Background: Recent outbreaks (epidemics) of Streptococcus pneumoniae conjunctivitis, involving hundreds of patients, underscore the importance of following recommended guidelines to minimize disease transmission. These include the use of antimicrobial agents capable of minimizing patients' symptoms and the duration of the infectious period when disease can be transmitted to others.
Purpose: To compare the amount of time required forvarious antibiotic solutions to kill S. pneumoniae, a common cause of bacterial conjunctivitis.
Materials and methods: Isolates of S. pneumoniae from three patients were exposed to selected ophthalmic antibiotic products: moxifloxacin 0.5%, tobramycin 0.3%, gentamicin 0.3%, and polymyxin B 10,000 IU-trimethoprim 1.0%. The products were diluted 1:100 and 1:1000 for testing. At 15, 30, 60, 120, and 180 minutes after exposure, aliquots of broth were withdrawn, the cells were separated and cultured, and the viable cell count was determined.
Results: Moxifloxacin killed actively growing S. pneumoniae faster and to a greater extent than did the other three antibiotic products when tested at concentrations corresponding to tear film concentrations 5 to 10 minutes and 30 to 60 minutes after instillation of the products.
Conclusions: Moxifloxacin killed S. pneumoniae in vitro faster than did the other antibiotics. Consequently, its use should complement other generally accepted measures for minimizing patients' symptoms and limiting the contagiousness of bacterial conjunctivitis. Also, this is consistent with the recommendations of other investigators to prescribe the most recent generation of fluoroquinolone antibiotics for the specific purpose of limiting the spread of bacterial resistance.