Simultaneous infection with multiple strains of Mycobacterium tuberculosis.

Drug-susceptible and drug-resistant isolates of Mycobacterium tuberculosis were recovered from 2 patients, 1 with isoniazid-resistant tuberculosis (patient 1) and another with multidrug-resistant tuberculosis (patient 2). An investigation included patient interviews, record reviews, and genotyping of isolates. Both patients worked in a medical-waste processing plant. Transmission from waste was responsible for at least the multidrug-resistant infection. We found no evidence that specimens were switched or that cross-contamination of cultures occurred. For patient 1, susceptible and isoniazid-resistant isolates, collected 15 days apart, had 21 and 19 restriction fragments containing IS6110, 18 of which were common to both. For patient 2, a single isolate contained both drug-susceptible and multidrug-resistant colonies, demonstrating 10 and 11 different restriction fragments, respectively. These observations indicate that simultaneous infections with multiple strains of M. tuberculosis occur in immunocompetent hosts and may be responsible for conflicting drug-susceptibility results, though the circumstances of infections in these cases may have been unusual.

Tuberculosis cases reported among migrant farm workers in the United States, 1993-97.

Migrant farm workers (MFWs) are considered a high-risk group for tuberculosis. MFW tuberculosis cases reported to the Centers for Disease Control and Prevention represented 1 percent of all reported tuberculosis cases from 1993 to 1997. Most of these cases (70 percent) were reported from Florida, Texas, and California. MFW tuberculosis cases were more likely to be male, foreign-born, or Hispanic and to have a history of alcohol abuse and homelessness than were non-MFWs. Most (79 percent) foreign-born MFWs were from Mexico. HIV status was poorly reported, with results available for only 28 percent of MFW and 33 percent of non-MFW cases. Of the MFWs tested, 28 percent were HIV infected, whereas 34 percent of non-MFWs were HIV infected. Twenty percent of MFWs move or are lost to follow-up before completing therapy; these cases pose a management challenge for the nation's tuberculosis control efforts.

Transmission of Mycobacterium tuberculosis from medical waste.

CONTEXT: Washington State has a relatively low incidence rate of tuberculosis (TB) infection. However, from May to September 1997, 3 cases of pulmonary TB were reported among medical waste treatment workers at 1 facility in Washington. There is no previous documentation of Mycobacterium tuberculosis transmission as a result of processing medical waste. OBJECTIVE: To identify the source(s) of these 3 TB infections. DESIGN, SETTING, AND PARTICIPANTS: Interviews of the 3 infected patient-workers and their contacts, review of patient-worker medical records and the state TB registry, and collection of all multidrug-resistant TB (MDR-TB) isolates identified after January 1, 1995, from the facility's catchment area; DNA fingerprinting of all isolates; polymerase chain reaction and automated DNA sequencing to determine genetic mutations associated with drug resistance; and occupational safety and environmental evaluations of the facility. MAIN OUTCOME MEASURES: Previous exposures of patient-workers to TB; verification of patient-worker tuberculin skin test histories; identification of other cases of TB in the community and at the facility; drug susceptibility of patient-worker isolates; and potential for worker exposure to live M tuberculosis cultures. RESULTS: All 3 patient-workers were younger than 55 years, were born in the United States, and reported no known exposures to TB. We did not identify other TB cases. The 3 patient-workers' isolates had different DNA fingerprints. One of 10 MDR-TB catchment-area isolates matched an MDR-TB patient-worker isolate by DNA fingerprint pattern. DNA sequencing demonstrated the same rare mutation in these isolates. There was no evidence of personal contact between these 2 individuals. The laboratory that initially processed the matching isolate sent contaminated waste to the treatment facility. The facility accepted contaminated medical waste where it was shredded, blown, compacted, and finally deactivated. Equipment failures, insufficient employee training, and respiratory protective equipment inadequacies were identified at the facility. CONCLUSION: Processing contaminated medical waste resulted in transmission of M tuberculosis to at least 1 medical waste treatment facility worker. JAMA. 2000;284:1683-1688.

