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Diagnostic Micro Exam 1 > Staphylococci > Flashcards

Staphylococci Flashcards

0
Q

What temperature is used for staph cultivation?

A

37C

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1
Q

What type of air requirements are needed for staphylococci?

A

Facultative anaerobes

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2
Q

What types of staph are spore forming?

A

Clostridium & bacillus

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3
Q

What can subspecies be classified as?

A

Phage groups
Ribotypes
Strains

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4
Q

How are staph encountered as?

A

Commensals

Pathogens

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5
Q

How do staph gram stain as?

A

Gram positive cocci

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6
Q

Staph are catalase positive or negative?

A

Positive

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7
Q

What do staph ferment?

A

Sugars

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8
Q

Are they motile or nonmotile?

A

Non motile

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9
Q

Air requirements include what?

A

Aerobic

Facultative anaerobes

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10
Q

What are they similar to?

A

Micrococcus

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11
Q

Staph aureus (halo) produces what?

A 
Boils
Folliculitis
Furuncles
Carbuncles
Purulent abcesses
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12
Q

S. aureus can cause infections including what?

A

Skin, wound, blood, & toxin related diseases

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13
Q

What are 3 types of cutaneous staph infections?

A

Folliculitis
Furuncle
Carbuncle

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14
Q

What is folliculitis?

A

Infection of the hair follicles

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15
Q

What are furuncles?

A

An acute, round, firm tender, circumscribed, perifollicular staph pyoderma that usually ends in central suppuration

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16
Q

What are carbuncles?

A

Two or more confluent furuncles with separate heads
Infection is deeper
May cause fever/chills

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17
Q

What is bullous impetigo?

A

Skin infection caused by staph that is highly infectious

By contact with patient, fomites, autoinnoculation

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18
Q

What are some staph toxin related diseases?

A

Scalded skin syndrome
Toxic shock syndrome
Food poisoning

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19
Q

Can staph cause food poisoning?

A

Yes

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20
Q

Staph food poisoning is what?

A

An enterotoxin

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21
Q

How is staph food poisoning gotten?

A

Contaminated food kept at a temp that allows bacterial growth & toxin release
Reheating food may kill bacteria but the toxin is heat stable
Symptoms occur 1-6 hours after ingestion
Self limit at 24 hours

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22
Q

Toxic shock syndrome is caused by what toxin?

A

TSST-1 toxin 1

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23
Q

What is toxic shock syndrome?

A

Rare potentially fatal multi-system disease with sudden fever, chills, vomiting, diarrhea, muscle aches, & desquamating rash

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24
Q

What is desquamating rash?

A

Rash that can lead to hypotension & shock

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25
Q

When was TSS originally described?

A

1978 - associated with highly absorbent tampon use

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26
Q

TSS is what kind of infection?

A

Localized infection

Caused by systemic toxin

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27
Q

Scalded skin syndrome is more common in what?

A

Infants

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28
Q

What type of toxin is involved in scalded skin syndrome?

A

Epidermolytic toxin

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29
Q

What does epidermolytic toxin do?

A

Dissolves skin

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30
Q

What is scaled skin syndrome also known as?

A

Ritter disease

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31
Q

What are the characteristics of scalded skin syndrome?

A

Lesion has purulent material
Then cutaneous erythema followed by peeling of the epidermis
Lasts 2-4 days & spontaneously heals

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32
Q

What are gram positive bacteria treated with & why?

A

Treated with cell wall inhibitors

Beta lactams & vancomycin

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33
Q

What are cell wall components for structural integrity?

A

b-lactams
Penicilins
Cephalosporins
Vancomycin

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34
Q

What are some 50S inhibitors?

A

Erythromycin
Clindamycin
Chloramphenicol

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35
Q

What are beta lactam antibiotics?

A

Naturally occurring
Synthetic
Semi-synthetic

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36
Q

What do cell walls do for organisms?

A

Helps organisms resist changes in osmotic conditions

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37
Q

How do b-lactams inhibit cell wall synthesis?

A

B-lactams are structural analogs to acyl D-alanyl-D-alanine

Inhibit the transpeptidation reactions

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38
Q

What are types of b-lactams?

A

Penicillins
Cephalosporins
Monobactams
Cabapenems

39
Q

What is vancomycin (glycopeptide)?

A

A narrow spectrum, limited to gram positive
Cannot penetrate outer cell membrane of gram negative
Links to peptide substrate to prevent transportation

40
Q

Beta lactams interfere with cell wall synthesis - what are their characteristics?

A

Look like the next building block for cell wall synthesis

If they are inserted by the penicillin binding proteins into the cell wall - cell wall synthesis will stop

41
Q

What is MRSA?

A

A major nosocomial infection - HA-MRSA

When acquired in the community - CA-MRSA

42
Q

What is SCCmec cassette in MRSA?

A

MRSA strains with a large insertion into the chromosome that brings several genes
Usually antibiotic resistance & virulence genes
All have mecA gene

43
Q

What gene do SCCmec cassette MRSA strains have?

A

mecA gene

44
Q

What does mecA code for?

A

An alternate penicillin binding protein - PBP2a

45
Q

Methicillin resistant staph are what?

A

Penicillin resistant strains can be treated with nfacillin or oxacillin - resistant to effects of penicillinase

46
Q

What is MRSA resistant to?

A

Any penicillin drug

47
Q

Why is MRSA resistant to penicillin drugs?

A

Due to the presence of the methicillin resistance gene (mecA) on the chromosome
mecA codes for PBP2a
PBP2a doesn’t bind to penicillins

48
Q

What is oxacillin used for?

