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Mycobacterium tuberculosis Transmission in a Health Clinic -- Florida, 1988

Between January 1 and July 1, 1988, 30 (42%) of 72 staff members tested at a western Palm Beach County, Florida, clinic were identified as having positive (greater than or equal to10-mm induration) tuberculin skin test (Mantoux) reactions. Seventeen (57%) of these 30 employees had a documented skin test conversion (reaction from less than 10 mm to greater than or equal to10 mm with an increase of greater than or equal to6-mm induration) within the past 18 months. The other 13 had no previous documented tuberculin skin tests. These findings indicated probable transmission of tuberculous infection in the clinic and prompted an environmental and epidemiologic investigation. The clinic, which provides primary care, is located in a two-storied building constructed in 1984. All patient-care activities occur on the first floor. The second floor contains the administrative offices and a conference room. Ventilation studies conducted as part of the epidemiologic investigation revealed that greater than 90% of the air in the building was recirculated, and 0.48 fresh air exchanges occurred per hour. Only large-particle air filters were used in the air-handling units; these filters were changed once per month. In the examination rooms, air supply exceeded exhaust volumes, causing air to move from the rooms into the hallways and be recirculated throughout the building. Based on preliminary findings, four possible sources of Mycobacterium tuberculosis infection were considered. 1) In June 1987, a clinic nurse was diagnosed with noncavitary pulmonary tuberculosis (TB). Although her sputum cultures were positive for M. tuberculosis, sputum smears were negative for acid-fast bacilli (AFB) (smear-negative patients are much less infectious than smear-positive patients (1)). 2) From January to July 1988, 39 patients with pulmonary TB were treated at the clinic; 14 of these had at least one positive sputum smear during that interval. 3) In late November 1987, the clinic began sputum inductions using an ultrasonic nebulizer to obtain diagnostic specimens from persons diagnosed with or suspected to have TB. On 14 different occasions between January 13 and May 18, 1988, 13 patients had induced sputum specimens that were culture-positive for M. tuberculosis. On nine of these 14 occasions, the patient was also smear-positive. 4) Aerosolized pentamidine treatments were initiated on January 29, 1988, for acquired immunodeficiency syndrome (AIDS) patients to prevent Pneumocystis carinii pneumonia (PCP). Between January 29 and June 17, 1988, six AIDS patients received a total of 31 such treatments. Two of these patients had positive sputum cultures for M. tuberculosis between January 29 and March 18, during a period when they received a total of 10 treatments with aerosolized pentamidine. One of these two patients, who received eight treatments, coughed profusely both during and after the therapy. This patient was also repeatedly sputum-smear-positive, even though he was reportedly taking several anti-TB medications. To determine which of these four possible sources was most likely associated with M. tuberculosis infection among the staff, the Florida Department of Health and Rehabilitative Services conducted a case-control study with 16 cases and 34 controls in July 1988. A case was defined as a clinic staffer who had worked at the clinic at least 6 months and who had had a documented skin test conversion within the previous 18 months. A control was a clinic staffer who had worked there at least 6 months and who had had a negative skin test in the month before the investigation. Cases were significantly more likely than controls to have worked at least 40 hours per week in the clinic, been present in the room when aerosolized pentamidine treatments were given, worked on the first floor, and been nonwhite (Table 1). Transmission caused by face-to-face exposure to TB patients not receiving aerosolized pentamidine could not be excluded. Many staff members were unaware which patients had TB. Aerosolized pentamidine treatments and sputum inductions were stopped in June 1988 pending construction of appropriate exhaust systems for rooms in which these procedures are performed and changes in the building's ventilation system. All clinic staff with negative tuberculin reactions were retested in September; no new skin test conversions occurred. Isoniazid prophylaxis was provided to all converters. Reported by: JT Howell, MD, WJ Scheel, VL Pryor, DR Tavris, MD, Palm Beach County Public Health Unit; RA Calder, MD, MH Wilder, MD, State Epidemiologist, Florida Dept of Health and Rehabilitative Svcs. Health Studies Br, Div of Environmental Hazards and Health Effects, Center for Environmental Health and Injury Control; Mycobacteriology Laboratory, Respiratory Diseases Br, Div of Bacterial Diseases, Center for Infectious Diseases; Surveillance and Epidemiologic Investigations Br, Div of Tuberculosis Control, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: Matching of AIDS and TB case registries in 43 states and 11 localities indicates that 4% of AIDS patients also have had TB; this is more than 400 times the 1986 national incidence of 9.4 cases per 100,000 population. TB has occurred in persons in all major transmission categories of human immunodeficiency virus (HIV) (2). Health-care workers and patients may be at risk for exposure to TB in settings where cough-inducing procedures, such as aerosolized administration of medications, sputum induction, and bronchoscopy, are performed on patients with TB. TB should be considered in the differential diagnosis of patients with unexplained pulmonary signs and/or symptoms, and especially in patients with HIV infection, because such patients are at high risk for TB (2). This investigation raises the question of whether aerosolized pentamidine administered to patients with pulmonary TB can play a role in TB transmission; however, in this investigation, transmission caused by exposure to TB patients not receiving aerosolized pentamidine could not be ruled out. During cough-inducing procedures, including aerosolized pentamidine treatments, recommendations for preventing transmission of tuberculous infection to health-care workers should be followed (3-5). Aerosolized pentamidine is widely used for the treatment and prophylaxis of PCP in AIDS patients (6-8). Before beginning aerosolized pentamidine therapy, patients should be evaluated for the presence of potentially infectious TB with a chest radiograph and sputum smears for AFB. If the chest radiograph is not suggestive of active TB and two to three sputum smears are negative for AFB, aerosolized pentamidine treatments can be initiated. Any patient suspected of having potentially infectious TB should be started on anti-TB therapy before starting aerosolized pentamidine treatment. If the clinical situation allows, it is preferable to observe a reduction in the number of AFB on smear before starting the aerosolized pentamidine. All cough-inducing procedures should be carried out in rooms or booths with negative air pressure in relation to adjacent rooms or hallways. Air in these rooms or booths should be exhausted directly to the outside of the building and away from intake vents (5). If possible, after completion of such procedures, patients who are coughing should be dismissed from the clinic and should not remain in common waiting areas. Although western Palm Beach County has a high prevalence of both tuberculous and HIV infections (9-11), clinics in other areas also treat substantial numbers of patients at risk for both infections (12-16). Therefore, health workers who take care of patients with undiagnosed pulmonary disease should be alerted to the potential for infectious TB and take appropriate measures to protect themselves, other staff, and patients from the transmission of tuberculous infection.


