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Catalase postive, gram positive cocci Flashcards

staphylococcus, Micrococcus and similar organisms

1
Q

What Gram stain result is typical for the Micrococcaceae family?

A

Gram positive.

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2
Q

What shape are bacteria in the Micrococcaceae family?

A

Cocci (spherical).

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3
Q

What is the catalase activity of the Micrococcaceae family?

A

Catalase positive.

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4
Q

What are the oxygen requirements for most members of the Micrococcaceae family?

A

Aerobic or facultative anaerobic.

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5
Q

Which two bacteria in the Micrococcaceae family are obligate anaerobes and catalase negative?

A

Staphylococcus aureus subsp. anaerobius and Staphylococcus saccharolyticus.

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6
Q

Where are most Micrococcaceae family members commonly found?

A

As members of the indigenous flora.

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7
Q

What Gram stain result is typical for the Staphylococcus genus?

A

Gram positive

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8
Q

What is the catalase activity of the Staphylococcus genus?

A

Catalase positive.

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9
Q

Are Staphylococcus bacteria motile or nonmotile?

A

Nonmotile.

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10
Q

What are the oxygen requirements for the Staphylococcus genus?

A

Facultative anaerobes.

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11
Q

How are species within the Staphylococcus genus initially differentiated?

A

By the coagulase test.

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12
Q

What family?

Gram Stain: Positive
Shape: Cocci
Catalase: Positive
Oxygen Requirement: Aerobic or facultative anaerobic

A

Micrococcaceae Family

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13
Q

What genus?
Gram Stain: Positive
Catalase: Positive
Motility: Nonmotile
Oxygen Requirement: Facultative anaerobes

A

Staphylococcus Genus

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14
Q

what organism?
Characteristics:
Gram Stain: Gram-positive cocci in grape-like clusters
Catalase: Positive
Coagulase: Positive
Hemolysis: β-hemolytic
Colony Appearance: Yellow or golden colonies on blood agar
Fermentation: Ferments mannitol

A

Staphylococcus aureus

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15
Q

What is the Gram stain result and typical arrangement of Staphylococcus aureus?

A

Gram-positive cocci in grape-like clusters.

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16
Q

Gram-positive cocci in grape-like clusters.

what organism?

A

Staphylococcus aureus

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17
Q

Is Staphylococcus aureus catalase positive or negative?

A

Catalase positive.

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18
Q

Is Staphylococcus aureus coagulase positive or negative?

A

Coagulase positive.

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19
Q

What type of hemolysis does Staphylococcus aureus exhibit?

A

β-hemolytic.

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20
Q

What is the appearance of Staphylococcus aureus colonies on blood agar?

A

Yellow or golden colonies due to staphyloxanthin.

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21
Q

The appearance of Staphylococcus aureus colonies on blood agar is Yellow or golden colonies due to

A

Staphyloxanthin

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22
Q

Does Staphylococcus aureus ferment mannitol?

A

Yes, it ferments mannitol.

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23
Q

Name three common habitats of Staphylococcus aureus.

A

Anterior nares, nasopharynx, and perineal area.

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24
Q

Can Staphylococcus aureus colonize the skin?

A

Yes, it can colonize the skin.

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25
Q

Is Staphylococcus aureus found as a colonizer of mucosa?

A

Yes, it is a colonizer of mucosa.

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26
Q

How can Staphylococcus aureus from an endogenous strain be transmitted to a sterile site?

A

By traumatic introduction.

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27
Q

How is Staphylococcus aureus transmitted through direct contact?

A

Through person-to-person contact or fomites.

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28
Q

How is Staphylococcus aureus transmitted through indirect contact?

A

Through aerosolized particles.

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29
Q

What is the role of the polysaccharide capsule in Staphylococcus aureus?

A

It inhibits phagocytosis.

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30
Q

what virulence of Staphylococcus aureus allows the organism to adhere to inorganic surfaces and inhibits the penetration of antibiotics.

A

slime layer or biofilm

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31
Q

What immune responses are activated by peptidoglycan in Staphylococcus aureus?

A

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

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32
Q

what virulence factor of Staphylococcus aureus decreases the immune-mediated clearance of organisms from the site of infection.

A

Protein A

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33
Q

What is the significance of coagulase in Staphylococcus aureus?

A

It is a major virulence factor that builds an insoluble fibrin capsule.

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34
Q

what virulence factor of Staphylococcus aureus prevents the spread of infection by hydrolyzing hyaluronic acid.

A

Hyaluronidase

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35
Q

what virulence factor of Staphylococcus aureus acilitates colonization on the skin surface and spreads in fat-containing areas of the body.