Using DNA fingerprinting to detect transmission of Mycobacterium tuberculosis among AIDS patients in two health-care facilities in Puerto Rico.

BACKGROUND: Fourteen cases of tuberculosis (TB) in Puerto Rico, diagnosed from April 1993 to April 1995, had the same DNA fingerprint, documenting disease caused by the same strain of Mycobacterium tuberculosis. The 14 cases were retrospectively investigated for epidemiologic links. METHODS: Records were reviewed and staffs of the TB program, hospital/clinic, and AIDS residential facilities were interviewed. RESULTS: Half of the AIDS cases were epidemiologically related, providing evidence of TB transmission in an emergency department, an AIDS inpatient ward, and an AIDS residential facility. DNA fingerprinting allowed detection of M tuberculosis transmission, but contact investigators could have documented it sooner. Factors contributing to transmission included delayed diagnosis, prolonged infectiousness, inadequate discharge planning and infection control procedures, and poor communication between health-care facilities. CONCLUSIONS: The numbers of AIDS residential facilities are increasing and must understand proper monitoring of TB patients and infection control measures that prevent transmissions.

Transmission of tuberculosis in a jail.

BACKGROUND: Outbreaks of tuberculosis are uncommonly recognized in jails. In 1996, an increase in active tuberculosis cases was noted among inmates of a large urban jail. OBJECTIVES: To determine the source and extent of a tuberculosis outbreak in an urban jail and to recommend control measures. DESIGN: Retrospective cohort study. SETTING: Urban jail. PATIENTS: Inmates and guards with tuberculosis. INTERVENTION: Outbreak evaluation and control. MEASUREMENTS: Medical records of inmates and guards with tuberculosis were reviewed, and inmates were interviewed. DNA fingerprinting was performed on Mycobacterium tuberculosis isolates. RESULTS: From 1 January 1995 through 31 December 1997, active tuberculosis was diagnosed in 38 inmates and 5 guards from the jail. Nineteen (79%) of the 24 culture-positive inmates had isolates with DNA fingerprints matching those of other inmates. Isolates from both culture-positive guards matched the predominant inmate strain; only 6 (14%) of 43 isolates from infected persons in the community had this pattern. The median length of incarceration of all inmates in the jail was 1 day; the median length of continuous incarceration before diagnosis of tuberculosis in inmates was 138 days. Inmates with tuberculosis had been incarcerated a median of 15 times. Forty-three percent of persons in this city with tuberculosis diagnosed from January 1995 through July 1997 had been incarcerated in the jail at some time before diagnosis. CONCLUSIONS: Traditional and molecular epidemiologic investigations suggest that tuberculosis was transmitted among inmates and guards in an urban jail. Aggressive measures to screen for active tuberculosis upon incarceration are important for preventing spread of disease in jails and to the surrounding community.

Spread of strain W, a highly drug-resistant strain of Mycobacterium tuberculosis, across the United States.

Strain W, a highly drug-resistant strain of Mycobacterium tuberculosis, was responsible for large nosocomial outbreaks in New York in the early 1990s. To describe the spread of strain W outside New York, we reviewed data from epidemiologic investigations, national tuberculosis surveillance, regional DNA fingerprint laboratories, and the Centers for Disease Control and Prevention Mycobacteriology Laboratory to identify potential cases of tuberculosis due to strain W. From January 1992 through February 1997, 23 cases were diagnosed in nine states and Puerto Rico; 8 were exposed to strain W in New York before their diagnosis; 4 of the 23 transmitted disease to 10 others. Eighty-six contacts of the 23 cases are presumed to be infected with strain W; 11 completed alternative preventive therapy. Strain W tuberculosis cases will occur throughout the United States as persons infected in New York move elsewhere. To help track and contain this strain, health departments should notify the Centers for Disease Control and Prevention of cases of tuberculosis resistant to isoniazid, rifampin, streptomycin, and kanamycin.

Immigration and tuberculosis among children on the United States-Mexico border, County of San Diego, California.

