36: Principles of infection control

Chapter 36 Principles of infection control

Cross infection

Cross infection may be defined as the transmission of infectious agents between patients and staff within a clinical environment. Transmission may result from person-to-person contact or via contaminated objects (fomites) (Fig. 36.1). Organisms capable of causing cross infection in humans are derived from:

image

Fig. 36.1 Routes and modes by which infection may spread in the dental clinic.

• other human sources (the most important)
• animal sources (less important)
• inanimate sources (of least importance).

Principles of infection transmission

Transmission of infection from one person to another requires:

1. a source of infection – the person with the infection is called the index case
2. a mode or vehicle by which the infective agent is transmitted, e.g. blood, droplets of saliva, instruments contaminated with blood, saliva and tissue debris. (Animals or insects may act as vehicles or vectors of transmission, for example, in malaria, but are not described here)
3. a route of transmission, e.g. inhalation, ingestion.

Source of infection

The sources of infection in clinical dentistry are mainly human; they include:

1. People with overt infections who liberate large numbers of organisms into the environment (e.g. droplets and discharges from the mouth or other portals; wounds, ulcers and sores on the skin). Fortunately, in routine clinical dentistry, few patients with acute diseases are seen.
2. People in the prodromal stage of certain infections. During the prodrome or the incubating period, the organisms multiply without evidence of infection; although patients are healthy at this stage, they are highly infectious. Viral infections, such as measles, mumps and chickenpox, easily spread in this manner.
3. People who are healthy carriers of pathogens and can be classified as:

image convalescent carriers
image asymptomatic carriers.

Convalescent carriers are those who suffer an illness and apparently recover, although blood and secretions of the individual act as persistent reservoirs of infective organisms. For example, following diphtheria or streptococcal sore throat, the organisms may persist in the throat for some time and infect others or, in the case of hepatitis B patients, may recover fully, although they may carry the infectious agent in the blood for a considerable period. The latter are called chronic carriers.

Asymptomatic carriers give no history of infection as they may have unknowingly had a non-apparent or subclinical infection (recognized merely because of the presence of specific antibodies in the person’s blood). Nevertheless, these individuals may carry infective microbes in the saliva, blood and other body secretions.

Hepatitis B is a classic example of a disease that may manifest with or without symptoms, and thus, the clinician may be faced with either a convalescent or an asymptomatic carrier of hepatitis B virus. Note: a convalescent carrier can be identified from the history of infection, as opposed to an asymptomatic carrier who cannot be diagnosed in this way.

Standard infection control

From the foregoing, it is clear that it is impossible to ascertain whether the patient who attends for dental treatment is a carrier of infectious agents. Therefore, all patients should be treated as if they were reservoirs of pathogens. The infection control procedures involved in such treatment are termed standard precautions (previously termed universal precautions), and all clinical procedures performed on any patient should be conducted using standard infection control. The corollary of this is that no additional infection control precautions should be necessary when a patient who is a carrier of infection such as HIV disease attends the clinic. The importance of this concept cannot be overemphasized and should be noted by all who practise dentistry.

Evolution of universal precautions, standard precautions and additional precautions (or transmission-based precautions)

The first set of recommendations on infection control in dentistry, issued in the late 1980s, focused primarily on the transmission of blood-borne pathogen transmission in dental care and other clinical settings and was termed universal precautions. These recommendations emphasized the need to treat blood and other bodily fluids contaminated with blood from all patients as potentially infectious.

However, the realization that moist body substances are equally important in disease transmission led to the development of standard precautions in the mid-1990s. Thus, standard precautions are similar to universal precautions as they are designed to reduce the risk of infection transmission from both recognized and unrecognized sources of infection to patients and clinicians. Standard precautions apply to contact with:

• blood
• all body fluids, secretions and excretions except sweat, regardless of whether they contain blood
• non-intact skin
• mucous membranes.

For the overwhelming majority of infectious diseases, including those possibly encountered routinely in dental settings, the application of standard precautions will arrest disease transmission.

However, in special situations where a known infection with a high transmission potential is suspected or encountered, additional precautions or transmission-based precautions have to be implemented. These incl/>

Related posts:

  1. 16: Vibrios, campylobacters and Wolinella
  2. 18: Fusobacteria, Leptotrichia and spirochaetes
  3. 11: Streptococci, staphylococci and micrococci
  4. 32: Microbiology of dental caries
  5. 26: Infections of the gastrointestinal tract
  6. 4: Viruses and prions

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Jan 4, 2015 | Posted by in General Dentistry | Comments Off on 36: Principles of infection control

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