Nosocomial transmission of Mycobacterium tuberculosis: role of health care workers in outbreak propagation

Tuberculosis among prisoners & health care workers

TB in prisons and among HCW is a major public health concern in countries having high burden of disease. Prompt detection of TB is must in prisons by screening on entry, passive screening, mass screening and contact screening via clinical evaluation, smear microscopy and chest X-rays. The new rapid diagnostic methods - True-NAAT, CBNAAT and Line Probe Assay are important tools in the diagnosis. Implementation of effective preventive measures at every steps in various settings, along with airborne infection control and protective measures for staff must be ensured.

Assessing infection control practices to protect health care workers and patients in Malawi from nosocomial transmission of Mycobacterium tuberculosis

Transmission of Mycobacterium tuberculosis (TB) in health settings threatens health care workers and people living with HIV in sub-Saharan Africa. Nosocomial transmission is reduced with implementation of infection control (IC) guidelines. The objective of this study is to describe implementation of TB IC measures in Malawi. We conducted a cross-sectional study utilizing anonymous health worker questionnaires, semi-structured interviews with facility managers, and direct observations at 17 facilities in central Malawi. Of 592 health care workers surveyed, 34% reported that all patients entering the facility were screened for cough and only 8% correctly named the four most common signs and symptoms of TB in adults. Of 33 managers interviewed, 7 (21%) and 1 (3%) provided the correct TB screening questions for use in adults and children, respectively. Of 592 health workers, only 2.4% had been screened for TB in the previous year. Most (90%) reported knowing their HIV status, 53% were tested at their facility of employment, and half reported they would feel comfortable receiving ART or TB treatment at their facility of employment. We conclude that screening is infrequently conducted and knowledge gaps may undercut its effectiveness. Further, health care workers do not routinely access TB and HIV diagnostic and treatment services at their facility of employment.

Tuberculosis and infection control: a review of the evidence

xposure to patients with infectious tuberculosis is a well-recognised hazard of health care and although the risks associated with this hazard cannot be completely eliminated, they can be controlled and minimised. Risk reduction strategies rely upon a hierarchy of control measures to prevent the nosocomial transmission of tuberculosis in healthcare settings. In this article, the authors discuss the background to these strategies and review the evidence that underpins clinically effective administrative and engineering controls and personal respiratory protection. The authors conclude with recommendations and guide readers to further sources of reliable information.

Risk factors for nosocomial tuberculosis transmission among health care workers

We conducted hospital-based contact investigations of 55 serial sputum smear-positive tuberculosis (TB) patients and 771 health care workers (HCWs) from 2006-2013. HCWs who made contact with TB patients in the absence of appropriate airborne precautions were evaluated using interferon gamma release assays to identify TB infection. Twenty-nine HCWs (3.8%) were newly diagnosed with TB infection. The 10 TB patients responsible for transmission had a duration of contact of >7 days by multivariate analysis.

Diabetes as an increasingly common comorbidity among patient hospitalizations for tuberculosis in the USA

OBJECTIVE

Diabetes is a risk factor for active tuberculosis (TB). The purpose of this paper was to estimate the risk of hospitalization for TB with and without a secondary diagnosis of diabetes in groups with different ethnic backgrounds.

RESEARCH DESIGN AND METHODS

We used the Nationwide Inpatient Sample from 1998 to 2011, identifying all patients with a primary diagnosis of TB and/or a secondary diagnosis of diabetes (type 1 or type 2) or HIV. Next, we performed logistic regression to investigate the association of diabetes status, HIV status, and race (and the interaction of diabetes and race) with the risk of hospitalization with a primary diagnosis of TB. We also included a time covariate, to determine whether potential risk factors changed during the study period.

RESULTS

Controlling for HIV status, diabetes did not increase the odds of TB in white and black patients. However, in Hispanic and Asian/Pacific Islander patients, diabetes increased the odds of TB by a factor of 1.7 (95% CI 1.51 to 1.83). Asian/Pacific Islanders who had diabetes but not HIV experienced 26.4 (95% CI 23.1 to 30.1) times the odds of TB relative to the white males without diabetes or HIV. In addition, the percent of TB cases that belong to these high-risk groups (Asian/Pacific Islander/Hispanic diabetics) has more than doubled from 4.6% in 1998 to 9.6% in 2011.

CONCLUSIONS

In specific demographic groups, diabetes was a strong risk factor for hospital admissions for TB.

Missed Opportunities to Diagnose Tuberculosis Are Common Among Hospitalized Patients and Patients Seen in Emergency Departments

Background. Delayed diagnosis of tuberculosis (TB) may lead to worse outcomes and additional TB exposures.

