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Eq ACVS Phase 1 > Ch.7 Surgical Site Infection and the Use of Antimicrobials > Flashcards

Ch.7 Surgical Site Infection and the Use of Antimicrobials Flashcards

1
Q

What is the reported SSI rate of fracture repair

A

27.6%

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2
Q

How does SSI of fracture repairs influence likelihood of survival to DC

A

7.25 times less likely to survive to DC

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3
Q

What is the SSI rate for horses undergoing radial fx repair and how does it influence the implant success

A

44%
17 times more likely to have implant failure

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4
Q

Incisional site infection occurs in up to what % of procedures

A

43%

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5
Q

A repeat laparotomy does what to the odds of SSI

A

Doubles it

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6
Q

How does the centre of disease control classify SSI

A

According to depth and tissue spaces involved

1 - Superficial incisional
2 - Deep incisional
3 - Organ/space involvement

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7
Q

The likelihood that a SSI will occur is a complex relationship between

A

1) Microbial characteristics -virulence and pathogen
2) Host characteristics - immune status, age
3) Wound characteristics - hemostasis, foreign material

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8
Q

When is the greatest risk for SSI

A

Time of open to time of closure

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9
Q

What are the most significant contributors to SSI

A

The hosts innate immune system
The dose and virulence of the bacteria

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10
Q

What are the criteria for a superficial incisional infection

A

Within 30 days of sx
Involves only skin or subq

Purulent drainage from the superficial incision
Organism isolated aseptically from sup incision
Pain or tenderness, localised swelling
Superficial incision is opened by surgeon unless it cultures negative

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11
Q

What are the criteria for a deep incisional infection

A

Within 30 days of sx
Within 1 year if an implant in place and infection appears to be related to the operation and involves deep soft tissue

Purulent drainage, fever, tender
An abscess

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12
Q

What are the criteria for an organ/space SSI

A

Within 30 days if no implant
Within 1 year if implant

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13
Q

Host related risk factors for SSI

A
  1. Extremities of age
  2. Gender - female
  3. Immunocompromised
  4. Weight >250-300kg
  5. Distant site of infection
  6. Hypoxia
  7. Foreign material
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14
Q

Surgery related factors for SSI

A
  1. Emergency procedure
  2. Patient and surgeon prep
  3. Duration of sx
  4. Sx skill
  5. Foreign material
  6. Bandage
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15
Q

A stent left in place for how long increases SSI

A

> 3 days

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16
Q

Within how long after closure is an incision resistant to microbial entry

A

24 hours

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17
Q

What % of bacterial skin flora are present in sebaceous glands, hair follicles and sweat glands

A

20%

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18
Q

What is the most common musculoskeletal pathogen

A

Staph aureus

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19
Q

What is the most common isolate of equine long bone fracture repair

A

Enterobacter spp.

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20
Q

What is considered to contribute most to SSI

A

Intraoperative pathogen burden

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21
Q

Contamination of a wound with how many microorganisms will lead to SSI

A

100,000

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22
Q

What are the main commensuals of the equine distal limb

A

Enterobacter spp.
Bacillus spp.
Micrococcus spp.

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23
Q

What methods can be used to reduce the minimum inoculum of Staph aureus

A

Surgical sutures
Polytetrafluoroethylene grafts
Dextran beads

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24
Q

How does biofilm evade the host response and antimicrobials

A

Physical barrier against antimicrobials, antibodies, activity of granulocytic cells
Microorganisms is encased

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25
Q

What are the primary exogenous bacteria of SSI

A

G+ Aerobes - Staph and Strep

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26
Q

What type of airflow is best for high risk procedures

A

Laminar air flow - fresh filtered air is blown down onto Sx site pushing air present, aerosols etc to the periphery

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27
Q

What are the guidelines from the centre of disease control and preventions recommendations on airflow

A
  1. Maintain positive air pressure in the OR
  2. Filtration of >90% of the air
  3. Exchange of air 15 times an hour
  4. Air introduced from ceiling exits at floor level
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28
Q

Clipping/removal of hair prior to intra-articular injection has shown an increased or decreased risk of septic arthritis

A

20 times greater risk

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29
Q

Microscopic skin trauma from clipping with a razor increases the risk of SSI by how much

