Eradication of Wound Biofilms by Electrical Stimulation - Antibiofilm Agents: From Diagnosis to Treatment and Prevention - page 422

6 Effect of Low-Intensity Current Alone Against
Bacterial Biofilms

6.1 In Vitro Studies with Low-Intensity Direct Current

and Biofilms

The antimicrobial potential of LIDC alone was first studied and shown to have a
bactericidal effect against both planktonic (Rowley 1972 ; Davis et al. 1989 ) and
bacterial biofilm cells. In 1974 Barranco et al. studied the effect of 0.4-400

A
against S. aureus biofilms grown on agar plates. These biofilms were treated for
24 h, with the anode and cathode coated in four different materials: silver, platinum,
gold, and stainless steel. The authors reported maximal bactericidal effects at
400

μ

A, with both electrodes and with all four materials. However, the silver
cathode exhibited the maximal bactericidal effects at

μ

the lower intensities

(0.4 A). Liu et al. ( 1997 ) went on to examine S. aureus and Staphylococcus

epidermidis biofilms treated with LIDC. Biofilms grown on agar plates were treated
with 10

μ A, 4 μ

A for 16 h, and significant zones of inhibition were observed around the
cathode. Merriman et al. ( 2004 ) treated S. aureus biofilms grown on agar plates
with LIDC for 3 consecutive days and observed significant zones of inhibition. The
LIDC treatment was applied for 1 h and generated with stainless steel electrodes
producing continuous 500

μ

A LIDC. Del Pozo et al. ( 2009a ) examined the antimi-
crobial effect of LIDC against mature biofilms. S. aureus , S. epidermidis , and
P. aeruginosa biofilms were grown on Teflon disks for 48 h and then treated
continuously for 2-7 days with 0.2-2 mA LIDC. When Staphylococcus biofilms
were treated for 2 days with 2 mA LIDC, a 4-6 log reduction in bacterial cells was
observed. However, P. aeruginosa biofilms had to be treated for 7 days with 2 mA
LIDC in order to cause only a 3.5-5 log reduction of bacteria. In this study the
authors coined the term, the “bioelectric effect,” to describe the bactericidal effect
of LIDC against bacterial biofilms.

μ

6.2 In Vivo Studies with Low-Intensity Direct Current

and Biofilms

In vivo studies examining LIDC against biofilms began in 1974 when Rowley
et al. ( 1974 ) reported that 200-1,000 A cathodic LIDC inhibited the growth of

24 h-old P. aeruginosa biofilms in rabbit dermal wounds. Van der Borden
et al. ( 2007 ) devised an interesting wound infection model where three stainless
steel pins were inserted into goat tibias and inoculated with S. epidermidis . Biofilms
were grown on two of the pins, with one receiving 100 μ A LIDC and the other used
as a negative control, while the third pin acted as structural support. Electricity was
given continuously for 21 days immediately following S. epidermidis infection, and

μ