Purulent Skin and Soft Tissue Infections
Purulent Skin and Soft Tissue Infections
References
- Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America — Clinical Infectious Diseases (Stevens DL, Bisno AL, Chambers HF, et al.). Clin Infect Dis 2014;59(2):e10-e52
- Clinical practice guidelines by the Infectious Diseases Society of America for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children — Clinical Infectious Diseases (Liu C, Bayer A, Cosgrove SE, et al.). Clin Infect Dis 2011;52(3):e18-e55
- Reserve list for antimicrobial drugs — Public Health Agency of Canada. Updated November 2024
- Treatment of skin abscesses: a review of wound packing and post-procedural antibiotics — South Dakota Medicine (List M, Headlee D, Kondratuk K). S D Med 2016;69(3):113-119
- Staphylococcus aureus decolonization for recurrent skin and soft tissue infections in children — Canadian Family Physician (Smith CH, Goldman RD). Can Fam Physician 2012;58(12):1350-1352
Clinical Snapshot
Purulent skin and soft-tissue infection is primarily a S. aureus problem, including both methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) strains. A furuncle originates in a hair follicle; a carbuncle is interconnected furuncles; an abscess is a localized pus collection in dermal/subcutaneous tissue.[1] Drainage is the treatment for drainable pus; antibiotics are added for host risk, surrounding cellulitis, systemic illness, a difficult location, or inadequate drainage.
Recognize the Condition
Focal painful, tender, raised lesion with fluctuance or purulent drainage.
The purulent SSTI spectrum
Furuncle
Deeper follicular nodule/boil.
Carbuncle
Cluster of interconnected draining furuncles.
Abscess
Localized collection of pus without required follicular origin.
Purulent cellulitis
Cellulitis with purulent drainage/exudate, even without an obvious discrete abscess.
Risk Factors
- Prior MRSA infection or colonization.
- Skin trauma and close-contact transmission.
- Crowded living conditions, contact sports, incarceration, or injection drug use.
- Diabetes or immunosuppression.
- Recurrent disease, hidradenitis suppurativa, pilonidal disease, or a retained foreign body.
Red Flags & Refer
Urgent referral/hospital assessment for any of the following:
- Severe systemic illness.
- Rapid progression.
- Deep-space infection.
- Facial/periorbital lesions not safely drainable.
- Hand infection with functional compromise.
- Necrosis.
- Crepitus.
- Severe pain out of proportion.
- Immunocompromise with major infection.
- Failure after adequate drainage plus therapy.
Assessment & Diagnosis
Examine for fluctuance, spontaneous drainage, surrounding cellulitis, lymphangitis, and systemic toxicity. Ultrasound is useful when a deep or occult abscess is uncertain.
Recurrent abscess at the same site
Do not repeatedly prescribe antibiotics without looking for hidradenitis suppurativa, a pilonidal cyst, a foreign body, or another local structural cause.
Treatment Targets
- Achieve source control by draining pus.
- Stop surrounding cellulitis and systemic spread.
- Use culture results to narrow therapy.
- Prevent recurrence by correcting colonization or structural causes when relevant.
Choose Initial Treatment
Drainable abscess
Incision and drainage first.
Add antibiotics only when systemic symptoms, extensive surrounding cellulitis, a difficult/nondrainable site, immunocompromise, or recurrent disease is present.[2]
When antibiotics are indicated and MRSA risk is low
1st line: cephalexin.
When MRSA risk is meaningful (systemic symptoms, prior MRSA, high local prevalence, immunocompromise)
1st line: trimethoprim-sulfamethoxazole or doxycycline.
Add streptococcal coverage if substantial surrounding nonpurulent cellulitis is also present.
Severe purulent infection / systemic illness
1st line (IV): vancomycin.
Reserve-list alternatives (specialist-directed): linezolid, dalbavancin, or daptomycin.[3]
Non-Pharmacologic Treatment
- Warm compresses for small early furuncles that have not yet organized into a drainable abscess.
- Do not squeeze boils.
- Cover draining wounds and use meticulous hand hygiene.
- Routine packing after uncomplicated drainage is optional rather than mandatory — it does not appear to influence clinical cure rates.[4]
- For selected recurrent S. aureus infection, consider a decolonization course of intranasal mupirocin plus chlorhexidine body cleansing.[5]
Pharmacologic Treatment Options
| Drug / intervention | Role | Dose / use | Important adverse effects | Teaching points |
|---|---|---|---|---|
| Incision and drainage Preferred | Primary treatment for any fluctuant abscess, furuncle, or carbuncle with drainable pus | Procedure, not a drug | Procedural risk only | Send purulent material for culture in recurrent, severe, MRSA-risk, or treatment-failure cases. |
| Cephalexin Preferred | MSSA when MRSA is unlikely, after drainage | 500 mg PO QID for about 5-7 days, adjusted to response | GI upset, hypersensitivity | Use when local MRSA risk is low. |
| Sulfamethoxazole/Trimethoprim Preferred | MRSA risk, culture-confirmed MRSA, or systemic symptoms | 1-2 DS tablets PO BID | Rash, hyperkalemia, renal effects, cytopenias | Add streptococcal coverage when surrounding nonpurulent cellulitis is significant. |
| Doxycycline Preferred | Alternative MRSA-active oral therapy | 100 mg PO BID | Photosensitivity, esophagitis | Avoid in pregnancy. |
| Clindamycin Alternative | MRSA + streptococcal coverage when susceptible | 300-450 mg PO TID | Diarrhea, C. difficile infection | Inducible resistance can occur — confirm susceptibility. |
| Vancomycin Special situation | Severe purulent infection / systemic illness | Weight-based IV dosing with institutional AUC monitoring | Nephrotoxicity, infusion reaction | Hospital/specialist use for severe disease. |
| Linezolid Special situation | MRSA when standard agents cannot be used or resistance is documented | 600 mg PO/IV Q12H | Myelosuppression, serotonin syndrome | Reserve-listed — infectious-disease guidance recommended.<cite data-reference-id="dd6d638d-375a-4623-95b4-3fec02e9eccd"></cite> |
Special Populations
Pregnancy
Drainage remains the primary intervention regardless of trimester. When antibiotics are needed, choose pregnancy-compatible agents guided by organism and susceptibility; avoid doxycycline, and generally avoid trimethoprim-sulfamethoxazole in the first trimester (neural tube defect risk) and near term (kernicterus risk) when a safer effective option exists.