Methods. To estimate the potential number of misdiagnosed TB cases, we linked all hospital and emergency department (ED) visits in California′s Healthcare Cost and Utilization Project (HCUP) databases (2005–2011). We defined a potential misdiagnosis as a visit with a new, primary diagnosis of TB preceded by a recent respiratory-related hospitalization or ED visit. Next, we calculated the prevalence of potential missed TB diagnoses for different time windows. We also computed odds ratios (OR) comparing the likelihood of a previous respiratory diagnosis in patients with and without a TB diagnosis, controlling for patient and hospital characteristics. Finally, we determined the correlation between a hospital′s TB volume and the prevalence of potential TB misdiagnoses.

Results. Within 30 days before an initial TB diagnosis, 15.9% of patients (25.7% for 90 days) had a respiratory-related hospitalization or ED visit. Also, within 30 days, prior respiratory-related visits were more common in patients with TB than other patients (OR = 3.83; P < .01), controlling for patient and hospital characteristics. Respiratory diagnosis-related visits were increasingly common until approximately 90 days before the TB diagnosis. Finally, potential misdiagnoses were more common in hospitals with fewer TB cases (ρ = −0.845; P < .01).

Conclusions. Missed opportunities to diagnose TB are common and correlate inversely with the number of TB cases diagnosed at a hospital. Thus, as TB becomes infrequent, delayed diagnoses may increase, initiating outbreaks in communities and hospitals.

Tuberculosis transmission from healthcare workers to patients and co-workers: a systematic literature review and meta-analysis

Healthcare workers (HCWs) are at risk of becoming infected with tuberculosis (TB), and potentially of being infectious themselves when they are ill. To assess the magnitude of healthcare-associated TB (HCA-TB) transmission from HCWs to patients and colleagues, we searched three electronic databases up to February 2014 to select primary studies on HCA-TB incidents in which a HCW was the index case and possibly exposed patients and co-workers were screened.We identified 34 studies out of 2,714 citations. In 29 individual investigations, active TB was diagnosed in 3/6,080 (0.05%) infants, 18/3,167 (0.57%) children, 1/3,600 (0.03%) adult patients and 0/2,407 HCWs. The quantitative analysis of 28 individual reports showed that combined proportions of active TB among exposed individuals were: 0.11% (95% CI 0.04-0.21) for infants, 0.38% (95% CI 0.01-1.60) for children, 0.09% (95% CI 0.02-0.22) for adults and 0.00% (95% CI 0.00-0.38) for HCWs. Combined proportions of individuals who acquired TB infection were: 0.57% (95% CI 7.28E-03 - 2.02) for infants, 0.9% (95% CI 0.40-1.60) for children, 4.32% (95% CI 1.43-8.67) for adults and 2.62% (95% CI 1.05-4.88) for HCWs. The risk of TB transmission from HCWs appears to be lower than that recorded in other settings or in the healthcare setting when the index case is not a HCW. To provide a firm evidence base for the screening strategies, more and better information is needed on the infectivity of the source cases, the actual exposure level of screened contacts, and the environmental characteristics of the healthcare setting.

Diagnosis of tuberculosis by using a nucleic acid amplification test in an urban population with high HIV prevalence in the United States

Background

Use of nucleic acid amplification tests (NAAT) for the diagnosis of Mycobacterium tuberculosis (TB) has been recommended on respiratory specimens submitted for acid-fast bacilli (AFB) testing. It also helps distinguish between TB and non-tuberculous mycobacteria (NTM) species in a setting where NTM rates are relatively high. The purposes of this study are to describe the trend and characteristics of all AFB smear-positive respiratory samples that underwent amplified Mycobacterium tuberculosis direct (MTD) testing, a type of NAAT, and to evaluate the clinical utility and necessity of the test for diagnosis of TB in a population with high-HIV prevalence.

Methods

Prospective diagnostic testing and retrospective data analyses were conducted on all AFB smear-positive respiratory samples that underwent MTD testing from 2001 to 2011 at Grady Memorial Hospital (GMH), Atlanta, USA. The test performance was compared to culture.

Results

A total of 2,240 AFB smear-positive specimens from 1,412 patients were tested and analyzed in the study. The proportion of specimens that were culture-positive for TB was 28.5%. Sensitivity, specificity, positive predictive value, and negative predictive value of the MTD were 99.0%, 98.0%, 95.3% and 99.6%, respectively. A downward trend was observed in the yearly numbers as well as the proportions of MTD-positive specimens during the study period (p<0.01). There were 2,027 (90.5%) specimens from patients with known HIV status, of which 70.6% was HIV positive and the majority of them (81.8%) had CD4 counts of less than 200 cells/µL. HIV-positives were more likely to have NTM compared to HIV negatives (67.7% vs. 35.4%, p<0.01).

