Guidelines for Preventing the Transmission of Tuberculosis in Health-Care Settings, with Special Focus on HIV-Related Issues
Samuel W. Dooley, Jr., M.D. Kenneth G. Castro, M.D. Mary D. Hutton, B.S.N., M.P.H. Robert J. Mullan, M.D. Jacquelyn A. Polder, B.S.N., M.P.H. Dixie E. Snider, Jr., M.D., M.P.H.
The transmission of tuberculosis is a recognized risk in health-care settings. Several recent outbreaks of tuberculosis in health-care settings, including outbreaks involving multidrug-resistant strains of Mycobacterium tuberculosis, have heightened concern about nosocomial transmission. In addition, increases in tuberculosis cases in many areas are related to the high risk of tuberculosis among persons infected with the human immunodeficiency virus (HIV). Transmission of tuberculosis to persons with HIV infection is of particular concern because they are at high risk of developing active tuberculosis if infected. Health-care workers should be particularly alert to the need for preventing tuberculosis transmission in settings in which persons with HIV infection receive care, especially settings in which cough-inducing procedures (e.g., sputum induction and aerosolized pentamidine (AP) treatments) are being performed.
Transmission is most likely to occur from patients with unrecognized pulmonary or laryngeal tuberculosis who are not on effective antituberculosis therapy and have not been placed in tuberculosis (acid-fast bacilli (AFB)) isolation. Health-care facilities in which persons at high risk for tuberculosis work or receive care should periodically review their tuberculosis policies and procedures, and determine the actions necessary to minimize the risk of tuberculosis transmission in their particular settings.
The prevention of tuberculosis transmission in health-care settings requires that all of the following basic approaches be used: a) prevention of the generation of infectious airborne particles (droplet nuclei) by early identification and treatment of persons with tuberculous infection and active tuberculosis, b) prevention of the spread of infectious droplet nuclei into the general air circulation by applying source-control methods, c) reduction of the number of infectious droplet nuclei in air contaminated with them, and d) surveillance of health-care-facility personnel for tuberculosis and tuberculous infection. Experience has shown that when inadequate attention is given to any of these approaches, the probability of tuberculosis transmission is increased.
Specific actions to reduce the risk of tuberculosis transmission should include a) screening patients for active tuberculosis and tuberculous infection, b) providing rapid diagnostic services, c) prescribing appropriate curative and preventive therapy, d) maintaining physical measures to reduce microbial contamination of the air, e) providing isolation rooms for persons with, or suspected of having, infectious tuberculosis, f) screening health-care-facility personnel for tuberculous infection and tuberculosis, and g) promptly investigating and controlling outbreaks.
Although completely eliminating the risk of tuberculosis transmission in all health-care settings may be impossible, adhering to these guidelines should minimize the risk to persons in these settings. This document was prepared in consultation with experts in tuberculosis, acquired immunodeficiency syndrome, infection-control and hospital epidemiology, microbiology, ventilation and industrial hygiene, respiratory therapy, nursing, and emergency medical services.
These recommendations consolidate and update previously published CDC recommendations (5-10). The recommendations are applicable to all settings in which health care is provided. In this document, the term "tuberculosis," in the absence of modifiers, refers to a clinically apparent active disease process caused by M. tuberculosis (or, rarely, M. Bovis or M. africanum). The terms "health-care-facility personnel" and "health-care-facility workers" refer to all persons working in a health-care setting--including physicians, nurses, aides, and persons not directly involved in patient care (e.g., dietary, housekeeping, maintenance, clerical, and janitorial staff, and volunteers). B. Epidemiology, Transmission, and Pathogenesis of Tuberculosis
Tuberculosis is not evenly distributed throughout all segments of the population of the United States. Groups known to have a high incidence of tuberculosis include blacks, Asians and Pacific Islanders, American Indians and Alaskan Natives, Hispanics, current or past prison inmates, alcoholics, intravenous (IV) drug users, the elderly, foreign-born persons from areas of the world with a high prevalence of tuberculosis (e.g., Asia, Africa, the Caribbean, and Latin America), and persons living in the same household as members of these groups (5).