Immunocompromised patients
Use a lower threshold for systemic therapy, culture, imaging, and referral because source control alone may be insufficient.
Monitoring & Follow-Up
After drainage, pain and pressure should fall quickly. Reassess within 24-48 hours when disease is extensive, packing was used, systemic therapy was started, or host risk is present. Worsening pain, spreading erythema, or new systemic symptoms requires urgent reassessment.
Treatment Failure / Next Step
- Confirm adequate drainage/source control.
- Review culture and susceptibility.
- Look for an undrained loculation or deeper collection.
- Assess adherence and whether the chosen therapy covers MRSA and streptococci as required.
- Investigate hidradenitis, pilonidal disease, or foreign body in recurrent same-site abscess.
Common Errors to Avoid
- Giving antibiotics without draining a clearly drainable abscess.
- Assuming every abscess needs antibiotics.
- Using trimethoprim-sulfamethoxazole alone when extensive nonpurulent streptococcal cellulitis also needs coverage.
- Repeatedly treating recurrent axillary/groin abscesses without considering hidradenitis suppurativa.
- Failing to culture severe or recurrent purulent infection.
Clinical Decision Algorithm
Drug Tables
How to use this table: Doses are adult doses and require patient-specific confirmation (renal/hepatic function, weight, allergy history). Pediatric dosing is weight-based per the current product monograph unless stated. Drug pricing is intentionally omitted. Select any drug name to open its complete Pharmasist Drug Database page.
MSSA-directed oral therapy
| Drug | Dosage | Adverse effects | Comments |
|---|---|---|---|
| Cephalexin | Adults: 500 mg PO QID for about 5-7 days, adjusted to response Children: 25-50 mg/kg/day divided Q6H PO | GI upset, hypersensitivity | Use after drainage when MSSA is expected. |
MRSA-active oral therapy
| Drug | Dosage | Adverse effects | Comments |
|---|---|---|---|
| Sulfamethoxazole/Trimethoprim | Adults: 1-2 DS tablets PO BID Infants (2 months+), children, adolescents: 8-12 mg/kg/day (TMP component) divided Q12H PO | Rash, hyperkalemia, renal effects, cytopenias | Add streptococcal coverage when surrounding nonpurulent cellulitis is significant. |
| Doxycycline | Adults: 100 mg PO BID Children over 8 years: 2-4 mg/kg/day divided Q8-12H PO (max 100 mg/dose) | Photosensitivity, esophagitis, chelation interactions | Add streptococcal coverage when needed. Avoid in pregnancy. |
| Clindamycin | Adults: 300-450 mg PO TID Children over 1 month: 25-40 mg/kg/day divided Q8H PO (max 450 mg/dose) | Diarrhea, C. difficile infection; inducible resistance can occur | Use when local isolate is susceptible. |
Severe / parenteral therapy
Reserve-list agents require infectious-disease guidance and should be used only when resistance has been established or other agents are contraindicated.
| Drug | Dosage | Adverse effects | Comments |
|---|---|---|---|
| Vancomycin | Adults: 1 g Q12H (or 15 mg/kg Q8-12H) IV, institutional AUC monitoring Children: 45-60 mg/kg/day divided Q6-8H IV | Nephrotoxicity, infusion reaction | Severe purulent SSTI/systemic illness. |
| Linezolid | Adults and children 12+: 600 mg PO/IV Q12H Infants and children under 12: 10 mg/kg/dose Q8H PO/IV (max 600 mg/dose) | Myelosuppression (>2 wk use), peripheral/optic neuropathy, serotonin syndrome | Reserve-listed; contraindicated with MAOIs.<cite data-reference-id="dd6d638d-375a-4623-95b4-3fec02e9eccd"></cite> |
| Dalbavancin | Adults: 1.5 g IV once, or 1 g then 500 mg one week later Children 6-17 years: 18 mg/kg IV once (max 1.5 g) Children 3 months-5 years: 22.5 mg/kg IV once (max 1.5 g) | GI effects, infusion reactions, headache | Long-acting specialist/ambulatory infectious-disease option. |
| Daptomycin | Adults: 4-6 mg/kg IV Q24H Children 12-17 years: 5 mg/kg IV Q24H Children 7-11 years: 7 mg/kg IV Q24H Children 2-6 years: 9 mg/kg IV Q24H Children 1 year: 10 mg/kg IV Q24H | Myopathy/rhabdomyolysis; monitor CPK | Last-line for resistant Gram-positive infection; statins increase muscle-toxicity risk.<cite data-reference-id="dd6d638d-375a-4623-95b4-3fec02e9eccd"></cite> |
Professional reference only. Apply clinical judgment and verify patient-specific decisions against current authoritative guidance and product information.