Levels of rifampin and ciprofloxacin in nasal secretions: correlation with MIC90 and eradication of nasopharyngeal carriage of bacteria

The nasopharyngeal carriage of Neisseria meningitidis, Haemophilus influenzae, and methicillin-resistant Staphylococcus aureus (MRSA) is commonly known to exist and precede invasive disease. The relation between the carrier state, invasive disease, and contagion suggests the need to eliminate the carrier state and interrupt the cycle of transmission of the associated diseases. Toward this end, investigations were designed to develop means of measuring concentrations of antibiotics in nasal secretions, determine concentrations of rifampin and ciprofloxacin in serum, saliva, and nasal secretions, and correlate the data with the MIC90 (90 percent of the minimal inhibitory concentration) of these drugs for Neisseria meningitidis, Haemophilus influenzae, and MRSA. Five healthy individuals received a single, daily oral dose of 600 milligrams (mg) of rifampin for 4 days, followed in 3 months by 750 mg of ciprofloxacin every 12 hours for 2 days. Serum, saliva, and nasal secretions were collected 2, 5, and 8 hours after the last dose of each antibiotic. Antibiotic levels were measured by high-performance liquid chromatography. Rifampin was detected variously, in each of the subjects, after each interval of collection. Ciprofloxacin levels in nasal secretions were detected, but at lower levels than rifampin. The levels of rifampin and ciprofloxacin varied from above to below the MIC90 of the test organisms. The results indicate that effective inhibitory concentrations were achieved in nasal secretions. (Consumer Summary produced by Reliance Medical Information, Inc.)