A

5.6%

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30
Q

Staph aureus, coag-neg Staph and Enterococcus faecalis have what specific virulence factors

A

MSCRAMMs -
microbial
surface components
recognising
adhesive
matrix molecules
which allow improved adhesion to collagen, fibrin, fibronectin and other extracellular matrix proteins

Also the ability to develop biofilm

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31
Q

What is biofilm

A

An organised community of bacteria attached to a surface and enveloped within a self produced matrix

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32
Q

What is unique about the biofilm produced by Staph. aureus

A
  1. Forms a unique matrix of fibrin and glycocalyx
  2. that anchors to the cell or inert device
  3. and functions as a partial physical barrier
  4. against antibiotics, antibodies, and granulocytic cell populations
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33
Q

Biofilm producing bacteria possess what unique characteristic

A

Phenotypic heterogeneity
- allows them to survive and grow at a slow rate
in localised nutrient and oxygen depletion
compared with other planktonic organisms in the same niche.

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34
Q

What is SarA and what does it do

A
  1. Regulatory element - controls Staph. virulence factors
    Is essential for polysaccharide intercellular adhesion (PIA) synthesis
    and therefor biofilm development.

a central regulatory element that controls the production of Staphylococcus aureus virulence factors, is essential for the synthesis of PIA/PNAG and the ensuing biofilm development in this species

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35
Q

How does biofilm survive

A

Release planktonic seeds
stim host immune response
derives nutrients from host exudate

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36
Q

What type of antimicrobials and biocides are effect against biofilm

A

Chlorhexidine
Gentamicin
can bind to sites within biofilm and limit it temporarily

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37
Q

What novel techniques are being developed to counteract biofilm

A
  1. surfactant surface modifications
  2. sol gel coating
  3. covalent antimicrobial tethering
  4. hydrophobic poly cat ionic coatings
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38
Q

How has age been associated with SSI

A

Horses <1yr reduced SSI at colic sx 15% compared with adults 43%

Horses >20yrs - 17 times greater risk of incisional site infection

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39
Q

Which gender has been associated with more SSI

A

Female

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40
Q

How has temperature been shown to affect SSI

A

Development of hypothermia (<36) or decrease in body temp by 2 intro can triple the risk of SSI

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41
Q

How is temperature thought to affect immune function

A

Hypothermia impairs neutrophil function
either through vasoconstriction or hypoxia
can affect platelet function resulting in increased blood loss and hematoma formation

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42
Q

How does surgical trauma affect immune function

A

25% less antimicrobial activity in neutrophils
reduced helper T cell response and proliferation

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43
Q

How has hyperbaric oxygen therapy been shown to affect wound healing

A

Has not been shown any adjunctive effect

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44
Q

How has hypoxia been shown to affect wound healing

A

Low intraop PaO2 <80mmHg increases risk of ventral midline infection

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45
Q

How do open fractures compare to closed for SSI

A

Open 4.2 times more likely to become infected

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46
Q

How has suture material been associated with SSI

A

Silk - 3.4 times more likely to develop a SSI compared with polyglactin 910

A single strand of silk can reduce the number of staph aureus required to cause infection by a factor of 10.

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47
Q

What helps bacteria to grow on an implant

A

Low vascularity at the site of the new implant
Adhesion of serum proteins
formation of a fibrous coating

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48
Q

What are the most commonly used implant materials

A

Stainless steel
Titanium
Titanium alloys

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49
Q

Which implant material has been associated with a higher rate of infection and why

A

Stainless steel
Development of a fibrous fluid-filled capsule at the bone-implant interface that
creates an ideal medium for bacterial proliferation

Latent infection development at a mean of 70months after sx
SSI rate of 4.6% compared with 1.3% for Titanium

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50
Q

Pros of titanium and titanium alloy

A

Decrease fibroblastic adhesion properties
Pure titanium - increased biocompatibility and increased soft tissue adherence

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51
Q

Rate of SSI in laparoscopic and arthroscopic procedures

A

Lap crypt - 0%
Arthroscopy 0.5-1.5%
Risk- draft breed/tarsocrural joint

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52
Q

Rate of SSI in celiotomy -emergency vs elective
Risk factors which increase SSI

A

Emergency - 7.4 - 39%

Risks -
Inexperienced surgeon,
near-far-far-near,
staples,
polyglactin 90
Sx time>2hrs

