Approach to initial antibiotic therapy of immunocompetent adults with suspected septic bursitis

MRSA: methicillin-resistant Staphylococcus aureus; MSSA: methicillin-susceptible S. aureus; IV: intravenously; AUC: area under the time-concentration curve.
* In addition to antibiotic therapy, bursa drainage may be warranted (refer to UpToDate topic on septic bursitis for further discussion).
¶ The decision to administer antimicrobial therapy parenterally should be individualized based on clinical presentation and patient characteristics. Parenteral antimicrobial therapy is generally appropriate when severe illness or any of these features is present. Comorbidities that increase the risk of severe or complicated infection, such as the presence of an immunocompromising condition (eg, neutropenia, recent organ transplant, advanced HIV infection, B cell or T cell deficiency, or use of immunosuppressive agents) should lower the threshold for parenteral therapy.
Δ Risk factors for MRSA include:

• Recent (eg, within the prior 1 to 2 months) hospitalization or surgery
• Residence in a long-term care facility
• Hemodialysis
• HIV infection

◊ IV antibiotic dosing as follows (if 2 doses are listed for a given agent, the higher one is for patients with higher weights [eg, >120 kg] or more severe illness):

• Cefazolin 1 to 2 g IV every 8 hours
• Clindamycin 600 to 900 mg IV every 8 hours
• Daptomycin 4 to 6 mg/kg IV every 24 hours
• Flucloxacillin 2 g IV every 6 hours
• Nafcillin 2 g IV every 4 hours
• Oxacillin 2 g IV every 4 hours
• Vancomycin: For severely ill patients, a loading dose (20 to 35 mg/kg) is appropriate; the loading dose is based on actual body weight, rounded to the nearest 250 mg increment and not exceeding 3000 mg. Within this range, we use a higher dose for critically ill patients. The initial maintenance dose and interval are determined by nomogram (typically 15 to 20 mg/kg every 8 to 12 hours for most patients with normal renal function). Subsequent dose and interval adjustments are based on AUC-guided or trough-guided serum concentration monitoring. Refer to the UpToDate topic on vancomycin dosing for sample nomogram and discussion of AUC-guided and trough-guided vancomycin dosing.

§ Vancomycin is the preferred parenteral anti-MRSA agent. Daptomycin is an acceptable alternative agent for patients who have prior infection or colonization with a MRSA isolate with minimum inhibitory concentration ≥2, do not respond to vancomycin, have prior treatment failure with vancomycin, or do not tolerate vancomycin. Additional alternative anti-MRSA agents include ceftaroline, linezolid, tedizolid, delafloxacin, telavancin, dalbavancin, oritavancin; use of these agents is limited by high cost and, in some cases, availability.
¥ Resolution of infection is frequently observed after 10 days of antibiotic therapy; in some cases, 14 to 21 days of therapy may be required.
‡ Flucloxacillin is not available in the United States.
† Oral antibiotic dosing as follows (if 2 doses are listed for a given agent, the higher one is for patients with higher weights [eg, >120 kg] or more severe illness):

• Amoxicillin 500 mg orally 3 times daily or 875 mg orally twice daily
• Cefadroxil 1 g orally daily
• Cephalexin 500 mg orally 4 times daily
• Clindamycin 300 to 450 mg orally 4 times daily
• Dicloxacillin 500 mg orally 4 times daily
• Doxycycline 100 mg orally twice daily
• Flucloxacillin 500 mg orally 4 times daily
• Minocycline 200 mg orally once, then 100 mg orally every 12 hours
• Trimethoprim-sulfamethoxazole 1 to 2 double-strength tablets orally every 12 hours

** For oral treatment of MRSA, we generally favor trimethoprim-sulfamethoxazole, doxycycline, or minocycline because of the greater associated risk of Clostridioides (formerly Clostridium) difficile infection with clindamycin. However, doxycycline and minocycline do not have good antistreptococcal activity and so are administered with amoxicillin. Other active options include linezolid, tedizolid, and delafloxacin, but these should be reserved for circumstances in which the other options cannot be used.