Surgical face masks and downward dispersal of bacteria

The ability of face masks to prevent forward dispersal of bacteria is offset by the possibility that they may increase vertical shedding of bacteria from the face during facial movement. To investigate this, a blood agar plate was placed 30 cm directly below the lips of 20 volunteers who were encouraged to talk for 20 min while moving their heads from side to side, without a face mask for the first 5 min and then with a standard, soft pleated face mask for the subsequent 15 min. The agar plates were changed at 5-min intervals. Analysis of the number of bacterial colonies grown on each agar plate showed a statistically significant reduction in the median number of colonies cultured per plate when the mask was worn. Our results suggest that for procedures lasting less than 15 min, the operator should wear a face mask, particularly when the face is in close proximity to the operative field and the need for speaking is anticipated.