Ajay Premkumar, Sita Nirupama Nishtala, Joseph T. Nguyen, Mathias Bostrom, Alberto V. Carli

The Journal of Arthroplasty, 2021, ISSN 0883-5403 (in press)
DOI: 10.1016/j.arth.2021.02.033

Summary by Jennifer Z. Mao, MBA

Plastic, acrylic cement, and porous titanium are common materials in orthopedics.¹ Biofilm formation from invading bacteria on these materials can cause periprosthetic joint infection, a rare but devastating complication.² To avoid this complication, intraoperative irrigation solution is used. However, there is a paucity of literature comparing the utility of the various commercially available solutions.

Using the bacterial strain Staphylococcus aureus Xen36 (Perkin Elmer), a methicillin-susceptible strain, which has intrinsic resistance to kanamycin the authors sought to compare the efficacy of 8 different antiseptic solutions commonly used by arthroplasty surgeons. The authors aliquoted 20 μl of planktonic bacterial suspension into 96-well plates and then aliquots of 180 μl of solution. All solutions were tested in triplicate at 1 and 3 minutes. In a separate 96-well plate, the authors deposited porous titanium caps, PMMA spheres, and Coated polystyrene immersed in TSB in 48 of the wells and incubated them at 37ºC for 24 hours. Pilot experiments were conducted to determine timeline for mature biofilm formation. Following 24h or 72h of biofilm formation, the three surfaces were rinsed with BPS, and transferred to a new well. The surfaces were exposed to 1 mL of one of the 8 irrigation solutions or a saline control for 3 minutes. The test surfaces were rinsed 3 times, placed in a fresh well with TSB media, and sonicated to dislodge biofilm-containing bacteria. Serial dilution was conducted and 100 μl of solution was plated on TSB-agar and incubated at 37ºC. Colony forming units were counted at 24 hours. Resazurin Assay was used to confirm CFU results. Resazurin dye was applied to quantify viable bacteria in suspension. A microplate reader was used to detect fluorescence every 30 minutes for 8 hours at 37ºC, and maximum fluorescence was recorded. A 3-log reduction in bacterial CFU counts as compared to saline was considered effective against biofilm on each surface.

The authors report that both Povidone-iodine diluted to 0.03%, Povidone-iodine diluted to 10% (with and without peroxide), Irrisept, and Bactissure, completely eradicated planktonic bacteria. Polyhexamethylene biguanide 0.04% met the criteria for efficacy, and Polymyxin-bacitracin did not significantly reduce planktonic CFU. Vancomycin significantly reduced CFU only after 1 minute but demonstrated no difference at 3 minutes. Regarding biofilms, bacteria readily grew on all surfaces without a significant difference between material types at 24 hours (p=0.222). At 72 hours, PMMA had significantly less biofilm growth compared to the other two materials, with no difference between titanium and plastic surfaces. CFU in biofilms significantly increased on plastic and titanium but decreased significantly on PMMA. Across all 3 test surfaces, only povidone-iodine 10% and povidone-iodine 10% mixed 1:1 with 4% hydrogen peroxide consistently met criteria for efficacy. Bactisure was effective against 24-hour biofilm formed on titanium and PMMA, but was only effective on titanium at 72-hour. Irrisept was only effective against 24-hour biofilm formed on porous titanium.

Limitations include the in-vitro study design and only testing irrigation solutions against one strain of MSSA, limiting generalizability of the results to other bacterial infection types. Moreover, the study did not account for mode of delivery for irrigation solution, which can cause mechanical debridement of biofilms. Nevertheless, the study demonstrates that commercial antibacterial solutions vary significantly in their efficacy against MSSA biofilm and became less efficacious as biofilm matured.

References:

1. Davies D. Understanding biofilm resistance to antibacterial agents. Nat Rev Drug Discov 2003;2:114–22.
2. Li C, Renz N, Trampuz A. Management of Periprosthetic Joint Infection. Hip Pelvis 2018;30:138.