Skin & Soft Tissue Infections Flashcards
Briefly explain the pathophysiology of SSTIs.
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
What are some predisposing factors that increase the risk of developing SSTIs?
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
What are the likely microorganisms involved in the clinical presentation of impetigo & ecthyma?
1) Staphylococcus aureus
2) Beta-hemolytic streptococci (e.g. S. pyogenes)
Is culture always required before Abx Tx of impetigo?
No. Reasonable to treat empirically without culture.
May culture if pus is present, but generally not practised.
Empiric treatment of ecthyma should always cover MRSA. True or false?
False.
Increasing prevalence in Singapore, but low (30-35%) as compared to other countries.
What is the recommended Tx for a patient diagnosed with mild impetigo?
Apply topical mupirocin to affected areas BD for 5 days.
What is the recommended empiric Tx for a patient diagnosed with ecthyma?
1) PO Cloxacillin 250-500mg QDS x 7 days
2) PO Cephalexin 250-500mg QDS x 7 days
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?
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.
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?
PO Clindamycin 300mg QDS x 7 days
What is the recommended Tx for a patient diagnosed with moderate purulent impetigo with a positive culture result of S. pyogenes?
PO Penicillin VK 250-500mg QDS x 7 days
What are some specific risk factors that increase the risk of developing purulent SSTIs?
1) Close physical contact
2) Crowded living quarters (e.g. dormitories, military camps, prisons)
3) Sharing of personal items
4) Poor personal hygiene
What is/are the likely microorganism(s) involved in the clinical presentation of purulent SSTIs?
Staphylococcus aureus
However, large skin abscesses may be polymicrobial.
The mainstay treatment of furuncles & carbuncles is systemic antibiotic therapy. True or false?
False! First-line therapy is incision & drainage (I&D).
Abx Tx is considered adjunctive therapy.
When will systemic Abx Tx be recommended for patients diagnosed with purulent SSTIs?
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)
List all of the systemic inflammatory response syndrome (SIRS) criteria.
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
What is the recommended adjunctive Tx for a patient discharged home for a diagnosis with purulent SSTI w/o MRSA coverage?
1) PO Cephalexin 250-500mg QDS x 5-7 days
2) PO Cloxacillin 250-500mg QDS x 5-7 days
What is the recommended adjunctive Tx for a patient discharged home for a diagnosis with purulent SSTI with MRSA coverage?
1) PO Clindamycin 300mg QDS x 5-7 days
2) PO Cotrimoxazole 960mg BD x 5-7 days
3) PO Doxycycline
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?
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
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?
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
Differentiate between cellulitis & erysipelas.
Cellulitis: purulent or non-purulent w/ poorly demarcated area of erythema
Erysipelas: always non-purulent w/ sharply demarcated area of erythema w/ raised border
What are two patient-specific comorbidities we should look out for identifying likely microorganisms causing cellulitis & erysipelas?
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
When is culture recommended in patients diagnosed with cellulitis?
1) Presence of discharge after I&D
2) Immunosuppression
3) Presence of SIRS criteria
List all MRSA risk factors for consideration in empiric Abx Tx of cellulitis, DFI & pressure ulcer infections
1) Critically ill (i.e. admission to ICU/emergency ward)
2) Immunosuppression
3) Previously failed Abx w/o MRSA activity
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?
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
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?
PO Clindamycin 300mg QDS x 5 days
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?
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
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?
1) PO Cloxacillin 250-500mg QDS x 5 days
2) PO Cephalexin 250-500mg QDS x 5 days
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?
1) IV Cloxacillin 1-2g q4-6h x 5 days
2) IV Cefazolin 1-2g q8h x 5 days
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?
First-line:
1) IV Vancomycin 15mg/kg q8-12h x 7-14 days
Alternatives:
1) IV Daptomycin
2) IV Linezolid
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?
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
What other microorganisms we should consider when presented with a patient diagnosed with cellulitis from a bite wound?
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.)
What is the usual recommended Abx Tx options for patients diagnosed with cellulitis from bite wounds w/o MRSA risk factors?
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)
When is it recommended to de-escalate IV antibiotics to PO antibiotics in the Tx of SSTIs?
Afebrile for at least 48 continuous hours with clinical improvements (i.e. decreased pain, fever, swelling, erythema & warmth)
Dependent on culture results as well.
Briefly describe the pathophysiology of diabetic foot infections (DFIs).
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.
Purulent discharge must be present to define a diabetic foot infection. True or false?
False. Either purulent discharge or >= 2 signs or symptoms of inflammation:
- Pain, tenderness, induration, erythema, warmth
What are the likely microorganisms involved in the clinical presentation of DFI?
- 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)
Empiric antibiotics for all patients with DFI must cover MRSA. True or false?
False. Empirically cover MRSA when: - Critically ill (i.e. admission to ICU) - Immunosuppression - Failure of Abx Tx w/o MRSA coverage.
Empiric antibiotics for all patients with DFI should not cover P. aeruginosa. True or false?
True
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?
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
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?
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
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?
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
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?
1) PO Cloxacillin 250-500mg QDS
2) PO Cephalexin 250-500mg QDS
Duration of Tx = 1-2 weeks
Should antibiotics be given to treat DFI until complete wound healing occur?
No
What are some adjunctive measures to be recommended to patients diagnosed with DFI?
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
List the risk factors that increase the risk of developing pressure ulcers.
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
Purulent discharge is one way to define a pressure ulcer infection. True or false?
True. Either purulent discharge or >= 2 signs or symptoms of inflammation:
- Pain, tenderness, induration, erythema, warmth
Pharmacological treatment of pressure ulcer infection is the same as the treatment for _____.
Diabetic foot infections (DFIs)
What are some adjunctive measures to be recommended to patients diagnosed with pressure ulcer infections?
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
