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Nelson - Exam 3 (IDS) > Nelson - Ch. 181 Staphylococcus > Flashcards

Nelson - Ch. 181 Staphylococcus Flashcards

1
Q

MCC of pyogenic infection of the skin and soft tissues

A

S. aureus

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2
Q

___ of staph interacts with fibrinogen to cause large clumps of organisms, interfering with phagocytosis

A

Clumping factor and/or coagulase

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3
Q

Produced by staph; may have an important role in localization of infection by forming an abscess

A

Coagulase

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4
Q

Staph: Reacts specifically with immunoglobulin G; located on the outermost coat of the cell wall; can absorb serum Ig preventing antibacterial antibodies from acting as opsonins and thus inhibiting phagocytosis

A

Protein A

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5
Q

Staph: Promotes intracellular survival

A

Catalase

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6
Q

Staph: Associated with skin infection

A

Lipase

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7
Q

A protein that S. aureus combines with phospholipids in the leukocytic cell membrane, producing increased permeability and eventual death of the cell

A

Panton-Valentine leukocidin

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8
Q

Strains of S. aureus that produce ___ are associated with more severe and invasive skin disease, pneumonia, and osteomyelitis

A

Panton-Valentine leukocidin

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9
Q

Staph: Serologically distinct proteins that produce localized or generalized dermatologic manifestations by producing skin separation

A

Exfoliatins A and B

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10
Q

Staph: Exfoliatins produce skin separation by

A

1) Splitting desmosome 2) Altering the intracellular matrix in the stratum granulosum

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11
Q

Staph: Ingestion of ___ can result in food poisoning

A

Preformed enterotoxin, particularly types A or B

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12
Q

Staph: By ___ years old, almost all individuals have antibodies to at least 1 enterotoxin

A

10

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13
Q

Staph: A super antigen that induces production of interleukin-1 and tumor necrosis factor, resulting in hypotension, fever, and multi system involvement

A

TSST-1

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14
Q

Staph: Associated with non-menstrual TSS

A

Enterotoxins A and B

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15
Q

Staph: Mediates adhesion to mucosal cell proteins that promote adhesion to fibrinogen, fibronectin, collagen, and the human proteins

A

Teichoic acid

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16
Q

Staph: Production of ___ in the bacterial cell wall mediates resistance to penicillinase resistant antibiotics

A

Penicillin binding proteins (PBP)

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17
Q

Responsible for the methicillin resistance of MRSA isolates

A

Altered PBP-2A

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18
Q

T/F Skin infections caused by S. aureus are considerably more prevalent among persons living in low socioeconomic circumstances

A

T

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19
Q

Most significant risk factors for development of staph infection

A

1) Disruption of intact skin 2) VPS 3) Indwelling intravascular or intrathecal catheters

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20
Q

Reason why patients with HIV have higher risk for developing staph infection

A

Neutrophils that are defective in their ability to kill S.aureus

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21
Q

T/F Infants may acquire type-specific humoral immunity to staphylococci transplacentally

A

T

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22
Q

T/F Antibody to the various S. aureus toxins appears to protect against those specific toxin-mediated diseases, but humoral immunity does not necessarily protect against focal or disseminated S. aureus infection with the same organisms.

A

T

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23
Q

T/F Staph most commonly affects the skin

A

T

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24
Q

T/F Infections of the upper respiratory tract (otitis media, sinusitis) caused by S. aureus are rare

A

T

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25
Q

Most common cause of osteomyelitis and suppurative arthritis in children

A

S. aureus

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26
Q

T/F Meningitis caused by S. aureus is not common

A

T

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27
Q

T/F S. aureus is a common cause of acute endocarditis on prosthetic valves

A

F, native valves

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28
Q

T/F S. aureus is a common cause of renal and perinephric abscess

A

T

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29
Q

T/F S. aureus is a common cause of pyelonephritis

A

F

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30
Q

The principal cause of TSS

A

S. aureus

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31
Q

Food poisoning caused by staph enterotoxin manifests approx ___ hrs after toxin ingestion

A

2-7

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32
Q

Fever associated with staph food poisoning is characteristically

A

Absent or low

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33
Q

T/F Symptoms associated with staph food poisoning usually persists longer than 12-24 hrs

A

F, rarely

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34
Q

T/F In suspected staph infection, cellulitic lesions are ideally cultured using injected saline and targeting the leading edge

A

F, using a needle aspirate from the most inflamed area

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35
Q

T/F Compared to that of Staph, skin lesions caused by Group A strep spread more rapidly and can be very aggressive

A

T

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36
Q

Staphylococcus pneumonia is often suspected on the basis of chest roentgenograms that reveal

A

Pneumatoceles, pyopneumothorax, or lung abscess

37
Q

Other than staph, 2 other etiologies of cavitary pneumonias include

A

1) K. pneumoniae 2) M. tuberculosis

38
Q

In bone and joint infections, ___ is the only reliable way to differentiate S. aureus from other less-common etiologies

A

Culture

39
Q

For most patients with serious S. aureus infections, IV treatment is recommended until

A

Patient has become afebrile and other signs of infection have improved

40
Q

Choices as initial treatment for serious infections thought to be caused by MSSA

A

1) Semisynthetic penicillin 2) first-gen cephalosporin

41
Q

Penicillin and ampicillin are not appropriate for MSSA because

A

> 90% of staph are resistant to these agents

42
Q

T/F Addition of a beta lactamase inhibitor to a penicillin-based drug improves its effect against MRSA

A

F

43
Q

Inducible Clindamycin resistance in isolates initially reported as susceptible must be ruled out by ___ or molecular methods

A

D test

44
Q

T/F Clindamycin is bacteriostatic and should not be used to treat endocarditis, brain abscess, or meningitis caused by S. aureus

