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MTAP FIRST SEM 2024-2025 > MICROBIOLOGY-CATALASE POSITIVE, GRAM-POSITIVE COCCI (STAPHYLOCOCCUS, MICROCOCCUS, AND SIMILAR ORGANISMS) > Flashcards

MICROBIOLOGY-CATALASE POSITIVE, GRAM-POSITIVE COCCI (STAPHYLOCOCCUS, MICROCOCCUS, AND SIMILAR ORGANISMS) Flashcards

1
Q
  • Gram positive cocci
  • Catalase positive
  • Aerobic or facultative anaerobic
  • Most are members of the indigenous flora and commonly isolated from a wide variety of diseases
A

Micrococcaceae

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2
Q

Name two species of the Micrococcaceae family that are obligate anaerobes.

A

Staphylococcus aureus subsp. anaerobius and Staphylococcus saccharolyticus

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3
Q

Are Staphylococcus aureus subsp. anaerobius and Staphylococcus saccharolyticus catalase positive or negative?

A

catalase negative

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4
Q
  • Gram-positive
  • Catalase-positive
  • Nonmotile
  • Facultative anaerobes
  • Species are initially differentiated by the coagulase test
A

Staphylococcus

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5
Q

What are the characteristics of Staphylococcus aureus

A
  • Gram-positive cocci in
    grape-like clusters
  • Catalase positive
  • Coagulase positive
  • β-hemolytic
  • Yellow or golden colonies on
    blood agar (staphyloxanthin)
  • Ferments mannitol
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6
Q

Where are common habitats of Staphylococcus aureus in the human body?

A
  • Anterior nares
  • Nasopharynx
  • Perineal area
  • Skin
  • Colonizer of
    mucosa
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7
Q

What are the modes of transmission for Staphylococcus aureus?

A
  • Endogenous strain: sterile site
    by traumatic introduction
  • Direct contact: person to
    person, fomites
  • Indirect contact: aerosolized
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8
Q

Identify

Inhibits phagocytosis

A

Polysaccharide capsule

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9
Q

Identify

Allows organism to adhere to inorganic surfaces or inhibits the penetration
of antibiotics

A

Slime layer or biofilm

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10
Q

Identify

Activates complement, interleukin 1 (IL-1), and acts as chemotactic factor for the recruitment of PMNs

A

Peptidoglycan

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11
Q

Identify

  • Surface protein
  • Bound to the cytoplasmic membrane of the organism
  • Decreases the immune-mediated clearance of organisms from the site of
    infection
A

Protein A

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12
Q

Identify

  • Major virulence factor of the specie
  • Builds and insoluble fibrin capsule
A

Coagulase

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13
Q

Identify

  • Prevents the spread of infection
  • Hydrolyzes hyaluronic acid
A

Hyaluronidase

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14
Q

Identify

  • Facilitates colonization on the skin surface
  • Spread in fat-containing areas of the body
A

Lipase

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15
Q

Identify

Hemolysis of RBCs

A

Alpha and beta hemolysis

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16
Q

Identify

Toxic to WBC

A

Panton-Valentine leucocidin (PVL)

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17
Q

IDENTIFY

  • Works in conjunction with alpha toxin
  • Catalyzes the hydrolysis of membrane phospholipids: cell lysis
A

Beta toxin

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18
Q

IDENTIFY

  • Cytolytic to erythrocytes
  • Nonspecific membrane toxicity to other mammalian cells
A

Delta toxin

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19
Q

IDENTIFY

  • Produced by all strains of S. aureus
  • Functions in association with Panton-Valentine leucocidin (PVL)
A

Gamma toxin

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20
Q

IDENTIFY

  • Resistant to hydrolysis by GI enzymes
  • Found in milk products
  • Associated with enterocolitis and toxic shock syndrome
A

Heat stable enterotoxin

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21
Q

IDENTIFY

  • Enterotoxin F
  • Superantigen leading to toxic shock syndrome
A

Toxic shock syndrome toxin (TSST-1)

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22
Q

IDENTIFY

  • Serine protease that splits the intracellular bridges of the epidermis
A

Exfoliative toxin or epidermolytic
toxin

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23
Q

IDENTIFY

  • Disrupts smooth muscles in blood vessels
  • Toxic to erythrocytes, leukocytes, hepatocytes, and platelets
A

Alpha toxin

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24
Q

Common SSTIs include?

A

folliculitis, furuncles, carbuncles, impetigo, mastitis, and surgical site infections.

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25
Q

is a toxin-mediated skin condition, usually affects neonates but can also occur in adults with chronic renal failure or those who are immunocompromised.

A

Scalded skin syndrome (Ritter’s disease)

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26
Q

A multisystem disease, characterized by high fever, rash, shock, hypotension, desquamation of the hands and feet, and potentially death.

A

Toxic shock syndrome (TSS)

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27
Q

What toxin is responsible for scalded skin syndrome?

A

exfoliative toxin

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28
Q

Which toxin is associated with toxic shock syndrome (TSS)

A

Enterotoxin F, also known as toxic shock syndrome toxin-1 (TSST-1).

