Differences in biofilm development and antibiotic susceptibility among Streptococcus pneumoniae isolates from cystic fibrosis samples and blood cultures

OBJECTIVES: To compare the capability of biofilm development between Streptococcus pneumoniae isolates from cystic fibrosis (CF) respiratory samples and those from non-CF blood cultures. Antibiotic susceptibility of biofilm-forming isolates, as well as differences between antibiotic susceptibility of sessile cells minimum biofilm inhibitory concentration (MBIC)] and their planktonic counterparts (conventional MIC), were also assessed. METHODS: Biofilm formation was performed using a microtitre method in 20 CF and 22 non-CF blood culture S. pneumoniae isolates. RESULTS AND CONCLUSIONS: Biofilm formation occurs more frequently among S. pneumoniae isolates from CF (80%) than among non-CF blood culture isolates (50%) (P = 0.04). Moreover MBICs were significantly higher than conventional planktonic MICs among CF but not among non-CF blood isolates, suggesting a high adaptability of CF strains to form biofilms in adverse conditions.