Figure 5
GM-CSF did not sensitize the persister cells of E. coli K12 and E. coli ATCC 53505 to antibiotics.
The persister cells were isolated from exponential phase cultures of E. coli K12 and E. coli ATCC 53505 by killing the normal cells with 100 μg/mL ampicillin and 20 μg/mL ofloxacin (ATTCC 53505 is resistant to ampicillin, data not shown) respectively for 3.5 h and then treated with or without 0.17 pM GM-CSF for 1 h, followed by adding an antibiotic as indicated and incubating for 3.5 h. The amount of BSA (contained in GM-CSF stocks) was adjusted to be the same in all samples. Following the treatment, the cell viability was determined by counting CFU. Cip: 2 μg/mL ciprofloxacin. Tob: 70 μg/mL tobramycin. Tet: 20 μg/mL tetracycline. Gen: 200 μg/mL gentamicin. The samples were tested in triplicate (n = 3). The number of CFU in the GM-CSF free sample (antibiotic only) varied depending on the antibiotic used, so the CFU of corresponding GM-CSF free control for each antibiotic was normalized as 100% for the convenience of comparison.
