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PR3124 PT3 > Skin & Soft Tissue Infections > Flashcards

Skin & Soft Tissue Infections Flashcards

1
Q

Briefly explain the pathophysiology of SSTIs.

A

Injuries or diseases causing disruptions of normal host defences

  • Penetration of normal skin bacteria into deeper layers
  • Introduction of other bacteria into skin
  • Excess bacterial growth
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2
Q

What are some predisposing factors that increase the risk of developing SSTIs?

A

1) High bacterial inoculum
2) Excessive moisture
3) Reduced blood supply
- e.g. peripheral vascular diseases
- less blood = less WBC to fight off infections
4) Presence of bacterial nutrients (e.g. diabetes)
5) Poor hygiene
6) Sharing of personal items

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3
Q

What are the likely microorganisms involved in the clinical presentation of impetigo & ecthyma?

A

1) Staphylococcus aureus

2) Beta-hemolytic streptococci (e.g. S. pyogenes)

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4
Q

Is culture always required before Abx Tx of impetigo?

A

No. Reasonable to treat empirically without culture.

May culture if pus is present, but generally not practised.

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5
Q

Empiric treatment of ecthyma should always cover MRSA. True or false?

A

False.

Increasing prevalence in Singapore, but low (30-35%) as compared to other countries.

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6
Q

What is the recommended Tx for a patient diagnosed with mild impetigo?

A

Apply topical mupirocin to affected areas BD for 5 days.

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7
Q

What is the recommended empiric Tx for a patient diagnosed with ecthyma?

A

1) PO Cloxacillin 250-500mg QDS x 7 days

2) PO Cephalexin 250-500mg QDS x 7 days

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8
Q

A patient is diagnosed with severe bullous impetigo & has reported that nausea & vomiting whenever she took Augmentin. What is the recommended empiric Tx for her?

A

1) PO Cloxacillin 250-500mg QDS x 7 days
2) PO Cephalexin 250-500mg QDS x 7 days

N/V is considered a side effect of amoxicillin-clavulanate, thus it is NOT a true penicillin allergy.

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9
Q

A doctor asks a pharmacist for his/her recommendation to empirically treat his patient who is diagnosed with ecthyma with reported penicillin allergy (hives). What should the pharmacist’s recommendation be?

A

PO Clindamycin 300mg QDS x 7 days

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10
Q

What is the recommended Tx for a patient diagnosed with moderate purulent impetigo with a positive culture result of S. pyogenes?

A

PO Penicillin VK 250-500mg QDS x 7 days

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11
Q

What are some specific risk factors that increase the risk of developing purulent SSTIs?

A

1) Close physical contact
2) Crowded living quarters (e.g. dormitories, military camps, prisons)
3) Sharing of personal items
4) Poor personal hygiene

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12
Q

What is/are the likely microorganism(s) involved in the clinical presentation of purulent SSTIs?

A

Staphylococcus aureus

However, large skin abscesses may be polymicrobial.

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13
Q

The mainstay treatment of furuncles & carbuncles is systemic antibiotic therapy. True or false?

A

False! First-line therapy is incision & drainage (I&D).

Abx Tx is considered adjunctive therapy.

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14
Q

When will systemic Abx Tx be recommended for patients diagnosed with purulent SSTIs?

A

Adjunctive to I&D and when:

1) Unable to drain abscesses completely
2) Lack of response to I&D (exclusive of erythema)
- Reassess after 48h to determine response (i.e. resolution of erythema)
3) Extensive disease involving several sites of infection
4) Extremes of age (i.e. very old or very young; weaker immune system)
5) Immunosuppression (e.g. chemotherapy, transplants)
6) Signs of systemic infections (SIRS)

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15
Q

List all of the systemic inflammatory response syndrome (SIRS) criteria.

A

1) HR > 90 beats per min
2) RR > 24 breaths per min
3) Temp > 38 degC or < 36 degC
4) WBC > 12 x 10^9/L or < 4 x 10^9/L

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16
Q

What is the recommended adjunctive Tx for a patient discharged home for a diagnosis with purulent SSTI w/o MRSA coverage?

A

1) PO Cephalexin 250-500mg QDS x 5-7 days

2) PO Cloxacillin 250-500mg QDS x 5-7 days

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17
Q

What is the recommended adjunctive Tx for a patient discharged home for a diagnosis with purulent SSTI with MRSA coverage?

