Hospital outbreak of multidrug-resistant Mycobacterium tuberculosis infections. Factors in transmission to staff and HIV-infected patients

Is the detection of Mycobacterium tuberculosis DNA by ligase chain reaction worth the cost: experiences from an inner London teaching hospital

AIMS

To evaluate the clinical usefulness and the costs of using a rapid, commercial ligase chain reaction test (LCx) to detect Mycobacterium tuberculosis directly from clinical samples.

METHODS

A prospective study of 2120 routine clinical specimens from 1161 patients over a 13 month period. Investigations for mycobacterial disease by microscopy, culture, and the Abbott LCx assay were performed. Sequential LCx assays were monitored in a cohort of patients undergoing treatment. The costs of the assay were calculated using the WELCAN system. Sensitivity, specificity, and positive and negative predictive values of the LCx assay were compared with conventional tests. The performance of the assay in patients undergoing treatment and cost in terms of WELCAN units converted to pounds/annum was studied.

RESULTS

The assay was 85%/88% sensitive and 98%/100% specific in culture confirmed/clinically confirmed cases of tuberculosis, respectively. The assay was not useful for the measurement of treatment outcomes. The test cost approximately 42,500 Pounds/annum.

CONCLUSIONS

The assay is a rapid, sensitive, and specific adjunct to clinical diagnosis, especially in differentiating non-tuberculous mycobacteria. However, it does not differentiate old and treated tuberculosis from reactivated disease, it is not useful to monitor adherence to treatment, and it is expensive.

Tuberculosis transmission in the family

OBJECTIVE

To evaluate the risk of tuberculosis (TB) transmission from family members with infectious TB to other family members, and to examine whether household contact investigations had an impact on tuberculosis patterns.

DESIGN

Under the direction of the Taipei Municipal Chronic Disease Hospital, 12 full-time public health nurses recruited the household contacts of TB patients. Chest X-ray examination was recommended for adult contacts. Child contacts received the Mantoux tuberculin skin test, and radiography was recommended if the results were positive.

SETTING

Family contacts of all TB index patients who attended one of 29 hospitals in Taipei, from July 1993 through June 1996. The medical records of index patients were obtained from the National Tuberculosis Registry.

RESULTS

During the study period, the families of 3903 index patients, comprising 11873 contacts, were investigated. Among these, 4595 received radiography, for a response rate of 38.7%. Of these, 284 had active pulmonary disease: 188 (66.3%) had minimal disease, 79 (27.8%) had moderately advanced disease, and only 17 (5.9%) had far advanced disease. Overall, the index patients had more advanced TB: only 1261 (32.3%) had minimal disease, while 2022 (51.8%) had moderately advanced disease and 620 (15.9%) had far advanced disease.

CONCLUSIONS

These data show a relatively high risk of intrafamily TB transmission. Our findings also show that family contact investigations may help to diagnose TB in earlier stages. Such an approach should greatly reduce the number of new TB cases and speed eradication of the disease.

Two-step tuberculin testing of passengers and crew on a commercial airplane

OBJECTIVES

We investigated the risk of tuberculosis transmission from a person with highly infectious pulmonary tuberculosis to fellow passengers and crew members on a 14-hour commercial flight. The 2-step tuberculin testing was used to minimize the effects of the booster phenomenon.

METHODS

Passengers and flight crew members identified from airline records were contacted by letter, telephone, or both to notify them of their potential exposure to Mycobacterium tuberculosis. The subjects were advised to undergo Mantoux tuberculin skin testing within the required time period to assess a conversion. In addition, information regarding tuberculosis history and other sources of potential exposure was solicited by means of a questionnaire.

RESULTS

Of the 277 passengers and crew members on the aircraft, 225 (81.2%) responded. Of these, 173 (76.9%) had positive tuberculin results on the first test (induration > 10 mm). Thirteen subjects with negative results refused further testing; 11 (28%) of the remaining 39 exhibited the booster phenomenon on the second test. Subjects who exhibited the booster phenomenon were significantly more likely to have received previous BCG vaccination. Nine contacts with negative results on the initial test had positive results on a third test administered at 12 weeks after the flight exposure Of these, 6 contacts had previous BCG vaccination, old tuberculosis, or a family member with tuberculosis; the remaining 3 reported on other risk factors for positive reactions. None of these 3 contacts had sat in the same section of the plan as the index patient.

CONCLUSIONS

The 2-step tuberculin testing procedure is an effective tool for minimization of the booster effect, thus allowing accurate monitoring of subsequent tuberculin conversion rates. Moreover, the clustering of tuberculin skin test conversions among passengers in this study demonstrates the possible risk of M tuberculosis transmission during air travel.

Phthisiology at the dawn of the new century

Tuberculosis (TB) has been and continues to be one of the most significant pathogens in terms of human morbidity and mortality. Although the resurgence of TB has been held in check in most developed countries, the epidemic rages on in most developing countries of the world. The specter of drug resistance is becoming a more credible challenge in many parts of the world, dimming the prospects of eventual elimination. However, great opportunities are arising as well, with an unprecedented focus on the global aspects of TB control. This article will review the status of TB today and put into perspective the prospects for its elimination in the coming century.

Implementation of an emergency department triage procedure for the detection and isolation of patients with active pulmonary tuberculosis

STUDY OBJECTIVES

To investigate the ability of an emergency department screening protocol to initiate respiratory isolation of patients with pulmonary tuberculosis at ED triage before chest radiography.

METHODS

We conducted a prospective cohort study with retrospective medical record review of adult patients who presented for care to an urban, university-affiliated hospital in Los Angeles County over a 4-month period. Ambulatory patients were administered a triage screening protocol that used patient-reported tuberculosis risk factors and symptoms in combination with selective chest radiography to screen patients at ED triage for active pulmonary tuberculosis.

RESULTS

A total of 10,674 patients were screened; 2, 218 were isolated at triage and underwent chest radiography, and 378 were kept in isolation in the ED. The respiratory isolation of pulmonary tuberculosis (RIPT) protocol detected 17 of 27 visits made by patients with unsuspected pulmonary tuberculosis, yielding a sensitivity of 63% (95% confidence interval [CI] 42% to 81%). The estimated specificity was 78%. For each patient with tuberculosis who was detected by the RIPT protocol, 624 patients were screened at triage, 130 chest radiographs were taken, and 22 patients were placed in respiratory isolation in the ED. Patients with undetected pulmonary tuberculosis more commonly had nonpulmonary chief complaints (76% versus 20%; odds ratio [OR] 13, 95% CI 2.1 to 78.3), and only 60% (95% CI 26% to 88%) were ultimately isolated in the hospital. Among RIPT screen-positive patients, radiographic findings predictive of pulmonary tuberculosis were cavitary lesions (OR 84.3, 95% CI 22.6 to 315), upper lobe infiltrates (OR 24.2, 95% CI 9.1 to 64.4), pleural effusions (OR 8.9, 95% CI 2.5 to 31.8), diffuse/interstitial infiltrates (OR 5.7, 95% CI 1.8 to 17.9), and non-upper lobe infiltrates (OR 3.1, 95% CI 1.0 to 9.5).