  1. Shaw JB, Wynn-Williams N. Infectivity of pulmonary tuberculosis in relation to sputum status. Am Rev Respir Dis 1954;69:724-32. 2.Pitchenik AE, Fertel D, Bloch AB. Mycobacterial disease: epidemiology, diagnosis, treatment, and prevention. Clin Chest Med 1988;9:425-41. 3.Garner JS, Simmons BP. Guideline for isolation precautions in hospitals. Infect Control 1983;4(suppl):245-325. 4.CDC. Guidelines for prevention of TB transmission in hospitals. Atlanta: US Department of Health and Human Services, Public Health Service, 1982; HHS publication no. (CDC)82-8371. 5.CDC. Tuberculosis and human immunodeficiency virus infection: recommendations of the Advisory Committee for the Elimination of Tuberculosis. MMWR 1989;38:236-8,243-50. 6.Montgomery AB, Debs RJ, Luce JM, et al. Aerosolised pentamidine as sole therapy for Pneumocystis carinii pneumonia in patients with acquired immunodeficiency syndrome. Lancet 1987;2:480-3. 7.Conte JE Jr, Hollander H, Golden JA. Inhaled or reduced-dose intravenous pentamidine for Pneumocystis carinii pneumonia. Ann Intern Med 1987;107:495-8. 8.Armstrong D, Bernard E. Aerosol pentamidine. Ann Intern Med 1988;109:852-4. 9.Pitchenik AE, Russell BW, Cleary T, et al. The prevalence of tuberculosis and drug resistance among Haitians. N Engl J Med 1982;307:162-5. 10.Castro KG, Lieb S, Jaffe HW, et al. Transmission of HIV in Belle Glade, Florida: lessons for other communities in the United States. Science 1988;239:193-7. 11.Pitchenik AE, Cole C, Russell BW, et al. Tuberculosis, atypical mycobacteriosis, and the acquired immunodeficiency syndrome among Haitian and non-Haitian patients in south Florida. Ann Intern Med 1984;101:641-5. 12.CDC. Tuberculosis and acquired immunodeficiency syndrome--Florida. MMWR 1986;35: 587-90. 13.CDC. Tuberculosis and acquired immunodeficiency syndrome--New York City. MMWR 1987;36:785-90,795. 14.CDC. Tuberculosis and AIDS--Connecticut. MMWR 1987;36:133-5. 15.Sunderam G, McDonald RJ, Maniatis T, et al. Tuberculosis as a manifestation of the acquired immunodeficiency syndrome (AIDS). JAMA 1986;256:362-6. 16.Chaisson RE, Schecter GF, Theur CP, et al. Tuberculosis in patients with the acquired immunodeficiency syndrome: clinical features, response to therapy, and survival. Am Rev Respir Dis 1987;136:570-4.

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