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29
Q

TSS has been associated with tampon use in women

T or F

A

T

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30
Q

Can toxic shock syndrome (TSS) affect both sexes?

A

Yes, TSS can occur in both sexes

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31
Q

What are the primary toxins involved in Staphylococcus aureus food poisoning?

A

staphylococcal enterotoxins A and D heat-stable toxins

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32
Q

How soon do symptoms of Staphylococcus aureus food poisoning appear after ingestion? Symptoms usually resolve within?

A

-symptoms appear rapidly, typically 2-6 hours

-8-10 hours after onset.

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33
Q

occur through hematogenous spread or local introduction at a wound site and most common cause of septic arthritis in prepubertal children.

A

osteomyelitis and septic arthritis

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34
Q

Can Staphylococcus aureus be responsible for septic arthritis in adults?

T or F

A

T

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35
Q

sequestered focus of osteomyelitis arising in the metaphyseal area of the long bone

A

Brodie abscess

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36
Q

o Common cause of nosocomial pneumonia
o Usually followed by aspiration of endogenous nasopharyngeal organisms

A

Pneumonia

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37
Q

What are some predisposing factors for Staphylococcus aureus pneumonia?

A

include measles, influenza A virus, cystic fibrosis, and immune deficiency.

38
Q

Left-sided valvular heart disease and IV drug users (tricuspid valve)

A

Acute endocarditis

39
Q

what are the Community-associated infections

A

o Serious soft tissue infections
o Frequently mediated by methicillin resistant S. aureus (community-acquired
MRSA or CA-MRSA)
o Associated with PVL

40
Q

What is typically observed in microscopy for Staphylococcus aureus infections?

A

Numerous gram-positive cocci in clusters with polymorphonuclear cells are usually seen.

41
Q

What type of colonies does Staphylococcus aureus form on sheep blood agar?

A

Round, smooth, white or pigmented (yellow-orange) colonies that are β-hemolytic.

42
Q

Which selective media can be used for the isolation of Staphylococcus aureus?

A

Phenylethyl alcohol (PEA) agar and Columbia colistin-nalidixic acid (CAN) agar.

43
Q

a selective and differential medium used for the identification of methicillin-resistant Staphylococcus aureus (MRSA) and contains cefoxitin, to which MRSA is resistant

A

CHROMagar

44
Q

What color of colonies does Staphylococcus aureus form on CHROMagar?

A

mauve-colored

45
Q

what is the concentration, carbohydrate present and pH indicator of mannitol salt agar?

A

High concentration of salt (10%)
Carbohydrate: mannitol
pH indicator: phenol red

46
Q

primary purpose of the Coagulase Test?

A

To separate Staphylococcus aureus from other species collectively referred to as coagulase-negative staphylococci.

47
Q

What are the two types of coagulase produced by Staphylococcus aureus?

A

Bound coagulase (clumping factor) and extracellular coagulase (free coagulase).

48
Q

How does the coagulase enzyme function in the Coagulase Test?

A

It binds to plasma fibrinogen, causing the plasma to clot.

49
Q

Which test is used to detect bound coagulase?

A

The rapid slide test.

50
Q

Which test is used to detect extracellular coagulase (free coagulase)?

A

The tube coagulase test.

51
Q

How long does it typically take for a positive result to appear in the tube coagulase test?

A

1-4 hours after inoculation.

52
Q

Differentiates catalase-positive micrococcal and staphylococcal species form
catalase-negative streptococcal species

A

Catalase test

53
Q

What is the function of the catalase enzyme in bacteria?

A

It converts hydrogen peroxide (H₂O₂) into water (H₂O) and oxygen (O₂).

54
Q

positive result for the Catalase Test?

A

copious bubbles

55
Q

negative result for the Catalase Test?

A

No or few bubbles are produced

56
Q

Which two species are the most common Coagulase-negative Staphylococci isolated in infections?

A

Staphylococcus epidermidis and Staphylococcus saprophyticus.

57
Q

What type of infections are Coagulase-negative Staphylococci often associated with?

A

associated with hospital-acquired infections.

58
Q

In which conditions are antibodies to teichoic acid commonly found?

A

In long-standing or deep-seated staphylococcal infections, such as osteomyelitis.

59
Q

What are some predisposing factors for CoNS infections?

A

Predisposing factors include catheterization, prosthetic device implants, and immunosuppressive therapy.

60
Q

How do CoNS compare in virulence to Staphylococcus aureus?

A

CoNS are less virulent than Staphylococcus aureus.

61
Q

VIRULENCE FACTORS OF STAPHYLOCOCCUS AUREUS

A

Polysaccharide capsule
Slime layer or biofilm
Peptidoglycan
Protein A
Coagulase
Hyaluronidase
Lipase
Alpha and beta hemolysis
Panton-Valentine leucocidin (PVL)

62
Q

CHARACTERISTICs of Staphylococcus
epidermidis

A
  • Gram-positive cocci in
    clusters
  • Catalase–positive
  • Coagulase-negative
  • Novobiocin sensitive
  • Whitish, non-hemolytic
    colonies on blood agar
63
Q

Where are common habitats of Staphylococcus epidermidis in the human body?