A

Lipase

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36
Q

What type of hemolysis is associated with Staphylococcus aureus?

A

Alpha and beta hemolysis, which cause hemolysis of red blood cells

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37
Q

What is the effect of Panton-Valentine Leukocidin (PVL) in Staphylococcus aureus?

A

It is toxic to white blood cells (WBCs).

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38
Q

what are the 8 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)

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39
Q

What toxin in S. aureus Disrupts smooth muscles in blood vessels and is toxic to erythrocytes, leukocytes, hepatocytes, and platelets.

A

Alpha toxin

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40
Q

What toxin in S. aureus works in conjunction with alpha toxin and catalyzes the hydrolysis of membrane phospholipids, leading to cell lysis.

A

beta toxin

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41
Q

What toxin in S. aureus is cytolytic to erythrocytes and has nonspecific membrane toxicity to other mammalian cells.

A

delta toxin

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42
Q

Which toxin in Staphylococcus aureus is associated with Panton-Valentine leucocidin (PVL)?

A

Gamma toxin.

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43
Q

what toxin in S. aureusis resistant to hydrolysis by gastrointestinal (GI) enzymes, found in milk products, and associated with enterocolitis and toxic shock syndrome.

A

heat stable enterotoxin

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44
Q

What is the role of Toxic Shock Syndrome Toxin (TSST-1) in Staphylococcus aureus infections?

A

It acts as a superantigen leading to toxic shock syndrome.

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45
Q

What type of enzyme is the exfoliative toxin in Staphylococcus aureus and what is its effect?

A

It is a serine protease that splits the intracellular bridges of the epidermis.

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46
Q

What are the main toxins involved in staphylococcal food poisoning?

A

Staphylococcal enterotoxins A and D.

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47
Q

How is staphylococcal food poisoning typically transmitted?

A

Through ingestion of food contaminated by an infected food handler.

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48
Q

How soon do symptoms of staphylococcal food poisoning appear and resolve?

A

Symptoms appear within 2-6 hours and resolve within 8-10 hours.

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49
Q

What is the most common cause of septic arthritis in prepubertal children?

A

Staphylococcus aureus.

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50
Q

How does Staphylococcus aureus cause osteomyelitis and septic arthritis?

A

Through hematogenous spread or local introduction at a wound site.

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51
Q

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

A

Brodie abscess

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52
Q

What is a common cause of nosocomial pneumonia?

A

Staphylococcus aureus.

53
Q

How does Staphylococcus aureus pneumonia typically develop?

A

It usually follows aspiration of endogenous nasopharyngeal organisms.

54
Q

What are some predisposing factors for Staphylococcus aureus pneumonia?

A

Measles, influenza A virus, cystic fibrosis, and immune deficiency

55
Q

Which population is commonly affected by acute endocarditis caused by Staphylococcus aureus?

A

Individuals with left-sided valvular heart disease and IV drug users.

56
Q

What is a common target of Staphylococcus aureus in IV drug users?

A

The tricuspid valve.

57
Q

What type of infections are commonly associated with community-acquired Staphylococcus aureus?

A

Serious soft tissue infections.

58
Q

What is a notable virulence factor associated with community-acquired MRSA (CA-MRSA)?

A

Panton-Valentine leucocidin (PVL).

59
Q

What population is primarily affected by Scalded Skin Syndrome (Ritter’s Disease)?

60
Q

Which toxin is responsible for Scalded Skin Syndrome (Ritter’s Disease)?

A

Exfoliative toxin

61
Q

What is the mortality rate for Scalded Skin Syndrome in children versus adults?

A

Low in children but high in adults.

62
Q

Which toxin is associated with Toxic Shock Syndrome (TSS)?

A

Enterotoxin F (TSST-1).

63
Q

What is a common association with Toxic Shock Syndrome in women?

A

Tampon use.

64
Q

Can Toxic Shock Syndrome occur in both sexes?

A

Yes, if a toxin-producing strain has caused the infection.

65
Q

What is observed under microscopy for Staphylococcus aureus?

A

Numerous gram-positive cocci in clusters with polymorphonuclear cells.

66
Q

Describe the colony characteristics of Staphylococcus aureus on sheep blood agar.

A

Round, smooth, white or pigmented (yellow-orange), and β-hemolytic.

67
Q

what organism has Round, smooth, white or pigmented (yellow-orange), and β-hemolytic in SBA

A

Staphylococcus aureus

68
Q

What is the purpose of using phenylethyl alcohol (PEA) or Columbia colistin-nalidixic acid (CAN) agar in the cultivation of Staphylococcus aureus?

