Marker Pen Device with Concentration Gradient Nib for Antibiotic Susceptibility Testing.

Background: Pen-based devices have emerged as useful tools for measuring pH and glucose, and for fabricating microchannels and microarrays. Pen-based devices take advantage of flexible patterning, inexpensive costs, and small volumes, thereby saving time and increasing efficiency. We have developed a gradient nib marker pen device that generated simultaneously different antibiotic concentrations in bacteria antibiotic susceptibility testing (AST). Methods: The device can deposit on the target surface with the antibiotic gradient. The designed polyester fiber nibs are a highly uniform porosity with unidirectional orientation and produce a visible gradient pattern. Results: We have demonstrated and quantitatively analyzed bacterial growth after antibiotic marking. The antibiotic marking produces an inhibition zone of bacterial growth. The inhibition zones of bacterial growth are captured and converted to 8-bit grayscale images, and then quantified by gray values using the Image J program. A profile of the inhibition zone showed different gray values in response to bacterial viability. Conclusion: The gradient nib marker pen device can be used to determine the quantitative antibiotic concentration based on the relationship between gray values and bacterial density conveniently without requiring a series of dilution tubes, including nutrient medium, and diversely diluted antibiotics.