Antibiotics Covering Both Streptococcus and MRSA
For dual coverage of streptococci and MRSA, use clindamycin alone (300-450 mg PO TID), or combine either trimethoprim-sulfamethoxazole (1-2 DS tablets PO BID) or doxycycline (100 mg PO BID) with a beta-lactam such as penicillin, cephalexin, or amoxicillin. 1
Oral Antibiotic Options
Single-Agent Coverage
- Clindamycin is the only single oral agent that covers both MRSA and beta-hemolytic streptococci, making it ideal when dual coverage is needed 1, 2
- Clindamycin dosing: 300-450 mg PO three times daily for adults 2
- Major caveat: Clindamycin resistance is now very common in MRSA, and approximately 50% of MRSA strains have inducible or constitutive clindamycin resistance 1, 3
- Clindamycin carries a higher risk of Clostridioides difficile infection compared to other oral agents 3
Combination Therapy Approach
- TMP-SMX (1-2 DS tablets PO BID) plus a beta-lactam (penicillin, cephalexin, or amoxicillin) provides reliable dual coverage 1
- Doxycycline (100 mg PO BID) plus a beta-lactam is an equally effective alternative combination 1
- The beta-lactam component covers streptococci, while TMP-SMX or doxycycline covers MRSA 1
- Critical pitfall: TMP-SMX and doxycycline alone have limited or no activity against beta-hemolytic streptococci, so monotherapy with these agents is inadequate for nonpurulent cellulitis where streptococcal coverage is essential 3, 1
Intravenous Options for Severe Infections
First-Line IV Agents
- Vancomycin (15-20 mg/kg/dose IV every 8-12 hours) remains the standard IV option for hospitalized patients requiring dual coverage 2, 1
- Linezolid (600 mg IV/PO BID) provides excellent coverage for both MRSA and streptococci with the advantage of seamless IV-to-oral transition 1, 4
- Daptomycin (4-10 mg/kg/dose IV once daily) is effective for complicated skin infections 1, 2
Newer IV Agents
- Ceftaroline, dalbavancin, tedizolid, and tigecycline all provide dual coverage for severe infections 1
- These newer agents are particularly useful when vancomycin or linezolid cannot be used 1
Treatment Duration and Monitoring
- Standard duration: 5-10 days for uncomplicated infections 2, 3
- Extended duration: 7-14 days for complicated infections based on clinical response 1, 2
- Reassess within 48-72 hours to ensure appropriate response to therapy 2
- Progression despite antibiotics suggests either resistant organisms or a deeper, more serious infection than initially recognized 1
Critical Clinical Pitfalls
- Beta-lactam antibiotics alone (penicillins, cephalosporins) are completely ineffective against MRSA and should never be used as monotherapy when MRSA is suspected 3
- Never use rifampin as monotherapy or adjunctive therapy for skin infections due to rapid resistance development 3
- Obtain cultures from purulent drainage before starting antibiotics to confirm pathogens and guide definitive therapy 2, 3
- Incision and drainage is the cornerstone of treatment for abscesses—antibiotics alone are insufficient 2, 3