Journal: Journal of visualized experiments : JoVE

Article Title: Antimicrobial synergy testing by inkjet printer-assisted automated checkerboard array and manual time-kill methods

doi: 10.3791/58636

Figure Lengend Snippet: (A) Spectrophotometric readout and growth interpretation of a checkerboard array. Values in cells are optical density readings at 600 nm (OD600). Cells with OD600 values below 0.07 (corresponding to no growth by visual inspection) are shaded red, while cells with OD600 values ≥0.07 (corresponding to growth by visual inspection) are shaded green. (B) Fractional inhibitory concentration index (FICI) calculation. Shading indicating growth or no growth has been retained. Values for colistin and minocycline along x- and y-axes, respectively, now represent the fractional inhibitory concentration (FIC), or the ratio of the concentration of the drug in that column or row to the minimum inhibitory concentration (MIC) of that drug alone. The value in each cell is the FICI, or the sum of the FICs of the two drugs in that well. The large broken line-bordered box encloses wells with an FICI of ≤0.5. The thick-bordered cell indicates the well with the lowest FICI in which growth is inhibited, or the minimum FICI. Because the minimum FICI is ≤0.5, the combination is considered synergistic.

Article Snippet: Minocycline hydrochloride , Chem-Impex , 14302 , .

Techniques: Concentration Assay

Journal: Journal of visualized experiments : JoVE

Article Title: Antimicrobial synergy testing by inkjet printer-assisted automated checkerboard array and manual time-kill methods

doi: 10.3791/58636

Figure Lengend Snippet: Colony counts are indicated in a logarithmic scale on the y-axis and time, in hours, on the x-axis. The difference between the concentration of bacteria in the combination at 24 hours and the starting inoculum in the tube is illustrated by the red bar and number. If the decline from starting inoculum to concentration at 24 hours is ≥3 log10 CFU/mL, the combination is considered bactericidal. The difference between the concentration of bacteria at 24 hours between the tube containing the combination and the tube containing the most active single agent alone is illustrated by the blue bar and number; if there is ≥2 log10 CFU/mL reduction, the combination is considered synergistic. (A) Colistin (CST) + minocycline (MIN), a combination that is both synergistic and bactericidal. (B) Colistin + clindamycin (CLI), a combination that is synergistic but not bactericidal. (C) Colistin + erythromycin (ERY), a combination that is neither synergistic nor bactericidal. These results were initially published as part of a study of the synergistic activity of colistin-containing combinations against colistin-resistant Enterobacteriaceae, in which we demonstrated that colistin was synergistic with a number of antibiotics that are active individually only (e.g. clindamycin) or primarily (e.g. erythromycin) against Gram-positive bacteria16. (Note that erythromycin was synergistic by checkerboard array against the strain shown, but not by time-kill, so it has been selected here as an example of a non-synergistic combination.) We hypothesized that colistin, which is known to act by permeabilization of the Gram-negative outer membrane, exerts a sub-inhibitory permeabilizing effect on colistin-resistant Gram-negative bacteria, allowing entry of drugs such as clindamycin that normally cannot enter the Gram-negative cell.

Article Snippet: Minocycline hydrochloride , Chem-Impex , 14302 , .

Techniques: Concentration Assay, Bacteria, Activity Assay, Membrane

Journal: Journal of visualized experiments : JoVE

Article Title: Antimicrobial synergy testing by inkjet printer-assisted automated checkerboard array and manual time-kill methods

doi: 10.3791/58636

Figure Lengend Snippet: Antimicrobial synergy materials list

Article Snippet: Minocycline hydrochloride , Chem-Impex , 14302 , .

Techniques: Software, Sterility, Transferring, Spectrophotometry