CONCLUSION

The RIPT screening protocol was only moderately sensitive for isolating patients with pulmonary tuberculosis at ED triage. Future studies should evaluate modified and abridged screening protocols, as well as the cost-effectiveness of triage screening.

PREVALENCE OF DRUG RESISTANT TUBERCULOSIS IN ARMED FORCES-STUDY FROM A TERTIARY REFERRAL CHEST DISEASES HOSPITAL AT PUNE

This study was conducted to find out the prevalence and pattern of primary and acquired resistance to antimycobacterial drugs among patients of pulmonary tuberculosis, in Armed Forces. Out of 2562 clinically diagnosed patients of tuberculosis, in a span of three years, 1146 were bacteriologically positive. The study included only 1120 smear and culture positive cases, and excluded 26 cases in which no growth was obtained on culture. 192 out of 1120 cases (17.14%), showed overall resistance to one or more antituberculous drugs (ATD). Primary drug resistance (PDR) was observed in 161 (14.37%) and acquired drug resistance (ADR) in 31 isolates (2.77%). Of the resistant cases on short course chemotherapy (SCC), single drug resistance was observed in 99 (51.56%), resistance to any two drugs in 63 (32.81%), and three or more drugs in 30 (15.62%) cases. Analysis of resistance to specific drug revealed 26.56% for streptomycin (S), 15.10% for rifampicin (R), 7.29% for isoniazid (H), 2.08% for pyrazinamide (P) and 0.52% for ethambutol (E). Resistance to H and R was present in 4.16% strain and their combination with other drugs resistance was in 16.14% of the drug resistant strains, thus constituting 2.76% of the total sputum positive cases. A group of 26 cases is also discussed, where there was discrepancy in clinical status and bacteriological parameters and treatment for multi-drug resistant tuberculosis (MDR-TB) was instituted.

Clusters of new tuberculosis cases in North-west London: a survey from three hospitals based on IS6110 RFLP typing

OBJECTIVES

The relative contributions of reactivation of latent infection and clusters of new infections to the overall incidence of tuberculosis in the U.K. is unknown. A study was carried out in North-West London to determine the feasibility of IS6110 RFLP strain typing as a tool to investigate the relative contributions of these two sources.

METHODS

All available isolates of M. tuberculosis from specimens collected over a calendar year at three participating hospitals were typed by RFLP using an IS6110 probe. Isolates exhibiting a single band pattern were subject to further typing using an oligonucleotide direct repeat probe. Demographic and clinical information on cases was obtained from the National Survey of Tuberculosis Notifications in England and Wales and further information sought on clustered cases as identified by RFLP typing.

RESULTS

Twenty-seven (23%) of the 118 cases had shared IS6110 RFLP patterns. Strains from nine cases had single band patterns, but these were all distinguishable from each other when subjected to further typing by direct repeat probe. The remaining 18 cases belonged to eight clusters. Epidemiological links were established between all the patients in each cluster. The likelihood of being in a cluster was increased in cases with pulmonary smear-positive disease. It was lower in cases of Indian Sub-continent ethnic origin. For 10 of the 18 clustered cases epidemiological links had not been established by conventional contact tracing.

CONCLUSIONS

Investigation of the relative contributions of reactivation of latent infection and new infection is feasible in a UJK population, using IS6110 RFLP typing of M. tuberculosis isolates and epidemiological enquiries. This study in London identified clustered, presumably new cases, the majority of whom had not been linked epidemiologically. Comprehensive IS6110 RFLP typing of UK isolates would probably identify many clusters of incident tubercular infection.

Nosocomial tuberculosis prevention measures among two groups of US hospitals, 1992 to 1996

OBJECTIVE

To compare trends in nosocomial tuberculosis (TB) prevention measures and health-care worker (HCW) tuberculin skin test (TST) conversion of hospitals with HIV-related Pneumocystis carinii pneumonia (PCP) patients and other US hospitals from 1992 through 1996.

DESIGN AND SETTING

Surveys in 1992 and 1996 of 38 hospitals with PCP patients in four high-HIV-incidence cities and 136 other US hospitals from the American Hospital Association membership list.

PARTICIPANTS

Twenty-seven hospitals with PCP patients and 103 other US hospitals.

RESULTS

In 1992, 63% of PCP hospitals and other US hospitals had rooms meeting Centers for Disease Control and Prevention (CDC) criteria (ie, negative air pressure, six or more air exchanges per hour, and air directly vented to the outside) for acid-fast bacilli isolation; in 1996, almost 100% had such isolation rooms. Similarly, in 1992, nonfitted surgical masks were used by HCWs at 60% of PCP hospitals and 68% at other US hospitals, while N95 respirators were used at 90% of PCP hospitals and 83% of other US hospitals in 1996. There was a significant decreasing trend in TST conversion rates among HCWs at both PCP and other US hospitals; however, this trend varied among all hospitals. HCWs at PCP hospitals had a higher risk of TST conversion than those at other US hospitals (relative risk, 1.71; p < 0.0001).

CONCLUSION

From 1992 through 1996, PCP and other US hospitals have made similar improvements in their nosocomial TB prevention measures and decreased their HCW TST conversion rate. These data show that most hospitals are compliant with CDC TB guidelines even before the enactment of an Occupational Safety and Health Administration TB standard.

Tuberculosis isolation: comparison of written procedures and actual practices in three California hospitals

OBJECTIVE

To evaluate implementation of healthcare worker exposure control measures for tuberculosis (TB)-patient isolation, as specified by Centers for Disease Control and Prevention (CDC) guidelines and the hospital's TB-control policy.

DESIGN

Prospective multihospital study comparing CDC guidelines and hospital policy for TB-patient isolation to once-weekly observations of TB-patient isolation practices over 14 consecutive weeks at each hospital.

SETTING

Three urban hospitals (two county, one private community) in counties in California with a high incidence rate of TB.

MEASUREMENTS

Work practices for TB-patient isolation were observed and ventilation performance of isolation rooms was assessed while patient rooms were in use for TB isolation.

