Source of bacterial shedding in laminar flow theatres.

In a previous unpublished observation, unacceptably high bacterial counts, presumably due to shedding episodes, occurred in two of 56 (3.57%) slit-air samples during arthroplasty surgery in a laminar flow operating theatre. The isolates matched those cultured from swab samples taken from the skin of one of the surgeons's foreheads on each of the two occasions. These findings occurred despite scrub staff wearing standard occlusive gowns, hats and masks with visors. In order to localize the potential source of such shedding more accurately, 20 members of theatre staff underwent anonymous microbiological swabbing from the facial areas not covered by theatre clothing, namely their foreheads, eyebrows and ears. These swabs were cultured and the growths were compared statistically. Significantly more colonies were cultured from swabs taken from the theatre staff's ears (P = 0.047, Freidman's test) compared with the other two facial areas studied. These data support the use of exhaust helmets in arthroplasty surgery, or at least mandatory coverage of the ears with theatre hats for scrub staff.