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Microbiology Lecture Slides > Gram (+) and Gram (-) Cocci I > Flashcards

Gram (+) and Gram (-) Cocci I Flashcards

1
Q

Factors that enable an organism to cause disease

A

Virulence factors

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2
Q

Adhesins/cell surface factors and secreted enzymes/toxins are examples of

A

Virulence factors

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3
Q

What are the three major genera of Gram (+) Cocci?

A

Staphylococci, streptococci, and enterococci

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4
Q

Gram-stains blue and the cells are in clusters like a bunch of grapes

A

Staphylococci

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5
Q

Are hardy bacteria, i.e. they are resistant to heat and drying

A

Staphylococci

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6
Q

Staphylococci persist on

A

Formites

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7
Q

Staphylococci are classified as

A

Factultative anaerobes

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8
Q

All pathogenic staphylococci are

A

Catalase (+)

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9
Q

Unlike streptococci, Staphylococci are

A

Catalase (+)

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10
Q

The catalase test is a quick method to distinguish between

A

Staphylococci and streptococci

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11
Q

The major pathogen of the staphylococci

A

S. aureus

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12
Q

S. aureus stands out from the other staphylococci because it is

A

Coagulase positive

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13
Q

All other pathogenic strains of staphylococci are

-Ex: S. epidermis and S. saprophyticus

A

Coagulase negative

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14
Q

Shows “Golden” colonies on agar

A

Staphylococcus aureus

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15
Q

Normal flora of the anterior nares in 1/3 of people

-most common bacterial human pathogen

A

S. aureus

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16
Q

What are the two cytotoxins of S. aureus?

A

Hemolysins and PVL (leukocidin)

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17
Q

What are the three superantigen toxins of S. aureus?

A

TSST-1, enterotoxin, and exfoliatin

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18
Q

What are the three invasins of S. aureus?

A

Staphylokinase, Collagenase, and Lipase

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19
Q

What are the three cell surface virulence factors of S. aureus?

A

Protein A. Capsule, and Adhesisn

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20
Q

Has an anti-opsoin effect by binding the Fc region of antibodies

A

Protein A

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21
Q

Facilitate attachment to host cells/connective tissue

A

Adhesins

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22
Q

S. aureus cytotoxin that lyses erythrocytes

A

Hemolysins (ex: a-Toxin)

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23
Q

S. aureus cytotoxin that lyses PMNs

A

Panton-Valentine Leukocidin (PVL)

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24
Q

Target mammalian cell membranes

A

S. aureus cytotoxins

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25
Q

Enzymes that facilitate penetration through extracellular tissue, eg. staphylokinase, hyaluronidase, lipase, DNase

A

“Spreading factors”/invasins

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26
Q

An example of enterotoxins is

A

Food poisoning

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27
Q

Skalded skin syndrome is an example of

A

Exfoliatin

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28
Q

Carriage rate for healthy adults is 20-30

A

S. Aureus

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29
Q

A very common hospital associated infection (facilitated by ability to persist on fomites)

A

S. aureus

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30
Q

Tissue injury, diabetes, immunodeficiency, and pre-existing primary infections are predisposition factors to

A

S. aureus infection

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31
Q

What are the 4 Skin and Soft Tissue Infections (SSTIs) that are common with S. aureus infection?

A
  1. ) Furuncles
  2. ) Carbuncles
  3. ) Impetigo
  4. ) Cellulitis
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32
Q

Small pus-filled local infections

A

Furuncles

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33
Q

Larger skin abcesses

A

Carbuncles

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34
Q

Spreading, crusted skin infection

A

Impetigo

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35
Q

Deep skin infection

A

Cellulitis

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36
Q

Infections of other tissues, potentially from metastasis of superficial infections can be seen with

A

S. aureus infection

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37
Q

In children, S. aureus is the most common cause of

A

Osteomyelitis (bone infection)

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38
Q

Can also cause a septic joint/septic arthritis

A

S. aureus

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39
Q

Often follows viral influenza infections, especially in hospitalized patients

-Manifestation of S. aureus

A

Pneumonia

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40
Q

A clinical manifestation of S. aureus that is frequently associated with IV drug abuse.

A

Acute endocarditis

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41
Q

Rapid onset of vegetation on valve that can embolize to other tissue including lungs or brain

A

Acute endocarditis

42
Q

A clinical manifestation of S. aureus that results in a high fever, hypotension, rash, and multi-organ failure

A

Toxic Shock Syndrome fro TSST-1

43
Q

With an S. aureus infection, you can get “food poisoning: or gastroenteritis from

A

Enterotoxins

44
Q

Presents as acute onset of GI distress with characteristic projectile vomitting

A

Food poisoning from enterotoxins

45
Q

Exfoliatin toxin induced bright red flush, blisters (bullae) causing bullous impetigo, then desquamation of the epidermis

-also a form of S. aureus infection

A

Scalded Skin Syndrome

46
Q

Most common clinical presentation of staphylococcal infections is

A

Skin and Soft Tissue Infections (SSTIs)

47
Q

By 1955, almot all S. aureus was resistant to penicillins due to the enzymes

A

Penicillinase/B-lactamase

48
Q

Penicillin modified with bulky side groups that prevented binding of penicillinase was developed to bipass

A

S. aureus drug resistance to penicillin

49
Q

What is the name of a common anti-staphylococcal “penicilinase-resistant” penicillin used in the clinic

A

Methicillin

50
Q

S. aureus acquired a new gene mecA that encodes for PBP2A, this lead to

A

Methicillin Resistant S. aureus (MRSA)

51
Q

Initially, MRSA emerged in hospitals. Hospital strains tend to be resistant to additonal antibiotics such as

A

Tetracycline and clindamycin

52
Q

Usually absent/less virulent in hospital MRSA

A

PVL genes

53
Q

Community strains of MRSA tend to be susceptible to a broader range of antibiotics. They are generally more virulent due to production of

A

Toxins

-PVL genes usually present

54
Q

Currently >95% of S. aureus isolates are

A

Penicillin resistant

55
Q

What percentage of S. aureus isolates are methicillin resistant?

