In vitro tigecycline subinhibitory concentrations were able to interfere with biofilm formation by E. faecalis.

Interference of cefditoren (CDN) and amoxicillin/clavulanic acid (AMC) with biofilm production was studied using 11 Streptococcus pneumoniae isolates with minimum inhibitory concentrations (MICs) ranging from 0.015 g/mL to 0.5 g/mL for CDN and from 0.06 g/mL to 2 g/mL for AMC (except for one isolate with an AMC MIC of 8 g/mL) and 5 Haemophilus influenzae isolates with MICs of 0.03-0.06 g/mL for CDN and 0.5-16 g/mL for AMC. Slime production was assessed in antibiotic-free medium and with 0.03 g/mL CDN or 1/0.5 g/mL AMC by pneumoniae versus H. influenzae for each antibiotic, no differences were found for AMC (15.92% vs. 9.40%; P = 0.36), with a tendency for CDN (24.02% vs. 13.79%; P = 0.069). Different -lactams may have different capabilities of interfering with S. pneumoniae biofilm development when tested under the same experimental conditions.