Infection Control in Surgical Practice

Upper Respiratory Tract Flora

Normal oral flora contains the microorganisms usually present in saliva and on the surfaces of oral tissues in healthy, immunocompetent individuals who have not been exposed to agents that alter the composition of oral organisms. A complete description of this flora can be found in Chapter 16 . In brief, normal oral flora consists of aerobic, gram-positive cocci (primarily streptococci), actinomycetes, anaerobic bacteria, and candidal species ( Table 5.1 ). The total number of oral organisms is held in check by the following four main processes: (1) rapid epithelial turnover with desquamation; (2) host immunologic factors such as salivary immunoglobulin A; (3) dilution by salivary flow; and (4) competition between oral organisms for available nutrients and attachment sites. Any agent—physical, biologic, or chemical—that alters any of the forces that keep oral microbes under control will permit potentially pathologic organisms to overgrow and set the stage for a wound infection.

The flora of the nose and paranasal sinuses consists primarily of gram-positive aerobic streptococci and anaerobes. In addition, many children harbor Haemophilus influenzae bacteria in these areas, and many adults have Staphylococcus aureus as a part of their transient or resident nasal and paranasal sinus flora. The normal flora in this region of the body is limited by the presence of ciliated respiratory epithelium, secretory immunoglobulins, and epithelial desquamation. The epithelial cilia move organisms trapped in blankets of mucus into the alimentary tract.

Maxillofacial Skin Flora

The skin of the maxillofacial region has surprisingly few resident organisms in its normal flora. The bacteria Staphylococcus epidermidis and Corynebacterium diphtheriae are the predominant species present. Propionibacterium acnes is found in pores and hair follicles, and many individuals carry S. aureus , spread from the nose on the facial skin (see Table 5.1 ).

Skin has several means of preventing the entry of surface organisms. The most superficial layer of skin is composed of keratinized epithelial cells that are able to resist mild trauma. In addition, epithelial cells are joined by tight bonds that resist bacterial entrance.

Processes that alter skin flora are, for example, the application of occlusive dressings (which prevent skin desiccation and desquamation), dirt or dried blood (which provide increased nutrients and niches for organisms), and antimicrobial agents (which disturb the balance between various organisms).

Nonmaxillofacial Flora

The flora below the region of the clavicles make up a gradually increasing number of aerobic gram-negative and anaerobic enteric organisms, especially moving toward the pelvic region and unwashed fingertips. General knowledge of these bacteria is important for dental surgeons when preparing themselves for surgery and when treating patients requiring venipuncture or other procedures away from the orofacial region.

Hepatitis Viruses

Hepatitis A, B, C, and D viruses are responsible for most infectious hepatic diseases. Hepatitis A is spread primarily by contact with the feces of infected individuals. Hepatitis C virus may spread through contaminated feces or by contaminated blood. Hepatitis B and D viruses are spread by contact with any human secretion.

Hepatitis B virus has the most serious risk of transmission for unvaccinated dentists, their staff members, and their patients. This virus is usually transmitted by the introduction of infected blood into the bloodstream of a susceptible person; however, infected individuals may also secrete large numbers of the virus in their saliva, which can enter an individual through any moist mucosal surface or epithelial (skin or mucosal) wound. Minute quantities of the virus have been found capable of transmitting disease (only 105 to 107 virions/mL blood). Unlike most viruses, hepatitis B virus is exceptionally resistant to desiccation and chemical disinfectants, including alcohols, phenols, and quaternary ammonium compounds. Therefore hepatitis B virus is difficult to contain, particularly when oral surgery is being performed.

Fortunately, means of inactivating the hepatitis B virus include halogen-containing disinfectants (e.g., iodophor and hypochlorite), formaldehyde, ethylene oxide gas, all types of properly performed heat sterilization, and irradiation. These methods can be used to minimize the spread of hepatitis from one patient to another.