A

1) PO Clindamycin 300mg QDS x 5-7 days
2) PO Cotrimoxazole 960mg BD x 5-7 days
3) PO Doxycycline

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18
Q

What is the recommended adjunctive Tx for a patient diagnosed with purulent SSTI with MRSA coverage & is currently hospitalised in a general ward with an NPO (nothing by mouth) label for 3 days?

A

1) IV Clindamycin 600mg q8h x 3 days
2) IV Doxycycline x 3 days

Followed by:

1) PO Clindamycin 300mg QDS x 4-11 days
2) PO Cotrimoxazole 960mg BD x 4-11 days
3) PO Doxycycline x 4-11 days

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19
Q

What is the recommended adjunctive Tx for a patient diagnosed with purulent SSTI w/o MRSA coverage & is currently hospitalised in a general ward with an NPO (nothing by mouth) label for 3 days?

A

1) IV Cefazolin 1-2g q8h x 3 days
2) IV Cloxacillin 1-2g q4-6h x 3 days

Followed by:

1) PO Cephalexin 250-500mg QDS x 4-11 days
2) PO Cloxacillin 250-500mg QDS x 4-11 days

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20
Q

Differentiate between cellulitis & erysipelas.

A

Cellulitis: purulent or non-purulent w/ poorly demarcated area of erythema
Erysipelas: always non-purulent w/ sharply demarcated area of erythema w/ raised border

21
Q

What are two patient-specific comorbidities we should look out for identifying likely microorganisms causing cellulitis & erysipelas?

A

1) Immunosuppression (e.g. chemotherapy, transplant)
- Additional causative organisms include P. aeruginosa, S. pneumoniae, E. coli & Serratia marcescens
2) CKD & chronic liver disease
- Additional causative organisms include P. aeruginosa, Vibrio spp. & E. coli

22
Q

When is culture recommended in patients diagnosed with cellulitis?

A

1) Presence of discharge after I&D
2) Immunosuppression
3) Presence of SIRS criteria

23
Q

List all MRSA risk factors for consideration in empiric Abx Tx of cellulitis, DFI & pressure ulcer infections

A

1) Critically ill (i.e. admission to ICU/emergency ward)
2) Immunosuppression
3) Previously failed Abx w/o MRSA activity

24
Q

A patient diagnosed with cellulitis of the left lower extremity, with no discharge observed, has the following vital signs & labs: Temp 37.8 degC, HR 78 bpm, BP 128/91, RR 22 bpm, WBC 9.8 x 10^9/L. What appropriate Abx regimen can be recommended to this patient?

A

First-line:
1) PO Penicillin VK 250-500mg QDS x 5 days

Alternatives:

1) PO Cloxacillin 250-500mg QDS x 5 days
2) PO Cephalexin 250-500mg QDS x 5 days

25
Q

A patient diagnosed with cellulitis of the right lower extremity, with yellowish pus-like discharge observed, has the following vital signs & labs: Temp 36.9 degC, HR 87 bpm, BP 119/89, RR 20 bpm, WBC 8.8 x 10^9/L. She is reported to have an allergy to penicillin (rash). What appropriate Abx regimen can be recommended to this patient?

A

PO Clindamycin 300mg QDS x 5 days

26
Q

A patient who recently received chemotherapy is currently diagnosed with cellulitis of the right upper extremity, with yellowish pus-like discharge observed. He has the following vital signs & labs: Temp 38.3 degC, HR 88 bpm, BP 108/70, RR 21 bpm, WBC 6.5 x 10^9/L and is reported to have an allergy to penicillin (nausea). What appropriate Abx regimen can be recommended to this patient?

A

1) PO Clindamycin 300mg QDS x 7-14 days
2) PO Cotrimoxazole 960mg BD x 7-14 days
3) PO Doxycycline x 7-14 days

27
Q

A patient diagnosed with cellulitis of the left lower extremity, with no discharge observed, has the following vital signs & labs: Temp 37.8 degC, HR 78 bpm, BP 128/91, RR 25 bpm, WBC 9.8 x 10^9/L. What appropriate Abx regimen can be recommended to this patient?

