ROUTINE SURGICAL ANTISEPTIC AGENTS ARE INEFFECTIVE IN THE ERADICATION OF TYPICAL PJI BIOFILM FORMED ON ORTHOPAEDIC IMPLANT MATERIAL IN VITRO AND THE ABSENCE OF AN ANTISEPTIC NEUTRALIZATION STAGE GIVES THE FALSE IMPRESSION OF EFFICACY

Abstract

Prosthetic joint infection (PJI) is a serious complication following joint replacement. Antiseptic solutions are often used for intraoperative wound irrigation particularly in cases of revision for PJI. Antiseptic irrigation is intended to eradicate residual bacteria which may be either free floating or in residual biofilm although there is no clear clinical efficacy for its use. Also, reviewing the scientific literature there is discordance in in vitro results where some studies questions antiseptic efficacy whilst others suggest that even at low concentration antiseptic agents are effective at eradicating bacterial biofilms.The aim of this in vitro study was to establish the efficacy of undiluted antiseptic agents at eradication of a typical PJI forming biofilm and determine the importance of an antiseptic neutralisation step in this assessment.Mature Staphylococcus epidermidis biofilms grown on TiAl6V4 discs were submerged in chlorohexidine (CHL) gluconate 4%, povidone-iodine (PI) 10% or phosphate-buffered saline (PBS) control solution. The discs were then rinsed, the biofilm bacteria suspended in solution using sonication and vortexing, and the viable count (CFU/ml) of the bacterial suspensions determined. The rinse/suspension solution was either (a) PBS or (b) Dey-Engley neutralization broth (NB).When PBS was used to rinse/suspend the biofilm a highly significant, 7.5 and 4.1, mean log reduction in biofilm vitality was observed from the control, for CHL 4% and PI 10%, respectively. However, when NB was the rinse/suspension solution the apparent antiseptic biofilm eradication efficacy was replaced with a statistically significant but clinically irrelevant less the one log-reduction in biofilm vitality.Clinical antiseptic agents are ineffective at eradicating S. epidermidis biofilm in an in vitro PJI model and absence of a neutralisation step gives the false impression of efficacy. Antiseptics alone are an ineffective treatment for biofilm related PJI and no substitute for meticulous debridement.