RESULTS

Of 170 TB-patient rooms observed, 119 (70%) involved a patient in a designated TB isolation room, the room was under negative pressure, the door was closed, and a "respiratory precautions" sign was on the door; 32 patient-room units (19%) were not under negative pressure or not designated as negative-pressure rooms. Of 151 patient-room units mechanically capable of negative pressure at a prior point in time, 16 (11%) were not under negative pressure at the time of use. Of 67 patient-room units equipped with continuous monitoring devices, 8 (12%) involved devices that did not accurately reflect the direction of airflow. Of the 62 healthcare workers observed using a respirator for TB, 40 (65%) did not don the respirator properly.

CONCLUSIONS

Implementing CDC guidelines for TB-patient isolation was feasible but imperfect in the three hospitals. Day-to-day work practices deviated from hospital policy. Prospectively quantifying the implementation of a hospital TB isolation policy while the room is in use may lead to improved estimates of risk and may help to identify and thereby prevent avoidable healthcare worker exposures to Mycobacterium tuberculosis aerosol. Auditing practices and verifying equipment performance is likely to identify unexpected problems in implementation of the TB control program.

A national survey of air medical infectious disease control practices

INTRODUCTION

Caring for an infectious patient in the air medical environment presents a special challenge to all air crew members (ACMs) involved. The purpose of this study was to survey the infectious disease control practices of air medical programs (AMPs) that are members of the Association of Air Medical Services.

METHODS

A structured telephone survey was designed to gather data. Using one interviewer (an undergraduate student) with no knowledge of the study's goal minimized experimental bias. AMPs from 151 geographically selected areas were called between June and August 1996. Only the programs' chief flight nurses (CFNs) were targeted as respondents.

RESULTS

The response rate was 91% (138 of 151). Although no program refused to participate, 13 CFNs were unavailable to be interviewed. Mission profile was 32% scene and 68% interhospital with an annual average of 950 patient transports per program. Transport type was 61% rotor-wing aircraft, 17% fixed-wing, and 22% both. Flight physicals for ACMs were required by 57% of the AMPs. Pre-employment screenings for rubella, tuberculosis (TB), and varicella were noted. Interestingly, 17% of the AMPs reported pre-employment HIV testing. Immunization was mandated by 57% of AMPs, including hepatitis B virus, measles, rubella, and tetanus. Nine percent of the respondents refused to accept a transport with specific contagious conditions, primarily TB. A formal decontamination policy was in effect at 88% of the AMPs, and OSHA-approved filter masks were available at 70%. Pathogen exposure reporting was required by 97%.

CONCLUSION

A current, comprehensive infection control program, continuing education, and 100% compliance with standard precautions will help reduce the possibility of accidental exposures. These strategies to reduce transmission also can be extended during training sessions to the prehospital and hospital personnel with whom the air medical program serves.

Transmission dynamics of tuberculosis in a high-incidence country: prospective analysis by PCR DNA fingerprinting

We have prospectively analyzed the DNA fingerprints of Mycobacterium tuberculosis strains from a random sample of patients with newly diagnosed tuberculosis in Windhoek, Namibia. Strains from 263 smear-positive patients in whom tuberculosis was diagnosed during 1 year were evaluated, and the results were correlated with selected epidemiological and clinical data. A total of 163 different IS6110 fingerprint patterns were observed among the 263 isolates. Isolates from a high percentage of patients (47%) were found in 29 separate clusters, with a cluster defined as isolates with 100% matching patterns. The largest cluster included isolates from 39 patients. One predominant strain of M. tuberculosis caused 15% of cases of smear-positive pulmonary tuberculosis in Windhoek. That strain was also prevalent in the north of the country, suggesting that in contrast to other African countries with isolates with high levels of diversity in their DNA fingerprint patterns, only a restricted number of different strains significantly contribute to the tuberculosis problem in Namibia.

Nosocomial infections in patients with HIV disease

Throughout the AIDS epidemic, nosocomial infection in the patient with HIV disease has presented a constant problem--not only for the hospitalized patient but also for the clinic attender. The nosocomial spread of multidrug-resistant tuberculosis has emphasized the need for effective control of infection measures in dealing with the immunodeficient. Increased recognition of nosocomial bacterial pneumonias has raised questions about the place, if any, of antimicrobial prophylaxis in preventing Gram-negative and Legionella infection. The use of long-term indwelling venous catheters for the administration of parenteral therapy is associated with an increased risk of nosocomial bloodstream infection--particularly from staphylococci and Pseudomonas spp. Evidence now exists for the nosocomial spread of opportunistic infections, including Cryptosporidium parvum, Mycobacterium avium complex and Pneumocystis carinii. The delay between exposure and diagnosis, the atypical presentation of infections such as tuberculosis and repeated hospital admissions of AIDS patients can combine to confuse the issue with the result that a nosocomial infection may be mis-classified as community-acquired. It seems likely that the burden of nosocomial infection in HIV disease is continually underestimated.

Treatment and prevention of multidrug-resistant tuberculosis

Multidrug-resistant tuberculosis (MDRTB), which is defined as combined resistance to isoniazid and rifampicin, is a 'man-made' disease that is caused by improper treatment, inadequate drug supplies or poor patient supervision. Patients with MDRTB face chronic disability and death, and represent an infectious hazard for the community. Cure rates of 96% have been achieved but require prompt recognition of the disease, rapid accurate susceptibility results, and early administration of an individualised re-treatment regimen. Such regimens are usually based on a quinolone and an injectable agent (i.e. an aminoglycoside or capreomycin) supplemented by other 'second-line' drugs. This therapy is prolonged (e.g. 24 months), expensive, and has multiple adverse effects. Prevention of MDRTB is therefore of paramount importance. The World Health Organization (WHO) has recommended a multifaceted programme, known by the acronym DOTS (directly observed therapy, short-course), that promotes effective treatment of drug-susceptible TB as the prime method of limiting drug resistance. DOTS was part of a successful MDRTB control programme in New York City, which also included treatment of prevalent MDRTB cases, streamlined laboratory testing, effective infection control procedures and wider application of screening and preventive therapy (although the optimal chemotherapy for MDRTB infection remains undefined). Industrialised countries have the resources to treat patients with MDRTB and to mount these extensive control programmes. Unfortunately, MDRTB is also prevalent in Asia, South America and the former Soviet Union. First world countries have a vested interest, as well as a moral responsibility, to assist in controlling MDRTB in these 'hot spots'.

Healthcare worker compliance with nosocomial tuberculosis control policies

To determine compliance with nosocomial tuberculosis control measures, 541 healthcare worker observations were made for 52 patients placed in respiratory isolation. Sixty-four total violations were noted, of which 45% occurred in physicians in training. Overall compliance with tuberculosis control measures appeared to be good, but additional educational efforts are warranted.

