Circular 95-09 Appendix B

TUBERCULOSIS INFECTION CONTROL POLICY

DEFINITIONS

Acid-Fast Bacilli (AFB) - Bacteria that retain certain dyes even when washed with an acid solution. Most acid-fast organisms are mycobacteria (M. tuberculosis). When seen on a stained smear of sputum or other clinical specimen, a diagnosis of TB should be considered; however, the diagnosis is not confirmed until a culture is grown and identified as M. tuberculosis.
Acquired Drug Resistance - Resistance to one or more anti-tuberculosis drugs which develops while a patient is on therapy, usually the result of non-adherence on the part of the patient or inadequate therapy prescribed by a health care provider.
Adherence - Refers to the completion by patients of all aspects of the treatment regimen as prescribed by the medical provider. Also refers to health care workers (HCWs) and employers following all guidelines pertaining to infection control.
Aerosol Aerosolization - In TB, it refers to the infectious droplet nuclei that are expelled from a person which can be transmitted to other people.
Air Changes - Air flow quantity to a space measured in terms of the room volume. i.e., volume of air delivered divided by room volume. Usually expressed as number of air changes per hour.
Alveoli - The small air sacs in the lungs which lie at the end of the bronchial tree. The site where carbon dioxide is replaced by oxygen in the lungs, and the site where TB infection usually begins.
Anergy - The inability of a person to react to skin-test antigens because of defects in the immune system, even if the person is infected with the organisms tested.
Anteroom - A small room located between an isolation room and a corridor that acts as an airlock, preventing escape of room contaminants into the corridor.
Asymptomatic - Showing or causing no symptoms.
Bactericidal - Capable of killing bacteria. Isoniazid and rifampin are the two most potent bactericidal antituberculosis drugs (See Bacteriostatic).
Bacteriostatic - Capable of preventing bacterial growth but not necessarily capable of killing bacteria. Drugs such as ethambutol and para-aminosalicylic acid are primarily bacteriostatic (see Bactericidal)
BCG (Bacillus of Calmette and Guerin) - A TB vaccine widely used in some parts of the world.
Booster Phenomenon - Seen when an individual with infection does not react to tuberculin because his/her body's cell responses to tuberculin have gradually waned over the years. An initial tuberculin test may stimulate (boost) the immune system so that the next test will be positive. This phenomenon is important in infection control in order to distinguish between recent converters and people who have been infected for a long time, and determine if in fact transmission is taking place. Although the booster phenomenon may occur at any age, it is most frequent among persons over 55.
Bronchoscopy - A procedure for examining the respiratory tract by inserting an instrument (bronchoscope) through the mouth or nose into the trachea. Diagnostic specimens can be obtained during bronchoscopy.
Cavity - A hole in the lung resulting from destruction of pulmonary tissue. May be caused by TB, but also by other pulmonary infections and conditions. TB patients with cavities in their lungs are said to have "cavitary disease" and are often more infectious than patients without cavities.
Chemotherapy - Treatment of an infection or disease by means of oral or injectable drugs.
Chest Radiograph - In patients showing signs or symptoms of TB, a radiograph of the chest is taken to view the respiratory system. Abnormalities, such as lesions or cavities in the lungs and enlarged lymph nodes, may indicate the presence of TB.
Contact - An individual who has shared the same air as a person with infectious TB for a sufficient amount of time so that there is a probability that transmission of TB has occurred.
Conversion, PPD - See PPD TEST CONVERSION
Culture - The process of growing bacteria in the laboratory so that organisms can be identified.
Dilution Ventilation - An engineering control technique to dilute and remove air-borne contaminants by the flow of air into and out of the area. Air that contains droplet nuclei is removed and replaced by air that is free of contaminants. If the flow is sufficient, droplet nuclei become dispersed, and their concentration in the air is diminished.
Droplet Nuclei - Microscopic particles (1 to 5 microns in diameter) produced when a person coughs, sneezes, shouts, or sings. The droplets can carry tubercle bacilli and remain in the air by normal air currents in the room.