OBJECTIVE: To identify factors contributing to a 400% increase in tuberculosis among children in San Diego County, California, from 1985 to 1993. DESIGN: Review of medical records of reported cases in 1989, 1991, and 1993 and their source case. RESULTS: Of 192 children with tuberculosis, the largest increase was observed in children younger than 5 years old, of whom 77.4% were born in the United States, 67.8% had a foreign-born parent, 73.1% came from a non-English-speaking household, and 46.2% were known to visit Mexico. Of 28 source cases, 82.1% were born outside the United States, primarily in Mexico (67.9%). Resistance to at least one first-line antituberculous drug was identified in 27.5% of isolates from children and in 33.3% of isolates from source cases. CONCLUSIONS: The increase in tuberculosis and high level of drug-resistance among children born in the United States may be attributed to transmission outside of the United States or within the United States from household contacts born in countries in which tuberculosis is highly endemic.

Tuberculin skin testing among economically disadvantaged youth in a federally funded job training program.

Low income, medically underserved communities are at increased risk for tuberculosis. Limited population-based national data are available about tuberculous infection in young people from such backgrounds. To determine the prevalence of a positive tuberculin skin test among economically disadvantaged youth in a federally funded job training program during 1995 and 1996, the authors evaluated data from medical records of 22,565 randomly selected students from over 100 job training centers throughout the United States. An estimated 5.6% of students had a documented positive skin test or history of active tuberculosis. Rates were highest among those who were racial/ethnic minorities, foreign born, and (among foreign-born students) older in age (p < 0.001). Weighted rates (adjusting for sampling) were 1.3% for white, 2.2% for Native American, 4.0% for black, 9.6% for Hispanic, and 40.7% for Asian/Pacific Islander students; rates were 2.4% for US-born and 32.7% for foreign-born students. Differences by geographic region of residence were not significant after adjusting for other demographic factors. Tuberculin screening of socioeconomically disadvantaged youth such as evaluated in this study provides important sentinel surveillance data concerning groups at risk for tuberculous infection and allows recommended public health interventions to be offered.

Tuberculosis screening in private physicians' offices, Pennsylvania, 1996.

OBJECTIVE: To assess tuberculin skin testing practices of physicians after community-wide screening of 1400 children exposed to a pediatrician with active tuberculosis (TB). DESIGN: A self-administered questionnaire. SETTING: Medium-sized city in eastern Pennsylvania. PARTICIPANTS: Pediatricians and family practitioners seeing pediatric patients. MAIN OUTCOME MEASURES: Percentages of physicians who followed published recommendations for placement and reading of TB skin tests published by the American Academy of Pediatrics (AAP) and the Centers for Disease Control and Prevention (CDC). RESULTS: Questionnaires were completed by 60/80 (75%) physicians. The 60 physicians had practiced a mean of 17 years (range 3-38 years), and only one did not do TB skin testing for pediatric patients. The 59 physicians doing TB skin testing reported routinely tuberculin testing more than 900 children per month. Only 8/59 (14%) physicians followed published guidelines for placement and reading of tuberculin tests. Those physicians screened 158 (17%) of the pediatric patients undergoing TB skin testing in a typical month. CONCLUSION: In this community where a highly publicized TB case prompted massive pediatric screening, most physicians seeing children in private practice do not follow standard TB skin testing guidelines. Increased understanding of how private-practice physicians learn about and decide to use recommended standards are needed if tuberculin tests are to be correctly performed and TB appropriately diagnosed.

A train passenger with pulmonary tuberculosis: evidence of limited transmission during travel.

In January 1996, smear- and culture-positive tuberculosis (TB) was diagnosed for a 22-year-old black man after he had traveled on two U.S. passenger trains (29.1 hours) and a bus (5.5 hours) over 2 days. To determine if transmission had occurred, passengers and crew were notified of the potential exposure and instructed to undergo a tuberculin skin test (TST). Of the 240 persons who completed screening, 4 (2%) had a documented TST conversion (increase in induration of > or = 10 mm between successive TSTs), 11 (5%) had a single positive TST (> or = 10 mm), and 225 (94%) had a negative TST (< 10 mm). For two persons who underwent conversion, no other risk factors for a conversion were identified other than exposure to the ill passenger during train and/or bus travel. These findings support limited transmission of Mycobacterium tuberculosis from a potentially highly infectious passenger to other persons during extended train and bus travel.