A

To inhibit the growth of gram-negative bacteria.

69
Q

How does mannitol salt agar differentiate Staphylococcus aureus from other staphylococci?

A

S. aureus ferments mannitol, leading to yellow colonies due to the pH indicator phenol red.

70
Q

What does the CHROMagar medium indicate when mauve-colored colonies are observed?

A

The presence of MRSA (methicillin-resistant Staphylococcus aureus).

71
Q

What is the purpose of the coagulase test in the laboratory diagnosis of Staphylococcus aureus?

A

To separate S. aureus from other coagulase-negative staphylococci.

72
Q

What indicates a positive result in the bound coagulase (clumping factor) test?

A

Clumping observed in the rapid slide test.

73
Q

What indicates a positive result in the extracellular coagulase (free coagulase) test?

A

Formation of a clot 1-4 hours after inoculation in the tube coagulase test.

74
Q

what lab diagnosis detects bound coagulase or clumping factor.

A

slide test

75
Q

What indicates a positive result in the slide coagulase test?

A

Macroscopic clumping in 10 seconds or less.

76
Q

Confirmatory test of slide test

77
Q

What does the tube coagulase test detect?

A

The tube test detects free coagulase.

78
Q

What indicates a positive result in the tube coagulase test?

A

formation of a clot of any size.

79
Q

How should the tube coagulase test be handled if no clot is observed after 4 hours?

A

Incubate at room temperature overnight and check again for clot formation.

80
Q

What is the purpose of the catalase test in differentiating bacterial species?

A

t differentiates catalase-positive micrococcal and staphylococcal species from catalase-negative streptococcal species.

81
Q

What indicates a positive catalase test?

A

Copious bubbles are produced when hydrogen peroxide is added.

82
Q

What are antibodies to teichoic acid used to detect in serodiagnosis?

A

They are used to detect long-standing or deep-seated staphylococcal infections such as osteomyelitis.

83
Q

What components are targeted in serodiagnostic tests for Staphylococcus aureus?

A

Staphylococcal toxins and other staphylococcal proteins, such as Protein A.

84
Q

Are coagulase-negative staphylococci considered normal flora in humans and animals?

A

Yes, coagulase-negative staphylococci are normal flora in humans and animals.

85
Q

What are some predisposing factors for infections caused by coagulase-negative staphylococci?

A

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

86
Q

What are the most common species of coagulase-negative staphylococci isolated in clinical settings?

A

The most common species isolated are Staphylococcus epidermidis and Staphylococcus saprophyticus.

87
Q

What type of colonies does Staphylococcus epidermidis produce on blood agar?

A

It produces whitish, non-hemolytic colonies on blood agar.

88
Q

SBA: It produces whitish, non-hemolytic colonies on blood agar.

A

Staphylococcus epidermidis

89
Q

How does Staphylococcus epidermidis differ from Staphylococcus aureus in terms of coagulase production?

A

Staphylococcus epidermidis is coagulase-negative, whereas Staphylococcus aureus is coagulase-positive.

90
Q

What is the sensitivity of Staphylococcus epidermidis to novobiocin?

A

Staphylococcus epidermidis is novobiocin sensitive.

91
Q

Where is Staphylococcus epidermidis commonly found in the human body?

A

skin and mucous membranes

92
Q

What are the primary modes of transmission for Staphylococcus epidermidis infections?

A

Infections are often endogenous, arising from the patient’s own flora, particularly after implantation of medical devices, and can also be transmitted through direct contact.

93
Q

What is a distinguishing feature of Staphylococcus epidermidis colonies compared to other staphylococci?

A

Staphylococcus epidermidis colonies are whitish and non-hemolytic on blood agar, and it is sensitive to novobiocin

94
Q

what are the virulence factors of S. epidermidis

A

Polysaccharide capsule
Slime layer or biofilm
Peptidoglycan
Delta toxin

95
Q

True or false:
Staphylococcus epidermidis is less virulent than Staphylococcus aureus.

96
Q

What is the most commonly encountered CoNS

A

Staphylococcus epidermidis

97
Q

In what settings is Staphylococcus epidermidis most commonly encountered?

A

It is most commonly encountered in healthcare settings, associated with medical procedures and practices.

98
Q

What type of infections is Staphylococcus epidermidis commonly associated with in patients with medical devices?

A

Staphylococcus epidermidis is commonly associated with infections related to the implantation of medical devices, such as bacteremia, endocarditis, and septic arthritis.

99
Q

What appearance would you expect to see under the microscope when identifying Staphylococcus epidermidis?

