Povidone-iodine and silver nitrate are equally effective in eradicating staphylococcal biofilm grown on a titanium surface: an in-vitro analysis

Abstract

BackgroundThere is no consensus on the irrigation solution and concentration that should be used when performing a debridement, antibiotics, and implant retention (DAIR)-surgery. AimTo determine the minimum-biofilm-eradication-concentration of five antibacterial solutions and compare their efficacy in eradicating Staphylococcal biofilm embedded on a titanium surface. MethodsMethicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) ATCC standard strains were grown over porous Ti-6Al-4V acetabular screw-caps. Antibacterial solutions were povidone iodine, rifampicin, silver nitrate, copper sulphate, chlorhexidine. Minimum biofilm eradication concentration (MBEC) values were calculated for MSSA and MRSA. After 24 hours, screw-caps were exposed 3 minutes to each solution. Bacterial separation from each specimen was performed with vortex agitation and footprint on agar plate in triplicate. Colony forming units (CFU) were counted pre- and post-agitation, and the delta of CFU/ml was calculated for each solution. A three-fold log reduction in CFU was considered a measure of solution efficacy. Comparison between groups was made with Fisher’s test. FindingsMBEC values for MSSA and MRSA, respectively, were as follows: 8000 ug/mL and 16000 ug/ml for povidone iodine; 64 ug/mL and 128 ug/mL for rifampicin; 10000 ug/mL and 5120 ug/mL for silver nitrate; 900 ug/mL and 900 ug/mL for copper sulphate; 16 ug/mL and 32 ug/mL for chlorhexidine. Rifampicin, copper sulphate and chlorhexidine were ineffective against MSSA and MRSA biofilm compared to povidone iodine (p<0.01) and silver nitrate (p=0.015) that had a delta CFU reduction >8 log. Povidone iodine and silver nitrate showed negative footprints without visible MSSA (p=0.005) and MRSA (p=0.014). ConclusionsPovidone iodine and silver nitrate were the only irrigating solutions capable of eradicating at least 99.9% of 24-hour biofilm.