Outcome of multi-drug-resistant tuberculosis in France: a nationwide case-control study

The factors related to the outcome of 51 cases of multi-drug-resistant tuberculosis (MDR-TB) reported in 1994 to the French National Reference Center were retrospectively analyzed. The patients (median age, 45 yr) were mainly male (75%), foreign-born (63%), and had pulmonary involvement (95%). Sixteen percent were human immunodeficiency virus (HIV)-coinfected. The number of drugs to which the Mycobacterium tuberculosis isolates were susceptible was four. Only 82% of the patients have been hospitalized at any time (median duration, 33 d). Five patients (9%) received no antituberculosis drugs, although three had drug susceptibility results, indicating that two or more active drugs were available; 46 (91%) received drugs, including 37 who received two or more active drugs. Among the nine cases who received only one active drug, three had drug susceptibility results, indicating that two or more active drugs were available. By December 1996, 10 patients were lost before treatment completion, 24 had treatment failure, and 17 had a favorable outcome. The median survival time was 31 mo. Factors related to a poorer outcome were HIV-coinfection (hazard ratio [HR] = 41), treatment with less than two active drugs (HR = 9.9), and MDR status knowledge at the time of diagnosis (HR = 3.3). The country of birth was not associated with a poorer outcome. The management and outcome of MDR-TB in France has to be improved. A solution would be to develop a specialized unit or team for the treatment of MDR-TB, as recommended by the World Health Organization (WHO).

Comparison of methods based on different molecular epidemiological markers for typing of Mycobacterium tuberculosis complex strains: interlaboratory study of discriminatory power and reproducibility

In this study, the currently known typing methods for Mycobacterium tuberculosis isolates were evaluated with regard to reproducibility, discrimination, and specificity. Therefore, 90 M. tuberculosis complex strains, originating from 38 countries, were tested in five restriction fragment length polymorphism (RFLP) typing methods and in seven PCR-based assays. In all methods, one or more repetitive DNA elements were targeted. The strain typing and the DNA fingerprint analysis were performed in the laboratory most experienced in the respective method. To examine intralaboratory reproducibility, blinded duplicate samples were included. The specificities of the various methods were tested by inclusion of 10 non-M. tuberculosis complex strains. All five RFLP typing methods were highly reproducible. The reliability of the PCR-based methods was highest for the mixed-linker PCR, followed by variable numbers of tandem repeat (VNTR) typing and spoligotyping. In contrast, the double repetitive element PCR (DRE-PCR), IS6110 inverse PCR, IS6110 ampliprinting, and arbitrarily primed PCR (APPCR) typing were found to be poorly reproducible. The 90 strains were best discriminated by IS6110 RFLP typing, yielding 84 different banding patterns, followed by mixed-linker PCR (81 patterns), APPCR (71 patterns), RFLP using the polymorphic GC-rich sequence as a probe (70 patterns), DRE-PCR (63 patterns), spoligotyping (61 patterns), and VNTR typing (56 patterns). We conclude that for epidemiological investigations, strain differentiation by IS6110 RFLP or mixed-linker PCR are the methods of choice. A strong association was found between the results of different genetic markers, indicating a clonal population structure of M. tuberculosis strains. Several separate genotype families within the M. tuberculosis complex could be recognized on the basis of the genetic markers used.

Drug resistance patterns among hospitalized tuberculous patients in Rio de Janeiro, Brazil, 1993-1994

The purpose of this study was to analyze the prevalence and risk factors for drug resistance among hospitalized patients in two tertiary care centers, an acquired immunodeficiency syndrome (AIDS) reference center and a sanatorium, in Rio de Janeiro, Brazil. From 1993-1994, 389 patients were diagnosed as having tuberculosis (TB). Isolates from 265 patients were tested for in vitro susceptibility to rifampin and isoniazid. Resistance to one or more drugs was detected in 44 patients (16.6%) and was significantly more common among recurrent cases in both hospitals (p=0.03 in the AIDS center and p=0.001 in the sanatorium). Twenty seven patients (10.2%) had isolates resistant to both isoniazid and rifampin. Multi-drug resistance was associated with human immunodeficiency virus (HIV) infection among patients who had never been treated for TB. In conclusion, drug-resistant TB is high in hospitalized patients in Rio de Janeiro, especially among HIV infected patients. Therefore, measures to control TB and prevent nosocomial transmission need urgently to be set up in the Brazilian hospitals.

Nosocomial tuberculosis exposure in an outpatient setting: evaluation of patients exposed to healthcare providers with tuberculosis

OBJECTIVE

To evaluate the risk of tuberculosis (TB) transmission to patients potentially exposed to two healthcare providers who worked in outpatient settings for several weeks prior to being diagnosed with acid-fast bacilli smear-positive pulmonary TB.

DESIGN

Potentially exposed patients were notified by letter and television reports of the recommended evaluation for TB infection or disease and availability of free screening at the hospital. Prevalence of infection in the screened patients and the incidence rate of TB over the subsequent 2 years were compared to those of a control group of unexposed outpatients.

SETTING

An urban inner-city hospital.

PATIENTS

1,905 patients with potential exposure to the ill healthcare workers; 487 (25%) presented for evaluation. Controls consisted of 951 unexposed patients.

RESULTS

361 potentially exposed patients had their tuberculin test read; 97 (27%) had a purified protein derivative > or = 10 mm. In the comparison group, 148 (25%) of 600 with test readings had a > or = 10-mm reaction (risk ratio, 1.18; 95% confidence interval, 0.86-1.60). In multivariate analysis, male gender, non-white race, and older age were significantly associated with a positive tuberculin test; exposure was not. No TB cases were identified during screening. Two years after the exposure, 7 TB cases had been reported to the state registry among 1,905 potentially exposed patients (184 cases/100,000 person-years) versus 4 cases in the comparison group of 951 (210 cases/100,000 person-years).

CONCLUSIONS

Evaluation of patients exposed to healthcare workers with TB disease in ambulatory settings of an inner-city hospital revealed no evidence of transmission of Mycobacterium tuberculosis due to the exposure.

Foci of tuberculosis transmission in central Los Angeles

To identify sites of tuberculosis transmission and to determine the contribution of HIV-infected patients to tuberculosis morbidity in an urban area, we prospectively evaluated 249 patients with culture-proven tuberculosis in central Los Angeles. Restriction fragment length polymorphism (RFLP) analysis was performed on Mycobacterium tuberculosis isolates to identify patients infected with the same strain. Using RFLP and clinical and epidemiologic data, we identified the most likely source case and site of transmission for 79 patients. Homelessness, birth in the United States and Native American ethnicity were independent predictors of being a source case, but HIV infection was not. Three homeless shelters were sites of tuberculosis transmission for 55 (70%) of the 79 patients. HIV-infected patients constituted 27% (66/249) of the study population, but only 17% (13/79) of patients were infected by an HIV-infected source case. We conclude that transmission of tuberculosis in central Los Angeles was highly focal, and that the major transmission sites were three homeless shelters. HIV- infected tuberculosis patients did not play a major role in spread of tuberculosis. Tuberculosis control measures targeted at specific homeless shelters can reduce tuberculosis morbidity in urban areas where homelessness is common and the incidence of tuberculosis is high.

