Is oral levofloxacin effective against Viridans streptococci?

From the Guidelines

Oral levofloxacin is effective against Viridans streptococci, with a broad-spectrum activity against this organism [ 1 ].

Key Points

• The preferred dosage of oral levofloxacin for treating Viridans streptococci infections is 500mg once daily [ 1 ].
• The duration of treatment is usually 10-14 days, depending on the severity and site of infection [ 1 ].
• In cases of endocarditis or other complicated infections, the dose may be increased to 750mg once daily, and treatment duration may be extended to 4-6 weeks [ 1 ].
• Levofloxacin is preferred over ciprofloxacin in situations with increased risk for oral mucositis-related invasive viridans group streptococcal infection [ 1 ].

Considerations

• The use of fluoroquinolone prophylaxis, including levofloxacin, should be considered for high-risk patients with expected durations of prolonged and profound neutropenia [ 1 ].
• A systematic strategy for monitoring the development of fluoroquinolone resistance among gram-negative bacilli is recommended [ 1 ].
• Patients and families should be informed about potential short- and long-term fluoroquinolone-related adverse effects prior to administration [ 1 ].

From the FDA Drug Label

The following in vitro data are available, but their clinical significance is unknown: Levofloxacin exhibits in vitro minimum inhibitory concentrations (MIC values) of 2 mcg/mL or less against most (≥ 90%) isolates of the following microorganisms; however, the safety and effectiveness of levofloxacin in treating clinical infections due to these bacteria have not been established in adequate and well-controlled clinical trials (Group C/F) (Group G) ... Viridans group streptococci

The FDA drug label indicates that levofloxacin exhibits in vitro activity against Viridans streptococci, but the clinical significance is unknown and the safety and effectiveness have not been established in adequate and well-controlled clinical trials 2. Therefore, based on the available information, it is unclear if oral levofloxacin is effective against Viridans streptococci.

From the Research

Efficacy of Oral Levofloxacin Against Viridans Streptococci

• The efficacy of oral levofloxacin against Viridans streptococci has been investigated in several studies 3, 4.
• One study found that levofloxacin was effective against Viridans group streptococci in vitro and in rats with experimental aortic endocarditis, with a minimum inhibitory concentration (MIC) of 1 mg/L for 20 independent isolates 3.
• However, another study found that levofloxacin was surprisingly ineffective against streptococcal endocarditis in a rabbit model, suggesting that it may not be effective against Viridans group streptococcal infections in humans 4.
• The effectiveness of levofloxacin against Viridans streptococci may depend on the specific strain and the dosage used, with higher doses (e.g. 1 g daily) potentially being more effective than standard doses (e.g. 500 mg daily) 3.

Comparison with Other Antibiotics

• Levofloxacin has been compared to other antibiotics, including ciprofloxacin, ceftriaxone, and amoxicillin/clavulanic acid, in the treatment of various infections 3, 5, 6, 7.
• In general, levofloxacin has been found to be effective against a broad range of Gram-positive and Gram-negative bacteria, including Streptococcus pneumoniae, and has been shown to be equivalent or superior to other antibiotics in many cases 5, 6, 7.
• However, the effectiveness of levofloxacin against Viridans streptococci specifically is less clear, and more research is needed to fully understand its efficacy against this type of bacteria.

Dosage and Administration

• The dosage and administration of levofloxacin can affect its efficacy against Viridans streptococci, with higher doses and more frequent administration potentially being more effective 3.
• Oral levofloxacin has been shown to be effective in the treatment of various infections, including respiratory tract infections, skin and soft tissue infections, and urinary tract infections 5, 6, 7.
• The use of levofloxacin in the treatment of Viridans streptococcal infections should be guided by the results of susceptibility testing and the clinical response of the patient 3, 4.