A

Numerous gram-positive cocci in clusters.

100
Q

SBA: Small to medium-sized, opaque, gray-white colonies; most colonies are non-hemolytic.

A

Staphylococcus epidermidis

101
Q

What is the novobiocin sensitivity profile of Staphylococcus saprophyticus?

A

Novobiocin resistant.

102
Q

Difference of S. epidermidis and S. saprophyticus

A

Novobiocin susceptibility testing

103
Q

Virulence factor of Staphylococcus saprophyticus

A

Peptidoglycan

104
Q

In which population is Staphylococcus saprophyticus a common cause of urinary tract infections?

A

Young, sexually active females

105
Q

Is Staphylococcus saprophyticus commonly associated with health care-associated infections similar with S. epidermidis?

A

No, it is not associated with health care-associated infections

106
Q

What is the rank of Staphylococcus saprophyticus as a cause of urinary tract infections in young females?

A

It is the second most common cause of UTIs, after E. coli.

107
Q

Sheep Blood Agar; colonies are large, glossy, smooth, opaque, butyrous, convex, and usually white but can range from yellow to orange.

A

Staphylococcus saprophyticus

108
Q

How is Staphylococcus saprophyticus identified using Novobiocin susceptibility testing?

A

S. saprophyticus is resistant to Novobiocin, whereas other coagulase-negative staphylococci are susceptible.

109
Q

What is the significance of using a 5mg Novobiocin disk in the laboratory diagnosis of Staphylococcus saprophyticus?

A

It helps differentiate S. saprophyticus from other coagulase-negative staphylococci based on resistance or susceptibility to Novobiocin.

110
Q

What is a common clinical misidentification issue with Staphylococcus intermedius?

A

It may be misidentified as S. aureus if only coagulase testing is performed.

111
Q

Which coagulase-positive staphylococcus is commonly associated with skin infections in dogs?

A

Staphylococcus pseudintermedius.

112
Q

What coagulase-positive staphylococci produce clumping factor and may give a positive slide coagulase test?

A

Staphylococcus lugdunensis and Staphylococcus schleiferi.

113
Q

Where can Micrococcus be found as part of the normal flora?

A

Skin, respiratory tract, and other sites in the body.

114
Q

What is the coagulase result for Micrococcus?

A

Coagulase-negative

115
Q

What is the result of the modified oxidase test for Micrococcus?

A

Modified oxidase positive, showing a dark blue color within 2 minutes.

116
Q

How is Micrococcus tested for bacitracin susceptibility?

A

By applying a 0.04 U bacitracin disk on sheep blood Mueller-Hinton medium and observing for a zone of inhibition.

117
Q

What is the result of the bacitracin susceptibility test for Micrococcus?

A

Micrococcus is susceptible to bacitracin, showing a clear zone of inhibition.

118
Q

How does Micrococcus respond to the furazolidone susceptibility test?

A

Micrococcus is resistant to furazolidone, with no zone of inhibition.

119
Q

What reagent is used in the modified oxidase test for Micrococcus?

A

6% tetramethylphenylene diamine hydrochloride in dimethyl sulfoxide.

120
Q

What percentage of Staphylococcus aureus isolates are typically resistant to penicillin?

A

About 85-90%.

121
Q

What enzyme do Staphylococci produce that contributes to resistance against β-lactam antibiotics?

A

β-lactamase.

122
Q

What is the term used for methicillin-resistant Staphylococcus aureus?

A

MRSA (Methicillin-Resistant Staphylococcus aureus) or ORSA (Oxacillin-Resistant Staphylococcus aureus)

123
Q

Why is vancomycin used in the treatment of MRSA infections, and what is the current challenge with this treatment?

A

Vancomycin is used as an alternative treatment for MRSA infections, but vancomycin resistance is increasing.

124
Q

What is the resistance characteristic of Methicillin-Resistant Staphylococcus epidermidis (MRSE)?

A

MRSE is resistant to methicillin and is also referred to as Oxacillin-Resistant Staphylococcus epidermidis (ORSE).

125
Q

Cocci
Gram +
Catalase +
Coagulase +

A

Staphylococcus aureus

126
Q

Cocci
Gram +
Catalase -

A

Steptococci

127
Q

Cocci
Gram +
Catalase +
Coagulase -
Modified oxidase +
Bacitracin susceptibility (S)

A

Micrococcus

128
Q

Cocci
Gram +
Catalase +
Coagulase -
Modified oxidase -
Bacitracin susceptibility (R)

A

Coagulase negative staphylococcus

Microbio (5 decks)

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