Healthy volunteers took part in this pilot study. All volunteers provided full informed consent for taking part in this study. After obtaining informed consent, they underwent skin preparation mimicking pre-surgical skin decontamination. Excluded were volunteers with onchomycosis, paronychia, nail abnormalities, immune deficiencies or recent antibiotic use.
Volunteers were treated as patients and disinfected on the operation table under the plenum. At first the right foot was submerged in a 1 l solution of 70% ethanol containing 10% isopropyl alcohol (IPA) (Orphi farma, Dordrecht, The Netherlands) in a sterile bag (Vi-Drape, MCD, MN, USA) for 5 min (Photo 1). It was made sure that both malleoli were just submerged.
After this the left foot, ankle and half of the lower leg were painted with chlorhexidine 0.5% in 70% alcohol (Denteck, Zoetermeer, The Netherlands) for 2 ½ min using a sterile cotton on a sterile surgical clamp. In total, three cottons were used for the whole foot. The left foot was subsequently placed on a sterile field and left to dry. After 2 ½ min, the foot had dried and swabs were taken.
When the 5 min had passed, the right foot was placed on the sterile field as well and was left to dry. After it had dried, the lower right leg, ankle and foot were painted with chlorhexidine 0.5% in 70% alcohol for 2 ½ min using a new sterile surgical clamp and three sterile cottons as well. After 2 ½ min, the foot had dried and swabs were taken.
The culture swabs were taken after 2 ½ min after the feet were painted with chlorhexidine. From each lower extremity, culture swabs were taken from four locations using e-swabs (Copan, Brescia, Italy). The four locations were: (1) under the nailfold of the first toe, (2) the first webspace, (3) over the sinus tarsi and (4) pre-tibial. These were chosen because they are frequently operated on. Location 4 was chosen to serve as a control site because it was not covered by the alcohol, but painted on both sides. Each location was swabbed for 5 s.
Specimens were sent to the laboratory for quantitative aerobic and anaerobic culture. The e-swabs were pressed to the wall of the container and removed. The remaining fluid was mixed and 100 µl was inoculated on each agar plate. Several agar plates (Biomerieux, Marcy l’Etoile, France) were inoculated for aerobic and anaerobic culture for 2 and 6 days, respectively. All microorganisms were identified by mass spectrometry (Malditof; Bruker, Karlsruhe, Germany) and counted. The incubation period for the cultures was at least 7 days.
Cultures were analyzed both in a quantitative matter as a qualitative matter. Quantitative analysis was performed by determining the number positive cultures and number of colony forming units (CFU) of each culture. Furthermore, a distinction was made between cultures with light (i.e., < 20 CFU’s) and heavy (i.e., ≥ 20 CFU’s) growth . Qualitative analysis was performed by determination of microorganisms cultured.
Categorical variables are presented as counts and percentages, continuous variables are presented as means and standard deviations or medians and interquartile ranges (IQR) where appropriate. Normality was assessed using histograms and plots. McNemar’s tests for related samples were used to compare categorical data, t test for related samples or Wilcoxon signed rank test was used for continuous data where appropriate. All calculations were performed using SPSS v 23.0 (IBM, Chicago, Ill).