Molecular evidence for heterogeneity of the multiple-drug-resistant Mycobacterium tuberculosis population in Scotland (1990 to 1997)

Multiple-drug-resistant Mycobacterium tuberculosis (MDR-MTB) has been well studied in hospitals or health care institutions and in human immunodeficiency virus-infected populations. However, the characteristics of MDR-MTB in the community have not been well investigated. An understanding of its prevalence and circulation within the community will help to estimate the problem and optimize the strategies for control and prevention of its development and transmission. In this study, MDR-MTB isolates from Scotland collected between 1990 and 1997 were characterized, along with non-drug-resistant isolates. The results showed that they were genetically diverse, suggesting they were unrelated to each other and had probably evolved independently. Several new alleles of rpoB, katG, and ahpC were identified: rpoB codon 525 (ACC-->AAC; Thr525Asn); katG codon 128 (CGG-->CAG; Arg128Gln) and codon 291 (GCT-->CCT; Ala291Pro); and the ahpC synonymous substitution at codon 6 (ATT-->ATC). One of the MDR-MTB isolates from an Asian patient had an IS6110 restriction fragment length polymorphism pattern very similar to that of the MDR-MTB W strain and had the same drug resistance-related alleles but did not have any epidemiological connection with the W strains. Additionally, a cluster of M. tuberculosis isolates was identified in our collection of 715 clinical isolates; the isolates in this cluster had genetic backgrounds very similar to those of the W strains, one of which had already developed multiple drug resistances. The diverse population of MDR-MTB in Scotland, along with a low incidence of drug-resistant M. tuberculosis, has implications for the control of the organism and prevention of its spread.

Estudo de efetividade de esquemas alternativos para o tratamento da tuberculose multirresistente no Brasil

Objetivo: Determinar a efetividade do tratamento com esquemas alternativos para casos confirmados de tuberculose multirresistente (TBMR) primária e adquirida, em pacientes ambulatoriais. Métodos: Casos de TBMR foram definidos como cultura e isolamento de M. tuberculosis e perfil de resistência in vitro a pelo menos à rifampicina, isoniazida e a uma terceira droga dos esquemas padronizados no Brasil, tanto pelo método convencional (LJ) quanto pelo sistema radiométrico BACTEC. Desenho: Ensaio clínico, multicêntrico, não randomizado e controlado. Os pacientes foram arrolados entre abril de 1995 e dezembro de 1997, no total de 197. Por diversas razões 10 casos foram excluídos da análise. Em abril de 1998 permaneciam em tratamento 36 pacientes. Foram analisados 149 casos com duração média de tratamento de 14 meses sem interrupção. Os regimes foram escolhidos conforme o perfil de sensibilidade: 1) estreptomicina, ofloxacina, terizidona, etambutol, clofazimina ou 2) amicacina, ofloxacina, terizidona, etambutol e clofazimina. Demografia: sexo: masculino - 68,4%, feminino - 31,5%; média de idade - 36,9 anos (14-71 anos); prevalência de HIV - 1,9%; taxa de resistência primária - 8%, taxa de resitência secundária - 92%. Resultados parciais: 120 (79,5%) pacientes negativaram a cultura no período de 3 meses; cura - 53%, falência - 31%, óbito - 6%, abandono - 10%. Definições: cura - tratado por 12 meses, com 6 meses de tratamento após 2 culturas consecutivas negativas; abandono - tratamento e consultas descontinuados; óbito - morte causada por TB após 2 meses de tratamento; falência - persistência de positividade na cultura em 12 meses seguidos. Conclusão: O maior preditor da multirresistência no estudo foi tratamento prévio irregular ou incompleto. Outros preditores (p < 0,05) foram: ser homem, ter lesão radiológica cavitária bilateral e ter mais de 2 anos de doença. A taxa de conversão bacteriológica em escarro e cultura foi alta em 6 meses de tratamento.

Tuberculin skin test conversion rates in New York City Emergency Medical Service health care workers

OBJECTIVE

To determine annual tuberculin skin test conversion (infection) rates for prehospital health care workers (EMTs and paramedics) in an urban environment with a high prevalence of Mycobacterium tuberculosis.

METHODS

We conducted a prospective study of prehospital health care workers for the New York City EMS, EMS Employee Health Service, and the Fire Department Bureau of Health Service to determine the tuberculin skin test conversion rates. In 1992, all current and new EMS prehospital health care workers without a known history of a positive tuberculin reaction received a baseline tuberculin purified protein derivative (PPD) skin test. Thereafter, (January 1, 1993-December 31, 1996) all EMS health care workers who had negative PPD skin test results received annual tuberculin PPD skin tests. Tuberculin skin test conversion was defined as induration of 10 mm or greater in a worker with a documented prior negative test result. The PPD skin test reaction was measured by trained professional readers.

RESULTS

A total of 7,290 PPD test results were read during this study. Compliance with annual testing was 75%. Annual tuberculin skin test conversion rates were 1.3% in 1993, .7% in 1994, .1% in 1995, and .2% in 1996 (average .5%). In a static subgroup with at least 15 years' seniority, compliance with annual testing was 100% and annual tuberculin skin test conversion rates were .5% in 1993, 0 in 1994, .5% in 1995, and 1.5% in 1996 (average .6%).

CONCLUSION

Despite the high prevalence of M tuberculosis infection in New York City and the potential for difficulty in the use of respiratory precautions during emergency response operations, EMS prehospital health care workers have an annual tuberculin conversion rate that is relatively low compared with hospital-based health care workers.

Characterization of infectious aerosols in health care facilities: an aid to effective engineering controls and preventive strategies

Assessment of strategies for engineering controls for the prevention of airborne infectious disease transmission to patients and to health care and related workers requires consideration of the factors relevant to aerosol characterization. These factors include aerosol generation, particle size and concentrations, organism viability, infectivity and virulence, airflow and climate, and environmental sampling and analysis. The major focus on attention to engineering controls comes from recent increases in tuberculosis, particularly the multidrug-resistant varieties in the general hospital population, the severely immunocompromised, and those in at-risk and confined environments such as prisons, long-term care facilities, and shelters for the homeless. Many workers are in close contact with persons who have active, undiagnosed, or insufficiently treated tuberculosis. Additionally, patients and health care workers may be exposed to a variety of pathogenic human viruses, opportunistic fungi, and bacteria. This report therefore focuses on the nature of infectious aerosol transmission in an attempt to determine which factors can be systematically addressed to result in proven, applied engineering approaches to the control of infectious aerosols in hospital and health care facility environments. The infectious aerosols of consideration are those that are generated as particles of respirable size by both human and environmental sources and that have the capability of remaining viable and airborne for extended periods in the indoor environment. This definition precludes skin and mucous membrane exposures occurring from splashes (rather than true aerosols) of blood or body fluids containing infectious disease agents. There are no epidemiologic or laboratory studies documenting the transmission of bloodborne virus by way of aerosols.

