Analysis of growth and biofilm formation of bacterial pathogens on frequently used spinal implant materials.

STUDY DESIGN: A microscopy-based investigation of the permissive factors leading towards bacterial adherence on commonly utilized spinal implants. OBJECTIVE: The adherence and subsequent colonization and biofilm formation of bacteria on orthopaedic implants represents one of the most serious problems facing orthopaedic surgeons. Once a biofilm is formed, surgeons may have to resort to implant removal, a strategy that may cause substantial patient morbidity and lead to additional cost to the healthcare system. This problem has been further compounded by the rise of antibiotic-resistant strains of bacterial pathogens. In this study, two commonly encountered bacterial pathogens in surgical site infections (SSI) were characterized for adherence pattern, density, and propagation on five commonly used spinal implant materials via scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The results show that bacterial adherence is largely dependent on the microtopographical features observed on the surface of the materials tested. METHODS: Five commonly utilized spinal implant materials were inoculated with two of the most common nosocomial pathogens and visualized via scanning electron microscopy and confocal laser scanning microscopy. RESULTS: Analysis of 90 spinal implant pieces showed that even though no material showed the ability to prevent adherence of both pathogens tested, the presence of surface imperfections and rougher microtopography was found to harbor the most bacterial presence. CONCLUSION: Our data suggests that implants materials with uniform surface and minimal imperfections may reduce the ability of bacterial to adhere to implants. LEVEL OF EVIDENCE: Level I evidence: "Investigation of a diagnostic test".

Early adherence and biofilm formation of Cutibacterium acnes (formerly Propionibacterium acnes) on spinal implant materials.

BACKGROUND: Cutibacterium acnes (C. acnes) is associated with infection following shoulder and spine surgery due to follicular pore concentrations in these anatomic regions. It has been established that it can form biofilms on surgical implant materials, which may contribute to its role in perioperative infection, but its behavior of early colonization on those materials is not yet well understood. PURPOSE: The purpose of this study was to evaluate the time to adherence and subsequent biofilm formation of C. acnes in the first 24 hours on implant materials commonly used in spinal surgery. STUDY DESIGN: We compared the colonization and behavior of C. acnes over time when applied to five commonly used spine implant materials - polyether ether ketone (PEEK), cobalt chromium (CC), stainless steel (SS), titanium, and titanium alloy. METHODS: C. acnes was applied onto the samples of PEEK, CC, SS, titanium, and titanium alloy, and allowed to adhere for periods of 4, 8, 12, 16, and 20 hours. Nonadherent bacteria were then washed from the samples. These samples were then allowed to continue incubating for a total 24 hours. Scanning electron microscopy and confocal laser scanning microscopy were used to visualize all samples for the presence and quantification of C. acnes adherence at each time period. Subsequent transition to biofilm formation on these samples was assessed via scanning electron microscopy at each time period. RESULTS: The PEEK specimens exhibited the highest amount of surface biological burden in the first 24 hours compared with the other materials, which displayed little or no adherence. Rapid biofilm formation first observed at 8 hours of allowed adhesion on PEEK, whereas no significant biofilm formation was seen on the other materials during the observed time period. CONCLUSIONS: Although C. acnes is known to have a slow proliferation rate, the results of this investigation demonstrate that it can rapidly adhere to and form a biofilm on PEEK. These data suggest that the use of PEEK implants placed during spinal surgery may facilitate early intraoperative colonization, and subsequent infection, compared with metallic implants. CLINICAL SIGNIFICANCE: The findings of this study suggest that PEEK may prove to be problematic as a choice of implant material in cases were C. acnes infection is a possibility.