ELECTRIC BLOCK CURRENT INDUCED DETACHMENT FROM SURGICAL STAINLESS STEEL AND DECREASED VIABILITY OF STAPHYLOCOCCUS EPIDERMIDIS

Abstract

Introduction: Biomaterial implants in the human body constitute passive surfaces that are prone to bacterial adhesion as the on-set of biomaterials-associated infection. Antibiotic treatment of infected biomaterial implants is little successful clinically, because the biofilm-mode of growth protects the adhering organisms. Percutaneous implants, such as bone screws used in orthopedics or dental implants, constitute a special class of implants with infection rates exceeding the infection rate of deep body implants by far. Especially fixation frames, used in orthopedic surgery for the treatment of complicated fractures, inevitably become infected during the course of a treatment.

The aim of this study is to determine whether it is possible to stimulate bacterial detachment from surgical stainless steel and decrease the viability of the remaining adhering bacteria using block currents. Method: Bacteria were allowed to adhere from a flowing suspension of high ionic strength in a parallel plate flow chamber, after which the suspension was replaced by a bacterium free solution with 10 mM potassium phosphate buffer. Block currents of 15, 60 and 100 ìA with different frequencies (0.1 to 2 Hz) and duty cycles (5 to 50%) were applied to induce bacterial detachment.

Results: Initial detachment rate increased with increasing frequency and duty cycle, namely from 0 to 3700 cm⁻²s⁻¹. The total detachment percentage for block currents of 100 ìA with 25% to 50% duty cycle and frequencies as of 0.5 Hz are similar for all conditions. The detachment percentage in this range amounts on average 76%, whereas DC currents around 100 ìA have an average of 60%, which was found to be significant lower (p=0.03).

The killing capacity of these current series can be up to two log scales depending on the current.

Conclusion: Current induced detachment of Staphylococcus epidermidis from surgical stainless steel seems very effective, especially for a 100 ìA, 50% duty cycle and 2 Hz block current. The viability of the remaining adhering bacteria decreased with 2 log scales. Clinically this could mean another way of preventing and curing pin tract infection.