Cellulitis

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cellulitis skin infection erythema swelling lower leg

This clinical photograph displays the lower extremity of a patient, demonstrating classic physical examination findings of cellulitis. The skin exhibits diffuse erythema and swelling extending across the anterior and lateral aspects of the leg. The texture is notably compromised, showing signs of desquamation (peeling), xerosis (dryness), and lichenification, particularly in the mid-to-lower portion. Multiple discrete skin lesions are visible, including areas of darker, crusted scabbing and potential ulceration that may serve as a portal of entry for infection. Small petechiae or ecchymotic spots are scattered within the erythematous region. The presentation is highly characteristic of an acute bacterial skin and soft tissue infection (SSTI), emphasizing the visual transition from healthy proximal skin to distal inflamed, edematous, and scaling tissue. This image is an educational resource for identifying inflammatory dermatological conditions and assessing secondary skin changes associated with chronic or severe cellulitis.

This clinical photograph displays the lower extremity of a patient, demonstrating classic physical examination findings of cellulitis. The skin exhibits diffuse erythema and swelling extending across the anterior and lateral aspects of the leg. The texture is notably compromised, showing signs of desquamation (peeling), xerosis (dryness), and lichenification, particularly in the mid-to-lower portion. Multiple discrete skin lesions are visible, including areas of darker, crusted scabbing and potential ulceration that may serve as a portal of entry for infection. Small petechiae or ecchymotic spots are scattered within the erythematous region. The presentation is highly characteristic of an acute bacterial skin and soft tissue infection (SSTI), emphasizing the visual transition from healthy proximal skin to distal inflamed, edematous, and scaling tissue. This image is an educational resource for identifying inflammatory dermatological conditions and assessing secondary skin changes associated with chronic or severe cellulitis.

This clinical photograph shows a posterior view of a patient's lower legs, providing a side-by-side comparison between a healthy limb and a symptomatic one. The left lower leg (right side of the image) exhibits classic clinical signs of cellulitis, characterized by significant unilateral edema and diffuse erythema. The affected skin shows a spectrum of inflammatory discoloration, ranging from bright red to deep purplish hues, particularly over the calf region. The skin texture appears tense and glossy due to underlying swelling. A thin, vertical line of serous fluid exudate is visible on the posterior-lateral aspect of the left calf. In contrast, the right lower leg (left side of the image) appears normal with healthy skin tone and no evidence of swelling. This visual demonstrates the acute presentation of a soft tissue infection, useful for teaching the differential diagnosis of unilateral leg swelling and redness, which may include cellulitis, deep vein thrombosis (DVT), or localized vasculitis.

This clinical photograph shows a posterior view of a patient's lower legs, providing a side-by-side comparison between a healthy limb and a symptomatic one. The left lower leg (right side of the image) exhibits classic clinical signs of cellulitis, characterized by significant unilateral edema and diffuse erythema. The affected skin shows a spectrum of inflammatory discoloration, ranging from bright red to deep purplish hues, particularly over the calf region. The skin texture appears tense and glossy due to underlying swelling. A thin, vertical line of serous fluid exudate is visible on the posterior-lateral aspect of the left calf. In contrast, the right lower leg (left side of the image) appears normal with healthy skin tone and no evidence of swelling. This visual demonstrates the acute presentation of a soft tissue infection, useful for teaching the differential diagnosis of unilateral leg swelling and redness, which may include cellulitis, deep vein thrombosis (DVT), or localized vasculitis.

A sequence of three clinical photographs illustrating the progression of cellulitis on the lower leg, categorized by clinical severity. The 'Mild' stage (left) shows a localized, erythematous patch with poorly defined borders and scattered red papules. The 'Moderate' stage (center) demonstrates expanding confluent erythema and edema covering a larger surface area; notably, ink markings are visible on the skin to monitor the spread of infection. The 'Severe' stage (right) depicts intense, deep red to violaceous erythema involving the majority of the limb, accompanied by significant inflammatory swelling, a shiny skin texture suggestive of severe edema, and focal areas of potential skin breakdown or desquamation. This comparison highlights key diagnostic features of skin and soft tissue infections (SSTIs), including changes in color intensity, surface area involvement, and signs of tissue tension associated with worsening bacterial infection.

