it is not typically considered UTI but there are certain exceptions, like S. saprophyticus

A

T

104
Q

T/F: When the organism identified is S. saprophyticus, we do not regard it as UTI even if the colony count is <100,000 CFU/mL

A

F; we regard it as UTI

105
Q

Also associated with nosocomial pneumonia

A

S. saprophyticus

106
Q

● A cause of nosocomial infections such as endocarditis, septicemia, meningitis, skin and soft tissue infections
● Coagulase (-)

A

S. lugdunensis

107
Q

This organism is more virulent than other and is known to contain the gene mecA, which encodes oxacillin resistance

A

S. lugdunensis

108
Q

Causes an aggressive type of endocarditis

A

S. lugdunensis

109
Q

Positive for the clumping factor for the Slide Coagulase Test

A

S. lugdunensis

110
Q

OTHER STAPHYLOCOCCI

Staph in scalp

A

S. capitis

111
Q

OTHER STAPHYLOCOCCI

is a commonly isolated CoNS. It has been reported in wounds, bacteremia, endocarditis, and UTIs. Vancomycin resistance exists

A

S. haemolyticus

112
Q

OTHER STAPHYLOCOCCI

In dogs

A

S. intermedius

113
Q

OTHER STAPHYLOCOCCI

In dolphins

A

S. delphini

114
Q

LABORATORY DIAGNOSIS

T/F: Aspirates are preferred (especially if there is inflammation); if swabs are submitted, it must be at least 2 (in duplicates)

A

T

114
Q

LABORATORY DIAGNOSIS

● Expect to find gram (+) cocci in clusters, singly, or in pairs
● Inflammation: you will find abundant neutrophils
● After doing the gram stain, you will be applying it to the culture medium

A

Direct Detection (Gram Stain)

114
Q

CULTURE MEDIA FOR ISOLATION AND IDENTIFICATION

To see if there is a hemolytic pattern

A
115
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

○ To allow only gram (+) cocci to grow in the medium
○ CCNA: Selective for gram (+)

A

SELECTIVE: CCNA, PEA

116
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

● Generally: round, Smooth, White or Yellow pigmented,
creamy colonies with smooth edges
● To check hemolytic pattern

A

BAP

116
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

■ Usually has mauve or pink coloration in colonies;
presumptive for S.aureus
■ Other than S.aureus will grow as blue organisms
■ Differentiates S. aureus from other organisms

A

SELECTIVE & DIFF: CHROMagar

117
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

Differentiates mannitol fermenters from the
non-mannitol fermenters

A

MSA

117
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

Non-mannitol fermenter result

A

Pink (S. epidermidis)

117
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

T/F: S. aureus is a beta hemolysis

A

T

117
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

Has phenol red as indicator

A

MSA

118
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

Mannitol fermenter result (color, pH, and example)

A

Yellow, acidic, S. aureus

119
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

BAP : Medium sized colonies; Beta-hemolytic

A

S. lugdunensis

119
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

BAP : small-medium sized, gray colonies; nonhemolytic or gamma hemolytic

A

S. epidermidis

120
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

BAP : Medium-sized colonies, yellow pigmented colonies

A

S. saprophyticus

121
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

For isolation and direct differentiation of Staphylococcus aureus in clinical and industrial sample

A

CHROMagar

122
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

T/F: On CAP, S. aureus has pinhead colonies with greenish discoloration

A

T

123
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

T/F: MSA

● Staphylococcus epidermidis (yellow)
● Staphylococcus aureus (pink)

A

F;
● Staphylococcus epidermidis (pink)
● Staphylococcus aureus (yellow)

124
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

CHROMagar:
○ Staphylococcus aureus → _________
○ Other bacteria are _________ or inhibited

A

pink to mauve
colorless, blue

125
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

Selective medium containing the antibiotic Cefoxitin, which inhibits other members of staph and allows the growth of S. aureus

A

CHROMagar

126
Q

CULTURE MEDIA FOR ISOLATION AND
IDENTIFICATION

CHROMagar that is very selective for MRSA

A

CHROMAgar Versa

127
Q

LABORATORY DIAGNOSIS

Detection of enzyme catalase

A

Catalase Test

128
Q

LABORATORY DIAGNOSIS

converts H2O2 to water and O2

A

Catalase

129
Q

LABORATORY DIAGNOSIS

Reagent for catalase tests

A

3% H2O2

130
Q

LABORATORY DIAGNOSIS

Important test to differentiate staphylococcus (+) and micrococcus (+) from streptococcus (-)