M. tuberculosis is carried in airborne particles, known as droplet nuclei, that can be generated when persons with pulmonary or laryngeal tuberculosis sneeze, cough, speak, or sing (11). The particles are so small (1-5 microns) that normal air currents keep them airborne and can spread them throughout a room or building (12). Infection occurs when a susceptible person inhales droplet nuclei containing M. tuberculosis, and bacilli become established in the alveoli of the lungs and spread throughout the body. Two to ten weeks after initial human infection with M. tuberculosis, the immune response usually limits further multiplication and spread of the tuberculosis bacilli. For a small proportion of newly infected persons (usually less than 1%), initial infection rapidly progresses to clinical illness. However, for another group (approximately 5%-10%), illness develops after an interval of months, years, or decades, when the bacteria begin to replicate and produce disease (11). The risk of progression to active disease is markedly increased for persons with HIV infection (3).
The probability that a susceptible person will become infected depends upon the concentration of infectious droplet nuclei in the air. Patient factors that enhance transmission are discussed more fully in section II.B.3. Environmental factors that enhance transmission include a) contact between susceptible persons and an infectious patient in relatively small, enclosed spaces, b) inadequate ventilation that results in insufficient dilution or removal of infectious droplet nuclei, and c) recirculation of air containing infectious droplet nuclei.
Tuberculosis transmission is a recognized risk in health-care settings (13-21). The magnitude of the risk varies considerably by type of health-care setting, patient population served, job category, and the area of the facility in which a person works. The risk may be higher in areas where patients with tuberculosis are provided care before diagnosis (e.g., clinic waiting areas and emergency rooms) or where diagnostic or treatment procedures that stimulate patient coughing are performed. Nosocomial transmission of tuberculosis has been associated with close contact with infectious patients, as well as procedures such as bronchoscopy (16), endotracheal intubation and suctioning with mechanical ventilation (17,18), open abscess irrigation (19), and autopsy (20,21). Sputum induction and aerosol treatments that induce cough may also increase the potential for tuberculosis transmission (22). Health-care workers should be particularly alert to the need for preventing tuberculosis transmission in health-care settings in which persons with HIV infection receive care, especially if cough-inducing procedures such as sputum induction and AP treatments are being performed. II. General Principles of Tuberculosis Control in Health-Care Settings
Specific actions to reduce the risk of tuberculosis transmission should include the following: --Screening patients for active tuberculosis and tuberculous infection. --Providing rapid diagnostic services. --Prescribing appropriate curative and preventive therapy. --Maintaining physical measures to reduce microbial contamination of the air. --Providing isolation rooms for persons with, or suspected of having, infectious tuberculosis. --Screening health-care-facility personnel for tuberculous infection and tuberculosis. --Promptly investigating and controlling outbreaks.
B. Preventing Generation of Infectious Droplet Nuclei
Early identification of persons with tuberculous infection and application of preventive therapy are effective in preventing the development of tuberculosis (5). Persons at increased risk of tuberculosis (see section I.B.), or for whom the consequences of tuberculosis may be especially severe, should be screened for tuberculous infection to identify those for whom preventive treatment is indicated. The tuberculin skin test is the only method currently available that demonstrates infection with M. tuberculosis in the absence of active tuberculosis (11). 2. Early identification and treatment of persons with active tuberculosis
An effective means of preventing tuberculosis transmission is preventing the generation of infectious droplet nuclei by persons with infectious tuberculosis. This can be accomplished by early identification, isolation, and treatment of persons with active tuberculosis. Tuberculosis may be more difficult to diagnose among persons with HIV infection; the diagnosis may be overlooked because of an atypical clinical or radiographic presentation and/or the simultaneous occurrence of other pulmonary infections (e.g., Pneumocystis carinii pneumonia (PCP)). Among persons with HIV infection, the difficulty in making a diagnosis may be further compounded by impaired responses to tuberculin skin tests (23,24), low sensitivity of sputum smears for detecting AFB (25), or overgrowth of cultures with Mycobacterium avium complex (MAC) among patients with both MAC and M. tuberculosis infections (26).