In addition to preventing patient-to-patient spread, the dentist and the staff also need to take precautions to protect themselves from contamination because in several instances, dentists have been the primary source of a hepatitis B epidemic. Dentists who perform oral surgical procedures are exposed to blood and saliva; therefore the dental surgery team should wear barriers to protect against contaminating any open wounds on the hands and any exposed mucosal surfaces. This includes wearing gloves, a facemask, hair coverage, and eyeglasses or goggles during surgery. During operative procedures the patient should also wear protective eyewear. The dental staff should continue to wear these protective devices when cleaning instruments and when handling impressions, casts, or specimens from patients. A common means of hepatitis inoculation is injury with a needle or blade that is contaminated with blood or saliva, so proper handling of sharp objects is important. In addition, members of the dental staff should receive hepatitis B vaccinations, which have been shown to effectively reduce an individual's susceptibility to hepatitis B infection, although the longevity of protection has not been definitively determined. Finally, office-cleaning personnel and commercial laboratory technicians can be protected by proper segregation and labeling of contaminated objects and by proper disposal of sharp objects ( Box 5.1 ).

Recognition of all individuals known to be carriers of hepatitis B and C viruses would aid in knowing when special precautions are necessary. However, only about half of the persons infected with hepatitis ever have clinical signs and symptoms of the infection, and some individuals who have completely recovered from the disease still shed intact virus particles in their secretions. The concept of universal precautions was developed to address the inability of health care providers specifically to identify all patients with communicable diseases. The theory on which the universal precautions concept is based is that protection of self, staff, and patients from contamination by using barrier techniques when treating all patients as if they all had a communicable disease ensures that everyone is protected from those who do have an unrecognized contagious process.

Universal precautions typically include having all doctors and staff who come in contact with patient blood or secretions, whether directly or in aerosol form, wear barrier devices, including a face-mask, hair coverage, eye protection, and gloves. Universal precaution procedures go on to include decontaminating or disposing of all surfaces that are exposed to patient blood, tissue, and secretions. Finally, universal precautions mandate avoidance of touching, and thereby contaminating, surfaces (e.g., the dental record, computer keyboard, uncovered light handles, and telephone) with contaminated gloves or instruments.

Human Immunodeficiency Virus

Because of its relative inability to survive outside the host organism, HIV (the causative agent of acquired immunodeficiency syndrome), acts in a fashion similar to other agents of sexually transmitted diseases. That is, transfer of the virions from one individual to another requires direct contact between virus-laden blood or secretions from the infected host organism and a mucosal surface or epithelial wound of the potential host. Evidence has shown that HIV loses its infectivity once desiccated. In addition, few persons carrying HIV secrete the virus in their saliva, and those who do, tend to secrete extremely small amounts. No epidemiologic evidence supports the possibility of HIV infection via saliva alone. Even the blood of patients who are HIV-positive has low concentrations of infectious particles (106 particles/mL compared with 1013 particles/mL in hepatitis patients). This probably explains why professionals who are not in any of the known high-risk groups for HIV positivity have an extremely low probability of contracting it, even when exposed to the blood and secretions of large numbers of patients who are HIV positive during the performance of surgery or if accidentally autoinoculated with contaminated blood or secretions. Nevertheless, until the transmission of HIV becomes fully understood, prudent surgeons will take steps to prevent the spread of infection from the HIV-carrying patient to themselves and their assistants through the use of universal precautions, including barrier techniques.

In general, the universal precautions used for bacterial, mycotic, and other viral processes protect the dentist, office staff, and other patients from the spread of the virus that causes acquired immunodeficiency syndrome (see Box 5.1 ). Also important is that patients with depressed immune function be afforded extra care to prevent the spread of contagions to them. Thus all patients infected with HIV who have CD4 ⁺ T lymphocyte counts of less than 200/µL or category B or C HIV infection should be treated by doctors and staff free of clinically evident infectious diseases. These patients should not be put in a circumstance in which they are forced to be closely exposed to patients with clinically apparent symptoms of a communicable disease.