Initial drug regimens for the treatment of tuberculosis: evaluation of physician prescribing practices in New Jersey, 1994 to 1995

STUDY OBJECTIVE

To evaluate physician prescribing practices for the initial therapy for tuberculosis (TB) according to the recommendations of the Centers for Disease Control and Prevention (CDC) and American Thoracic Society (ATS).

DESIGN

Cross-sectional study.

SETTING

Statewide TB surveillance system in New Jersey, 1994 to 1995.

PATIENTS

We studied 1,230 culture-positive TB patients who were alive at diagnosis and whose isolates were tested for isoniazid susceptibility.

RESULTS

Almost all TB patients (98%) were reported from counties with an isoniazid-resistant proportion of 4% or more, which is the minimum level for implementation of an initial four-drug regimen recommended by CDC/ATS. Overall, 36% of the 1,230 patients were not initially treated with four or more drugs. Multivariate analyses found that non-Hispanic white patients were more likely to be treated with fewer than four drugs than were non-Hispanic black patients. Private practitioners and physicians at chest clinics were about five times more likely to prescribe fewer than four drugs initially than were physicians at the hospital where a national TB center is located.

CONCLUSION

A substantial proportion of physicians did not initially treat their TB patients according to the CDC/ATS recommendations. The results suggest that New Jersey physicians should be better informed about the recommendation and the high level of drug resistance in the communities they serve to assure that TB patients receive appropriate initial therapy.

Tuberculosis risk in funeral home employees

In order to estimate the risk of tuberculosis infection among employees in the funeral service industry, we conducted a risk-assessment study of a convenience sample of funeral home employees. Study participants completed a risk-assessment questionnaire and underwent tuberculin skin testing. Of 864 employees tested, 101 (11.7%) had a reactive tuberculin skin test. Reactivity to the tuberculin skin test was significantly associated with job category; funeral home employees with a present or past history of embalming deceased-human remains were twice as likely to be reactive as were non-embalming personnel (14.9% versus 7.2%, P < 0.01). Reactivity was also associated with age, gender, race, past history of close contact with a person diagnosed with tuberculosis, and work history. After controlling for age and other factors, tuberculin reactivity was found to be associated in embalming personnel with the number of years spent performing embalmings (> or = 20), and, in non-embalming personnel, with a history of close contact with infected individuals. Based on these results, it is recommended that funeral home employees who routinely embalm cadavers undergo annual tuberculin skin testing, receive initial training on tuberculosis prevention, and wear respiratory protection when preparing known tuberculosis cases.

Effectiveness of a nosocomial tuberculosis control program at an urban teaching hospital

STUDY OBJECTIVE

To assess the effectiveness of a nosocomial tuberculosis (TB) program at an urban teaching hospital.

DESIGN

Retrospective review.

SETTING

An urban teaching hospital, the University of California, San Diego Medical Center (UCSD), which cares for 25 to 30 culture-proven pulmonary TB cases (>80% of which are smear-positive) per year.

STUDY POPULATION

Health-care workers.

MEASUREMENTS

(1) Purified protein derivative (PPD) conversion rates. (2) Cases of active TB among health-care workers. (3) Compliance rates with isoniazid (INH) preventive therapy.

RESULTS

The UCSD program was evaluated for the years 1993 to 1995. The PPD conversion rate among established employees was 0.6%. Of 556 employees who had an exposure, 494 (88.8%) were compliant with follow-up. Three hundred thirty-seven were skin-tested (the other 157 already had a known PPD >10 mm). Only 2 of 337 (0.6%) converted. One case of active TB, unrelated to any documented hospital exposure, was discovered in 3 years among approximately 5,000 employees per year (follow-up for convertors, 18 to 54 months). Only 48.4% of eligible employees completed at least 6 months of INH preventive therapy.

CONCLUSIONS

UCSD's TB control measures appear to be effective in the prevention of nosocomial transmission of TB. Despite poor compliance with INH preventive therapy, cases of active TB among health-care workers were rare.

Risk factors for the spread of antibiotic-resistant bacteria

The emergence of antibiotic resistance is primarily due to excessive and often unnecessary use of antibiotics in humans and animals. Risk factors for the spread of resistant bacteria in hospitals and the community can be summarised as over-crowding, lapses in hygiene or poor infection control practices. Increasing antibiotic resistance in bacteria has been exacerbated by the slow pace in developing newer antibiotics. Methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE) and multiresistant Gram-negative bacteria are spread primarily by direct or indirect person-to-person contact. Independent risk factors for MRSA include the use of broad spectrum antibiotics, the presence of decubitus ulcers and prosthetic devices while those for VRE include prolonged hospitalisation and treatment with glycopeptides or broad spectrum antibiotics. For the spread of resistant Gram-negative bacteria risk factors include urinary catheterisation, excessive use of antibiotics and contamination of humidifiers and nebulisers. The spread of penicillin-resistant pneumococci (PRP) and drug-resistant and multidrug-resistant tuberculosis (MDRTb) is due to airborne transmission. Risk factors for the spread of PRP include overcrowding, tracheostomies and excessive use of penicillins for viral respiratory infections; for MDRTb they include poor compliance, convergence of immunosuppressed patients, delayed diagnosis or treatment, and poor or inadequate ventilation and isolation facilities. Recent developments in the genomic mapping of many bacteria and advances in combinatorial chemistry promise to usher in a new era of antibiotic development. While this may result in our regaining some of the ground lost to resistant bacteria, there will still be a continuing need to minimise the spread of antibiotic resistance through the rational use of antibiotic agents and stringent infection control practice.