Conclusion

Despite the decrease in the incidence of TB, NAAT continues to be an accurate and important diagnostic test in a population with high HIV prevalence, and it differentiates TB and NTM organisms.

Transmission of tuberculosis within family-households

OBJECTIVE

The introduction of molecular typing methods in the 1990s to study the epidemiology of tuberculosis (TB) has significantly improved the possibilities of quantifying transmission of Mycobacterium tuberculosis in different human settings. The purpose of this study was to investigate transmission of TB in 35 family-households in Poland.

METHODS

Two PCR-based genotyping methods: spoligotyping and mycobacterial interspersed repetitive unit-variable number of tandem repeats (MIRU-VNTR) typing were used.

RESULTS

Of 78 patients, 49 (63%), could be assigned to intra-household transmission on the basis of identical DNA fingerprints upon a combined typing approach. However, if a single spoligotype spacer or a single MIRU-VNTR locus variation was tolerated in the cluster definition, the intra-household transmission raised to 85% of all patients. For 12 patients in 6 households, the M. tuberculosis isolates were clearly distinct in either spoligotyping or VNTR typing or in both genotyping methods, suggesting that these patients were infected by the sources in the community.

CONCLUSIONS

This study is the first to provide the results of a molecular epidemiological investigation performed within family-households in Poland. It shows the household setting as an important reservoir of M. tuberculosis transmission, and thus argues in favor of routine and extensive screening of the family contacts of TB patients.

Health care-associated infection outbreak investigations by the Centers for Disease Control and Prevention, 1946-2005

Since 1946, Centers for Disease Control and Prevention (CDC) personnel have investigated outbreaks of infections and adverse events associated with delivery of health care. CDC Epidemic Intelligence Service officers have led onsite investigations of these outbreaks by systematically applying epidemiology, statistics, and laboratory science. During 1946-2005, CDC Epidemic Intelligence Service officers conducted 531 outbreak investigations in facilities across the United States and abroad. Initially, the majority of outbreaks involved gastrointestinal tract infections; however, in later years, bloodstream, respiratory tract, and surgical wound infections predominated. Among pathogens implicated in CDC outbreak investigations, Staphylococcus aureus, Enterococcus species, Enterobacteriaceae, nonfermentative Gram-negative bacteria, or yeasts predominated, but unusual organisms (e.g., the atypical mycobacteria) were often included. Outbreak types varied and often were linked to transfer of colonized patients or health care personnel between facilities (multihospital outbreaks), national distribution of contaminated products, use of invasive medical devices, or variances in practices and procedures in health care environments (e.g., intensive care units, water reservoirs, or hemodialysis units). Through partnerships with health care facilities and local and state health departments, outbreaks were terminated and lives saved. Data from investigations invariably contributed to CDC-generated guidelines for prevention and control of health care-associated infections.

Epidemic Intelligence Service investigations of respiratory illness, 1946-2005

Infectious respiratory pathogens were the suspected cause of 480 outbreaks investigated by the Centers for Disease Control and Prevention's Epidemic Intelligence Service officers during 1946-2005. All epidemic-assistance investigation reports and associated articles from scientific journals were reviewed. Investigations identified 25 different infectious respiratory pathogens including, most frequently, tuberculosis, influenza, and legionellosis. Other bacterial-, viral-, and fungal-related pathogens also were identified. Epidemic-assistance investigations were notable for first identifying Legionnaires disease and Pontiac fever, hantavirus pulmonary syndrome, and new strains of human and avian influenza, as well as emerging challenges (e.g., multidrug-resistant tuberculosis and pneumococcus). The investigations provided clinical insights into such diseases as pulmonary anthrax and identified high risks of serious respiratory illnesses for persons infected with human immunodeficiency virus, other immunocompromised persons, and persons with diabetes. They identified settings placing persons at high risk of acquiring disease, including nursing homes, prisons, homeless shelters, and hospitals. Travel also placed persons at risk. Key environmental factors related to spread of diseases and occupational risks for brucellosis and psittacosis were identified. The outbreak investigations constitute a wealth of prevention experience and provide the basis for recommendations to mitigate outbreaks and reduce future risks.

Protecting health care workers from tuberculosis: a 10-year experience

BACKGROUND

Cook County Hospital (CCH) is an inner-city, large public hospital. Twenty-five percent of Chicago's tuberculosis (TB) cases are diagnosed at CCH. We wanted to review and analyze interventions implemented over a 10-year period at CCH to prevent TB infection in health care workers.

