Galvanic current dosage and bacterial concentration are determinants of the bactericidal effect of percutaneous needle electrolysis: an in vitro study

Abstract

Percutaneous needle electrolysis (PNE) is a physiotherapy technique that has been shown to be effective in different pathologies such as tendinopathies or mammary fistula. For many years, theoretical bactericidal and germicidal effects have been attributed to this type of galvanic currents, partly explained by the changes in pH that it generates. However, these effects have not yet been demonstrated. The aim of this study was to evaluate the bactericidal effect and the changes in pH caused by PNE. S. aureus were prepared in two different solutions (TSB and saline solution) and in different concentrations (from 9 to 6 Log₁₀ CFU/mL). Bacteria were treated with three experimental PNE doses to assess bacterial death levels and the changes caused to the pH of the medium. The viable cell count showed that all experimental PNE doses had a bactericidal effect against a high concentration (9 Log₁₀ CFU/mL) of S. aureus in saline solution (p < 0.001). Furthermore, we found that when the concentration of bacteria decreased, a lower dose of galvanic current generated the same effect as a higher dose. Changes in pH were registered only in experiments performed with saline solution. PNE had a bactericidal effect against S. aureus and the level of this effect was mainly modulated by the solution, the bacterial concentration and the dose. Changes affecting pH were modulated by the type of solution and there was no relationship between this and bacterial death.

Figure 1

Flow-chart of the experimental design.

Figure 2

Procedure for PNE in vitro. Galvanic currents generate a cathodic flow in the bacterial suspension.

Figure 3

Effect of different doses of galvanic current on a 9 Log₁₀ CFU/mL concentration of S. aureus in TSB (blue) and saline solution (red). All the doses were applied during 5 s and repeated 5 times. The error bars represent CI (95%).

Figure 4

Complementary study of the effect of the application of different doses of galvanic current on a 9 Log₁₀ CFU/mL concentration of S. aureus in saline solution. All the doses were applied during 5 s and repeated 5 times. The error bars represent the CI (95%).

Figure 5

Effect of the application of a different dose of galvanic current in saline solution on three bacterial concentrations: 8 log₁₀ CFU/mL (green), 7 log₁₀ CFU/mL (red) and 6 log₁₀ CFU/mL (blue). Dashed black line represent the reference data for 9 log₁₀ CFU/mL using the data shown in Fig. 3. The error bars represent the CI (95%).

Figure 6

Effects of the application of different doses on the increase in pH in TSB (blue) and in saline solution (red). Baseline pH values had a mean of 6.04 (SD = 0.14) for TSB and 7.1 (SD = 0.07) for saline solution.