A

To detect methicillin resistance

A plate with high salt & polymixin make the media select for staph

49
Q

What does CLSI recommend using for methicillin resistant staph?

A

Cefotoxin plates to induce the mecA gene because MR can show heteroresistance

50
Q

How is staph resistant to vancomycin?

A

Vancomycin interferes with cell wall synthesis but is not a beta lactam

51
Q

What are two vancomycin resistant staphs?

A

VISA

VRSA

52
Q

What is VISA?

A

Vancomycin intermediate S. aureus

Can arise from vancomycin overuse

53
Q

What is VRSA?

A

Resistant S. aureus

54
Q

How can you find out if it is vancomycin resistant staph?

A

Screening by a vancomycin agar plate

55
Q

How are staph resistant to macrolide?

A

Macrolide antibiotics that inhibit protein synthesis at the level of the ribosome - 50s

56
Q

What are two examples of macrolide resistant staph?

A

Clindamycin & erythromycin

57
Q

What do clindamycin & erythromycin do?

A

Usually don’t have the same susceptibility pattern
When they don’t, it could be because the organisms can be induced to be resistant once the patient starts to take the antibiotic

58
Q

What is used to test inducible macrolide resistance?

A

D test

59
Q

How does the D test work?

A

Places clindamycin & erythromycin in close proximity to each other on a Kinky Bauer plate
Erythromycin makes the bacteria around it express its erm gene
This demonstrates its resistance to the clindamycin

60
Q

What does the D test do?

A

Determines in advance if the organism will respond to clindamycin
If the test is positive - report all macrolides as resistant

61
Q

What color will MRSA turn a mannitol salt plate?

A

Pink

62
Q

What happens when MRSA is on a chromagar plate?

A

Has color

63
Q

What are rapid detection tests in positive blood cultures for MRSA?

A

PCR

Fluoresenct in situ hybridization for mecA & staph aureus

64
Q

What are virulence factors of staph aureus?

A 
Enterotoxins
TSST-1
Exfoliative toxin
Cytolytic toxin
Enzymes
Protein A binds to Fc portion of antibody, blocks phagocytosis
65
Q

What are types of cytolytic toxins?

A 
alpha toxin
beta toxin
panton valentine - kills WBC
leucocidin
delta toxin
66
Q

What does S. aureus gram stain as & what shape?

A

Gram positive cocci in clusters

67
Q

What do S. aureus colonies look like on blood agar and what type of hemolysis do they have?

A

Smooth white creamy colonies with beta hemolysis

68
Q

Are S. aureus catalase positive or negative?

A

Positive (virulence factor) that causes the release of oxygen (bubbles) from H2O2

69
Q

Are S. aureus coagulase positive or negative?

A

Positive (virulence factor) that clumps plasma - clumping factor
May be on the bacterial surface & agglutinate immediately
May be secreted as extracellular staphylocoagulase which takes longer, & is demonstrated in a tube

70
Q

What are characteristics of S. epidermidis?

A

Commensal

Pathogen

71
Q

What makes S. epidermidis a commensal?

A

Found on skin

Common contaminant of wound, blood cultures

72
Q

What makes S. epidermidis a pathogen?

A

Slime/biofilm
Endocarditis - in blood stream
Nosocomial UTI

73
Q

What is the result of catalase test for S. epidermidis?

A

Positive

74
Q

What is the result of coagulase test for S. epidermidis?

A

Negative

75
Q

What is the bacitracin test result for S. epidermidis?

A

Resistant

Negative

76
Q

What is the novobiocin test result for S. epidermidis?

A

Positive

Susceptible

77
Q

What is S. saprophyticus?

A

A saprophyte

78
Q

What is a saprophyte?

A

An organisms that grows on & derives its nourishment from dead or decaying organic matter

79
Q

What is an example of S. saprophyticus?

A

Honeymoon cystitis - UTI from sex

80
Q

Results of coagulase test for S. lugdunensis?

A

Negative with tube test

Positive with agglutination test

81
Q

What types of infections does S. lugdunensis cause?

A

CA - community acquired

HA - hospital acquired

82
Q

S. lugdunensis may contain what gene?

A

mecA gene

83
Q

Why has S. lugdunensis been confused with S. aureus?

A

Can identified as PYR positive & ornithine decarboxylate positive

84
Q

What is the microdase (oxidase) test result for micrococcus?

A

Positive

85
Q

What type of fermenter is micrococcus?

A

Nonfermenter - staph ferment

86
Q

What type of response to sugars does micrococcus give?

A

Asacchrolytic - no response

87
Q

Is micrococcus susceptible to lysozyme?

A

Yes

88
Q

Is micrococcus susceptible or resistant to lysostaphin?

A

Resistant

89
Q

What is the bacitracin (A disk) test result of micrococcus?

A

Sensitive/Positive

90
Q

Is micrococcus susceptible or resistant to Furazolidone?

A

Resistant

91
Q

Stomatococcus mucilaginous is what?

A

Normal flora

92
Q

What does is the colony morphology of Stomatococcus mucilaginous?

A

Medium white colony

93
Q

What type of hemolysis is stomatococcus mucilaginous?

A

Nonhemolytic

94
Q

What is the transmission of Stomatococcus mucilaginous?

A

Same as micrococcus

Seen in bone marrow & malignancies

95
Q

What is the result of A disk test for Stomatococcus mucilanginous?

A

Negative

Micrococcus is positive

Diagnostic Micro Exam 1 (6 decks)

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