Cross-infection and sterilization
Publisher Summary
Cross-infection might be defined as the transmission of infectious agents among patients and staff within a hospital environment. Transmission can occur between individuals by direct contact but it involves fomites, that is, contaminated inanimate objects. In dentistry, the three main sources of infection are: (1) patients suffering from the infectious disease; (2) patients in the prodromal stage of certain infections; and (3) individuals who are carriers of pathogenic microorganisms. It is rare for a patient who is suffering from an acute infectious disease to require dental treatment, although this might occur in an emergency situation. A more likely source of infection is a patient who attends for treatment during the prodromal stage of an infectious disease. At this stage of the infection, the secretions and blood of the patient might be infectious to others, although the patient might appear and feel relatively well. Certain bacterial and viral infections have a prodromal stage, although the phenomenon is more common with viral agents than with bacteria.
Cross-infection in the dental surgery
Route of infection
The microorganisms which can be transmitted by infected aerosols are shown in Table 17.1. The majority of these are common viral infections. When aerosols are produced by high-speed instruments, two different types of particles are produced. The characteristics of these are shown in Table 17.2 and, while the smaller particles are involved in transmission by inhalation, the larger particles coat surfaces and may enter the tissues via cuts. The microorganisms involved in transmission by direct contact and by injection are hepatitis B virus, human immunodeficiency virus, herpes simplex virus and Treponema pallidum. Details about the microorganisms involved in cross-infection in dentistry are given in Chapters 8, 10, 15 and 16.
Table 17.1
Microorganisms transmitted by infected aerosols
Viruses | Bacteria |
Influenza | B. pertussis |
Rhinovirus | M. tuberculosis |
Adenovirus | Strep. pyogenes |
Mumps virus | |
Measles | |
Rubella | |
Varicella zoster | |
Epstein–Barr |
Table 17.2
Characteristics of aerosols produced by high-speed instruments
Particles | Droplet nuclei | |
Diameter | <100 μm | >100 μm |
Time spent airborne | Minutes | Hours |
Penetration into respiratory tract | Unlikely | Possible |
Likely mode of transmission | Direct contact or in dust | Inhalation |