Lack of influence of body exhaust gowns on aerobic bacterial surface counts in a mixed-ventilation operating theatre. A study of 62 hip arthroplasties.

Aerobic bacterial surface contamination was studied with and without the use of body exhaust gowns in an operating room equipped with mixed/turbulent ventilation and separate operating and anaesthetic areas during 62 hip joint arthroplasties. In 31 operations conventional gowns were used, and 31 were performed with body exhaust gowns. Bacterial surface contamination was monitored in the operating and anaesthetic area using 9 cm diameter settle plates (1+1) and nitrocellulose membranes (2+2) transferred after sampling to nutrient pads. Compared with conventional clothing, the use of body exhaust gowns did not significantly reduce the microbial contamination (P=0.1-0.7). On the settle plates 1 m from the patient 279+/-326 cfu/m(2)/h were observed with conventional clothing compared with 142+/-227 cfu/m(2)/h with body exhaust gowns. The first membrane located on the patient in the sterile area detected 250+/-590 cfu/m(2)/h with conventional clothing and 210+/-320 cfu/m(2)/h with exhaust gowns. For the second membrane on the floor, the counts were 1790+/-2700 and 1590+/-1590 cfu/m(2)/h. For all operations the settle plates yielded 210+/-287 cfu/m(2)/h in the operating area and 720+/-564 cfu/m(2)/h in the anaesthetic area (P=0.01). Compared with the membrane placed on the anaesthetic equipment the counts on the membrane placed on patient were also significantly lower (P=0.01) while the membranes placed on the floor in each area showed no difference in counts. In conclusion, compared with conventional clothing, the use of body exhaust gowns could not be proven to provide more protection against microbial contamination. The low number of colony forming units found in the operating area was similar to that expected from an ultraclean laminar airflow unit, although achieved with a cheaper and more energy saving system.

The index of microbial air contamination.

The standard index of microbial air contamination (IMA) for the measurement of microbial air contamination in environments at risk is described. The method quantifies the microbial flow directly related to the contamination of surfaces coming from microbes that reach critical points by falling on to them. The index of microbial air contamination is based on the count of the microbial fallout on to Petri dishes left open to the air according to the 1/1/1 scheme (for 1h, 1m from the floor, at least 1m away from walls or any obstacle). Classes of contamination and maximum acceptable levels have been established. The index of microbial air contamination has been tested in many different places: in hospitals, in food industries, in art galleries, aboard the MIR space station and also in the open air. It has proved to be a reliable and useful tool for monitoring the microbial surface contamination settling from the air in any environment.