Protective - lavage linea, topical abs

Elective - 9%

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53
Q

How does closed reduction and fixation of a fx compare to open

A

2.5 times lower SSI

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54
Q

SSI incidence of extensive long bone fx compared to articular surface only

A

5.1 times more likely to develop an SSI

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55
Q

SSI rate of P3 fx repair

A

37.5%

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56
Q

SSI infection of clean orthopaedic and clean-contaminated orthopaedic procedures

A

Clean - 8.1%
Clean contaminated - 52.6%

Risks - Sx duration >90mins

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57
Q

SSI rate of long bone fx
A sx time of what duration increases the risk
What else related to the fx can increase the risk of SII

A

28-32%

Risks - Sx duration >180mins.
Open fx, configuration

58
Q

SSI rate of routine castration

A

2-3.2%

59
Q

SSI rate of laryngoplasty

A

0-4%

60
Q

Alcohol based solutions pro and con

A

Rapid bactericidal effect
Limited persistent antimicrobial effect
Avagard, Sterillium, Monorapid - more effective than aqueous solutions

61
Q

What % of surgical gloves become defective (in small animal procedures)

A

26.2%

62
Q

Risk of SSI increases by how much when 1st/2nd yr resident closes the abdomen

A

Doubles

63
Q

How does time affect SSI rates

A

Double with every hour (clean wounds)

64
Q

Post op incisional infection are more likely in abdominal surgeries exceeding how long and what % occurrence

A

> 2 hours
47%

65
Q

Orthopedic procedures >90mins are how many times more likely to develop a SSI

A

3.6

66
Q

Is polyglycolic acid for closure of the subcutaneous tissue associated with an increased or decreased risk of SSI?

A

Increased

67
Q

How does the use of surgical staples affect the SSI rate in celiotomy

A

Increases it 4 fold
1.3 times the likelihood of incisional drainage

68
Q

Does irrigation of the SS with antibiotic containing sterile fluids decrease the SSI

A

Yes
Use drugs not commonly used systemically - vancomycin/polymixin

69
Q

Pros and cons of using a stent bandage

A

Pro: 2.7% SSI vs 21.8% without a stent

Con: If left in place for 3 days or more have an increased rate of SSI

70
Q

Use of belly bandage on a paramedian celiotomy …

A

Increased SSI

71
Q

What % of hospital admissions develop nosocomial infections

A

20%

72
Q

Horses undergoing celiotomy are how likely to develop nosocomial Salmonella infections

A

2 - 8 times

73
Q

Clinical indicators associated with acute salmonellosis

A

Fever >103
Abnormal leukocyte count
Acute colitis

74
Q

Horses presenting with acute colic that become more lethargic and inappetent are how likely to shed salmonella

A

17 times

75
Q

C. diff has been isolated from what % of veterinary hospital samples

A

3-17%

76
Q

What % of horses experience catheter site inflammation and infection

A

9%

77
Q

Most commonly isolated pathogens from catheters

A

Staph
Corynebacterium
Bacillus
Enterobacter
Pseudomonas

78
Q

Catheter related complications are high in IVC left in place for how long

A

> 3.5 days

79
Q

Nasal colonisation of MRSA in vet personnel is how prevalent

A

9.4-22.2%

80
Q

In horses undergoing complicated orthopaedic procedures SSI increased the hospitalisation and duration of antimicrobial therapy by how long

A

32.1 days in Hospital
17.3 days abx

81
Q

When is incisional drainage likely to occur

A

6-10 days post op

82
Q

How long after injury does fibrinogen peak

A

7-10 days

83
Q

How many mg/dl fibrinogen has been associated with osteomylitis

A

900mg/dl

84
Q

When does SAA peak and return to baseline

A

36-48hrs
Returns to baseline in 1-2weeks

85
Q

Cell/uL, %Neutrophils and TP of normal synovial fluid

A

1000 cells/uL
10% Neutrophils
2 g/dl TP

86
Q

A nucleated cell count of what is pathognomonic for infection

A

75,000 cells/uL

87
Q

Intraarticular TP concentrations have been shown to increase how long after arthrocenthesis

