Figure 4

Determination of bacterial growth in co-culture with bone marrow-derived mesenchymal stem cells (BMMSCs). BMMSC line 407 was used to determine the bacterial growth rate in co-culture system. Identical culture conditions without BMMSCs were used as a control. Pseudomonas aeruginosa PA01, Staphylococcus aureus strains Cowan I and KK1089, and Staphylococcus epidermidis strains ATCC14990 and KK1087 were inoculated at an indicated initial inoculum (0 hours), and bacterial growth was determined by viable counting after 4 and 24 hours of infection. Series of 10-fold dilutions were prepared from each sample, and the number of colony-forming units (CFU) was determined from at least two different 10-fold dilutions per sample. (a) All the bacterial strains grew exponentially within 24 hours of infection. However, there were some differences in growth rate at the beginning of the infection. (b) P. aeruginosa PA01 showed rapid proliferation whereas S. aureus Cowan I showed negligent growth in the presence of BMMSCs within the first 4 hours of infection. Moreover, both S. aureus strains grew more rapidly in medium without BMMSCs within the first 4 hours than when compared with bacterial growth on top of the BMMSCs. Both S. epidermidis strains showed relatively active proliferation within the first 4 hours of infection.