A

Catalase Test

131
Q

LABORATORY DIAGNOSIS

T/F: If doing catalase test, get colonies from blood agar plate

A

F; AVOID GETTING FROM BAP

132
Q

LABORATORY DIAGNOSIS

Oxidase reagent reacts with cytochrome C in the cytochrome oxidase

A

Modified Oxidase Test

133
Q

LABORATORY DIAGNOSIS

Uses filter paper; get a loopful of the specimen then apply on the filter paper then drop the reagent

A

Modified Oxidase Test

134
Q

LABORATORY DIAGNOSIS

Reagent used in modified oxidase test

A

6% tetramethyl phenylenediamine HCl in
dimethyl sulfoxide (DMSO)

135
Q

LABORATORY DIAGNOSIS

Positive result for Modified Oxidase Test

A

Dark Blue

136
Q

LABORATORY DIAGNOSIS

Differentiates staphylococcus (most members are (-) from micrococcus (+)

A

Modified Oxidase Test

137
Q

LABORATORY DIAGNOSIS

T/F: MOT : Staphylococcus are negative except for three species
■ S. sciuri
■ S. lentus
■ S. vitulinus

A

T

138
Q

LABORATORY DIAGNOSIS

T/F: Use nichrome or iron loops in MOT

A

F; DO NOT USE. False (+) and iron is a component of the cytochrome. Use applicator stick or plastic loop instead

139
Q

LABORATORY DIAGNOSIS

Detection of staphylocoagulase (coagulase)

A

Coagulase Test

140
Q

LABORATORY DIAGNOSIS

Coagulase Test Reagent

A

Rabbit Plasma

141
Q

LABORATORY DIAGNOSIS

● For screening
● Detect bound coagulase or clumping factor (sand-like)

A

Slide Coagulase

142
Q

LABORATORY DIAGNOSIS

Positive & negative result for slide coagulase

A

P : Grainy / Clumping
N : Homogenous / No Clumping

143
Q

LABORATORY DIAGNOSIS

● Detection of free coagulase enzyme
● Will not confirm if it is coagulase positive because this test would have many false positive result

A

Slide Coagulase

144
Q

LABORATORY DIAGNOSIS

T/F: Rabbit plasma are added in Slide Coagulase then add colony from MSA, not BAP & CAP

A

F; colony from BAP & CAP, not MSA

145
Q

LABORATORY DIAGNOSIS

T/F: In slide coagulase, high amounts of salt can interfere with the test

A

T

146
Q

LABORATORY DIAGNOSIS

● Confirms if the test is really coagulase positive
● Detects free coagulase
● More specific

A

Tube Coagulase

147
Q

LABORATORY DIAGNOSIS

Tube Coagulase (+) result

A

Clot formation

148
Q

LABORATORY DIAGNOSIS: TUBE COAGULASE

T/F: If 4 hours, there is still no clot formation, that is not yet a negative result. Continue the incubation at room temperature. After 20 hrs from the time you put it at room temperature, check again if there is already a clot. If there is, it is positive, if there is no clot formed, it is negative

A

T

148
Q

LABORATORY DIAGNOSIS: TUBE COAGULASE

Prepare a test tube, add colony on rabbit plasma, incubate the tube for ____ hrs at ___ C. Every 30 minutes, check if it is coagulase positive

A

4 hours at 37 degrees C

149
Q

LABORATORY DIAGNOSIS

Why don’t we just put the tube in the incubator for 24
hours?