Evaluation of four DNA typing techniques in epidemiological investigations of bovine tuberculosis

DNA fingerprinting techniques were used to type 273 isolates of Mycobacterium bovis from Australia, Canada, the Republic of Ireland, and Iran. The results of restriction fragment length polymorphism (RFLP) analysis with DNA probes from IS6110, the direct repeat (DR), and the polymorphic GC-rich sequence (PGRS) were compared with those of a new PCR-based method called spacer oligonucleotide typing (spoligotyping) developed for the rapid typing of Mycobacterium tuberculosis (J. Kamerbeek et al., J. Clin. Microbiol. 35:907-914, 1997). Eighty-five percent of the isolates harbored a single copy of IS6110, and 81.5% of these carried IS6110 on the characteristic 1.9-kb restriction fragment. RFLP analysis with IS6110 identified 23 different types, RFLP analysis with the DR probe identified 35 types, RFLP analysis with the PGRS probe identified 77 types, and the spoligotyping method identified 35 types. By combining all results, 99 different strains could be identified. Isolate clusters were frequently associated within herds or were found between herds when epidemiological evidence confirmed animal movements. RFLP analysis with IS6110 was sufficiently sensitive for the typing of isolates with more than three copies of IS6110, but RFLP analysis with the PGRS probe was the most sensitive typing technique for strains with only a single copy of IS6110. Spoligotyping may have advantages for the rapid typing of M. bovis, but it needs to be made more sensitive.

Nosocomial transmission of Mycobacterium bovis resistant to 11 drugs in people with advanced HIV-1 infection

BACKGROUND

Since 1990, several nosocomial outbreaks of multidrug-resistant (MDR) tuberculosis have occurred, none of which have involved Mycobacterium bovis. We describe an epidemic of nosocomial and primary MDR M bovis tuberculosis from December, 1993, to February, 1995, among HIV-1-infected patients in a district of Madrid.

METHODS

We undertook genetic characterisation of the M bovis strain and investigated its presence in a tuberculosis epidemic in a Madrid hospital in a case-controlled study. We assessed 19 cases diagnosed with MDR tuberculosis due to M bovis during the study period. For the control group, we randomly selected 33 patients with HIV-1 infection and isolation of a strain of M tuberculosis susceptible to isoniazid, rifampicin, or both, who were treated in Ramón y Cajal Hospital. Infection-control policies and practices were implemented.

FINDINGS

We detected 19 cases in HIV-1-infected patients of primary MDR tuberculosis produced by M bovis resistant to 11 antituberculosis drugs. We found phenotypic and genotypic similarities in the strains of M bovis. In the case group, the index case and two other cases had had previous contact with another hospital that had had an MDR tuberculosis outbreak. All patients died after a mean of 44 days (range 2-116), despite multidrug treatment with first-line and second-line antituberculosis drugs. The cases with M bovis MDR tuberculosis were significantly more likely than controls to have been admitted to a hospital ward at the same time as patients already infected with MDR tuberculosis during the 10 months before their diagnosis (adjusted odds ratio 94.6 [95% CI 9.4-956.3], p < 0.0001). Advanced HIV-1 immunosuppression was associated with the development of MDR tuberculosis. Implementation of control measures stopped the epidemic.

INTERPRETATION

An M bovis primary MDR tuberculosis epidemic that cannot be treated effectively and with high mortality has emerged in Europe and has been transmitted between hospitals.

Outbreak of drug-resistant tuberculosis with second-generation transmission in a high school in California

BACKGROUND

In spring 1993, four students in a high school were diagnosed with tuberculosis resistant to isoniazid, streptomycin, and ethionamide.

METHODS

To investigate potential transmission of drug-resistant tuberculosis, a retrospective cohort study with case investigation and screening by tuberculin skin tests and symptom checks was conducted in a high school of approximately 1400 students. Current and graduated high-school students were included in the investigation. DNA fingerprinting of available isolates was performed.

RESULTS

Eighteen students with active tuberculosis were identified. Through epidemiologic and laboratory investigation, 13 cases were linked; 8 entered 12th grade in fall 1993; 9 of 13 had positive cultures for Mycobacterium tuberculosis with isoniazid, streptomycin, and ethionamide resistance, and all 8 available isolates had identical DNA fingerprints. No staff member had tuberculosis. One student remained infectious for 29 months, from January 1991 to June 1993, and was the source case for the outbreak. Another student was infectious for 5 months before diagnosis in May 1993 and was a treatment failure in February 1994 with development of rifampin and ethambutol resistance in addition to isoniazid, streptomycin, and ethionamide. In the fall 1993 screening, 292 of 1263 (23%) students tested had a positive tuberculin skin test. Risk of infection was highest among 12th graders and classroom contacts of the two students with prolonged infectiousness. An additional 94 of 928 (10%) students tested in spring 1994 had a positive tuberculin skin test; 22 were classroom contacts of the student with treatment failure and 21 of these had documented tuberculin skin test conversions.

CONCLUSION

Extensive transmission of drug-resistant tuberculosis was documented in this high school, along with missed opportunities for prevention and control of this outbreak. Prompt identification of tuberculosis cases and timely interventions should help reduce this public health problem.

Tuberculosis in the hospice--a cause for concern?

Open pulmonary tuberculosis has been increasingly seen in HIV-infected patients in this hospice. Multidrug-resistant tuberculosis is a new and serious threat and two cases have occurred in our hospice in the past two years. This infection poses a health risk to staff, patients, relatives and volunteers. Palliative care teams in the hospice and community must have an index of suspicion for this infection, take active measures to ensure patient compliance with tuberculosis treatment and be prepared to implement infection control guidelines when needed.

Molecular diagnostics of infectious diseases

Over the past several years, the development and application of molecular diagnostic techniques has initiated a revolution in the diagnosis and monitoring of infectious diseases. Microbial phenotypic characteristics, such as protein, bacteriophage, and chromatographic profiles, as well as biotyping and susceptibility testing, are used in most routine laboratories for identification and differentiation. Nucleic acid techniques, such as plasmid profiling, various methods for generating restriction fragment length polymorphisms, and the polymerase chain reaction (PCR), are making increasing inroads into clinical laboratories. PCR-based systems to detect the etiologic agents of disease directly from clinical samples, without the need for culture, have been useful in rapid detection of unculturable or fastidious microorganisms. Additionally, sequence analysis of amplified microbial DNA allows for identification and better characterization of the pathogen. Subspecies variation, identified by various techniques, has been shown to be important in the prognosis of certain diseases. Other important advances include the determination of viral load and the direct detection of genes or gene mutations responsible for drug resistance. Increased use of automation and user-friendly software makes these technologies more widely available. In all, the detection of infectious agents at the nucleic acid level represents a true synthesis of clinical chemistry and clinical microbiology techniques.

Issues in the management of contacts of patients with active pulmonary tuberculosis

The evidence regarding the transmission of tuberculosis and risk of infection and disease in several specific clinical situations has been reviewed. There is considerable epidemiologic evidence that contagiousness is not an all-or-nothing phenomenon and is affected by several factors, only one of which is the bacteriologic status of the patient's sputum. Although untreated smear negative, culture positive patients are less contagious on average, they still may transmit infection to their close and casual contacts. Compared with contacts with tuberculin conversion, persons who are already tuberculin positive have much lower risk of developing active tuberculosis after exposure, and persons with prior BCG vaccination are at somewhat lower risk. Preventive therapy will be of less benefit, but should still be recommended for contacts who are heavily exposed or are immune compromised. Epidemiologic studies using RFLP techniques could provide more precise answers to the questions in this review.

