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CLINICAL BACTERIOLOGY > Staphylococcus, Micrococcus, and Similar Organisms > Flashcards

Staphylococcus, Micrococcus, and Similar Organisms Flashcards

1
Q

General characteristics of Staphylococcus

A
  1. Catalase-producing gram (+) cocci
  2. Nonmotile, non–spore-forming
  3. Aerobic or facultative anaerobic except for S. aureus subsp. anaerobius and S. sacchrolyticus
  4. Spherical cells (0.5 to 1.5 μm) that appear singly, in pairs, and in clusters
  5. Normal inhabitants of skin, mucous membranes and intestines
  6. On BAP, the colonies are medium sized (4 to 8 mm) and appear cream-colored, white or rarely light gold, and “buttery-looking”
  7. Other spp. may have gray colonies; some may be β-hemolytic (S. aureus)
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2
Q

A biochemical test used to separate Staphylococci (+), Micrococci (+), and Streptococci (-)

A

Catalase Test

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3
Q

Positive result of Catalase Test

A

Vigorous bubbling

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4
Q

Concentration of Hydrogen Peroxide (H2O2) used in Catalase Test for Staphylococci and Micrococci

A

3% H2O2

15% H2O2 used in anaerobes
30% H2O2 used in Mycobacterium and Neisseria

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5
Q

Why can’t we use colonies from BAP when performing Catalase Test?

A

BAP is positive for hemoglobin; hgb + H2O2 = bubbles (False positive)

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6
Q

Staphylococci are able to grow in what concentration of NaCl?

A

7.5-10% NaCl

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7
Q

Staphylococci are resistant in how many units of Bacitracin?

A

0.04 units

S. pyogenes is susceptible

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8
Q

Hemolytic pattern of Staphylococci on BAP

A

Beta-hemolytic

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9
Q

The most virulent species of staphylococci encountered

A

Staphylococcus aureus

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10
Q

General characteristics of Staphylococcus aureus

A

Most virulent
Normal flora of anterior nares and nasopharynx
Facultative anaerobe

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11
Q

Colony appearance of SAU in BAP

A

Creamy, white with pinhead colonies

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12
Q

Colony appearance of SAU in Tellurite agar/Vogel Johnson Medium

A

Jet-black colonies

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13
Q

Staphylococcus aureus is a true coagulase positive. True or False?

A

True

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14
Q

Appearance of SAU on solid media

A

Colonies are round, smooth, opaque and butyrous

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15
Q

Contain ribitol teichoic acid in cell wall

A

Teichoic Acid

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16
Q

Together with teichoic acid, it protects the bacteria from lysis and
probably aids in adherence

A

Peptidoglycan

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17
Q

Group specific antigen unique to S. aureus

A

Protein A

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18
Q

Prevents antibody-mediated phagocytosis by PMN—competes for the Fc portion

A

Protein A

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19
Q

Component on cell wall responsible for clumping of the whole
staphylococci in the presence of plasma

A

Clumping Factor

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20
Q

Protects SAU from phagocytosis

A

Capsular Polysaccharide

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21
Q

Coagulates fibrinogen in the plasma

A

Coagulase (Staphylocoagulase)

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22
Q

Promotes fibrin layer formation around the staphylococcal abscess protecting the bacteria from phagocytosis

A

Coagulase (Staphylocoagulase)

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23
Q

Two types of Coagulase (Staphylocoagulase)

A

Cell-bound Coagulase or Clumping Factor: bound to the cell wall and clots human, rabbit or pig plasma

Unbound or Free Coagulase: extracellular enzymes not bound to the cell wall and cause clot formation when bacterial cells are incubated with plasma

24
Q

Hydrolyzes hyaluronic acid present in the intracellular ground substance, permitting the spread of infection

A

Hyaluronidase (Spreading Factor)

25
Q

Hyaluronidase (Spreading Factor) is also known as

A

T Factor or DUran-Raynal Factor

26
Q

Fibrinolytic activities by dissolving fibrin clot and may enable infection to spread once the clot is dissolved

A

Staphylokinase (Fibrinolysin)

27
Q

Act on lipids present on the surface of the skin, particularly fats and oil
secreted by the sebaceous glands

A

Lipase (Fat-splitting Enzyme)

28
Q

Important in the formation of furuncles, carbuncles and boils

A

Lipase (Fat-splitting Enzyme)

29
Q

Lipase (Fat-splitting Enzyme) is produced by both coagulase (+) and coagulase (-) staphylococci. True or False?

A

True

30
Q

Destroys DNA and lowers viscosity of exudates giving the pathogen more mobility

A

Deoxyribonuclease (DNAse) and Phosphatase

31
Q

Deoxyribonuclease (DNAse) is also known as

A

Thermonuclease

32
Q

Breaks down Penicillin and β-lactam drugs

A

β-Lactamase

33
Q

Breaks down gelatin to produce an and-product amino acid

A

Gelatinase

34
Q

Breaks down peptide bonds in proteins

A

Protease

35
Q

Cytolytic toxins produced by SAU

A

Hemolysin
Leukocidins

36
Q

4 types of hemolysin

A

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

37
Q

Hemolysin that disrupts the smooth muscle in blood vessels and is toxic to erythrocytes, leukocytes, hepatocytes, and platelets

A

α-Hemolysin

38
Q

Predominant hemolysin

A

α-Hemolysin

39
Q

A heat-labile sphingomyelinase, which catalyzes the hydrolysis of membrane phospholipids resulting in cell lysis

A

β-Hemolysin (Sphingomyelinase C)

40
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)

41
Q

Hemolysin which is cytolytic to erythrocytes and demonstrates nonspecific membrane toxicity to other mammalian cells

A

δ-Hemolysin

42
Q

Produced by all S. aureus strain that cause RBC injury in culture and produce edematous lesions

A

δ-Hemolysin

43
Q

Hemolysin associated with Panton-Valentine leukocidin (PVL)

A

γ-Hemolysin

44
Q

Exotoxin lethal to polymorphonuclear leukocytes

A

Staphylococcal Leukocidin/ Panton-Valentine leukocidin

45
Q

Pore forming exotoxin that suppress phagocytosis and associated with severe cutaneous infections and necrotizing pneumonia

A

Staphylococcal Leukocidin/ Panton-Valentine leukocidin

46
Q

Characteristics of SAU enterotoxins

A
  1. Heat-stable exotoxin at 100° C for 30 minutes
  2. Resistant to hydrolysis by gastric and jejunal enzymes
  3. Act as neurotoxins that stimulate vomiting through the vagus nerve
  4. Produced by 30% to 50% of S. aureus isolates
47
Q

Toxic Shock Syndrome Toxin-1 (TSST-1) is also known as

A

Enterotoxin F
Pyrogenic Exotoxin C

48
Q

TSS associated with tampon use

A

Menstruating-associated TSS

49
Q

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

A

Exfoliative Toxin

50
Q

Causes Staphylococcal scalded skin syndrome/Ritter’s disease

A

Exfoliative Toxin

51
Q

Exfoliative Toxin is also known as

A

Epidermolytic toxin A and B or Exfoliatin serotypes A and B

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

A

Bullous Impetigo

CLINICAL BACTERIOLOGY (3 decks)

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