A diagnosis of tuberculosis should be considered for any patient with persistent cough or other symptoms compatible with tuberculosis, such as weight loss, anorexia, or fever. Diagnostic measures for identifying tuberculosis should be instituted among such patients. These measures include history, physical examination, tuberculin skin test, chest radiograph, and microscopic examination and culture of sputum or other appropriate specimens (11,27). Other diagnostic methods, such as bronchoscopy or biopsy, may be indicated in some cases (28,29). The probability of tuberculosis is increased by finding a positive reaction to a tuberculin skin test or a history of a positive skin test, a history of previous tuberculosis, membership in a group at high risk for tuberculosis (see section I.B.), or a history of exposure to tuberculosis. Active tuberculosis is strongly suggested if the diagnostic evaluation reveals AFB in sputum, a chest radiograph is suggestive of tuberculosis, or the person has symptoms highly suggestive of tuberculosis (e.g., productive cough, night sweats, anorexia, and weight loss). Tuberculosis may occur simultaneously with other pulmonary infections, such as PCP.
A negative skin test does not rule out tuberculosis disease or infection. Because of the possibility of a false-negative result, the tuberculin skin test should never be used to exclude the possibility of active tuberculosis among persons for whom the diagnosis is being considered, even if reactions to other skin-test antigens are positive. Persons with HIV infection are more likely to have false-negative skin tests than are persons without HIV infection (23,24,30). The likelihood of a false-negative skin test increases as the stage of HIV infection advances (CDC/Florida Department of Health and Rehabilitative Services/New York City Department of Health, unpublished data). For this reason, a history of a positive tuberculin reaction is meaningful, even if the current skin-test result is negative.
b. Chest radiograph.
The radiographic presentation of pulmonary tuberculosis among patients with HIV infection may be unusual (31). Typical apical cavitary disease is less common among persons with HIV infection. They may have infiltrates in any lung zone, often associated with mediastinal and/or hilar adenopathy, or they may have a normal chest radiograph.
Smear and culture examination of three to five sputum specimens collected on different days is the main diagnostic procedure for pulmonary tuberculosis (11). Sputum smears that fail to demonstrate AFB do not exclude the diagnosis of tuberculosis. Studies indicate that 50%-80% of patients with pulmonary tuberculosis have positive sputum smears. Sputum smears from patients with HIV infection and pulmonary tuberculosis may be less likely to reveal AFB than those from immunocompetent patients, a finding believed to be consistent with the lower frequency of cavitary pulmonary disease observed among HIV-infected persons (23,25).
A positive sputum culture, with organisms identified as M. tuberculosis, provides a definitive diagnosis of tuberculosis. Conventional laboratory methods may require 4-8 weeks for species identification; however, the use of radiometric culture techniques and genetic probes facilitates more rapid detection and identification of mycobacteria (32,33). Mixed mycobacterial infection (either simultaneous or sequential) may occur and may obscure the recognition of M. tuberculosis clinically and in the laboratory (26). The use of genetic probes for both MAC and M. tuberculosis may be useful for identifying mixed mycobacterial infections in clinical specimens.
3. Determining infectiousness of tuberculosis patients
The infectiousness of a person with tuberculosis correlates with the number of organisms that are expelled into the air, which, in turn, correlates with the following factors: a) anatomic site of disease, b) presence of cough or other forceful expirational maneuvers, c) presence of AFB in the sputum smear, d) willingness or ability of the patient to cover his or her mouth when coughing, e) presence of cavitation on chest radiograph, f) length of time the patient has been on adequate chemotherapy, g) duration of symptoms, and h) administration of procedures that can enhance coughing (e.g., sputum induction).
The most infectious persons are those with pulmonary or laryngeal tuberculosis. Those with extrapulmonary tuberculosis are usually not infectious, with the following exceptions: a) nonpulmonary disease located in the respiratory tract or oral cavity, or b) extrapulmonary disease that includes an open abscess or lesion in which the concentration of organisms is high, especially if drainage from the abscess or lesion is extensive (19). Although the data are limited, findings suggest that tuberculosis patients with acquired immunodeficiency syndrome (AIDS), if smear positive, have infectiousness similar to that of tuberculosis patients without AIDS (CDC/New York City Department of Health, unpublished data).