A sequence of three clinical photographs illustrating the progression of cellulitis on the lower leg, categorized by clinical severity. The 'Mild' stage (left) shows a localized, erythematous patch with poorly defined borders and scattered red papules. The 'Moderate' stage (center) demonstrates expanding confluent erythema and edema covering a larger surface area; notably, ink markings are visible on the skin to monitor the spread of infection. The 'Severe' stage (right) depicts intense, deep red to violaceous erythema involving the majority of the limb, accompanied by significant inflammatory swelling, a shiny skin texture suggestive of severe edema, and focal areas of potential skin breakdown or desquamation. This comparison highlights key diagnostic features of skin and soft tissue infections (SSTIs), including changes in color intensity, surface area involvement, and signs of tissue tension associated with worsening bacterial infection.

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cellulitis skin AND infection management

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Cellulitis

Cellulitis is an acute bacterial infection of the skin and subcutaneous tissue, characterized by spreading erythema, warmth, edema, and tenderness. It is one of the most common skin infections seen in clinical practice, with a misdiagnosis rate as high as 30% in emergency settings.
Cellulitis of the lower leg - severe erythema, edema, and skin breakdown
Fig. 14.17 - Severe cellulitis of the lower leg showing intense erythema, edema, vesicle formation, and skin breakdown. (Andrews' Diseases of the Skin)

Definition & Pathophysiology

Cellulitis is a suppurative inflammation involving the subcutaneous tissue. It may be:
  • Nonpurulent - most common form; typically caused by beta-hemolytic streptococci (Group A Streptococcus accounts for ~75% of cases)
  • Purulent - drains freely; primarily caused by Staphylococcus aureus, including CA-MRSA
The inflammation involves increased local blood flow, edema, and recruitment of neutrophils. When localized edema becomes severe, epidermal layers can separate, leading to vesicles or bullae. Streaks of lymphangitis extending proximally are commonly seen, especially with streptococcal and Pasteurella multocida infections (bite wounds).
  • Andrews' Diseases of the Skin, p. 14.17
  • Rosen's Emergency Medicine, p. 2741

Etiology by Clinical Setting

SettingCommon Pathogens
Typical nonpurulent cellulitisStreptococcus pyogenes (Group A), other beta-hemolytic streptococci
Purulent cellulitis / abscessesS. aureus (CA-MRSA in most US cases)
Diabetic footS. aureus, streptococci (acute); polymicrobial with gram-negatives and anaerobes (chronic)
Cat bitesPasteurella multocida
Human bitesPolymicrobial (Eikenella, Fusobacterium, Group A Streptococcus, S. aureus)
Seawater exposureVibrio vulnificus (especially in liver disease), Erysipelothrix rhusiopathiae
Freshwater exposureAeromonas spp.
  • Rosen's Emergency Medicine, p. 2741

Risk Factors

  • Disruption of the skin barrier: wounds, tinea pedis, dermatophyte infections
  • Venous insufficiency and stasis
  • Lymphedema (impaired lymphatic drainage)
  • Obesity
  • Diabetes mellitus
  • Immunocompromised states (HIV, malignancy, immunosuppressive drugs)
  • Prior saphenous vein harvesting, lymphadenectomy, or radiation
  • Alcoholism
  • Goldman-Cecil Medicine, Chapter 408
  • Andrews' Diseases of the Skin

Clinical Features

Symptoms: fever, chills, malaise, pain/tenderness at the site
Signs:
  • Erythema - rapidly spreading, poorly defined and irregular borders
  • Warmth and edema - the affected skin may pit on pressure
  • Vesicles or bullae - from severe localized edema
  • Lymphangitis - streaks extending proximally toward regional lymph nodes
  • Lymphadenopathy (regional)
Erysipelas is a distinct superficial form where the border is well-demarcated, raised, and palpable - most often caused by S. pyogenes.
Key clinical pearl: Cellulitis is rarely bilateral. Bilateral lower leg redness should strongly prompt consideration of other diagnoses (e.g., venous stasis dermatitis).
  • Rosen's Emergency Medicine, p. 2740-2741

