What oral antibiotics cover Staphylococcus aureus (S. aureus) bacteremia?

From the Guidelines

For staph aureus bacteremia, the recommended oral antibiotic is typically linezolid, 600 mg twice daily for 2-6 weeks, depending on the severity and complications of the infection. Linezolid is effective because it has excellent oral bioavailability and good tissue penetration, as noted in the guidelines by the Infectious Diseases Society of America 1. It's active against methicillin-resistant Staphylococcus aureus (MRSA) as well as methicillin-sensitive strains. However, oral therapy is generally only appropriate for uncomplicated cases or as step-down therapy after initial intravenous treatment. Most cases of staph aureus bacteremia require initial intravenous antibiotics due to the severity of the infection.

Before starting oral therapy, ensure that:

• The patient has clinically improved
• Blood cultures have cleared
• Any source of infection (e.g., abscess) has been addressed
• The strain is susceptible to the chosen antibiotic

Monitor for potential side effects of linezolid, including myelosuppression and serotonin syndrome, as highlighted in the guidelines 1. Regular blood counts should be performed during treatment. In cases where linezolid cannot be used, alternatives like trimethoprim-sulfamethoxazole or doxycycline may be considered, but these are generally less preferred for bacteremia due to their lower efficacy compared to linezolid 1.

Key considerations for the treatment of staph aureus bacteremia include:

• The need for initial intravenous antibiotics in most cases
• The importance of addressing any source of infection
• The potential for linezolid to be used as step-down therapy after initial intravenous treatment
• The need to monitor for potential side effects of linezolid, including myelosuppression and serotonin syndrome.

From the FDA Drug Label

The cure rates by pathogen for microbiologically evaluable patients are presented in Table 16. Table 16 Cure Rates at the Test-of-Cure Visit for Microbiologically Evaluable Adult Patients with Nosocomial Pneumonia Pathogen Cured ZYVOX n/N (%) Vancomycin n/N (%) Staphylococcus aureus 23/38 (61) 14/23 (61) Methicillin-resistant S. aureus 13/22 (59) 7/10 (70)

• Linezolid is an oral antibiotic that covers Staphylococcus aureus (S. aureus) bacteremia, with a cure rate of 61% in microbiologically evaluable patients.
• The cure rate for methicillin-resistant S. aureus is 59%.
• Vancomycin is also effective against S. aureus, with a cure rate of 61%.
• However, vancomycin is typically administered intravenously, not orally.
• Based on the available data, linezolid is an oral antibiotic option for treating S. aureus bacteremia, including methicillin-resistant strains 2.

From the Research

Oral Antibiotics for Staphylococcus aureus Bacteremia

• The choice of oral antibiotics for Staphylococcus aureus bacteremia depends on the susceptibility of the strain, with methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) requiring different treatments 3, 4, 5, 6, 7.
• For MSSA, penicillinase-resistant penicillins such as flucloxacillin and dicloxacillin are the preferred treatment, while first-generation cephalosporins, clindamycin, lincomycin, and erythromycin may be used for less severe infections or in patients with penicillin hypersensitivity 3.
• For MRSA, vancomycin or teicoplanin are typically used for severe infections, while oral antibiotics such as linezolid, cotrimoxazole, or lincosamides (clindamycin, lincomycin) may be used for less severe infections or in outpatient settings 3, 6, 7.
• Some studies suggest that oral step-down therapy with linezolid or fluoroquinolone plus rifampin may be effective for uncomplicated Staphylococcus aureus bacteremia 5.
• The selection of oral antibiotics should consider factors such as local antibiotic resistance, type of infection, potential adverse effects, and cost 6.

Specific Oral Antibiotics

• Linezolid: effective against MRSA and has been shown to be effective in treating uncomplicated Staphylococcus aureus bacteremia 5, 6.
• Cotrimoxazole: may be used for less severe MRSA infections, but its efficacy is not well established 3, 6.
• Lincosamides (clindamycin, lincomycin): may be used for less severe MRSA infections, but resistance is a concern 3, 6.
• Fluoroquinolone plus rifampin: may be effective for uncomplicated Staphylococcus aureus bacteremia, but more studies are needed to confirm its efficacy 5.