Cell free preparations of probiotics exerted antibacterial and antibiofilm activities against multidrug resistant E. coli

Abdelhamid, Ahmed G.; Esaam, Aliaa; Hazaa, Mahmoud M.

The anti-biofilm formation activity of CFSM prepared from probiotics was assessed as previously described (Jadhav et al., 2013) . Two groups labeled test agents (probiotic CFSM) along with their experimental control (broth medium) were prepared in the microtitre plate. Supplementation with 10% (vol/vol) of all probiotic CFSM was used as suggested previously (Medellin-Pena et al., 2007; Medellin-Peña and Griffiths, 2009 ). In each group, 40 ml of the test antibiofilm CFSM prepared was added in triplicate to the corresponding wells of sterile 96-well microtitre plate (Sigma Aldrich, USA) except for the negative controls. Then, 160 ml of E. coli cultures were added into wells in all the groups (the same volume of broth medium was added instead in case of experimental control) in a final volume of 200 ml per well. The microtitre plates were sealed and incubated for 16 h at 37°C. The biofilm biomass compared to negative control was determined using crystal violet (CV) assay. The results were expressed as the percentage of inhibition.