A

Clot will be dissolved by Staphylokinase or Staphylococcal fibrinolysin or Muller’s Factor

150
Q

LABORATORY DIAGNOSIS

Result when the clot is destroyed by Staphylokinase

A

False negative

151
Q

LABORATORY DIAGNOSIS

Oxidation Fermentation Test color for fermenter in open and oxidizer in closed tube

A

O : Yellow
C: No color (oxidizer; can be microccocus)

151
Q

LABORATORY DIAGNOSIS

● To differentiate organisms based on the ability to oxidize or ferment sugars
● Use of OF Medium

A

Oxidation Fermentation Test

151
Q

LABORATORY DIAGNOSIS

DNAse Test positive result

A

Hydrolysis of surrounding medium (clear zone)

151
Q

LABORATORY DIAGNOSIS

Would react with a thermostable thrombin like molecule (coagulase reacting factor)

A

Tube Coagulase

152
Q

LABORATORY DIAGNOSIS

● Detection of DNAse activity
● Useful to identify S. aureus
● Use of special DNA Agar

A

DNAse Test

152
Q

LABORATORY DIAGNOSIS

DNA agar contains (2)?

A

DNA & toluidine blue / methyl green

153
Q

LABORATORY DIAGNOSIS

DNAse reagent

A

Toluidine Blue or Methyl Green

154
Q

LABORATORY DIAGNOSIS

Gelitinase Liquefaction Test (-)

A

Not melted

154
Q

LABORATORY DIAGNOSIS

● Makes use of 12% gelatin in a tube medium where the suspected organism is inoculated
● Incubate for 4-5 days

A

Gelitinase Liquefaction Test

155
Q

LABORATORY DIAGNOSIS

Formation of acetoin from glucose (Butylene Glycol
Pathway)

A

Voges Proskauer Test

156
Q

LABORATORY DIAGNOSIS

Gelitinase Liquefaction Test (+)

A

Liquified - S. aureus

157
Q

LABORATORY DIAGNOSIS

is a byproduct of the metabolism of glucose
following the Butylene Glycol Pathway

A

Voges Proskauer Test

158
Q

LABORATORY DIAGNOSIS

Useful test to differentiate Coagulase-negative
Staphylococcus (CONS)

A

Novobiocin (5ug) Susceptibility

158
Q

LABORATORY DIAGNOSIS

● Differentiates Coagulase (+) Staphylococcus
● Can differentiate S. aureus from S. intermedius

A

Voges Proskauer Test

158
Q

LABORATORY DIAGNOSIS

Voges Proskauer Test (+)

A

Red coloration in MRVP broth

159
Q

LABORATORY DIAGNOSIS

● Differentiates Coagulase (+) Staphylococcus
● Used to differentiate S. aureus (-) from S. lugdunensis, S. intermedius, and S. schleiferi (+).

A

PYR (Pyrrolidonyl) Test

160
Q

LABORATORY DIAGNOSIS

PYR (Pyrrolidonyl) Test (+)

A

Pink or Cherry-Red Color

161
Q

LABORATORY DIAGNOSIS

Urine isolates that are coagulase-negative are tested further to identify S. saprophyticus.

A

Novobiocin (5ug) Susceptibility

162
Q

LABORATORY DIAGNOSIS

is resistant to novobiocin

A

S. saprophyticus

162
Q

LABORATORY DIAGNOSIS

T/F: Most CoNS are susceptible (usually S. epidermidis) to Novobiocin

A

T

163
Q

LABORATORY DIAGNOSIS

Most useful test for confirming S. lugdunensis

A

Ornithine Decarboxylase Test

163
Q

LABORATORY DIAGNOSIS

Helpful for Coagulase Negative Staphylococcus

A

Susceptibility to Polymyxin B (300 Units)

164
Q

LABORATORY DIAGNOSIS

Ornithine Decarboxylase Test (+)

A

Violet Coloration on OCD Tube

165
Q

LABORATORY DIAGNOSIS

T/F: S. lugdunensis is also usually slide coagulase-positive, however, we don’t consider it coagulase-positive

A

T

166
Q

LABORATORY DIAGNOSIS

T/F: After slide coagulase test, S. lugdunensis should be confirmed through tube coagulase test

A

T

167
Q

LABORATORY DIAGNOSIS

Identify certain species of Staphylococcus

A

Urease Production

168
Q

RAPID METHODS FOR DIAGNOSIS

To differentiate S. aureus from CONS (Coagulase
Negative Staphylococci). A variation or an improvement of the slide coagulase test

A

Commercially Available Rapid Agglutination Kits

169
Q

RAPID METHODS FOR DIAGNOSIS

● Use of plasma coated latex beads
● More specific and sensitive from traditional methods
● Useful for identification of MRSA