A

4 hours

88
Q

Normal synovial fluid lactate

A

3.9mmol/L

89
Q

What difference between peritoneal fluid glucose and peripheral indicates peritonitis

A

> 50mg/dl

90
Q

Obtaining a positive culture is dependent on

A
  1. Method of culture
  2. Number and virulence of the organism
  3. Defence mechanism of the organism
91
Q

Tissue culture vs swab culture sens/specif

A

Tissue sensitivity 98% specificity 93%
Swab sensitivity 89% specificity 70%

92
Q

Incidence of positive culture from synovial fluid

A

64-89%

93
Q

How large a volume of fluid is required for most blood culture vials

A

8-10ml

94
Q

How much bone demineralisation must occur before it is radiographically evident

A

50%

95
Q

What MRI sequences are advised for imaging of SSI

A

T1-weighted
T-2 weighted
Short Tau inversion recovery

96
Q

Photopenia in nuclear scintigraphy may be an indication of

A

osteitis

97
Q

Common isolate of cellulitis

A

60% Staph. aureus
Strep

98
Q

Most common isolates of post op synovial structures

A

34-52% Staph. aureus
22% haemolytic staph
25% gram neg

99
Q

Most commonly isolated pathogens of neonates

A

Escherichia coli
Actinobacillus
Klebsiella

100
Q

% G+ vs G- isolates from joints of septic foals

A

62.5% G-
37.5% G+

101
Q

Which is the most commonly isolated G- in musculoskeletal inf

A

Enterobacter cloacae

102
Q

Penetrating wounds are most likely to culture what bacteria

A

Staph
Pseudomonas
Proteus
Enterobacter
Yeast
Fungi

103
Q

Most common isolates of foot wounds

A

Enterobacter
Strep zooepidemicus

104
Q

Post op peritonitis is associated with which bacteria

A

Strep
Enterobacteriaceae
Actinobacillus
Anaerobes

105
Q

Most common isolates of paranasal sinus and guttural pouch

A

Strep equi asp equo
Strep zooepidemicus
Aspergillus
Cryptococcus

106
Q

Most common isolates of septic physitis/arthritis in foals

A

Escherichia coli
Rhodococcus equi

107
Q

Most common isolates of chronic wounds

A

Pseudomonas
Staph
Serratia
Enterococcus
Providencia

108
Q

Most common isolates of orthopaedic sx

A

Enterobacteriaceae
Staph
Strep
Pseudomonas

109
Q

Most common isolates of penetrating wounds to synovial structures

A

Enterobacteriaceae
Anaerobes

110
Q

Common time dependent antimicrobials

A

Beta lactams
Trimethoprom sulphonamides
Macrolides
Tetracyclines
Chloramphenicol

111
Q

Common concentration dependent antimicrobials

A

Aminoglycosides
Fluoroquinolones
Metronidazole

112
Q

What is the optimal ratio for peak concentration to MIC of concentration dependent drugs

A

10:1 or 12:1

113
Q

How is the peak concentration of conc dependent drugs monitored

A

Serum sample 60 mins after IV or 90 mins after IM administration

114
Q

What through level of amikacin is advised to reduced nephrotoxicity

A

<1ug/ml

115
Q

When should antimicrobials be redosed in surgery

A

If surgical procedure exceeds 1 to 2 times the half life of the antibiotic

116
Q

When should prophylactic antibiotics be used

A

When risk of SSI is >5% without their use or if a SSI would be life threatening

117
Q

Within how long of surgical incision should abs be administered

A

1 hour

118
Q

The risk of SSI increases from 6.3-28% for surgeries lasting longer than…

A

2 hours

119
Q

Failure to redose abs during long surgeries increases the SSI risk by how much?