A

1) PO Cloxacillin 250-500mg QDS x 5 days

2) PO Cephalexin 250-500mg QDS x 5 days

28
Q

A patient diagnosed with cellulitis of the right lower extremity, with yellowish pus-like discharge observed, has the following vital signs & labs: Temp 38.9 degC, HR 89 bpm, BP 119/89, RR 20 bpm, WBC 12.1 x 10^9/L. What appropriate Abx regimen can be recommended to this patient, who complains of episodes of nausea & vomiting in the past 24h?

A

1) IV Cloxacillin 1-2g q4-6h x 5 days

2) IV Cefazolin 1-2g q8h x 5 days

29
Q

A patient who recently received chemotherapy is currently diagnosed with cellulitis of the right upper extremity, with yellowish pus-like discharge observed. He has the following vital signs & labs: Temp 38.3 degC, HR 92 bpm, BP 108/70, RR 21 bpm, WBC 8.2 x 10^9/L and is reported to have an allergy to penicillin (nausea). What appropriate Abx regimen can be recommended to this patient, who complains of episodes of nausea & vomiting in the past 24h?

A

First-line:
1) IV Vancomycin 15mg/kg q8-12h x 7-14 days

Alternatives:

1) IV Daptomycin
2) IV Linezolid

30
Q

A patient who recently received chemotherapy is currently in ICU & is diagnosed with cellulitis of the left upper extremity, with yellowish pus-like discharge observed. He has the following vital signs & labs: Temp 39.2 degC, HR 92 bpm, BP 98/56, RR 22 bpm, WBC 14.4 x 10^9/L. What appropriate Abx regimen can be recommended to this patient?

A

1) IV Piperacillin-tazobactam 4.5g q6-8h OR
2) IV Cefepime 2g q8h
AND additional
1) IV Vancomycin 15mg/kg q8-12h for MRSA coverage

31
Q

What other microorganisms we should consider when presented with a patient diagnosed with cellulitis from a bite wound?

A

Besides S. aureus & S. pyogenes,

1) Pasteurella multocida (from animal bites)
2) Eikenella corrodens (from human bites)
3) Oral anaerobes (e.g. Prevotella spp. & Peptostreptococcus spp.)

32
Q

What is the usual recommended Abx Tx options for patients diagnosed with cellulitis from bite wounds w/o MRSA risk factors?

A

Mild/moderate:

1) PO Amoxicillin-clavulanate 625mg BD-TDS x 5 days
2) PO Cefuroxime 500mg BD + PO Clindamycin 300mg QDS / PO Metronidazole 500mg TDS x 5 days
3) PO Ciprofloxacin 500mg BD / PO Levofloxacin 750mg OD + PO Clindamycin 300mg QDS / PO Metronidazole 500mg TDS x 5 days (for penicillin allergy)

Severe:

1) IV Amoxicillin-clavulanate 1.2g q8h for at least 5 days
2) IV Ceftriaxone 1g q12h + IV Clindamycin 600mg q8h / IV Metronidazole 500mg TDS for at least 5 days
3) IV Ciprofloxacin 400mg q8h / IV Levofloxacin 750mg OD + IV Clindamycin 600mg q8h / IV Metronidazole 500mg TDS for at least 5 days (for penicillin allergy)

33
Q

When is it recommended to de-escalate IV antibiotics to PO antibiotics in the Tx of SSTIs?

A

Afebrile for at least 48 continuous hours with clinical improvements (i.e. decreased pain, fever, swelling, erythema & warmth)
Dependent on culture results as well.

34
Q

Briefly describe the pathophysiology of diabetic foot infections (DFIs).

A

1) Neuropathy
- Peripheral: less pain sensation & altered pain response, resulting in increased risk of injuring w/o notice
- Motor: muscle imbalance increased risk of fall & injuries
- Autonomic: increased dryness, cracks & fissures increase risk of bacterial entry
2) Vasculopathy: Early atherosclerosis & peripheral vascular disease worsened by hyperglycemia & hyperlipidemia
3) Immunopathy: Impaired immune response -> increased susceptibility to infection & worsened by hyperglycaemia

Leads to ulcer formation or wounds & increase risk for colonisation, penetration & proliferation for DFIs to occur.

35
Q

Purulent discharge must be present to define a diabetic foot infection. True or false?

A

False. Either purulent discharge or >= 2 signs or symptoms of inflammation:
- Pain, tenderness, induration, erythema, warmth

36
Q

What are the likely microorganisms involved in the clinical presentation of DFI?