Infectiousness is greatest among patients who have a productive cough, pulmonary cavitation on chest radiograph, and AFB on sputum smear (6). Infection is more likely to result from exposure to a person who has unsuspected pulmonary tuberculosis and who is not receiving antituberculosis therapy or from a person with diagnosed tuberculosis who is not receiving adequate therapy, because of patient noncompliance or the presence of drug-resistant organisms. Administering effective antituberculosis medications has been shown to be strongly associated with a decrease in infectiousness among persons with tuberculosis (34). Effective chemotherapy reduces coughing, the amount of sputum, and the number of organisms in the sputum. However, the length of time a patient must be on effective medication before becoming noninfectious varies (35); some patients are never infectious, whereas those with unrecognized or inadequately treated drug-resistant disease may remain infectious for weeks or months. Thus, decisions about terminating isolation precautions should be made on a case-by-case basis.
In general, persons suspected of having active tuberculosis and persons with confirmed tuberculosis should be considered infectious if cough is present, if cough-inducing procedures are performed, or if sputum smears are known to contain AFB, and if these patients are not on chemotherapy, have just started chemotherapy, or have a poor clinical or bacteriologic response to chemotherapy. A person with tuberculosis who has been on adequate chemotherapy for at least 2-3 weeks and has had a definite clinical and bacteriologic response to therapy (reduction in cough, resolution of fever, and progressively decreasing quantity of bacilli on smear) is probably no longer infectious. Most tuberculosis experts agree that noninfectiousness in pulmonary tuberculosis can be established by finding sputum free of bacilli by smear examination on three consecutive days for a patient on effective chemotherapy. Even after isolation precautions have been discontinued, caution should be exercised when a patient with tuberculosis is placed in a room with another patient, especially if the other patient is immunocompromised.
C. Preventing Spread of Infectious Droplet Nuclei via Source-Control Methods
In high-risk settings, certain techniques can be applied to prevent or to reduce the spread of infectious droplet nuclei into the general air circulation. The application of these techniques, which are called source-control methods because they entrap infectious droplet nuclei as they are emitted by the patient, or "source" (36), is especially important during performance of medical procedures likely to generate aerosols containing infectious particles.
The exhaust fan should maintain negative pressure in the booth with respect to adjacent areas, so that air flows into the booth. Maintaining negative pressure in the booth minimizes the possibility that infectious droplet nuclei in the booth will move into adjacent rooms or hallways. Ideally, the air from these booths should be exhausted directly to the outside of the building (away from air-intake vents, people, and animals, in accordance with federal, state, and local regulations concerning environmental discharges). If direct exhaust to the outside is impossible, the air from the booth could be exhausted through a properly designed, installed, and maintained high-efficiency particulate air (HEPA) filter; however, the efficacy of this method has not been demonstrated in clinical settings (see section II.D.2.a.). 2. Other source-control methods
A simple but important source-control technique is for infectious patients to cover all coughs and sneezes with a tissue, thus containing most liquid drops and droplets before evaporation can occur (38). A patient's use of a properly fitted surgical mask or disposable, valveless particulate respirator (PR) (see section II.D.2.c.) also may reduce the spread of infectious particles. However, since the device would need to be worn constantly for the protection of others, it would be practical in only very limited circumstances (e.g., when a patient is being transported within a medical facility or between facilities).
D. Reducing Microbial Contamination of Air
Once infectious droplet nuclei have been released into room air, they should be eliminated or reduced in number by ventilation, which may be supplemented by additional measures (e.g., trapping organisms by high-efficiency filtration or killing organisms with germicidal ultraviolet (UV) irradiation (100-290 nanometers)). Health-care-facility workers may also reduce the risk of inhaling contaminated air by using PRs.
