What is the treatment for staph (Staphylococcus) infections?

Treatment for Staphylococcal Infections

The treatment of staph infections depends critically on whether the organism is methicillin-susceptible (MSSA) or methicillin-resistant (MRSA), and whether the infection is localized to skin/soft tissue versus invasive/systemic.

Initial Assessment and Culture

• Obtain cultures from any purulent drainage before starting antibiotics to confirm the organism and guide definitive therapy 1, 2.
• Distinguish between MSSA and MRSA, as this fundamentally changes antibiotic selection 3.
• For skin infections, determine if the infection is purulent (with drainage/exudate) versus nonpurulent (dry cellulitis without drainage) 1.

Methicillin-Susceptible Staphylococcus aureus (MSSA)

Oral Therapy for Mild-Moderate Infections

• Dicloxacillin 250-500 mg every 6 hours for adults is the preferred oral agent for MSSA 4, 3.
• For children weighing <40 kg: dicloxacillin 12.5-25 mg/kg/day divided every 6 hours 4.
• Take dicloxacillin on an empty stomach (1 hour before or 2 hours after meals) with at least 4 ounces of water 4.
• Alternative: cephalexin (cefalexin) is a cost-effective option with broader coverage 5.

Parenteral Therapy for Severe Infections

• Oxacillin 1-2 grams IV every 4-6 hours for adults for severe MSSA infections 6.
• For children: oxacillin 100-200 mg/kg/day IV divided every 4-6 hours depending on severity 6.
• Nafcillin is an equivalent alternative to oxacillin 3.

Methicillin-Resistant Staphylococcus aureus (MRSA)

Skin and Soft Tissue Infections (Outpatient)

For simple abscesses: incision and drainage alone is the primary treatment 1.

Add antibiotics if any of the following are present:

• Severe/extensive disease involving multiple sites 1
• Rapid progression with associated cellulitis 1
• Signs of systemic illness (fever, tachycardia) 1
• Immunosuppression or comorbidities 1
• Extremes of age 1
• Difficult-to-drain locations (face, hand, genitalia) 1
• Lack of response to drainage alone 1

First-line oral antibiotic options for MRSA skin infections:

• Clindamycin 300-450 mg orally three times daily (covers both MRSA and streptococci as monotherapy) 1, 7, 8

  • Only use if local clindamycin resistance is <10% 8
  • For children: 10-13 mg/kg/dose every 6-8 hours (max 40 mg/kg/day) 7, 2

• Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets twice daily 1, 7

  • Must add a beta-lactam (like amoxicillin) if streptococcal coverage is needed 1, 8
  • For children: 4-6 mg/kg/dose (trimethoprim component) every 12 hours 2
  • Avoid in elderly patients on renin-angiotensin inhibitors or with chronic renal insufficiency due to hyperkalemia risk 1
  • Avoid in third trimester pregnancy and infants <2 months 1

• Doxycycline 100 mg twice daily or minocycline 200 mg once, then 100 mg twice daily 1, 2

  • Must add a beta-lactam if streptococcal coverage is needed 1, 8
  • Do not use in children <8 years of age 7, 2

• Linezolid 600 mg twice daily (covers both MRSA and streptococci but significantly more expensive) 1, 8

Treatment duration: 5-10 days for uncomplicated infections 1, 2.

Complicated/Severe MRSA Infections (Inpatient)

For hospitalized patients with complicated skin/soft tissue infections, deep infections, or systemic involvement:

• Vancomycin 15-20 mg/kg/dose IV every 8-12 hours is the standard of care 1, 2, 9.
• Linezolid 600 mg IV/PO twice daily (excellent oral bioavailability allows transition to outpatient therapy) 1, 2.
• Daptomycin 4 mg/kg/dose IV once daily for complicated skin infections 1, 2.
• Telavancin 10 mg/kg/dose IV once daily 1.
• Clindamycin 600 mg IV/PO three times daily (if susceptible) 1.

Treatment duration: 7-14 days for complicated infections 1, 2.

Invasive MRSA Infections (Bacteremia, Endocarditis, Osteomyelitis)

• Vancomycin remains the standard of care for invasive MRSA infections 9, 3.
• Minimum 14 days of therapy for severe staphylococcal infections 6, 4.
• Continue therapy for at least 48 hours after patient becomes afebrile and asymptomatic with negative cultures 6, 4.
• Endocarditis and osteomyelitis require longer duration (often 4-6 weeks) 6, 4, 3.

Special Considerations

Rifampin Use

• Do not use rifampin as monotherapy or routine adjunctive therapy for skin/soft tissue infections 1.
• Rifampin may be considered in selected scenarios (prosthetic device infections, osteomyelitis) but only in combination with another active agent due to rapid resistance development 1.

Beta-Lactam Combination Therapy

• Emerging evidence suggests beta-lactams may show synergy with vancomycin or daptomycin for MRSA, but insufficient data currently exist to recommend routine use 10.

Nonpurulent Cellulitis

• Empirically treat for beta-hemolytic streptococci (not MRSA) with a beta-lactam 1.
• Add MRSA coverage only if patient fails to respond to beta-lactam therapy or has systemic toxicity 1.

MRSA Bacteriuria

• TMP-SMX 1-2 double-strength tablets twice daily for 7-14 days for uncomplicated MRSA urinary tract infection 7.
• Obtain blood cultures if systemic symptoms present 7.
• Follow-up urine cultures 48-72 hours after starting therapy 7.

Prevention of Recurrence

• Keep draining wounds covered with clean, dry bandages 7, 2.
• Maintain good hand hygiene 7, 2.
• Consider decolonization strategies for recurrent MRSA infections 7, 2.

Common Pitfalls

• Do not use oral therapy as initial treatment for serious, life-threatening infections 4.
• Monitor for thrombophlebitis with IV administration, especially in elderly patients 6, 4.
• Reassess clinically within 48-72 hours to ensure appropriate response 2.
• Adjust therapy based on culture results and local resistance patterns 2, 3.