A
  • S. aureus & S. pyogenes are the most common.
  • Gram-negatives like E. coli, Klebsiella spp. & Proteus spp. (P. aeruginosa less common) in chronic wounds
  • Anaerobes like Peptostreptococcus spp. Veillonella spp., Bacteriodes spp. (particularly in ischaemic/necrotic wounds)
37
Q

Empiric antibiotics for all patients with DFI must cover MRSA. True or false?

A 
False.
Empirically cover MRSA when:
- Critically ill (i.e. admission to ICU)
- Immunosuppression
- Failure of Abx Tx w/o MRSA coverage.
38
Q

Empiric antibiotics for all patients with DFI should not cover P. aeruginosa. True or false?

A

True

39
Q

A patient diagnosed with DFI has the following vital signs & labs: Temp 38.8 degC, HR 78 bpm, BP 128/91, RR 22 bpm, WBC 9.8 x 10^9/L & is currently in ICU. What appropriate Abx regimen can be recommended to this patient?

A

1) IV Piperacillin-tazobactam 4.5g q6-8h OR
2) IV Cefepime 2g q8h + IV Clindamycin 600mg q8h
AND additional
1) IV Vancomycin 15mg/kg q8-12h for MRSA coverage
Duration of Tx = 2-4 weeks

40
Q

A patient diagnosed with DFI has the following vital signs & labs: Temp 37.8 degC, HR 102 bpm, BP 128/91, RR 22 bpm, WBC 9.8 x 10^9/L. He is currently on IV Cefepime 2g q8h + IV Clindamycin 600mg q8h as empiric Abx Tx. 3 days later, his culture results return and mentioned that E. coli is present and is resistant to cefepime. What appropriate Abx regimen should the patient be changed to?

A

IV Meropenem 1g q8h, due to likely presence of ESBL-producing strain of E. coli (indicated by 3rd & 4th generation cephalosporins).
Duration of Tx = 2-4 weeks

41
Q

What appropriate Abx regimen can be recommended to a patient diagnosed with DFI with erythema > 2cm around ulcer w/o MRSA risk factor & w/o any SIRS criteria met?

A

1) IV Amoxicillin-clavulanate 1.2g q8h
2) IV Ceftriaxone 1g q12h + IV Clindamycin 600mg q8h / IV Metronidazole 500mg TDS
Duration of Tx = 1-3 weeks

42
Q

What appropriate Abx regimen can be recommended to a patient diagnosed with DFI with erythema < 2cm around ulcer w/o MRSA risk factor w/o any SIRS criteria met?

A

1) PO Cloxacillin 250-500mg QDS
2) PO Cephalexin 250-500mg QDS
Duration of Tx = 1-2 weeks

43
Q

Should antibiotics be given to treat DFI until complete wound healing occur?

A

No

44
Q

What are some adjunctive measures to be recommended to patients diagnosed with DFI?

A

1) Proper wound care
- Debridement
- “Off-loading” via wearing supportive shoes to relieve pressure applied to wound area
- Apply dressings to promote a moist wound healing environment & control excess exudation
2) Foot care
- Daily inspection
- Active prevention of wounds and ulcers

45
Q

List the risk factors that increase the risk of developing pressure ulcers.

A

1) Reduced mobility (i.e. spinal cord injuries, paraplegic/hemiplegic)
2) Debilitated by severe chronic diseases (e.g. multiple sclerosis, cancer, stroke)
3) Reduced consciousness
4) Sensory & autonomic impairment
5) Extremes of age
6) Malnutrition

46
Q

Purulent discharge is one way to define a pressure ulcer infection. True or false?

A

True. Either purulent discharge or >= 2 signs or symptoms of inflammation:
- Pain, tenderness, induration, erythema, warmth

47
Q

Pharmacological treatment of pressure ulcer infection is the same as the treatment for _____.

A

Diabetic foot infections (DFIs)

48
Q

What are some adjunctive measures to be recommended to patients diagnosed with pressure ulcer infections?

A

1) Proper wound care
- Debridement
- Normal saline is preferred to clean wound
- Avoid harsh chemicals like soap (pH 10 vs skin pH 5.6)
- Apply dressings to promote a moist wound healing environment & control excess exudation
2) Relief / prevention of pressure ulcers
- Turn or reposition every 2 hours

PR3124 PT3 (12 decks)

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