Although for the past 2-3 decades ventilation and, to a lesser extent, UV lamps and face masks have been used in health-care settings to prevent tuberculosis transmission, few published data exist on which to evaluate their effectiveness and liabilities or to draw conclusions about the role each method should play. From a theoretical standpoint, none of the four methods (ventilation, UV irradiation, high-efficiency filtration, and face masks) appears to be ideal. None of the methods used alone or in combination can completely eliminate the risk of tuberculosis transmission; however, when used with the other infection-control measures outlined in this document, they can substantially reduce the risk.
In an area occupied by a patient with infectious tuberculosis, air should flow into the potentially contaminated area (the patient's room) from adjacent areas. The patient's room is said to be under lower or negative pressure.
Proper air flow and pressure differentials between areas of a health-care facility are difficult to control because of open doors, movement of patients and staff, temperature, and the effect of vertical openings (e.g., stairwells and elevator shafts) (40). Air-pressure differentials can best be maintained in completely closed rooms. An open door between two areas may reduce any existing pressure differential and could reduce or eliminate the desired effect. Therefore, doors should remain closed, and the close fit of all doors and other closures of openings between pressurized areas should be maintained. For critical areas in which the direction of air flow must be maintained while allowing for patient or staff movement between adjacent areas, an appropriately pressurized anteroom may be indicated.
Examples of factors that can change the direction of air flow include the following: a) dust in exhaust fans, filters, or ducts, b) malfunctioning fans, c) adjustments made to the ventilation system elsewhere in the building, or d) or automatic shut down of outside air introduction during cold weather. In areas where the direction of air flow is important, trained personnel should monitor air flow frequently to ensure that appropriate conditions are maintained.
Each area to which an infectious tuberculosis patient might be admitted should be evaluated for its potential for the spread of tuberculosis bacilli. Modifications to the ventilation system, if needed, should be made by a qualified ventilation engineer. Individual evaluations should address factors such as the risk of tuberculosis among the patient population served, special procedures that may be performed, and ability to make the necessary changes.
Too much ventilation in an area can create problems. In addition to incurring additional expense at marginal benefits, occupants bothered by the drafts may elect to shut down the system entirely. Furthermore, if the concentration of infectious droplet nuclei in an area is high, the levels of ventilation that are practical to achieve may be inadequate to completely remove the contaminants (43). 2. Potential supplemental approaches
Applications in preventing nosocomial Aspergillus infection have included using HEPA filters in centralized air-handling units and using whole-wall HEPA filtration units with laminar air flow in patient rooms. In addition, portable HEPA filtration units, which filter the air in a room rather than filtering incoming air, have been effective in reducing nosocomial Aspergillus infections (45,46). Such units have been used as an interim solution for retrofitting old areas of hospitals. Although these units should not be substituted for other accepted tuberculosis isolation procedures, they may be useful in general-use areas (e.g., waiting rooms and emergency rooms) where an increased risk of exposure to tuberculosis may exist, but where other methods of air control may be inadequate.
When HEPA filters are to be installed at a facility, qualified personnel must assess and design the air-handling system to assure adequate supply and exhaust capacity. Proper installation, testing, and meticulous maintenance are critical if a HEPA filter system is used (40). Improper design, installation, or maintenance could permit infectious particles to circumvent filtration and escape into the ventilation (42). The filters should be installed to prevent leakage between filter segments and between the filter bed and its frame. A regular maintenance program is required to monitor HEPA filters for possible leakage and for filter loading. A manometer should be installed in the filter system to provide an accurate means of objectively determining the need for filter replacement. Installation should allow for maintenance without contaminating the delivery system or the area served.
HEPA-filtered, recirculated air should not be used if the contaminants contain carcinogenic agents. Qualified personnel should maintain, decontaminate, and dispose of HEPA filters. b. Germicidal UV irradiation.