Tuberculin skin test screening practices among US colleges and universities.

CONTEXT: Concern about transmission of Mycobacterium tuberculosis on college campuses has prompted some schools to institute tuberculin skin test screening of students, but this screening has never been evaluated. OBJECTIVE: To describe tuberculin skin test screening practices and results of screening in colleges and universities in the United States. DESIGN AND SETTING: Self-administered mail and telephone questionnaire in November and December 1995 to a stratified random sample of US 2-year and 4-year colleges and universities. MAIN OUTCOME MEASURES: Type of tuberculin screening required; types of schools requiring screening; number and rate of students with positive skin test results and/or diagnosed as having tuberculosis. RESULTS: Of the 3148 US colleges and universities, 624 (78%) of 796 schools surveyed responded. Overall, 378 schools (61%) required tuberculin screening; it was required for all new students (US residents and international students) in 161 (26%) of 624 schools, all new international students but not new US residents in 53 (8%), and students in specific academic programs in 294 (47%). Required screening was more likely in 4-year vs 2-year schools, schools that belonged to the American College Health Association vs nonmember schools, schools with immunization requirements vs schools without, and schools with a student health clinic vs those without (P<.001 for all). Public and private schools were equally likely to require screening (64% vs 62%; P=.21). In the 378 schools with screening requirements, tine or multiple puncture tests were accepted in 95 (25%); test results were recorded in millimeters of induration in 95 (25%); and 100 (27%) reported collecting results in a centralized registry or database. Of the 168 (27%) of 624 schools accepting only Mantoux skin tests and reporting results for school years 1992-1993 through 1995-1996, 3.1% of the 348 368 students screened had positive skin test results (median percentage positive, 0.8%). International students had a significantly higher case rate for active tuberculosis than US residents (35.2 vs 1.1 per 100000 students screened). CONCLUSIONS: Widespread tuberculin screening of students yielded a low prevalence of skin test reactors and few tuberculosis cases. To optimize the use of limited public health resources, tuberculin screening should target students at high risk for infection.

Evaluation of transmission of Mycobacterium tuberculosis in a pediatric setting.

OBJECTIVE: To determine the extent of transmission of Mycobacterium tuberculosis to pediatric patients exposed to a pediatrician with smear- and culture-positive pulmonary tuberculosis (TB). METHODS: Clinic billing and hospital admission records were used to identify patients seen during the pediatrician's infectious period. Patients were notified of the potential exposure and were offered screening. RESULTS: A total of 1416 pediatric patients were identified as exposed. Of the 606 who completed screening, 12 (2%) had a skin test result > or = 10 mm, 2 (0.3 had a result 5 to 9 mm, and 592 (98%) had a negative test result (0 to 4 mm). No active TB cases were identified. Of the 14 children with a skin test result > or = 5 mm, 7 were U.S.-born and had no other risk for a positive skin test. The remaining seven had either been exposed to another person with infections TB or were from countries with a high prevalence of TB. CONCLUSION: We found evidence of limited transmission of Mycobacterium tuberculosis in the outpatient pediatric setting. Despite extensive resources dedication, only 43% of exposed children completed screening. In similar situations decision should balance the responsibility to protect children exposed to Mycobacterium tuberculosis with other public health priorities and available resources.

An outbreak involving extensive transmission of a virulent strain of Mycobacterium tuberculosis.