A
  • Skin
  • Mucous
    membranes
64
Q

What are the modes of transmission for Staphylococcus epidermidis

A
  • Endogenous strains:
    implantation of medical devices
    (shunts, prosthetic devices)
  • Direct contact: person-to person
65
Q

VIRULENCE FACTORS of Staphylococcus
epidermidis

A

-Polysaccharide capsule
-Slime layer or biofilm
-Peptidoglycan
-Delta toxin

66
Q

What is typically observed in microscopy for Staphylococcus epidermidis?

A

Numerous gram-positive cocci in clusters

67
Q

What type of colonies does Staphylococcus epidermidis form on sheep blood agar?

A

small to medium; opaque, gray-white colonies; most colonies are nonhemolytic; slime-producing strains are extremely sticky and adhere to agar surfaces

68
Q

Characteristics of Staphylococcus
saprophyticus

A
  • Gram-positive cocci in
    clusters
  • Catalase-positive
  • Coagulase-negative
  • Novobiocin resistant
  • Whitish, non-hemolytic
    colonies on blood agar
69
Q

Where are common habitats of Staphylococcus saprophyticus in the human body?

A
  • Skin
  • Genitourinary
    tract
  • Mucosa
70
Q
  • Community-acquired urinary tract infections in young, sexually active females
  • Not associated with health care-associated infections
  • Second most common cause of UTI (after E.coli) in young females
A

Staphylococcus saprophyticus

71
Q

What are the modes of transmission for Staphylococcus saprophyticus

A
  • Endogenous strain: sterile
    urinary tract (young sexually active females)
72
Q

VIRULENCE FACTOR NI Staphylococcus
saprophyticus

A

Peptidoglycan

73
Q

What type of colonies does Staphylococcus saprophyticus form on sheep blood agar?

A

large; entire very glossy, smooth, opaque butyrous, convex; usually white but colonies can be yellow to orange

74
Q

How many milligrams are used in a Novobiocin disk?

A

A 5mg Novobiocin disk is used.

74
Q

How does Staphylococcus saprophyticus differ from Staphylococcus epidermidis in Novobiocin susceptibility?

A

Staphylococcus saprophyticus is resistant, while Staphylococcus epidermidis is susceptible to Novobiocin.

75
Q

What are some coagulase-positive or variable staphylococci that are part of the normal microbiota of various animal species?

A

Staphylococcus intermedius, Staphylococcus pseudintermedius, and Staphylococcus delphini

75
Q

What reagent is used in the modified oxidase test?

A

6% tetramethyl phenylenediamine hydrochloride in dimethylsulfoxide + growth on filter paper

76
Q

Which staphylococcal species is an important agent in dog bite wound infections and may be misidentified as Staphylococcus aureus?

A

Staphylococcus intermedius.

77
Q

Identify

  • Environmental organisms
  • Gram-positive
  • Coagulase-negative
  • Low pathogenic significance
  • Normal flora in the respiratory tract or other sites in the body
A

Micrococcus

78
Q

What is the result of a positive modified oxidase test for Micrococci?

A

Dark blue color within 2 minutes.

79
Q

On what medium is the bacitracin susceptibility test performed?

A

Sheep blood Mueller-Hinton medium.

80
Q

How many unit of the bacitracin disk used in the susceptibility test?

A

0.04 U

81
Q

Micrococcus are resistant to bacitracin

T or F

A

F; Susceptible to bacitracin.

82
Q

How many micrograms of furazolidone used in the susceptibility test?

A

100 mcg

83
Q

What is the expected result for Micrococcus in the furazolidone susceptibility test?

A

Resistant to furazolidone.

84
Q

Identify

  • Normal oral flora
  • Rarely isolated from infection
  • Colonies adhere strongly to the agar surface
A

Stomatococcus

85
Q

What is the percentage of penicillin resistance in S. aureus isolates?

A

85-90%

86
Q

is an enzyme produced by Staphylococci that inactivates β-lactam antibiotics. It’s a common resistance mechanism.

A

β-lactamase

87
Q

-MRSA stands for?
-MRSE stands for?

A

-Methicillin-resistant S. aureus
-Methicillin-resistant S. epidermidis.

88
Q

-ORSA stands for?
-ORSE stands for

A

-Oxacillin-resistant S. aureus, which is another name for MRSA.
-Oxacillin-resistant S. epidermidis, another name for MRSE.

89
Q

What is the alternative treatment for MRSA and how effective is it?

A

Vancomycin is an alternative treatment for MRSA. However, vancomycin resistance has also been increasing.

90
Q

What kind of infections are MRSA known to cause?

A

MRSA are etiologic agents of serious nosocomial (hospital-acquired) and community-acquired infections.

MTAP FIRST SEM 2024-2025 (15 decks)

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