Differential Diagnosis ("Pseudocellulitis")

The misdiagnosis rate can be as high as 30%. Key mimics:
MimicDistinguishing Features
Venous stasis dermatitisUsually bilateral, centered over medial malleoli, no fever, no pain, often improves with elevation
Deep vein thrombosis (DVT)Unilateral leg swelling, confirmed on Doppler ultrasound
Contact dermatitisPruritic rather than painful, no systemic signs
Erythema migrans (Lyme)Target/bullseye appearance, >5 cm, central clearing, tick exposure history
Eosinophilic cellulitisExuberant insect bite reaction; eosinophilia rather than neutrophilia
GoutAcute joint involvement, hyperuricemia, responds to NSAIDs
Fixed drug eruptionDrug exposure history
Necrotizing fasciitisPain out of proportion, rapid progression, bullae with dark fluid, systemic toxicity - surgical emergency
The ALT-70 score (Asymmetry, Leukocytosis, Tachycardia, age ≥70) has been proposed to help differentiate cellulitis from pseudocellulitis, though it requires further validation.
  • Rosen's Emergency Medicine, p. 2741
  • Andrews' Diseases of the Skin

Diagnosis

Cellulitis is primarily a clinical diagnosis.
  • Blood cultures: Not indicated in uncomplicated cases. Recommended for immunocompromised patients or systemic infection
  • Wound cultures: Needle aspiration, superficial swabs, and skin biopsy are low-yield in nonpurulent cellulitis and not routinely recommended. Useful in: purulent cellulitis, immunocompromised hosts, bite wounds, immersion injuries
  • Lab work (CBC, CRP, ESR): Not routinely needed but may help assess severity and guide hospitalization decisions
  • Bedside ultrasound: High-frequency linear probe helps differentiate cellulitis (hyperechoic/cobblestoning) from abscess (hypoechoic with posterior acoustic enhancement)
  • CT/MRI: Consider if necrotizing fasciitis is suspected
  • Rosen's Emergency Medicine, p. 2741-2742

Management

Outpatient (mild, non-toxic, immunocompetent)

DrugDoseDuration
Cephalexin (first-line)500 mg QID orally5-10 days
Dicloxacillin500 mg QID orally5-10 days
Clindamycin300-450 mg QID orally10 days
TMP-SMX160/800 mg BID orally10 days
Penicillin VK (streptococcal)500 mg QID orally10 days
If MRSA is strongly suspected (prior MRSA, failed beta-lactam, purulent infection), use clindamycin or TMP-SMX.

Inpatient / Severe

Criteria for hospitalization: systemic symptoms (fever), immunosuppression, diabetic foot infections, infected lymphedema, large or multifocal cellulitis, or failure of outpatient antibiotics.
  • IV nafcillin or oxacillin for MSSA
  • IV vancomycin (15-20 mg/kg BID) for MRSA or when pathogen unclear
  • Vancomycin + imipenem (or piperacillin-tazobactam) for severe/polymicrobial cases
  • If Group A Strep confirmed: IV Penicillin G (4 million units q4h) + IV Clindamycin (600-900 mg q8h) for 10-14 days

Adjunctive Measures

  • Limb elevation to reduce edema
  • Mark the borders of erythema with a skin marker to monitor progression
  • Compression therapy in lymphedema to reduce recurrence risk
  • Treat underlying risk factors (tinea pedis, venous insufficiency)
  • Goldman-Cecil Medicine
  • Andrews' Diseases of the Skin
  • Rosen's Emergency Medicine, p. 2742

Complications

  • Lymphangitis and regional lymphadenopathy
  • Bacteremia and sepsis
  • Necrotizing fasciitis - the most feared complication; requires emergent surgical debridement (mortality 30-60%, up to 70-85% when diagnosis delayed)
  • Metastatic abscesses
  • Gangrene
  • Chronic lymphedema / elephantiasis nostras verrucosa (from recurrent episodes)
Complications are unusual in immunocompetent adults but occur more often in children and immunocompromised adults. Most cases in immunocompetent adults improve within 4-6 days of treatment.