BACKGROUND AND METHODS: From 1994 to 1996, there was a large outbreak of tuberculosis in a small, rural community with a population at low risk for tuberculosis. Twenty-one patients with tuberculosis (15 with positive cultures) were identified; the DNA fingerprints of the 13 isolates available for testing were identical. To determine the extent of transmission, we investigated both the close and casual contacts of the patients. Using a mouse model, we also studied the virulence of the strain of Mycobacterium tuberculosis that caused the outbreak. RESULTS: The index patient, in whom tuberculosis was diagnosed in 1995; the source patient, in whom the disease was diagnosed in 1994; and a patient in whom the disease was diagnosed in 1996 infected the other 18 persons. In five, active disease developed after only brief, casual exposure. There was extensive transmission from the three patients to both close and casual contacts. Of the 429 contacts, 311 (72 percent) had positive skin tests, including 81 [corrected] with documented skin-test conversions. Mice infected with the virulent Erdman strain of M. tuberculosis had approximately 1000 bacilli per lung after 10 days and about 10,000 bacilli per lung after 20 days. In contrast, mice infected with the strain involved in the outbreak had about 10,000 bacilli per lung after 10 days and about 10 million bacilli per lung after 20 days. CONCLUSIONS: In this outbreak of tuberculosis, the growth characteristics of the strain involved greatly exceeded those of other clinical isolates of M. tuberculosis. The extensive transmission of tuberculosis may have been due to the increased virulence of the strain rather than to environmental factors or patient characteristics.

Tuberculosis transmission among five school bus drives and students in two New York countries

OBJECTIVE: Between November 1994 and April 1995, more than 3300 students in 49 schools in two countries in New York were potentially exposed to five school bus drivers with tuberculosis. This investigation was carried out to determine the extent of transmission of Mycobacterium tuberculosis among students. METHODS: Components of the epidemiologic investigation included tuberculin skin-test screening and collection of demographic information for students exposed to a driver with tuberculosis, chest radiography and medical evaluation of individuals with positive skin tests, and DNA fingerprinting of M tuberculosis isolates. A positive skin test was defined as >/=10 mm induration, and a converter was an individual with an increase in reaction size of >/=10 mm in the past 2 years. RESULTS: The rates of positive skin tests were 0.8 percent, 0.3 percent, 9.9 percent, 1.1 percent and 0.7 percent among US-born student exposed to drivers 1 through 5, respectively. The relative risk for a positive tuberculin skin test was significant only for student expose to driver 3 and the only secondary case identified among students was exposed to driver 3. The DNA fingerprinting patterns of isolates from drivers 3 and 4 matched. CONCLUSION: There was no clear evidence of transmission of M tuberculosis to students from driver 1, 2, 4, or 5. However, evidence suggests the driver 3 transmitted M tuberculosis to students and another driver. Routine annual tuberculin skin-test screening of drivers would not have prevented these tuberculosis exposures(AU)

A nosocomial outbreak of multidrug-resistant tuberculosis.

BACKGROUND: An outbreak of seven cases (in six patients and one health care worker, all of whom had AIDS) of multidrug-resistant tuberculosis occurred in a hospital in Chicago. The hospital had a respirator-fit testing program but no acid-fast bacilli isolation rooms. OBJECTIVE: To identify risk factors for transmission of Mycobacterium tuberculosis. DESIGN: Retrospective cohort study. SETTING: Private hospital. PARTICIPANTS: Patients and health care workers exposed to M. tuberculosis. MEASUREMENTS: Analysis of M. tuberculosis isolates, tuberculin skin testing, assessment of exposure, and assessment of participant characteristics. RESULTS: All seven M. tuberculosis isolates had matching DNA fingerprints. Of patients exposed to M. tuberculosis, those who developed tuberculosis had lower CD4+ T-lymphocyte counts (P = 0.02) and were more likely to be ambulatory (P = 0.03) than those who did not. Of 74 exposed health care workers, the 11 (15%) who had conversion on tuberculin skin testing were no more likely than those who did not have conversion to report that they always wore a respirator with a high-efficiency particulate air filter. CONCLUSIONS: Transmission of M. tuberculosis occurred in a hospital that did not have recommended isolation rooms. A respirator-fit testing program did not protect health care workers in this setting.

Mycobacterium tuberculosis transmission from a pediatrician to patients.

