A Reduction in Subungual Bacterial Flora with a Novel Water-Powered Hand Washer: A Proof of Concept Study

Background:

The subungual spaces may harbor the highest bacterial counts on the hand and may be resistant to routine hand hygiene methods, including the surgical scrub. Residual subungual flora may serve as a reservoir for persistent hand contamination and subsequent bacterial transmission.

Objective:

This preliminary study was designed to test the hypothesis that subungual bacterial contamination persists after a surgical hand scrub and that these bacterial counts could be significantly reduced with a novel water-powered hand washer.

Methods:

Twelve subjects volunteered at Porter Medical Center in Middlebury, VT. Prior to the intervention, eight surgeons performed their routine 5 minute hand scrub prior to the first case of the day using chlorhexidine, water, brush and a nail pick. Residual antimicrobial activity was reduced with a one minute water rinse. Four laboratory technicians were also studied upon arrival at work without any prior hand hygiene. Cultures were then taken of the subungual space of the first three fingers of the right hand using two passes across the nail bed with a swab moistened with transport media. The swabs were vortexed in sterile saline and calibrated loops were used to inoculate blood agar plates. All 12 subjects then used a novel water-powered hand washer directed at the subungual spaces of the first 3 fingers for 60 seconds per finger. The device delivered 40 psi pressure of untreated water at a flow rate of 1.5 gallons/minute and a velocity of 69.4 feet/second. The subungual cultures were then repeated as above.

Results:

There were a total of 72 observations: 36 cultures before and after the power wash from the first 3 fingers of 12 subjects. Bacterial counts ranged from <300 to 888,000 CFUs. Prior to use of the water-powered hand washer, the median bacterial count recovered from the subungual space was 4.5 log₁₀ CFU, and did not differ between surgeons who had performed a hand scrub and lab technicians who had not (4.5 vs. 4.6 log₁₀ CFUs, p = .53). Following use of the water-powered hand washer, bacterial counts recovered from the subungual space dropped significantly to a median of 3.1 log₁₀ CFUs (p < .01). The decrease was greater for surgeons (2.9 log₁₀ CFU) than for lab techs (3.8 log₁₀ CFUs, p = .13).

Conclusions:

Bacteria are present in high numbers in the subungual space, and counts persist after surgical hand scrub including a nail pick. These organisms provide a reservoir for hand contamination and potential transmission despite standard hand hygiene practices. A novel water-powered hand washer that is easy to install on existing water lines without additional plumbing, and is simple to use, rapidly provides a significant reduction in subungual bacterial counts. The optimal duration of use and whether to combine with an antimicrobial agent require further study. This device could improve hand hygiene in critical areas such as the operating room, hospital wards and in food preparation.