A

4.5 times more likely

120
Q

Mechanism of action and adverse effects of penicillin

A

Bactericidal - Time dependent
Inhibit cell wall synthesis by binding to penicillin-binding proteins, leading to cell lysis

Adverse effects
Autoimmune haemolytic anemia anaphylaxis
Transient hypotension
Increased large intestine motility
Cardiac arrhythmia

121
Q

Mechanism of action and adverse effects of cephalosporins

A

Bactericidal - Time dependent
Inhibit cell wall synthesis by binding to penicillin-binding proteins, leading to cell lysis

Adverse effects
Enterocolitis

122
Q

Mechanism of action and adverse effects of Aminoglycosides

A

Bactericidal - Concentration dependent
Inhibit protein synthesis by binding to 30S ribosomal subunit

Adverse effects
Nephrotoxicity
Neuromuscular blockade
Ototoxicity

123
Q

Mechanism of action and adverse effects of Fluoroquinolones

A

Bactericidal
Inhibit bacterial DNA gyrase

Adverse effects
Cartilage disorders in young <3yo
Oral ulceration

124
Q

Mechanism of action and adverse effects of metronidazole

A

Bactericidal
Disrupt bacterial DNA by free radicals and unstable intermediate compounds after structural change once in target organism

Adverse effects
Enterocolitis
Inappetence

125
Q

Mechanism of action and adverse effects of trimethoprim/sulfonamide

A

Bactericidal
Synergistic action to inhibit folic acid Synthesis
Sulfa block 1st step:
Para-aminobenzoic acid to dihydrofolic acid
Bacteriostatic when used alone

Trimethoprim 2nd step
Inhibits dihydrofolic acid reductase

Adverse effects
Idiosyncratic

126
Q

Mechanism of action and adverse effects of Tetracyclines

A

Bacteriostatic
Inhibit protein synthesis by reversibly binding to 30S Ribosomal subunit

Adverse effects
Nephrotoxicity
Discolouration of urine and erupting teeth

127
Q

Mechanism of action and adverse effects of Chloramphenicol

A

Bacteriostatic
Inhibit protein synthesis by reversibly binding to 50S ribosomal subunit

Adverse effects
Reversible aplastic anaemia

128
Q

Mechanism of action and adverse effects of Microlides

A

Bacteriostatic
Inhibit protein synthesis by reversibly binding to 50S Ribosomal subunit

Adverse effects
Intestinal pro-kinetic

129
Q

Common bacteriostatic antimicrobials in equine medicine

A

Tetracyclines
Chloramphenicol
Macrolides - foals

130
Q

Common bactericidal antimicrobials in equine medicine

A

Penicillin
Cephalosporins
Aminoglycosides
Fluoroquinolones
Metronidazole
Trimethoprim/sulfonamide

131
Q

Why do neonates require a higher dose of aminoglycosides than adults up to 4-6 weeks

A

Aminoglycosides are distributed within the extracellular space - foals have a larger ecf than adults

132
Q

Nephrotoxicity occurs due to prolonged exposure of renal tubules or exposure to a high concentration

A

Prolonged

133
Q

Ratio of Potentiated sulphonamides to trimethoprim

A

1:5

134
Q

Local concentration of abs from PMMA beads reach what level compared to systemic

A

200 times greater than systemic

135
Q

How long do AIPOP beads remain active when stored at room temperature

A

5 months

136
Q

At what % antimicrobial is there
a- inhibition of hardening process
b- weakening of biomechanics properties
of PMMA

A

> 20% of antimicrobial inhibits hardening

> 10% weakens the biomechanics

137
Q

Which antibiotics are not suitable for PMMA beads

A

Non heat stabile ones - must be stable to 100*C (low tissue toxicity)

Not suitable:
Polymyxin B
Chloramphenicol
Tetracyclines

138
Q

Drug combinations which enhance elution

A

Vancomycin-amikacin
Gentamicin-metronidazole
Cefazolin-amikacin

139
Q

Alternative delivery systems to PMMA and AIPOP

A

Bovien collagen sponge
Hydroxyapatite (HAP)
Beta tricalcium phosphate (B-TCP)

140
Q

Complication rate of RLP using 22g butterfly catheter

A

12%

141
Q

What dose of an abx is advised in a RLP

A

One third of the systemic dose

However doses less than 0.5g are not effective

142
Q

Parenteral antimicrobial tx increases the risk of developing Salmonellosis
1) by how much?
2) if combined with enteral abx

A

6.4 times

40 times if combined with enteral

Eq ACVS Phase 1 (72 decks)

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