A

Commercially Available Rapid Agglutination Kits

170
Q

RAPID METHODS FOR DIAGNOSIS

Negative results should be confirmed with the tube
coagulase test, nucleic acid amplification test, or
MALDI-TOF

A

Commercially Available Rapid Agglutination Kits

171
Q

RAPID METHODS FOR DIAGNOSIS

T/F: Third-generation agglutination kits contain antibodies that bind capsular antigens 5 and 8, or other surface
molecules. Thus, these assays are more sensitive but less specific – false positive results

A

T

172
Q

RAPID METHODS FOR DIAGNOSIS

To identify the presence of certain genes, such as the
mecA gene, to confirm MRSA & MSSA

A

Molecular Methods

173
Q

RAPID METHODS FOR DIAGNOSIS

Able to directly identify staphylococci from a positive blood culture sample as an aid in the diagnosis of sepsis and for targeted antimicrobial therapy treatment.

A

Molecular Methods

174
Q

RAPID METHODS FOR DIAGNOSIS

Gold standard for MRSA

A

Detection of mecA gene - RT-PCR

175
Q

RAPID METHODS FOR DIAGNOSIS

Cannot distinguish genetic differences, such as MRSA versus MSSA strains.

A

MALDI-TOF

176
Q

RAPID METHODS FOR DIAGNOSIS

● A rapid diagnostic method that can identify antibiotic
susceptibility
● Automated machine to identify organisms

A

MALDI-TOF

177
Q

DETECTION OF RESISTANCE: MRSA

Recommended for screening MRSA

A

Cefoxitin Test

178
Q

DETECTION OF RESISTANCE: MRSA

Found in patients who lack traditional healthcare-associated risk factors, such as recent hospitalization, long-term care, hemodialysis, or indwelling devices

A

Community-acquired MRSA (CA-MRSA)

179
Q

DETECTION OF RESISTANCE: MRSA

○ Infection and outbreaks have been reported in
athletes, military recruits in close contact
environments, correctional facility inmates, pediatric
patients, and tattoo recipients.
○ Can cause nosocomial infections

A

Community-acquired MRSA (CA-MRSA)

180
Q

DETECTION OF RESISTANCE: MRSA

Drug of choice

A

Vancomycin

181
Q

DETECTION OF RESISTANCE: MRSA

Using oxacillin and with 2-4% NaCl; growth indicates methicillin resistance

A

MRSA Screen Agar

182
Q

DETECTION OF RESISTANCE: MRSA

T/F: MRSA isolates should be considered susceptible to all βlactam antibiotics, including the carbapenems, except for fifth-generation cephalosporins with MRSA activity

A

F; resistant

183
Q

DETECTION OF RESISTANCE

Detection with the use of oxacillin disks and cefoxitin

A

MRSE

184
Q

DETECTION OF RESISTANCE

● Screen plates with 2-4% NaCl
● Use of ChromAGAR

A

MRSE

185
Q

DETECTION OF RESISTANCE

Gold standard for MRSE

A

Detection of mecA gene

186
Q

DETECTION OF RESISTANCE

Use of vancomycin agar plate (spot inoculation) for
screening

A

VRSA

187
Q

DETECTION OF RESISTANCE

MIC for VRSA

A

: ≥16 μg/mL

188
Q

DETECTION OF RESISTANCE

MIC for Cefoxitin & Oxacillin

A

C : ≥8 μg/L
O : ≥4 μg/L

189
Q

DETECTION OF RESISTANCE

Detection of resistance to macrolides such as clindamycin

A

Macrolide Resistance

190
Q

DETECTION OF RESISTANCE

T/F: Staphylococcal resistance to clindamycin is occasionally inducible, meaning it is only detectable in vitro when the
bacteria is exposed to erythromycin

A

T

191
Q

DETECTION OF RESISTANCE

Macrolide Resistance Method

A

D-Zone Test

192
Q

DETECTION OF RESISTANCE: MACROLIDE RESISTANCE

Place erythromycin and clindamycin disk close together (____ distance between the two disks)

A

15 mm

[MT 6320] Clinical Bacteriology Lecture (8 decks)

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