| Grade | Infection Severity | Clinical Manifestations | Treatment Location | Treatment |
| 1 | Uninfected | Wound without purulence or inflammation | Outpatient | Topical antibiotics |
| 2 | Mild | >2:purlence or erythema, pain, tenderness, warmth, or induration, cellulitis <2cm around ulcer; infection limited to skin/subQ tissue, no complications | Mostly Outpatient—Oral | 1. Cephalexin 500 mg PO every 6 hours 2. Trimethoprim/sulfamethoxazole 2 160 -800 mg tablets PO every 12 hours 3. Levofloxacin 500 mg every 24 hours (or, if there is concern for P. aeruginosa, 750 mg every 24 hours) 4. Amoxicillin clavulanate 5. Clindamycin 300 to 450 mg PO every 6 to 8 hours |
| 3 | Moderate | Above plus >1: cellulitis >2cm, streaking, deep tissue abscess, gangrene, and involvement of muscle, tendon, joint, or bone. | Hospital—IV or PO | 1. Ceftriaxone 1 g every 24 hours + metronidazole 500 mg every 8 hours 2. Ertapenem 1 g every 24 hours 3. Ampicillin-sulbactam 3 g every 6 hours |
| 4 | Severe | Infection plus systemic toxicity or metabolic instability, fever, chills, tachycardia, hypotension, confusion, vomiting, severe, hyperglycemia, acidosis, or azotemia | Hospital, possibly ICU—IV | 1. Cefepime 2 g every 8 hours PLUS metronidazole 500 mg every 8 hours 2. Imipenem-cilastin 500 mg every 6 hours 3. Meropenem 1 g every 8 hours 4. Piperacillin-tazobactam 3.375 g every 6 hours or 4.5 g every 6 to 8 hours if pseudomonas suspected 5. Levofloxacin 750 mg IV every 24 hours PLUS metronidazole 500 mg every 8 hours. |
| 1. Add vancomycin if MRSA suspected |
Duration of therapy should be individualized. For those treated in outpatient settings with oral antibiotics, duration of treatment is usually 7-14 days. Treat for 1-2 weeks for moderate to severe infections. Extended duration for osteomyelitis. After amputation, continue 2-5 days.
Osteomyelitis:
Signs and symptoms – fever, chills, localized pain, tenderness, swelling
Treatment:
- Peds: cefazolin, nafcillin, oxacillin, clindamycin (MRSA resistance >10), vancomycin (if MRSA and clindamycin resistance >10)
- Adults: nafcillin, oxacillin, cefazolin, ceftriaxone, clindamycin, vancomycin
- Treat 4-6 weeks.
- Add rifampin for prosthetic joints.
**New IDSA Guidelines 2023**
| Infection severity | Additional factors | Usual pathogen(s) | Potential empirical regimens |
| Mild | No complicating features | GPC | Semisynthetic penicillinase-resistant penicillin (cloxacillin) or 1st generation cephalosporin (cephalexin) |
| ß-lactam allergy or intolerance | GPC | Clindamycin, Fluoroquinolone (levo/moxifloxacin), trimethoprim-sulfamethoxazole or doxycycline | |
| Recent antibiotic exposure | GPC + GNR | ß-lactam- ß lactamase inhibitor (amoxicillin /clavulanate, ampicillin/sulbactam), Fluoroquinolone (levo/moxi-floxacin) or Trimethoprim-sulfamethoxazole | |
| High risk for MRSA | MRSA | Linezolid, Ttrimethoprim-sulfamethoxazole, Clindamycin, Doxycycline, or Fluoroquinolone (levofloxacin, moxifloxacin) | |
| Moderate or severed | No complicating features | GPC ± GNR | ß-lactam- ß lactamase inhibitor1 (amoxicillin /clavulanate, ampicillin/sulbactam), or 2nd , 3rd generation cephalosporins (cefuroxime, cefotaxime, ceftriaxone) |
| Recent antibiotics | GPC ± GNR | ß-lactam- ß lactamase inhibitor2 (ticarcillin /clavulanate, piperacillin/tazobactam), 2nd , 3rd generation cephalosporins (cefuroxime, cefotaxime, ceftriaxone), or group 1 carbapenem (ertapenem) (depends on prior therapy; seek advice) | |
| Macerated ulcer or warm climate | GNR, including Pseudomonas sp. | ß-lactam- ß lactamase inhibitor2 (ticarcillin /clavulanate, piperacillin/tazobactam), semisynthetic penicillinase-resistant penicillin (cloxacillin) + ceftazidime or ciprofloxacin, or group 2 carbapenem (meropenem) | |
| Ischaemic limb/necrosis/gas forming | GPC ± GNR ± strict Anaerobes | ß-lactam- ß lactamase inhibitor1 (amoxicillin /clavulanate, ampicillin/sulbactam) or ß-lactam- ß lactamase inhibitor2 (ticarcillin /clavulanate, piperacillin/tazobactam), Group 1 (ertapenem) or 2 (meropenem) carbapenem, 2nd (cefuroxime) /3rd (cefotaxime, ceftriaxone) generation cephalosporin + clindamycin or metronidazole | |
| MRSA risk factors | MRSA | Consider adding, or substituting with glycopeptides (vancomycin, teicoplanin), Linezolid; daptomycin, trimethoprim-sulfamethoxazole, or doxycycline | |
| Risk factors for resistant GNR | ESBL | Carbapenem (meropenem), fluoroquinolone (ciprofloxacin), aminoglycoside (amikacin), colistin | |
| Abbreviations: GNR, gram-negative rod; GPC, gram-positive cocci (staphylococci and streptococci); MRSA, methicillin-resistant Staphylococcus aureus ; ESBL: extended-spectrum ß-lactamase | |||