Recurrent Cellulitis - Prevention

Predisposing factors for recurrence: alcoholism, diabetes, immunodeficiency, tinea pedis, venous stasis, lymphedema, prior knee prosthesis, saphenous phlebectomy, lymphadenectomy, or irradiation.
Secondary prophylaxis: Penicillin 250 mg orally BID is effective for preventing recurrent cellulitis in patients with chronic lymphedema and 3 or more episodes per year. A 2026 systematic review (Sierla et al., PMID 41275489) and a 2025 review on non-pharmacological prevention (Jacka et al., PMID 40530782) both highlight that managing the underlying predisposing condition (lymphedema, tinea pedis) is central to reducing recurrence.

Recent Evidence

A 2024 meta-analysis on diagnostic stewardship (Lin et al., PMID 39614879) found that dermatology consultation significantly reduces cellulitis misdiagnosis and inappropriate antibiotic use. Given the high pseudocellulitis rate, early specialist input is worthwhile in uncertain cases.

Clinical Image Gallery

Cellulitis posterior lower legs - unilateral erythema and edema
Posterior view showing unilateral erythema and edema of the left lower leg - a classic presentation of cellulitis compared to the normal right leg.
Cellulitis severity progression - mild, moderate, severe stages

Sources: Andrews' Diseases of the Skin (Clinical Dermatology) | Rosen's Emergency Medicine | Goldman-Cecil Medicine | Textbook of Family Medicine 9e

Treatment

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PMID: 39240378

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Cellulitis: Treatment

Treatment is guided by two key axes: purulent vs. nonpurulent infection, and severity (mild / moderate / severe).

General Measures (All Cases)

  • Elevate the affected limb - reduces edema and promotes drainage
  • Mark the border of erythema with a skin marker at presentation to monitor spread
  • Incision and drainage (I&D) if an abscess component is identified
  • Treat predisposing conditions: tinea pedis, venous insufficiency, lymphedema, skin dryness/cracking (topical emollients)
  • Optimize comorbidities: glycemic control in diabetes, compression therapy in lymphedema
  • Tintinalli's Emergency Medicine, p. 3890
  • Fischer's Mastery of Surgery 8e, p. 7912

Classification of Severity

ClassFeatures
MildNo systemic symptoms; able to take oral medications
ModerateSystemic symptoms (fever, tachycardia) but not septic; may need IV then step-down
SevereSepsis, rapid spread, immunocompromised, failed oral therapy, necrotizing features

A. Nonpurulent Cellulitis (Most Common)

The dominant pathogens are beta-hemolytic streptococci (Group A, B, C, G). MRSA is not a common cause of nonpurulent cellulitis.

Mild - Outpatient (Oral)

DrugDoseDuration
Cephalexin (first-line)500 mg QID5-10 days
Dicloxacillin500 mg QID5-10 days
Penicillin VK (confirmed streptococcal)500 mg QID10 days
Amoxicillin500 mg TID5-10 days
Clindamycin300-450 mg QID10 days
For uncomplicated cases, 5 days of cephalexin is often sufficient and as effective as longer courses. Adding TMP-SMX (dual MRSA/strep coverage) to cephalexin does not reduce treatment failure in uncomplicated nonpurulent cellulitis.

