Understanding the factors involved in determining the bioburdens of surgical masks.

Background: Surgical site infection (SSI) continues to be one of the most common postoperative complications. In our previous study, surgical mask (SM) bioburden was identified to be a potential source of SSI. In the present study, we investigated the factors involved in SM bioburden.

Methods: Bioburdens of the disposable SM (A: medical mask; B: medical surgical mask) and newly laundered cloth SM (C) were tested by immediately making an impression of the external surface of the mask on sterile culture media. SM microstructure was observed using a scanning electron microscope (SEM). Filtering efficiency and airflow resistance were evaluated with TSI Automated Filter Tester 8130 (TSI Incorporated) according to GB/19083-2010. Whether speaking during operation and washing the face pre-operatively affect SM bioburdens was also evaluated. Surgical procedures were performed in a dynamic operation room. Fifty cases of mask use were enrolled in this study.

Results: The bioburden of mask A was the highest. The bioburden of mask B was the lowest. Mask C possessed the lowest filtering efficiency and the highest airflow resistance. SM bioburden was higher in the speaking group. SM bioburden showed no significant difference after washing the face, despite the finding that washing could significantly reduce facial bioburden.

Conclusions: Multiple factors influence SM bioburdens. Mask B showed the lowest bioburden and best protection effects. Mask C is not recommended to be used, especially considering that surgeons do not wash the cloth masks daily. Unnecessary talking during operation is not recommended, and washing the face before surgery is not strictly necessary.