The use of germicidal UV lamps (wavelengths 100-290 nm) to prevent tuberculosis transmission in occupied spaces is controversial. UV lamps installed in the exhaust air ducts from the rooms of patients with infectious tuberculosis were shown to prevent infection of guinea pigs, which are highly susceptible to tuberculosis (34). On the basis of this finding, other studies (47-50), and the experience of tuberculosis clinicians and mycobacteriologists during the past 2-3 decades, CDC has continued to recommend UV lamps (with appropriate safeguards to prevent short-term overexposure) as a supplement to ventilation in settings where the risk of tuberculosis transmission is high (6,8,11,51-54). Their efficacy in clinical settings has not been demonstrated under controlled conditions, but there is a theoretical and experiential basis for believing they are effective (43,55,56). Thus, individual health-care facilities may need to consider, on a case-by-case basis, using these lamps in settings with a high risk of tuberculosis transmission (see section I.B.). UV lamps are less effective in areas with a relative humidity of greater than 70% (57). The potential for serious adverse effects of short- and long-term exposure to germicidal UV has been identified as a major concern (58; NIOSH, unpublished report (Health Hazard Evaluation Report, HETA 90-122-L2073)).
The two most common types of UV installation are wall- or ceiling-mounted room fixtures for disinfecting the air within a room and irradiation units for disinfecting air in supply ducts. Wall- or ceiling-mounted fixtures act by disinfecting upper room air, and their effectiveness depends in part upon the mixing of air in the room. Organisms must be carried by air currents from the lower portion of the room to within the range of the UV radiation from the fixtures. These fixtures are most likely to be effective in locations where ceilings are high, but some protection may be afforded in areas with ceilings as low as 8 feet. To be maximally effective, lamps should be left on day and night (59).
Installing UV lamps in ventilation ducts may be beneficial in facilities that recirculate the air. UV exposure of air in ducts can be direct and more intense than that provided by room fixtures and may be effective in disinfecting exhaust air. Duct installations provide no protection against tuberculosis transmission to any person who is in the room with an infectious patient. As with HEPA filters, UV installations in ducts may be used in general-use areas but should not be used to recirculate air from a tuberculosis isolation room back into the general circulation.
The main concern about UV lamps is safety. Short-term overexposure to UV irradiation can cause keratoconjunctivitis and erythema of the skin (60). However, with proper installation and maintenance, the risk of short-term overexposure is low. Long-term exposure to UV irradiation is associated with increased risk of basal cell carcinoma of the skin and with cataracts (58). To prevent overexposure of health-care-facility personnel and patients, UV lamp configurations should meet applicable safety guidelines (60).
When UV lamps are used in air-supply ducts, a warning sign should be placed on doors that permit access to the duct lamps. The sign should indicate that looking at the lamps is a safety hazard. In addition, warning lights outside doors permitting access to duct lamps should indicate whether the lamps are on or off. The duct system should be engineered to prevent UV emissions from the duct from radiating into potentially occupied spaces.
Consultation from a qualified expert should be obtained before and after UV lamps are installed. After installation, the safety and effectiveness of UV irradiation must be checked with a UV meter and fixtures adjusted as necessary. Bulbs should be periodically checked for dust, cleaned as needed, and replaced at the end of the rated life of the bulb. Maintenance personnel should be cautioned that fixtures should be turned off before inspection or servicing. A timing device that turns on a red light at the end of the rated life of the lamp is available to alert maintenance personnel that the lamp needs to be replaced. c. Disposable PRs for filtration of inhaled air. 1.) For persons exposed to tuberculosis patients.
Appropriate masks, when worn by health-care providers or other persons who must share air space with a patient who has infectious tuberculosis, may provide additional protection against tuberculosis transmission. Standard surgical masks may not be effective in preventing inhalation of droplet nuclei (61), because some are not designed to provide a tight face seal and to filter out particulates in the droplet nucleus size range (1-5 microns). A better alternative is the disposable PR. PRs were originally developed for industrial use to protect workers. Although the appearance and comfort of PRs may be similar to that of cup-shaped surgical masks, they provide a better facial fit and better filtration capability. However, the efficacy of PRs in protecting susceptible persons from infection with tuberculosis has not been demonstrated.