Drug Sensitivity - See Drug Susceptibility Pattern
Drug Susceptibility Pattern - The antituberculosis drugs to which a tubercle bacillus is susceptible and those to which it is resistant based on susceptibility tests.
Drug Susceptibility Tests - Laboratory tests which determine if the tubercle bacilli cultured from a patient is susceptible or resistant to various antituberculosis drugs.
Exposure - The condition of being subjected to something, such as infectious agents, which may have a harmful effect. A person exposed to TB does not necessarily become infected (see Transmission).
Fomites - Linens, books, dishes, or other objects touched by a patient. They are not involved in the used or transmission of TB.
HEPA (High-Efficiency Particulate Air) - Filter -Specialized filter that is capable of removing 99.97% of. particles 0.3 microns in diameter. It may be of assistance in control of TB transmission. Requires expertise in installation and maintenance.
Human Immunodeficiency Virus (HIV) or HIV Infection - Infection with the virus that causes the acquired immunodeficiency syndrome (AIDS). It is the most potent risk factor for progression from TB infection to active TB.
HCW - Health Care Worker.
High Risk - High risk areas or groups are those in which (1) the PPD test conversion rate is significantly greater than areas without occupational exposure to TB patients or than previous rates in the same area or group, or (2) there is a cluster of PPD test conversions, or (3) there is other evidence of patient-to-patient or patient-to-HCW transmission of TB.
Immunosuppressed - Persons with severe cellular immunosuppression (i.e HIV infected or organ transplant patients on immunosuppressive therapy). These patients are at greatly increased risk for developing TB once infected. There are no data available on whether they are also at higher risk of becoming infected with M. tuberculosis, if exposed.
Induced Sputum - Sputum obtained from a patient unable to cough up a spontaneous specimen. The patient inhales a mist of saline (salt water), which stimulates a cough from deep within the lungs.
Induration - The area of swelling that surrounds the site of injection of tuberculin. The diameter of the indurated area is measured (in millimeters) 48-72 hours after the injection and is recorded as the result of the PPD test.
Infection - The condition in which organisms capable of causing disease (e.g., M. Tuberculosis) multiply within the body and cause a response from the host's immune defenses. Infection may or may not lead to clinical disease.
Infectious - Capable of causing infection. In TB a person is infectious only if he/she has clinically active TB TB patients whose sputum is AFB smear positive are often infectious.
Intermediate Risk - Intermediate risk areas or groups are those in which; (1) the PPD test conversion rate is not greater than in areas or groups without occupational exposure to TB patients or than previous rates in the same area or group; (2) there are no clusters of PPD test conversions; (3) there is no evidence of patient-to-patient transmission; and (4) there are 6 or more TB patients hospitalized per year.
Intradermal - Within the layers of the skin.
Local Exhaust Ventilation - Used as a source control technique to capture and remove air-borne contaminants by enclosing the contaminant source or by means of a hood placed very near the contaminant source.
Low Risk - Low risk areas or groups are those in which (1) the PPD test conversion rate is not greater than in areas or groups without occupational exposure to TB patients or than previous rates in the same area or group, (2) there are no clusters of PPD test conversions, (3) there is no evidence of patient-to-patient transmission, and (4) (in the case of an area) there are < 6 TB patients hospitalized per year.
Mantoux Test - A tuberculin test given by injecting a measured amount of liquid tuberculin into the dermis (second layer of the skin) with a needle and syringe. It is the most reliable and best standardized technique for tuberculin testing (see Tuberculin Skin Test and Purified Protein Derivative Test).
MDR (Multidrug Resistant) Tuberculosis - Tuberculosis bacteria resistant to multiple drugs which normally kill them (see Resistance).
Minimal Risk - Facilities may be described as having a minimal risk of TB exposure if no TB cases are present in the community and no TB patients were seen as inpatients or outpatients.
Mycobacterium Tuberculosis Complex - The complex of mycobacterial species that causes TB; it includes M. tuberculosis, M. bovis, and M. africanum.