Moderate to Severe - Inpatient (IV)

DrugDose
Cefazolin (first-line IV)1-2 g q8h
Nafcillin / Oxacillin1-2 g q4-6h
Penicillin G (confirmed streptococcal)2-4 million units q4-6h
Clindamycin (penicillin allergy)600-900 mg q8h IV
Vancomycin (MRSA coverage needed, or severe)15-20 mg/kg q8-12h IV
Step down to oral therapy once systemic symptoms resolve (usually 48-72 h).
  • Goldman-Cecil Medicine
  • Tintinalli's Emergency Medicine
  • Andrews' Diseases of the Skin

B. Purulent Cellulitis / MRSA-Suspected

CA-MRSA is the leading cause of purulent skin and soft tissue infections.

Mild - Outpatient (Oral)

DrugDoseDuration
TMP-SMX (first-line MRSA)160/800 mg (1 DS tab) BID5-10 days
Doxycycline100 mg BID5-10 days
Clindamycin (check D-zone test)300-450 mg QID10 days

Moderate to Severe - Inpatient (IV)

DrugDose
Vancomycin15-20 mg/kg q8-12h
Daptomycin4-6 mg/kg/day
Linezolid600 mg q12h IV/PO
Tedizolid200 mg daily
  • Rosen's Emergency Medicine
  • Fischer's Mastery of Surgery 8e

C. Special Situations

Penicillin Allergy

  • Non-IgE-mediated: first-generation cephalosporin is safe
  • IgE-mediated (anaphylaxis): use clindamycin, linezolid, or vancomycin

Diabetic Foot Infection

  • Acute: covers Staph/Strep - cephalexin or amoxicillin-clavulanate (oral); piperacillin-tazobactam or carbapenem (IV) for severe/chronic
  • Chronic/polymicrobial: broad-spectrum coverage including gram-negatives and anaerobes
  • Always add MRSA coverage (vancomycin) in severe or previously treated cases
  • Wound care, debridement, and revascularization as needed

Immunocompromised Patients

  • Lower threshold for hospitalization and IV therapy
  • Vancomycin + anti-gram-negative coverage (e.g., vancomycin + piperacillin-tazobactam or carbapenem)
  • Blood and wound cultures are indicated

Water/Environmental Exposure

  • Seawater (Vibrio vulnificus): doxycycline + ceftriaxone (especially in liver disease - high mortality risk)
  • Freshwater (Aeromonas): ciprofloxacin or TMP-SMX
  • Fish tank / aquarium (Mycobacterium marinum): clarithromycin or minocycline + rifampicin

Bite Wounds

  • Cat bites (Pasteurella multocida): amoxicillin-clavulanate - presumptive treatment appropriate given high infection rate
  • Dog bites: amoxicillin-clavulanate if prophylaxis indicated (hand, face, immunocompromised)
  • Human bites: amoxicillin-clavulanate or ampicillin-sulbactam (polymicrobial including Eikenella)

D. Indications for Hospitalization

Admit if any of the following are present:
  • Systemic toxicity (fever, tachycardia, hypotension)
  • Failure of 48-72 h of oral antibiotics
  • Immunosuppression (HIV, chemotherapy, steroids, transplant)
  • Diabetic foot infection
  • Infected lymphedema
  • Large or rapidly spreading cellulitis
  • Cellulitis overlying a joint, vascular graft, or prosthetic implant
  • Toxic shock syndrome features
  • Suspected necrotizing fasciitis (surgical emergency)
  • Rosen's Emergency Medicine, p. 2742
  • Fischer's Mastery of Surgery 8e, p. 7912

E. Duration of Therapy

ScenarioDuration
Uncomplicated mild cellulitis5-6 days
Moderate cellulitis10 days
Severe / immunocompromisedUp to 14 days
Streptococcal cellulitis (confirmed)10-14 days
Hospitalized patients benefit from daily digital photographs of the involved area to objectively document response to treatment.

F. Recurrence Prevention (Secondary Prophylaxis)

Indicated when the patient has chronic lymphedema + 3 or more episodes/year:
DrugDose
Penicillin V250 mg BID orally (long-term)
Erythromycin250-500 mg daily (penicillin allergy)
Compression therapy to manage lymphedema is equally important for reducing recurrence. A 2026 systematic review (Sierla et al., PMID 41275489) confirmed that management of underlying predisposing conditions is the cornerstone of secondary prevention.

