FIG 1.

Effect of a sublethal concentration of carbapenems on biofilm formation and viability in K. pneumoniae. (A) To determine the effect of carbapenems on biofilm formation, the cells were grown for 24 h in Luria-Bertani liquid medium (LB) with 2 μg/ml imipenem/meropenem or 1 μg/ml doripenem. There was no significant effect seen on biofilm formation (P = 0.14) with imipenem; however, there was a significant effect seen with meropenem and doripenem. (B) To determine the effect of carbapenems on preformed biofilms, biofilms were grown for 24 h in LB. The discs were rinsed and placed in LB with the indicated carbapenems for 2 or 24 h. There was no significant effect on viability after 2 or 24 h of treatment (P = 0.31 and 0.59, respectively), with the exception of 2 h after treatment with doripenem. Data are representative of three independent experiments. *, P < 0.05; ***, P < 0.001.