Negative Pressure - A term used to describe the relative air pressure difference between two areas of the health-care facility. Air will flow from the higher pressure area into the lower pressure area.
Non Contagious Tuberculosis - See Tuberculosis Infection.
Pathogenesis - The natural development of a disease in the body without intervention (i.e., without treatment).
PPD - See Purified Protein Derivative.
Portable Filtration Units - Portable devices that provide contaminant dilution by recirculating air within a room through a HEPA filter.
Positive PPD Reaction - A reaction to the purified protein derivative (PPD) test that suggests the individual tested is infected with tubercle bacilli. Determination of the reaction is largely dependent on interpretation by the person evaluating the test given the patient's or HCW's medical history and risk factors.
Preventive Therapy - Chemotherapy of TB infection, primarily used to prevent progression of infection to clinically active disease.
Primary Drug Resistance (PDR) - Resistance of bacteria to drugs which exists before the beginning of treatment (see Acquired Drug Resistance).
Purified Protein Derivative (PPD) - A type of purified tuberculin preparation derived from old tuberculin (OT) and developed in the 1930's. The standard Mantoux test uses 5 TU (tuberculin units) of PPD.
Purified Protein Derivative (PPD) Reactor - A person with a positive skin test, who does not have a documented negative skin test within the last two years.
Purified Protein Derivative (PPD) Test - A method to determine whether a person is infected with Mycobacterium tuberculosis. A small dose of the antigen from M. tuberculosis is injected just beneath the surface of the skin and the area is examined 48-72 hours after the injection. A positive reaction is measured according to the size of the induration. The classifications for positive reactions depend on the patient's medical history and various risk factors (see Mantoux Test).
Purified Protein Derivative (PPD) Test Conversion - Growth in induration within a two-year period after an initial negative reaction with a difference of 10 or more millimeters of induration. Such "conversion" may represent new infection which is associated with high risk of developing disease, or may occur as a result of the Booster Phenomenon.
Reaction - See Purified Protein Derivative (PPD) Reactor.
Recirculation - Ventilation where all or most of the air exhausted from an area is returned to the area.
Regimen - Any particular treatment plan for TB specifying which drugs are used, in what doses, according to what schedule, and for how long.
Registry - A record-keeping method to collect clinical, laboratory, and radiographic data on TB or any other pathological field so the data can be organized and properly processed to be made available for epidemiologic study.
Resistance - The ability of some strains of bacteria (including M. tuberculosis) to grow and multiply even in the presence of certain drugs which normally kill them. (such strains are referred to as "drug resistant strains.?)
Respirator Fit Check - A fit check is a maneuver that a HCW performs before each use of the respiratory protective device to check the fit. The fit check should be performed according to the manufacturer's facepiece fitting instructions.
Respirator Fit Test - A fit test is used to determine whether a respiratory protective device adequately fits a particular HCW. Determination of facepiece fit can involve qualitative or quantitative tests. A qualitative test relies on the wearer's subjective response. A quantitative test uses detectors to measure inward leakage.
Qualitative Fit Test - A subjective test utilized to determine if a respirator fits the wearer appropriately. The wearer is exposed to a test agent (irritant smoke or other suitable agent) easily detectable by irritation or taste. If the wearer is unable to detect penetration of the test agent the respirator is probably tight enough.
Quantitative Fit Test - A quantitative fit test uses a probe inserted through the device to determine the concentration of a substance inside the respirator compared to the concentration of the substance outside the respirator.
Secondary Drugs - Antituberculosis drugs used in difficult cases (such as for retreatment or when there is resistance to primary drugs). Examples are cycloserine, ethionamide, capreomycin.
Single Pass Ventilation - Ventilation in which 100% of the air supplied to an area is exhausted to the outside.
Smear (AFB Smear) - A laboratory technique for visualizing mycobacteria. The specimen is smeared onto a slide and stained, and then placed under the microscope for examination. Smear results should be available within 24 hours. A large number of mycobacteria usually indicates infectiousness; however, a "positive" result is not definitive for TB.
