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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.
References
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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