A

T

45
Q

T/F MRSA is resistant to carbapenems and unreliably susceptible to quinolones

A

T

46
Q

___ or ___ may be added to a beta lactam or vancomycin for synergy in serious infections such as endocarditis, particularly when prosthetic valve material is involved

A

Rifampin, Gentamicin

47
Q

Despite in vitro susceptibility of S. aureus to ___, these agents should not be used in serious staph infections because their use is associated with rapid development of resistance

A

Cipro and other quinolones

48
Q

DOC: Initial empiric therapy for life threatening MRSA infections

A

Vancomycin (15) q6 + Nafcillin or Oxacillin

49
Q

DOC: Initial empiric therapy for non life threatening infection when rates of MRSA infection in the community are substantial

A

Vancomycin (15) q8

50
Q

DOC: Initial empiric therapy for non life threatening infection when rates of MRSA infection in the community are substantial and prevalence of clindamycin resistance is low

A

Clindamycin

51
Q

DOC: MSSA

A

Nafcillin or Oxacillin

52
Q

DOC: MRSA

A

Vanco+Genta

53
Q

DOC: Community, not multi drug-resistant for life threatening infections

A

Vanco+Genta

54
Q

___ is the most effective measure for preventing the spread of staph from 1 individual to another

A

Strict attention to hand washing techniques

55
Q

Use of hand wash containing ___ is recommended

A

Chlorhexidine or alcohol

56
Q

T/F Food poisoning may be prevented by excluding individuals with S.aureus infections of the skin from preparation and handling food

A

T

57
Q

T/F Most strains of S. aureus associated with TSS are methicillin susceptible

A

T

58
Q

Mechanism of TSST-1 and enterotoxins that cause TSS

A

They act as superantigens, which trigger cytokine release causing massive loss of fluid from the intravascular space and end-organ cellular injury

59
Q

Toxins that cause TSS are selectively produced in a clinical environment consisting of

A

1) Neutral pH 2) High pCO2 3) Aerobic pO2

60
Q

Approx ___% of adults have antibody to TSST-1 without a history of clinical TSS

A

90%

61
Q

Recovery from TSS occurs within ___

A

7-10 days

62
Q

Major criteria for toxic shock syndrome (All Required)

A

1) Acute fever; temp >38.8C 2) Hypotension 3) Rash

63
Q

Minor criteria for TSS (any 3 or more required)

A

1) Mucous membrane inflammation 2) Vomiting, diarrhea 3) Liver abnormalities 4) Renal abnormalities 5) Muscle abnormalities 6) CNS abnormalities 7) Thrombocytopenia

64
Q

Exclusionary criteria for TSS

A

1) Absence of another explanation 2) Negative blood cultures

65
Q

Recommended antibiotic therapy for TSS

A

b-lactamase resistant antistaphylococcal antibiotic plus clindamycin

66
Q

TSS is most commonly caused by

A

MSSA

67
Q

In order to prevent TSS, changing tampons at least every ___ is recommended

A

8 hours

68
Q

CoNS: Common cause of UTI in sexually active females

A

S. saprophyticus

69
Q

CoNS produce ___ that surrounds the organism and may enhance adhesion to foreign surfaces, resist phagocytosis, and impart penetration of antibiotics.

A

Exopolysaccharide protective biofilm or slime layer

70
Q

Risk factors for development of CoNS infection

A

1) Presence of medical device (most significant) 2) Immature or immunocompromised immunity 3) Significant exposure to antibiotics

71
Q

MCC of nosocomial bacteremia

A

CoNS, specifically S. epidermidis

72
Q

T/F CoNS are a rare cause of acute endocarditis on native valves

A

T

73
Q

T/F CoNS are a common cause of acute endocarditis on native valves

A

F, prosthetic

74
Q

MC pathogen that causes central venous catheter infection

A

S. epidermidis (owing partly to its high rate of cutaneous colonization)

75
Q

MC pathogen associated with CSF shunt meningiits

A

CoNS (introduced at the time of surgery)

76
Q

Most CSF shunt meningitis occur within ___ after surgery

A

2 months

77
Q

True bacteremia should be suspected if blood cultures grow within

A

rapidly, within 24hr

78
Q

T/F No blood culture that is positive for CoNS in a neonate or patient with intravascular catheter should be considered contaminated without a careful assessment

A

T

79
Q

T/F Before initiating presumptive antimicrobial therapy in patients that grow CoNS, it is always prudent to draw 2 separate blood cultures to facilitate subsequent interpretation

A

T

80
Q

T/F Most CoNS are resistant to methicillin

A

T

81
Q

___ is the drug of choice for methicillin resistant CoNS

A

Vancomycin

82
Q

The addition of ___ to vancomycin for the treatment of CoNS may increase antimicrobial efficacy

A

Rifampin

83
Q

A trial of ___ is indicated to attempt to preserve the use of central line as long as systemic manifestations of infection are not severe

A

IV Vancomycin

84
Q

May increase the likelihood of curing CoNS line sepsis without line removal

A

1) Antibiotic therapy given through an infected central venous catheter (alternating lumens if multiple) 2) Use of antibiotic locks

85
Q

T/F Peritonitis caused by S. epidermidis in patients on CAPD is an infection that may be treated with IV or intraperitoneal antibiotics WITHOUT removing the dialysis catheter

A

T

86
Q

Unlike most CoNS, ___ is usually methicillin susceptible

A

S. saprophyticus

87
Q

UTI caused by S. saprophyticus can usually be treated with

A

1) 1st gen cephalosporin 2) CoAmox 3) TMP-SMX

88
Q

Poor prognosis with CoNS infection is associated with

A

1) Malignancy 2) Neutropenia 3) Infected prosthetic or native heart valves

Nelson - Exam 3 (IDS) (21 decks)

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