Source Case - An infectious individual who has transmitted tubercle bacilli to another person or persons.
Source Control - Control of a contaminant at the source of generation rather than permitting it to enter the general work space.
Specimen - Any body fluid, secretion, or tissue sent to the laboratory where smears and cultures for tubercle bacilli will be performed. The specimen may consist of sputum, urine, spinal fluid, material obtained at biopsy, etc.
Sputum - Material coughed up from deep within the lungs. If a patient has a pulmonary infection, an examination of the sputum by smear and culture can indicate what organism is responsible for the infection. It should not be confused with saliva or with nasal secretions.
Sputum Smear Positive - The AFB are visible after staining when viewed under a microscope. The TB culture positive individuals with sputum smear positive for AFB are considered more infectious than those with smear negative sputum.
Suspect Case - A person suspected of having active contagious tuberculosis disease.
Symptomatic - Having symptoms which may be clues to the presence of TB or another disease (see Asymptomatic).
Transmission - The spread of an infectious agent like Mycobacterium tuberculosis from one individual to another. The duration and intensity of exposure to TB is directly related to the likelihood that transmission will occur and a person will become infected (see Exposure).
Treatment Failures - Refers to individuals who fail to improve even after a course of chemotherapy is begun, and to individuals whose disease worsens after having initially improved.
Tubercle Bacilli - The term often used to refer to the organism Mycobacterium tuberculosis.
Tuberculin Skin Test - A method to determine whether a person is infected with Mycobacterium tuberculosis. A small dose of the antigen from M. tuberculosis is injected just beneath the surface of the skin and the area in examined 48 - 72 hours after the injection. A positive reaction is measured according to the size of the swelling. The classifications for positive reactions depend on the patient's medical history and various risk factors (see Mantoux Test, PPD Test).
Tuberculosis (TB) - A clinically apparent active disease process caused by Mycobacterium tuberculosis, complex (usually M. tuberculosis, or, rarely, M. bovis or M. africanum).
Tuberculosis Case - A particular instance of clinically active TB. It is sometimes used incorrectly to designate the individual with the disease.
Tuberculosis Infection - A condition in which living tubercle bacilli are present in the body, without producing clinically active disease. Although the infected individual has a positive tuberculin reaction, he/she has no symptoms related to the infection and is not infectious. However, the infected individual remains at lifelong risk of developing disease unless preventive therapy is given.
Tuberculosis (TB) Isolation Precautions - Infection control procedures that should be applied when persons with known or suspected infectious TB are hospitalized or residing in other inpatient facilities. These precautions include the use of a private room with negative pressure in relation to surrounding air and removal of air from the room directly to the outside. Not the same as "respiratory isolation" which calls for a private room, but does not require negative pressure and exhaust of room air to the outside.
Two-Step Testing - A procedure used among people who receive tuberculin skin tests periodically (such as health care workers) to reduce the likelihood of mistaking a boosted reaction for a recent infection. If the initial tuberculin test is classified as negative, a second test is repeated one week later. If the reaction to the second test is positive, it probably represents a boosted reaction. If the second test result remains negative, the person is classified as being uninfected.
Ultraviolet (UW) Lamps - Lamps that destroy germs by emitting radiation predominantly at a wavelength of 254 nanometers (intermediate between visible light and X-rays). They can be used in ceiling or wall fixtures or within air ducts of ventilation systems. The effectiveness for infection control in health care facilities is not yet proven.
Very Low Risk - A facility may be described as having a very low risk if no TB patients were admitted as inpatients nor examined as outpatients in the preceding year, and the exposure control plan states that any patients with confirmed or suspected TB will be referred to another facility.
Virulence - Refers to the ability of a microorganism, such as M. tuberculosis, to produce serious disease. The M. tuberculosis is a virulent organism. Some nontuberculous mycobacteria are virulent (e.g., M. kansasii), while others (e.g., M. gordnae) are not. (Pathogenicity is a related, though not identical, concept).