G. Necrotizing Fasciitis - When to Suspect & Escalate

Never miss this. Red flags warranting urgent surgical consultation:
  • Pain out of proportion to exam findings
  • Rapid progression despite antibiotics
  • Bullae with dark/bloody fluid
  • Skin necrosis or crepitus
  • Systemic shock
Management:
  • Immediate surgical exploration and aggressive debridement
  • Empiric broad-spectrum IV: vancomycin + piperacillin-tazobactam (or carbapenem + clindamycin)
  • Once Group A Strep confirmed: IV Penicillin G (4 million units q4h) + IV Clindamycin (600-900 mg q8h) for 10-14 days
  • Mortality: 30-60% even with appropriate treatment; up to 70-85% when diagnosis is delayed

Recent Evidence

A 2024 network meta-analysis (Shu et al., PMID 39240378) analyzing 10 RCTs with 1,936 patients found:
  • No significant differences in cure rates among the major antibiotics studied for cellulitis (cephalexin, clindamycin, TMP-SMX, ceftriaxone, flucloxacillin, penicillin)
  • Cefaclor had the most favorable curative profile for cellulitis
  • Ceftriaxone had the fewest GI side effects
  • This supports current guidelines that multiple agents are acceptable first-line options

Sources: Tintinalli's Emergency Medicine | Rosen's Emergency Medicine | Andrews' Diseases of the Skin | Goldman-Cecil Medicine | Fischer's Mastery of Surgery 8e

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Cellulitis: Injectable (IV/IM) Antibiotics

Injectable antibiotics are used when oral therapy is not appropriate - due to severity, systemic toxicity, failed oral treatment, immunosuppression, or the need for rapid drug levels. The choice depends on purulent vs. nonpurulent infection and MRSA risk.

When to Use Injectables

IndicationRoute
Systemic symptoms (fever, tachycardia, hypotension)IV
Failed 48-72 h of oral antibioticsIV
Immunocompromised (HIV, steroids, transplant, chemotherapy)IV
Diabetic foot infection (moderate-severe)IV
Infected lymphedemaIV
Large, rapidly spreading, or multifocal cellulitisIV
Sepsis / suspected necrotizing fasciitisIV (urgent)
Unable to tolerate oral medicationsIV or IM

1. Nonpurulent Cellulitis (Streptococcal, No MRSA Risk)

First-Line IV

DrugAdult DoseFrequencyNotes
Cefazolin1-2 gq8h IVFirst-line IV agent; well tolerated
Nafcillin1-2 gq4-6h IVAnti-staphylococcal penicillin; MSSA coverage
Oxacillin1-2 gq4-6h IVEquivalent to nafcillin
Penicillin G2-4 million unitsq4-6h IVWhen Group A Strep confirmed
Ampicillin-sulbactam1.5-3 gq6h IVAdds anaerobic/gram-negative coverage

Penicillin-Allergic (Non-anaphylactic)

DrugAdult DoseFrequency
Cefazolin1-2 gq8h IV (safe if non-IgE allergy)
Clindamycin600-900 mgq8h IV

Penicillin-Allergic (IgE-mediated / Anaphylaxis)

DrugAdult DoseFrequency
Clindamycin600-900 mgq8h IV
Vancomycin15-20 mg/kgq8-12h IV
Linezolid600 mgq12h IV/PO

2. Purulent Cellulitis / MRSA Suspected or Confirmed

DrugAdult DoseFrequencyNotes
Vancomycin15-20 mg/kgq8-12h IVStandard MRSA agent; monitor trough levels or AUC
Daptomycin4-6 mg/kgOnce daily IVAlternative to vancomycin; cannot use in pneumonia
Linezolid600 mgq12h IV or POIV bioequivalent to oral; useful step-down
Tedizolid200 mgOnce daily IVNewer oxazolidinone; good MRSA coverage
Vancomycin is the recommended parenteral agent for MRSA in cellulitis.

