The classification for medical and surgical instruments as critical, semicritical, and noncritical is predicated on their potential to transmit infection if the items are contaminated prior to use.1 The CDC expanded the original classification by adding fomites, i.e., environmental surfaces that generally do not come in direct contact with patients, but may serve as a reservoir for pathogens.1,2 Factors that influence the number and types of microorganisms on environmental surfaces are presented in Box B.1

Box B. Factors Affecting the Number and Types of Microorganisms on Environmental Surfaces.

  1. Number of people in the environment.
  2. Amount of activity.
  3. Amount of moisture.
  4. Presence of material capable of supporting microbial growth.
  5. Rate at which organisms suspended in air are removed.
  6. Type of surface orientation (i.e., horizontal or vertical).

In comparison to air and water, environmental surfaces carry the least risk of disease transmission in healthcare settings. When implicated, the transmission of pathogenic organisms from the source to the host is primarily through indirect means such as via hand transfer.1 Infection prevention strategies related to hand hygiene and glove use with special reference to the oral healthcare setting are discussed elsewhere.4,5