Controlling tuberculosis in an urban emergency department: a rapid decision instrument for patient isolation

OBJECTIVES

This study examined whether data routinely available in emergency departments could be used to improve isolation decisions for tuberculosis patients.

METHODS

In a large emergency department in New York City, we compared the exposure histories of tuberculosis culture-positive and culture-negative patients and used these data to develop a rapid decision instrument to predict culture-positive tuberculosis. The screen used only data that are routinely available to emergency physicians.

RESULTS

The method had high sensitivity (.96) and moderate specificity (.54).

CONCLUSIONS

The method is easily adaptable for a broad range of settings and illustrates the potential benefits of applying basic epidemiologic methods in a clinical setting.

Evaluation of spoligotyping in a study of the transmission of Mycobacterium tuberculosis

Spoligotyping (for spacer oligotyping) is an easy, economical, and rapid way of typing Mycobacterium tuberculosis complex strains with the DR spacer markers (J. Kamerbeek et al., J. Clin. Microbiol. 35:907-914, 1997; D. van Soolingen et al., 33:3234-3248, 1995). The stability of the markers was demonstrated by showing that all the Mycobacterium bovis BCG strains tested gave the same spoligotyping pattern. None of the 42 atypical mycobacterial strains tested gave a spoligotyping signal, indicating the specificity of the technique for M. tuberculosis complex. The utility of the spoligotyping method was demonstrated by analyzing 106 isolates of M. tuberculosis obtained over 1 year in three Paris hospitals. The results obtained by this technique were compared to those obtained by Torrea et al. (G. Torrea et al., J. Clin. Microbiol. 34:1043-1049, 1996) by IS6110-based restriction fragment length polymorphism (RFLP) analysis. Strains from patients with epidemiological relationships that were in the same IS6110-RFLP cluster were also in the same spoligotyping group. Spoligotyping was more discriminative than RFLP analysis for strains with one or two copies of IS6110. RFLP analysis did not discriminate between the nine strains with one or two IS6110 bands with no known epidemiological relation, whereas spoligotyping distinguished between eight different types. IS6I10-RFLP analysis split some of the spoligotyping clusters, particularly when the IS6110 copy number was high. Therefore, we propose a strategy for typing M. tuberculosis strains in which both markers are used.

Modeling the impact of HIV on the spread of tuberculosis in the United States

Tuberculosis (TB) was thought to be safely in decline in the United States in the mid-1980s because the number of cases had dropped by 74% between 1953 and 1985. An increase in TB cases was reported, however, in 1986, and an upward trend in TB incidence has continued. The turnaround in TB is well correlated with the rise of the HIV (human immunodeficiency virus) epidemic. The purpose of this work is to investigate, through the use of mathematical models, the magnitude and duration of the effect that the HIV epidemic may have on TB. Models are developed which reflect the transmission dynamics of both TB and HIV, and the relative merits of these models are discussed. The models are then linked together to form a model for the combined spread of both diseases. A numerical study is performed to investigate the influence of certain key parameters. The effect that HIV will have on the general population is found to be dependent on the contact structure between the general population and the HIV risk groups, as well as a possible shift in the dynamics associated with TB transmission.

Status of tuberculosis infection control programs in Canadian acute care hospitals, 1989 to 1993 - Part 1

OBJECTIVE

To document tuberculosis (TB) prevention and control activities in Canadian acute care hospitals from 1989 to 1993.

DESIGN

Retrospective questionnaire.

PARTICIPANTS

All members of the Community and Hospital Infection Control Association-Canada and l'Association des professionnels pour la prévention des infections who lived in Canada and worked in an acute care hospital received a questionnaire. One questionnaire per hospital was completed.

OUTCOME

The study documented the number of respiratory TB cases admitted to the hospital, the type of engineering and environmental controls available, and the type of occupational tuberculin skin test (TST) screening programs offered by the hospital.

RESULTS

Questionnaires were received from 319 hospitals. Ninety-nine (32%) hospitals did not admit a respiratory TB case during the study. Thirty-one (10%) hospitals averaged six or more TB cases per year. TST results were reported for 47,181 health care workers, and 819 (1.7%) were reported as TST converters; physicians had a significantly higher TST conversion rate than other occupational groups. Most hospitals did not have isolation rooms with air exhausted outside the building, negative air pressure and six or more air changes per hour. Surgical masks were used as respiratory protection by 74% of staff.

CONCLUSIONS

Canadian hospitals can expect to admit TB patients. Participating hospitals did not meet TB engineering or environmental recommendations published in 1990 and 1991. In addition, occupational TB screening programs in 1989 to 1993 did not meet Canadian recommendations published in 1988.

Descriptive profile of tuberculin skin testing programs and laboratory-acquired tuberculosis infections in public health laboratories

The increase in numbers of cases of tuberculosis in the United States has placed greater demands on mycobacteriology laboratory workers to produce rapid and accurate results. The greater number of specimens generated by the increased emphasis on detecting the disease has placed these workers at greater risk of laboratory-acquired infection. We surveyed 56 state and territorial public health laboratories to determine the status of existing tuberculin skin testing (TST) programs and to evaluate the frequency of probable laboratory-acquired tuberculosis for each responding mycobacteriology laboratory. Probable laboratory-acquired infections were determined by each laboratory's evaluation of occupational positions, duties, and employee histories and review of medical records. Two-step TST for new employees was routinely practiced in only 33% of responding laboratories, and mycobacteriology laboratorians were found to be most frequently screened when they were compared to employees of other departments. Of 49 (88%) responding laboratories, 13 reported that 21 employees were TST converters from 1990 to 1994. Seven of these 21 employees were documented to have laboratory-acquired infections based on evaluations by their respective laboratories. Based on Centers for Disease Control and Prevention guidelines, converters are categorized on the basis of both a change in the size of the zone of induration and the age of the person being tested. By the definitions in the guidelines, 14 mycobacteriologists were identified as recent converters, 7 of whom were > or = 35 years of age and 4 of whom were exposed in the laboratory within a 2-year period. Inadequate isolation procedures, the high volume of specimen handling, and faulty ventilation accounted for these laboratory-associated infections. These results suggest that more frequent periodic evaluations based on documented TST conversions for workers in mycobacterial laboratories should be performed, since this population is at increased risk of becoming infected with Mycobacterium tuberculosis. Although general assessments are necessary to accurately and effectively evaluate the risk of tuberculosis transmission, they are especially important for those working in high-risk areas within a public health laboratory.