This study in UCA (ultra clean air) during TKR (total knee replacement) quantified wound bacterial counts, assessed the relationship to air counts and compared BES (body exhaust suits) with Rotecno occlusive clothing.

Fifty TKR were randomly allocated to scrub teams wearing BES or Rotecno occlusive clothing. Air bacterial counting within 30cm of a wound is the established methodology to define air cleanliness. Reliable wound bacterial counting should be a more precise index of infection risk however, to date, there is no established accurate method. The TSMI (tetrazolium stained membrane imprint) method of bacterial wound counting has been validated in a tissue model and human surgical wounds in conventionally ventilated theatres.

This method remains to be assessed in UCA where wounds may be too clean for bacteria to be detected accurately. We used air counts within 30cm of the wound and tested the TSMI method in wounds.

Bacteria were recovered from 62% of the wounds. The mean air count wearing BES was 0. 5 cfu/m3 compared with 1. 0 cfu/m3 with Rotecno. The air counts were significantly higher with Rotecno clothing (p=0. 014, Toeplitz covariance analysis). The mean wound count was 14 bacteria/ wound with BES and 8 bacteria/wound with Rotecno. Although the counts were higher with BES the difference was not significant (p=0. 7, MannWhitney U test). There was no significant correlation between air and wound counts (r = 0. 108, Spearman’s).

On first impression Rotecno occlusive clothing would appear to be less effective than BES on account of the higher air counts. However wounds were equally contaminated with both clothing types. As there is no relationship between wound and air counts, this suggests that at very low levels of air contamination the contribution of bacteria to the wound from the air is irrelevant. Even doubling of air counts from 0. 5 to 1. 0 cfu/m3 had no detectable effect on the wound.