METHODS

We performed a retrospective review of interventions to prevent health care-associated tuberculosis. We collated and analyzed tuberculin skin test conversions in our employees for the same time period.

RESULTS

From 1990 to 2002, we cared for over 1800 in-patients with tuberculosis. During 1992-1997, multiple interventions to eliminate health care-associated spread of tuberculosis were implemented. Tuberculin skin test conversions in our employees decreased markedly from January 1994 through December 2002. Two drops in tuberculin skin test conversion rates occurred: one after introduction of basic administrative and engineering controls and a second after we experienced a decrease in missed TB cases and the introduction of N-95 personal respirators with 1-time qualitative fit testing.

CONCLUSION

Our annual health care worker skin test conversion rate fell significantly when our primary interventions were relatively simple administrative and engineering controls. Educating health care workers to promptly recognize patients with TB and placing exhaust fans to create negative-pressure respiratory isolation rooms were probably our 2 most potent infection control measures.

Epidemiological profile of tuberculosis cases reported among health care workers at the University Hospital in Vitoria, Brazil

OBJECTIVE

To describe the epidemiological profile of tuberculosis cases reported among health care workers in the Tuberculosis Control Program of the Cassiano Antonio of Moraes University Hospital in Vitoria, Brazil.

METHODS

A retrospective descriptive study of secondary data was conducted between 2002 and 2006.

RESULTS

Twenty-five cases of health care workers with tuberculosis were reported: 8 in nursing technicians (32%); 4 in doctors (16%); 3 in nurses (12%); 2 in radiology technicians (8%) and 8 in professionals from other categories (32%). Of those 25 health care workers, 14 (56%) were male and 11 (44%) were female. The incidence of the disease was highest among those from 35 to 39 years of age. The predominant clinical presentation was extrapulmonary (12 cases, 48%), followed by pulmonary (11 cases, 44%) and a combination of the two (2 cases, 8%). Regarding comorbidities, AIDS, alcoholism and smoking, respectively, were present in 33.3% of the study population. Outcomes were as follows: 22 cases of cure (88%); 2 transfers (8%); and 1 death (4%). The proportion of health care workers diagnosed with tuberculosis in the period studied was 2.53%.

CONCLUSIONS

The results show the need for heath care workers who work in the tuberculosis control program to fill out the field "professional occupation" on the tuberculosis case registry database reporting forms. In addition, this situation draws attention to the need to implement an occupational tuberculosis control program.

Delayed suspicion, treatment and isolation of tuberculosis patients in pulmonology/infectious diseases and non-pulmonology/infectious diseases wards

BACKGROUND/PURPOSE

Delayed diagnosis and isolation increases the risk of nosocomial transmission of tuberculosis (TB). To assess the risk of delayed management of TB, we analyzed the risk factors of prolonged delay in isolation of smear-positive TB patients in pulmonology/infectious diseases and other wards in a tertiary teaching hospital.

METHODS

We enrolled smear-positive TB patients aged > 16 years with delayed respiratory isolation following hospitalization. Medical records were reviewed retrospectively. Time intervals between admission, order of sputum acid-fast staining, initiation of anti-tuberculous treatment and isolation were compared between pulmonology/infectious diseases wards (PIWs) and other wards. Risk factors were analyzed in patients with prolonged isolation delay of > 7 days in individual groups.

RESULTS

Isolation was delayed in 191 (73.7%) of 259 hospitalized smear-positive TB patients. Median suspicion, treatment and isolation delays were 0, 3 and 4 days in PIWs and 1, 5 and 7 days in other wards. For patients admitted to non-PIWs, atypical chest radiographs, symptoms without dyspnea or not being admitted from the emergency department (ED) were risk factors for prolonged isolation delay exceeding 7 days. The only risk factor for delayed isolation in patients admitted to PIWs was age >or= 70 years.

CONCLUSION

Delays in suspicion, treatment and isolation of TB patients were longer in non-PIWs. Clinicians should be alert to those admitted to non-PIWs with atypical chest radiographs, atypical symptoms, or not admitted from the ED.