UNLABELLED: The following report describes the contact investigation of a pediatrician with tuberculosis (TB). The pediatrician's disease was discovered in late February 1993 after tuberculin skin testing (TST) of his 15-month-old son was positive (13-mm induration). Further investigation to identify the source of the child's infection revealed a positive (15-mm induration) TST in the pediatrician. The pediatrician had been symptomatic with a cough since September 1992. The pediatrician had a chest radiograph that revealed numerous cavitary lesions and a sputum smear that was positive for acid-fast bacilli. An investigation was initiated to assess whether the transmission of Mycobacterium tuberculosis had occurred in the pediatrician's office to patients, families, or other visitors. The investigation was later extended to include the hospitals and the day care center where the pediatrician worked. METHODS: A letter was mailed to parents of children served by the practice, explaining the potential exposure to TB and requesting that all persons who visited the office after September 1, 1992 complete an interview and Mantoux TST. Mass interviewing, testing, and test interpretation within the practice took place seven times during March and April 1993. RESULTS: At the completion of screening, 181 (87%) of 208 children who had close contact with the index case were reliably skin-tested and returned for interpretation. Three (1.7%) of the 181 children were TST-positive (>/=5 mm). Thirty-seven (13%) of the 286 adults tested and returning for interpretations were TST-positive (>/=10 mm). Thirty-two (86%) of the 37 adults who tested positive were foreign-born. CONCLUSION: This investigation highlighted the need for identifying childhood TB infection as a sentinel event for adult disease. It also demonstrated the difficulty associated with deciding the extent of contact investigation of a health care worker with TB. Finally, the investigation emphasized the importance of maintaining regularly scheduled and appropriate testing for TB infection in health care workers and the need for health care workers to be cognizant of their own risk and be able to identify, especially in themselves, signs and symptoms of potential TB disease.

Retrospective detection of laboratory cross-contamination of Mycobacterium tuberculosis cultures with use of DNA fingerprint analysis.

In 1992-1993, we investigated possible cross-contamination of Mycobacterium tuberculosis cultures as part of a study of tuberculosis in Arkansas by using DNA fingerprint analysis. Of patients whose isolates were matched, those for whom smears were negative and only one culture was positive were identified from laboratory records. Clinical, laboratory, DNA fingerprint, and epidemiological data were reviewed. Of 259 patients, nine (3.5%) were judged to be due to cross-contamination. None of these patients had a clinical course consistent with tuberculosis. All nine specimens were processed with another isolate with a matching DNA fingerprint, and epidemiological connections were not identified among any of the patients. To avoid erroneous diagnoses and unnecessary therapy and public health investigations, specimens from patients with tuberculosis whose smears are negative and only one culture is positive should be investigated for cross-contamination. An inconsistent clinical course and a DNA fingerprint that matches those of other culture-positive specimens processed concurrently, coupled with the lack of an epidemiological connection, suggest cross-contamination.

Tuberculosis transmission among five school bus drivers and students in two New York counties.

OBJECTIVE: Between November 1994 and April 1995, more than 3300 students in 49 schools in two counties in New York were potentially exposed to five school bus drivers with tuberculosis. This investigation was carried out to determine the extent of transmission of Mycobacterium tuberculosis among students. METHODS: Components of the epidemiologic investigation included tuberculin skin-test screening and collection of demographic information for students exposed to a driver with tuberculosis, chest radiography and medical evaluation of individuals with positive skin tests, and DNA fingerprinting of M tuberculosis isolates. A positive skin test was defined as >/=10 mm induration, and a converter was an individual with an increase in reaction size of >/=10 mm in the past 2 years. RESULTS: The rates of positive skin tests were 0.8%, 0.3%, 9.9%, 1.1%, and 0.7% among US-born students exposed to drivers 1 through 5, respectively. The relative risk for a positive tuberculin skin test was significant only for students exposed to driver 3, and the only secondary case identified among students was exposed to driver 3. The DNA fingerprint patterns of isolates from drivers 3 and 4 matched. CONCLUSION: There was no clear evidence of transmission of M tuberculosis to students from drivers 1, 2, 4, or 5. However, evidence suggests that driver 3 transmitted M tuberculosis to students and another driver. Routine annual tuberculin skin-test screening of drivers would not have prevented these tuberculosis exposures.