Table 4.

Pneumococcal titers from biofilms and biofilm effluents after vortex mixing and subsequent titration in the presence and absence ofB. cereus β-lactamasea

Antibiotic concn (mg/liter)Pneumococcal titer after exposure to:
BenzylpenicillinAmoxicillin
BHIBHI with β-lactamaseBHIBHI with β-lactamase
BiofilmEffluentBiofilmEffluentBiofilmEffluentBiofilmEffluent
16.011.958.4411.817.0410.325.2510.235.04
4.013.439.2813.568.6810.276.0610.496.34
1.014.419.3614.399.5314.439.4614.369.59
0.2514.5110.3014.5010.1714.609.4714.649.43
0.06414.5910.4414.5510.3414.499.2014.279.20
0.01614.5610.7014.4110.68NDNDNDND
  • a Individual biofilms were inoculated with mixtures of S. pneumoniae serotype 19 and β-lactamase-positive M. catarrhalis and, after 24 h, were exposed to a single concentration of an antibiotic for 18 h; effluent was then collected for 15 min. Individual biofilms were sacrificed in BHI or BHI containing 104 mU ofB. cereus β-lactamase per ml. Titrations of the biofilm and effluent were then performed in the absence or presence of the B. cereus enzyme. Titers in biofilm (log10) are expressed as recoverable CFU per biofilm; titers in effluent are expressed as CFU per milliliter. ND, not done.