PRs may be most beneficial in the following situations: a) when appropriate ventilation is not available and the patient's signs and symptoms suggest a high potential for infectiousness, b) when the patient is potentially infectious and is undergoing a procedure that is likely to produce bursts of aerosolized infectious particles or to result in copious coughing or sputum production, regardless of whether appropriate ventilation is in place, and c) when the patient is potentially infectious, has a productive cough, and is unable or unwilling to cover coughs.
Comfort influences the acceptability of PRs. Generally, the more efficient the PRs, the greater is the work of breathing through them and the greater the perceived discomfort. A proper fit is vital to protect against inhaling droplet nuclei. When gaps are present, air will preferentially flow through the gaps, allowing the PR to function more like a funnel than a filter, thus providing virtually no protection (61). 2.) For tuberculosis patients.
Masks or PRs worn by patients with suspected or confirmed tuberculosis may be useful in selected circumstances (see section II.C.2.). PRs used by patients should be valveless. Some PRs have valves to release expired air, and these would not be appropriate for patients to use. E. Decontamination: Cleaning, Disinfecting, and Sterilizing
Guidelines for cleaning, disinfecting, and sterilizing equipment have been published (10,62,63). The rationale for cleaning, disinfecting, or sterilizing patient-care equipment can be understood more readily if medical devices, equipment, and surgical materials are divided into three general categories (critical items, semi-critical items, and noncritical items) based on the potential risk of infection involved in their use.
Critical items are instruments such as needles, surgical instruments, cardiac catheters, or implants that are introduced directly into the bloodstream or into other normally sterile areas of the body. These items should be sterile at the time of use.
Semi-critical items are items such as noninvasive flexible and rigid fiberoptic endoscopes or bronchoscopes, endotracheal tubes, or anesthesia breathing circuits that may come in contact with mucous membranes but do not ordinarily penetrate body surfaces. Although sterilization is preferred for these instruments, a high-level disinfection procedure that destroys vegetative microorganisms, most fungal spores, tubercle bacilli, and small, nonlipid viruses may be used. Meticulous physical cleaning before sterilization or high-level disinfection is essential.
Noncritical items are those that either do not ordinarily touch the patient or touch only intact skin. Such items include crutches, bedboards, blood pressure cuffs, and various other medical accessories. These items do not transmit tuberculous infection. Consequently, washing with a detergent is usually sufficient.
Facility policies should identify whether cleaning, disinfecting, or sterilizing an item is indicated to decrease the risk of infection. Procedures for each item depend on its intended use. Generally, critical items should be sterilized, semi-critical items should be sterilized or cleaned with high-level disinfectants, and noncritical items need only be cleaned with detergents or low-level disinfectants. Decisions about decontamination processes should be based on the intended use of the item and not on the diagnosis of the patient for whom the item was used. Selection of chemical disinfectants depends on the intended use, the level of disinfection required, and the structure and material of the item to be disinfected.
Although microorganisms are normally found on walls, floors, and other surfaces, these environmental surfaces are rarely associated with transmission of infections to patients or health-care-facility personnel. This is particularly true with organisms such as tubercle bacilli, which generally require inhalation by the host for infection to occur. Therefore, extraordinary attempts to disinfect or sterilize environmental surfaces are rarely indicated. However, routine cleaning (which can be achieved with a hospital-grade, Environmental Protection Agency-approved germicide divided by isinfectant) is recommended (63). The same routine daily cleaning procedures used in other hospital or facility rooms should be used to clean rooms of patients who are on AFB isolation precautions. F. Conducting Surveillance for Tuberculosis Transmission to Health-Care-Facility Personnel
A tuberculosis screening and prevention program for health-care-facility personnel should be established for protecting both health-care-facility personnel and patients. Personnel with tuberculous infection without evidence of current (active) disease should be identified, because preventive treatment with isoniazid may be indicated (5). In addition, the screening program will enable public health personnel to evaluate the effectiveness of current infection-control practices. Recommendations for screening and surveillance are detailed in section III.A.7. III. Recommendations
The following recommendations are divided into two categories:
3. Emergency medical services --When emergency-medical-response personnel or others must transport patients with confirmed or suspected active tuberculosis, a mask or valveless PR should be fitted on the patient. If this is not possible, the worker should wear a PR (see sections II.C.2. and II.D.2.c.). If feasible, the rear windows of the vehicle should be kept open and the heating and air conditioning system set on a nonrecirculating cycle. --Emergency-response personnel should be routinely screened for tuberculosis at regular intervals. They should also be included in the follow-up of contacts of a patient with infectious tuberculosis (see section III.A.7.).
