Session V - Fracture Healing

Can Topical Antiseptics or Antibiotics Normalize the Bacterial Count of Superficial Dermal Abrasions, Effectively Extending the Safe Surgical Window for Closed Fractures?

Laura S. Phieffer, MD; Scott Porter, MD; Kent Ellington, BS; Michael Hudson, PhD; James Kellam, MD; Michael Bosse, MD, Carolinas Medical Center, Charlotte, NC

Purpose: The goal of this study was to determine if prompt pre-operative treatment of contaminated abraded dermis with topical antimicrobials could normalize the bacterial colony count at the operative site before and/or after standard surgical preparation.

Methods: This protocol was approved by the Institutional Animal Care and Use Committee. After appropriate anesthesia, 2 standardized 2.0 x 2.0 cm abrasion sites were created on 56 New Zealand white rabbits using an electric dermatome (Davol, Inc., subsidiary of C.R. Bard, Inc., Cranston, RI). Each abraded site was subsequently inoculated with encapsulated S. aureus strain Wood 46 (one of the most common organisms associated with diseases of the skin). An initial dermal punch biopsy (Sklar Tru-Punch disposable sterile biopsy punch, West Chester, PA) was taken from each site to quantify initial colonization. Two hours after inoculation, one of the two surgical sites was selected to receive one of 2 topical treatments: Bacitracin ointment or a Betadine-soaked sponge dressing. The other site served as the control. Rabbits were then divided into 3 cohort groups with 9 animals per group, and surgical preparations were done at 12, 24 and 48 hours after abrasion and inoculation. Each group underwent a standard surgical preparation of both control and treated sites at the times indicated. Prior to the surgical preparation, a second biopsy was obtained to quantify the colonization present. The preparation consisted of a 2-minute manual scrub with Betadine scrub solution (7.6% povidone-iodine, Purdue-Frederick Co., Norwalk, CT) followed by Betadine solution (10% povidone-iodine). A third biopsy, after surgical preparation, and a fourth, 2 hours after surgical preparation, were taken to determine the effectiveness of the surgical scrub. All biopsies were taken under aseptic conditions. Each punch biopsy was placed in tryptic soy broth supplemented with 1%- sodium thiosulfate and held on ice until quantitative bacterial testing. Tissue biopsies were sterilely homogenized, then serial dilutions were spot plated, in triplicate, onto mannitol salt agar plates that are selective for the genus Staphylococcus and differential for S. aureus for bacterial count determination. Standard statistical methods were used, using a SAS (System for Windows, version 6.12, SAS, Cary, NC) analysis of variance (ANOVA) and paired t-tests when data were normally distributed and Wilcoxon signed rank test when data were not normally distributed. A P value of <0.05 was considered significant.

Results: Bacterial counts were obtained for 9 rabbits in each group with 4 biopsies at each site. Table I shows the mean bacterial counts for all 4 biopsies obtained for each treatment group at the 12-hour time interval (similar results seen in the 24- and 48-hour time intervals). Initial biopsies, just after abrasion and inoculation, confirmed similar contamination at all sites at all time points. Pre-surgical scrub biopsy results revealed that bacteria flourished at all sites in similar concentrations. No significant differences were found between pre- and post-surgical scrub bacterial counts for any group at any time-point. At all time points the bacterial counts remained prohibitively high.

Table 1: Bacterial Quantification Values

Time from abrasion to surgical prep	Treatment group	Initial Inoculation biopsy Mean ± S.D.	Pre-surgical scrub biopsy Mean ± S.D.	Post- surgical scrub biopsy Mean ± S.D.	Post-2 hour surgical wait biopsy Mean ± S.D.
12 hours	Bacitracin treated site (control site)	8.0E6 ± 7.2E6 (1.5E7 ± 1.1E7)	8.8E6 ± 1.0E7 (1.9E7 ± 1.5E7)	5.8E6 ± 8.7E6 (1.2E7 ± 1.1E7)	5.9E6 ± 8.4E6 (1.5E7 ± 7.5E6)
	Betadine treated site (control site)	1.0E7 ± 9.2E6 (1.6E7 ± 1.0E7)	5.4E6 ± 7.0E6 (1.9E7 ± 2.1E7)	7.3E6  ± 8.1E6 (1.0E7 ± 8.7E6)	1.7E7 ± 2.3E7 (6.8E6 ± 6.6E6)

Discussion: Preliminary studies completed at our institution evaluated the difference between the reduction of bacteria on contaminated normal dermis and contaminated superficially abraded dermis following standard surgical preparations at 6, 12, 24 and 48 hours from the time of the injury. At the abraded sites, the bacteria flourished. Only at the 6-hour time period was the surgical scrub effective at removing bacteria to similar low (counts <1E3) levels at both the abraded and non-abraded (control) sites. The previous study results revealed that a contaminated abrasion could not be sterilized with a standard surgical preparation after as few as 6 hours >from the time of injury. The non-abraded control sites, however, could be sterilized with a standard surgical preparation so that no bacteria were detectable on the skin.

The role of preoperative disinfecting of abraded skin at the operative site in preventing postoperative wound infection remains uncertain. A process that could stabilize the bacterial count at the abrasion site, combined with an aggressive preoperative standard scrub, yielding bacterial counts equal to those found with scrubs of normal skin could possibly safely extend the surgical window beyond the current 6- to 8-hour period. This study shows that common antimicrobials applied promptly to abraded sites appear to have no effect on modulating the ability to obtain an effective surgical preparation of abraded tissue sites at extended time points. Results of this study imply that abrasions at or near the planned surgical incision can remain a source of contamination throughout the operative case.

Conclusions: Prompt pre-operative treatment of contaminated abraded dermis with topical antimicrobials is unable to normalize the bacterial colony count at the operative site before or after standard surgical preparation.