A

65%

56
Q

What is the first line of treatment for MRSA infections?

A

Vancomycin

57
Q

Relatively uncommon but growing in importance

A

Vancomycin Intermediate and Vancomycin Resistant S. aureus (VISA nd VRSA)

58
Q

A lipopeptide that can be used for VISA and VRSA treatment

A

Daptomycin

59
Q

An oxazolidone that can be used for VISA and VRSA treatment

A

Linezolid

60
Q

A cephaolosporin with affinity for PBP2a used to treat VISA an VRSA

A

Ceftaroline

61
Q

What are two examples of coagulase negative staphylococci?

A

S. epidermidis and S. saprophyticus

62
Q

Major component of normal skin flora

-seen in wound infections through broken skin

A

S. epidermidis

63
Q

Produces cell surface polysaccharide “slime” that adheres to bioprosthetic materials and acts as a barrier to antibiotics

-Less virulent

A

S. epidermidis

64
Q

Frequently involved in nosocomial and opportunistic infections

–Catheters or Medical Devices, IV lines

A

S. epidermis

65
Q

Most strains of S epidermidis are highly resistant to

A

Penicillins and methicillins

66
Q

Normal in vaginal flora

-infections include UTI and cystitis in women

A

S. saprophyticus

67
Q

S. saprophyticus is distinguished from other CoNS and S. aureus by its natural resistance to

A

Novobiocin

68
Q

S. saprophyticus is sensitive to

A

Penicillin G

69
Q

Gram-positive spherical/ovoid cocci arranged in long chains; commonly in pairs

A

Streptococcus

70
Q

A distinguishing feature of Streptococcus is that they are

A

Catalase (-)

71
Q

Most parasitic forms of Streptococcus are

-require an enriched media

A

Fastidious

72
Q

Streptococcus are sensitive to drying and heat and aerobically they are considered to be

A

Aerotolerant anaerobes

73
Q

The classification of streptococci is based on

A

Hemolysis pattern on blood agar and cell wall antigen

74
Q

Complete erythrocyte destruction resulting in YELLOW zone of clearance around colony

A

Beta-hemolysis

75
Q

Partial destruction of hemoglobin, agar below/around colony appears GREEN/BROWN

A

Alpha-hemolysis

76
Q

No hemolysis, hemoglobin remains red around colony

A

Gamma-hemolysis

77
Q

Serological classification based on an antigenic cell wall polysaccharide called C-substance

A

Streptococcus Lancefield groups

78
Q

Reaction with specific antisera tested in a slide agglutination assay. Common Lancefield groups are

A

A, B, D and none

79
Q

Streptococci pyogenes is called

A

Group A Streptococci (GAS)

80
Q

What are the 4 virulence factors of GAS?

A

M-potein, streptolysin O and S, Streptococcal Pyrogenic Exotoxins (SPE) A, B, C, and the enzyme streptokinase

81
Q

Lyse red blood cells

-ASO titers

A

Streptolysin O and S

82
Q

Essential for GAS infection

-highly variable antigenic

A

M-protein

83
Q

What are the three major clinical manifestations of GAS infection?

A
  1. ) Streptococcal pharyngitis
  2. ) Streptococcal skin infections
  3. ) Streptococcal toxic shock syndrome
84
Q

Also known as “strep throat”: purulent inflammation in the pharynx.

-Can be associated with scarlet fever, a toxin mediated skin rash

A

Streptococcal pharyngitis

85
Q

Impetigo or erysipelas which could lead to cellulitis or more severe necrotizing fasciitis

A

Streptococcal skin infections

86
Q

Superantigen pyrogenic exotoxin (SPE) mediated shock and multi-organ failure

A

Streptococcal toxic shock syndrome

87
Q

What is an example of post-infection sequelae of GAS infections?

-antibody mediated

A

Acute Rheumatic Fever (ARF)

88
Q

Occurs within 2-3 weeks following pharyngitis due to antibodies that also recognize cardiac myocytes

A

Acute Rheumatic Fever

89
Q

Can occur 1-2 weeks after pharyngitis or a skin infection

A

Acute Post-Streptococcal Clomerulonephritis (APSGN)

90
Q

What are three symptoms of APSGN?

A

Hematouria, oliguria, proteinuria

91
Q

Inhabits throat, nasopharynx, occasionally skin in humans

A

S. pyogenes

92
Q

S. pyogenes can be transmitted by

A

Contact, droplets, and food

93
Q

The portal of entry for S. pyogenes is generally the

A

Skin or pharynx

94
Q

Children are the predominant group affected for cutaneous and throat infections. In fact, ~30% of all bacterial pharyngitis in children due to

A

GAS

95
Q

Group B Streptococci (GBS) is called

A

S. agalactiae

96
Q

Makes up the normal flora of female reproductive tract

-Colonization can be intermittent, transient, or persistent

A

S. agalactiae (GBS)

97
Q

S. agalactiae is the leading cause of

A

Neonatal sepsis, meningitis, or pneumonia

98
Q

Pregnant women are routinely screened at 35-37 weeks for

A

GBS colonization

99
Q

Distinguishing Group A Streptococci from Group B Streptococci is based upon

A

Bacitracin Sensitivity

100
Q

Beta-hemolytic sensitive to Bacitracin

A

GAS

Microbiology Lecture Slides (24 decks)

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