4. Home-health services --For persons visiting the home of patients with suspected or confirmed infectious tuberculosis, precautions may be necessary to prevent exposure to air containing droplet nuclei until infectiousness has been eliminated by chemotherapy. These precautions include instructing patients to cover coughs and sneezes. The worker should wear a PR when entering the home or the patient's room. --Respiratory precautions in the home may be discontinued when the patient is improving clinically, cough has decreased, and the number of organisms in the sputum smear is decreasing. Usually this occurs within 2-3 weeks after tuberculosis medications are begun. Failure to take medications as prescribed and the presence of drug-resistant disease are the two most common reasons for a patient's failure to improve clinically. Home health-care personnel can assist in preventing tuberculosis transmission by educating the patient about the importance of taking medications as prescribed (unless adverse effects are seen). --If immunocompromised persons or young children live in the home with a patient who has infectious pulmonary or laryngeal tuberculosis, temporary relocation should be considered until the patient has negative sputum smears. --If cough-inducing procedures (such as AP) are performed in the home of a patient who may have infectious tuberculosis, they should be administered in a well-ventilated area away from other household members. Persons who perform these procedures should wear PRs while performing them. --Home health-care workers should be included in an employer-sponsored tuberculosis screening and prevention program (see section III.A.7.). --Early identification and treatment of persons with tuberculosis is important. Home health-care personnel and patients who are at risk for contracting active tuberculosis should be reminded periodically of the importance of having pulmonary symptoms evaluated. --Close contacts of any patient with active infectious tuberculosis should be evaluated for tuberculous infection and managed according to CDC and American Thoracic Society guidelines (5,65).
IV. Research Needs
Additional research is needed regarding the airborne transmission of tuberculosis including the following: a) better quantitating the risk of tuberculosis transmission in a variety of health-care settings, b) assessing the acceptability, efficacy, adverse impact, and cost-effectiveness of currently available methods for preventing transmission, and c) developing better methods for preventing transmission. These needs also extend to other infections transmitted by the airborne route. Currently, large numbers of immunosuppressed persons, including patients infected with HIV, are being brought together in health-care settings in which procedures are used that induce the generation of droplet nuclei. Research is needed to fill many of the gaps in current knowledge and to lead to new and better guidelines for protecting patients and personnel in these settings.
V. Glossary of Abbreviations
AFB Acid-fast bacilli--organisms that retain certain stains, even after being washed with acid alcohol. Most are mycobacteria. When seen on a stained smear of sputum or other clinical specimen, a diagnosis of tuberculosis should be considered.
AIDS Acquired immunodeficiency syndrome--an advanced stage of disease caused by infection with the human immunodeficiency virus (HIV). A patient with AIDS is especially susceptible to other infections.
AP Aerosolized pentamidine--drug treatment given to patients with HIV infection to treat or to prevent Pneumocystis carinii pneumonia. The drug is put into solution, the solution is aerosolized, and the patient inhales the aerosol.
ASHRAE American Society of Heating, Refrigerating, and Air Conditioning Engineers, Inc.
HEPA High-efficiency particulate air filter. HIV Human immunodeficiency virus--the virus that causes AIDS. HRSA Health Resources and Services Administration. PCP Pneumocystis carinii pneumonia--this organism does not cause disease among persons with a normal immune system.
PR A disposable, particulate respirator (respiratory protective device (face mask)) that is designed to filter out particles 1-5 microns in diameter.
Tuberculous infection A condition in which tuberculosis organisms (M. tuberculosis, M. bovis, or M. africanum) are present in the body, but no active disease is evident.
Tuberculosis transmission Spread of tuberculosis organisms from one person to another, usually through the air.
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