3. Severe / Sepsis / Unknown Source

Broad-spectrum empiric coverage while awaiting cultures:
RegimenIndication
Vancomycin + Piperacillin-tazobactamSepsis with suspected skin source; covers MRSA + gram-negatives + anaerobes
Vancomycin + Carbapenem (imipenem/meropenem)Severe immunocompromised; MDR organisms possible
Vancomycin + CefepimeNeutropenic or high gram-negative risk
Standard dosing for the combination agents:
DrugDoseFrequency
Vancomycin15-20 mg/kgq8-12h
Piperacillin-tazobactam3.375 g (or 4.5 g)q6h (or q8h extended infusion)
Imipenem500 mgq6h
Meropenem1 gq8h
Cefepime1-2 gq8-12h

4. Necrotizing Fasciitis (Surgical Emergency)

Requires immediate surgical debridement + broad-spectrum IV antibiotics:
Empiric (polymicrobial coverage):
DrugDoseFrequency
Vancomycin15-20 mg/kgq8-12h IV
+ Piperacillin-tazobactam3.375-4.5 gq6-8h IV
OR + Carbapenem500 mg (imipenem)q6h IV
+ Clindamycin600-900 mgq8h IV (anti-toxin effect)
Once Group A Strep confirmed (narrow down to):
DrugDoseFrequencyDuration
Penicillin G4 million unitsq4h IV10-14 days
+ Clindamycin600-900 mgq8h IV10-14 days
Clindamycin is kept even with penicillin because it inhibits toxin production by Group A Strep via ribosomal (50S) blockade - this is the rationale for dual therapy.

5. Novel Long-Acting Lipoglycopeptides (Single/Weekly Dose)

These agents cover all major cellulitis pathogens including MRSA, with extremely long half-lives:
DrugDoseRegimenNotes
Oritavancin (Orbactiv)1200 mgSingle IV infusion (3 h)Entire course in one dose; useful to avoid admission
Dalbavancin (Dalvance)1500 mgSingle IV infusion OR 1000 mg then 500 mg on Day 8Once-weekly regimen
These are particularly useful for patients who need IV-level treatment but lack an absolute indication for hospitalization (e.g., no sepsis, no surgical emergency, concerns about oral compliance).
  • Rosen's Emergency Medicine, p. 2742

6. Special Scenarios - Injectable Choice

ScenarioPreferred IV Agent
MSSA confirmedNafcillin / Oxacillin / Cefazolin
MRSA confirmedVancomycin (first-line); Daptomycin or Linezolid (alternatives)
Seawater exposure (Vibrio)Doxycycline 100 mg IV q12h + Ceftriaxone 1-2 g IV once daily
Freshwater (Aeromonas)Ciprofloxacin 400 mg IV q12h
Necrotizing (polymicrobial)Vancomycin + Pip-tazo + Clindamycin
Penicillin allergy + MSSAClindamycin or Vancomycin IV
Diabetic foot (severe)Vancomycin + Pip-tazo or Carbapenem
NeutropenicVancomycin + antipseudomonal agent

Step-Down to Oral

Once the patient is afebrile, erythema is improving/stable, and they can tolerate oral medications (usually 48-72 h after starting IV):
IV Drug UsedStep Down To
CefazolinCephalexin 500 mg QID
Nafcillin / OxacillinDicloxacillin 500 mg QID
Vancomycin (MRSA)TMP-SMX DS 1 tab BID or Doxycycline 100 mg BID
Clindamycin IVClindamycin 300-450 mg QID orally
Linezolid IVLinezolid 600 mg q12h orally (bioequivalent)
Total duration: 5-6 days (uncomplicated) to 10-14 days (severe or immunocompromised), counting both IV and oral phases together.

Sources: Rosen's Emergency Medicine (Table 126.2, 127.3) | Goldman-Cecil Medicine | Fischer's Mastery of Surgery 8e | Andrews' Diseases of the Skin
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