What is the recommended treatment for a Staphylococcus aureus infection in a patient with a wound culture showing moderate growth of oxacillin-susceptible Staphylococcus aureus?

From the Guidelines

For a patient with a wound culture showing moderate growth of oxacillin-susceptible Staphylococcus aureus, the recommended treatment is a beta-lactam antibiotic, with first-line therapy being a first-generation cephalosporin such as cephalexin (500 mg orally four times daily for 7-10 days) or dicloxacillin (500 mg orally four times daily for 7-10 days) 1. The choice of antibiotic should be guided by the local patterns of susceptibility of S. aureus, especially local rates of MRSA.

• Methicillin-susceptible S. aureus typically is treated with oral penicillinase-resistant β-lactam drugs, such as a first- or second-generation cephalosporin.
• For patients who are allergic to penicillin, or if MRSA is a significant consideration, the alternatives are trimethoprim-sulfamethoxazole, doxycycline, or clindamycin for susceptible isolates 1. Some key points to consider in the treatment of S. aureus infections include:
• The use of topical mupirocin for localized and nonbullous impetigo 1.
• The potential for low-level and high-level resistance to mupirocin in S. aureus 1.
• The recommendation for oral therapy for ecthyma or impetigo with an agent active against S. aureus unless cultures yield streptococci alone 1. Proper wound care, including regular cleaning, debridement of necrotic tissue if present, and appropriate dressing changes, is also essential for effective treatment of S. aureus infections 1. In more severe infections, intravenous therapy with cefazolin (1-2 g every 8 hours) may be necessary. Treatment duration depends on infection severity, with uncomplicated skin infections typically requiring 7-10 days and more complex infections potentially needing 14 days or longer. Oxacillin-susceptible S. aureus infections respond well to these narrow-spectrum beta-lactams because the bacteria have not developed resistance mechanisms that alter penicillin-binding proteins, which are the targets of beta-lactam antibiotics.

From the FDA Drug Label

Oxacillin (cefoxitin)-susceptible staphylococci can be considered susceptible to: amoxicillin-clavulanate, ampicillin-sulbactam, piperacillin-tazobactam, ticarcillin-clavulanate, cefaclor, cefdinir, cephalexin, cefpodoxime, cefprozil, cefuroxime, loracarbef, cefamandole, cefazolin, cefepime, cefmetazole, cefonicid, cefoperazone, cefotaxime, cefotetan, ceftizoxime, ceftriaxone, cefuroxime, cephalothin, ceftaroline, moxalactam, doripenem, ertapenem, imipenem, meropenem.

STAPHYLOCOCCUS AUREUS Drug MIC Interps CEFTAROLINE <=0.5 S CIPROFLOXACIN <=1 S CLINDAMYCIN <=0.5 S DAPTOMYCIN <=0.5 S ERYTHROMYCIN 2 I GENTAMICIN <=4 S LEVOFLOXACIN <=1 S LINEZOLID 2 S OXACILLIN <=0.25 S RIFAMPIN <=1 S TETRACYCLINE <=4 S TIGECYCLINE S TRIMETHOPRIM/SUL <=0.5/9.5 S VANCOMYCIN 1 S

The recommended treatment for a Staphylococcus aureus infection in a patient with a wound culture showing moderate growth of oxacillin-susceptible Staphylococcus aureus is antibiotics such as:

• Ceftaroline
• Ciprofloxacin
• Clindamycin
• Daptomycin
• Gentamicin
• Levofloxacin
• Linezolid
• Oxacillin
• Rifampin
• Tetracycline
• Tigecycline
• Trimethoprim/Sulfamethoxazole
• Vancomycin as these are listed as susceptible in the provided information 2.

From the Research

Treatment Options for Staphylococcus aureus Infections

• The recommended treatment for a Staphylococcus aureus infection in a patient with a wound culture showing moderate growth of oxacillin-susceptible Staphylococcus aureus is typically an antibiotic that is active against MSSA, such as cefazolin or an antistaphylococcal penicillin 3.
• Empirical antibiotic treatment should include vancomycin or daptomycin, which are active against MRSA, until the susceptibility results are available 3.
• For MSSA infections, ceftriaxone has been evaluated as a potential treatment option, with some studies suggesting that it may be associated with a lower risk of toxicity requiring therapy alteration compared to antistaphylococcal antibiotics (ASAs) 4.
• The choice of antibiotic should be based on the severity of the infection, local susceptibility patterns, and drug-related safety, tolerability, and cost 5.

Antibiotic Susceptibility and Resistance

• Staphylococcus aureus is categorized as methicillin-susceptible (MSSA) or methicillin-resistant (MRSA) based on susceptibility to β-lactam antibiotics 3.
• More than 90% of S. aureus are resistant to penicillin in the United States, making routine testing for penicillin susceptibility not always indicated 3.
• The glycopeptide drug vancomycin is commonly used to treat severe MRSA infections, while MSSA infections are usually treated with drugs in the β-lactam class, such as cephalosporins, oxacillin, or nafcillin 6.

Clinical Management

• Source control is a critical component of treating S. aureus bacteremia and may include removal of infected intravascular or implanted devices, drainage of abscesses, and surgical debridement 3.
• Identifying sites of metastatic infection and pursuing source control for identified foci of infection is also important in the management of S. aureus infections 3.
• Response to therapy is expected within the first few days, and 5 to 7 days of therapy is typically adequate to achieve cure 5.