Bacterial infections remain a danger as resistance to antibiotics increases

Aug. 1, 1996
The main source of cross-contamination in the office is the patient`s mouth. Since oral fluids may contain microbial pathogens that could spread to other patients or the dental team, the majority of infection control procedures are aimed at reducing or preventing contact with saliva and blood.

Chris Miller, PHD

The main source of cross-contamination in the office is the patient`s mouth. Since oral fluids may contain microbial pathogens that could spread to other patients or the dental team, the majority of infection control procedures are aimed at reducing or preventing contact with saliva and blood.

The potential presence of the bloodborne agents of hepatitis B, C, or D, and HIV disease is now deeply ingrained in our brains. While the importance of viral bloodborne pathogens in hygiene and dentistry clearly remains, the existence of bacterial disease agents must not be forgotten. Not only are bacterial pathogens present in oral fluids, but some also have developed antibiotic resistance which truly challenges the management of any harmful infections caused by these agents.

These antibiotic resistant strains also cause an important number of the two million or so hospital-derived infections acquired by people while they are in the hospital. The presence of bacterial pathogens in oral fluids simply lends more importance to the necessity of maintaining high infection control standards in the office.

Not to be forgotten

Streptococcus pneumoniae. This bacterium lives in the nose and throat of humans and is carried without symptoms in a number of adults and some children. Thus, as with the viral airborne diseases, these asymptomatic carriers serve as very important and unknown sources of infection.

Every year, S. pneumoniae causes about 3,000 cases of meningitis, 50,000 cases of bacteremia, 500,000 cases of pneumonia, and 7,000,000 cases of middle ear infections. The elderly who acquire this pneumonia become susceptible to even more serious forms of bacterial lung infections which kill about 25,000 a year.

While S. pneumoniae used to be uniformly susceptible to penicillin, its resistance to this important antibiotic was first reported in 1967 and has steadily increased in the last 10 years. A 60-fold increase in the number of penicillin-resistant strains causing diseases occurred between 1987 and 1992. Although a vaccine has been available since 1982, and is strongly recommended for the elderly, only about 27 percent of those over 65 have been vaccinated.

Staphylococcus aureus. About 10 percent of the population are nose/throat carriers of this bacterium which can cause a variety of harmful infections throughout the body (for example, boils, abscesses, wound infections, pneumonia, acute dental infections, osteomyelitis, toxic shock syndrome, and food poisoning).

When S. aureus began to show resistance to penicillin back in the 1950s, vancomycin came into use to solve the problem. Later, methacillin and other related antibiotics were developed for use against these penicillin-resistant strains. Methacillin-resistant S. aureus (MRSA) has also emerged. Today, most of the clinical isolates of S. aureus are resistant to penicillin, and some are resistant to methacillin.

The fear is that some will become resistant to the vancomycin that is being used in treatment. Vancomycin resistance has been seen in other bacteria.

Streptococcus faecalis. This bacterium is one of a group of species referred to as enterococci because they mostly occur in the intestinal tract. However, S. faecalis also may be carried in the mouth. It was once thought to be very important in causing dental caries until more detailed studies revealed that Streptococcus mutans played this role. Streptococcus faecalis causes endocarditis, urinary tract infections, wound infections, and cellulitis. Vancomycin is used against those strains resistant to penicillin. However, vancomycin-resistant enterococci (VRE) have developed and cause an important number of hospital-derived infections.

Streptococcus pyogenes. This group-A, ?-hemolytic streptococcus causes Ostrep throat,O scarlet fever (basically strep throat with a rash), and skin infections. It is also associated with rheumatic fever and rheumatic heart disease as well as inflammation of the kidney. About 10 percent of the population are asymptomatic nose/throat carriers of this bacterium.

Mycoplasma pneumoniae. This bacterium causes about 10 percent of all pneumonias in children under age 12 and at least 15 percent of pneumonia cases in teenagers and adults. It may be present without causing symptoms in the nose/throat area and is totally resistant to penicillin.

Other bacteria. Other pathogenic bacteria besides the normal oral bacterial flora may be present in oral fluids. These include Hemophilus influenzae type b that causes conjunctivitis, meningitis, and epiglottitis, and is present in about 1 percent of asymptomatic children. A vaccine called OHibO is available and recommended for infants. This vaccine is often confused with the hepatitis B vaccine (because of its name) which is also recommended for infants and for 12-year-olds if not previously vaccinated.

Past studies have suggested that as high as a third of normal adults may also carry Neisseria meningditis which is an important cause of bacterial meningitis.

The infection control procedures currently recommended for dental offices not only relate to the viral bloodborne pathogens but also to bacterial pathogens. Faithful use of masks and eyeglasses during patient care will help reduce mucous membrane contact with these bacteria. The proper use of gloves and protective clothing will help reduce the spread of these bacteria not only between patients and the dental team but also between patients themselves. Also, proper cleaning and sterilization of instruments and appropriate management of saliva-contaminated surfaces touched during patient care will help reduce bacterial spread.

Chris Miller is director of Infection Control Research and Services and professor of oral biology at Indiana University.