Tuberculose em profissionais de saúde: um novo olhar sobre um antigo problema

Este artigo tem o objetivo de contribuir para o debate sobre a transmissão nosocomial da TB em profissionais de saúde em um país onde esta é endêmica. Verificamos que até 1900 não se aceitava que os profissionais envolvidos no cuidado de pacientes portadores de TB pudessem ser mais susceptíveis à infecção pelo bacilo que a população geral. Vários estudos entre 1920 e 1930 apresentaram achados significativos nas taxas de conversão do teste tuberculínico dos estudantes da área de saúde, mas a maioria dos clínicos continuava se recusando a reconhecer a suscetibilidade dos profissionais de saúde em relação à TB. Nos diferentes locais onde o cuidado ao paciente com TB foi implantado, os profissionais de saúde são descritos como uma população especialmente exposta ao risco de contrair a infecção e adoecer. É urgente que a comunidade científica e os trabalhadores de saúde se organizem, que se reconheçam como uma população sujeita ao risco de adoecimento, e que ações se efetivem no sentido de minimizar os riscos potenciais nos locais onde acontece o cuidado a pacientes com TB.

Nosocomial tuberculosis in India

India is well positioned to address the problem of nosocomial tuberculosis transmission.

Most high-income countries implement tuberculosis (TB) infection control programs to reduce the risk for nosocomial transmission. However, such control programs are not routinely implemented in India, the country that accounts for the largest number of TB cases in the world. Despite the high prevalence of TB in India and the expected high probability of nosocomial transmission, little is known about nosocomial and occupational TB there. The few available studies suggest that nosocomial TB may be a problem. We review the available data on this topic, describe factors that may facilitate nosocomial transmission in Indian healthcare settings, and consider the feasibility and applicability of various recommended infection control interventions in these settings. Finally, we outline the critical information needed to effectively address the problem of nosocomial transmission of TB in India.

Tuberculin reactivity among health care workers in nonhospital settings

BACKGROUND

We used workers' compensation data to identify health care workers at risk of tuberculosis exposure in the hospital and nonhospital environment.

METHODS

We identified State Fund workers' compensation claims having a documented tuberculin skin test (TST) conversion (size >or=10 mm) with a previous negative skin test between 1996 and 2000 in the State of Washington.

RESULTS

Health care workers experienced an overall accepted workers' compensation claim rate of 2.3 claims/10,000 full-time equivalent employees (FTEs) per year for tuberculin reactivity. Receptionists accounted for the largest number, with 18.4% tuberculin reactivity claims. The number of tuberculin reactivity claims was the highest for offices and clinics of doctors of medicine (3.7 per 10,000 FTEs), followed by medical laboratories (2.6 per 10,000 FTEs).

CONCLUSION

This study allowed characterization of employees in various nonhospital health services locations with higher number of tuberculin reactivity.

Accuracy of healthcare worker recall and medical record review for identifying infectious exposures to hospitalized patients

OBJECTIVE

To determine the validity of using healthcare worker (HCW) recall of patient interactions and medical record review for contact tracing in a critical care setting.

DESIGN

Trained observers recorded the interactions of nurses, respiratory therapists, and service assistants with study patients in a medical-surgical intensive care unit. These observers' records were used as the reference standard to test the criterion validity of using HCW recall data or medical record review data to identify exposure characteristics. We assessed the effects of previous quarantine of the HCW (because of possible exposure) and the availability of patients' medical records for use as memory aids on the accuracy of HCW recall.

SETTING

A 10-bed medical-surgical intensive care unit at Mount Sinai Hospital in Toronto, Ontario.

PATIENTS

Thirty-six HCWs observed caring for 16 patients, for a total of 55 healthcare worker shifts.

RESULTS

Recall accuracy was better among HCWs who were provided with patient medical records as memory aids (P<.01). However, HCWs tended to overestimate exposures when they used patient medical records as memory aids. For 6 of 26 procedures or care activities, this tendency to overestimate was statistically significant (P<.05). Most HCWs with true exposures were identified by means of this technique, despite the overestimations. Documentation of the activities of the 4 service assistants could not be found in any of the patients' medical records. Similarly, the interactions between 6 (19%) of 32 other patient-HCW pairs were not recorded in patients' medical records.

CONCLUSIONS

Data collected from follow-up interviews with HCWs in which they are provided with patient medical records as memory aids should be adequate for contact tracing and for determining exposure histories. Neither follow-up interviews nor medical record review alone provide sufficient data for these purposes.

Increased efficiency in evaluating patients with suspected tuberculosis by use of a dedicated airborne infection isolation unit

BACKGROUND

The resurgence of tuberculosis (TB) in the 1980s and early 1990s in the United States was also accompanied by numerous hospital outbreaks of TB and nosocomial transmission to health care workers.

OBJECTIVE

To determine whether a dedicated airborne infection isolation (AII) unit improves efficiency in "ruling-out" patients suspected of having pulmonary TB. This is important because, to prevent nosocomial transmission of TB, the number and ratio of patients isolated who are subsequently found to have TB is much higher than those "ruled out" and have TB excluded.

METHODS

A prospective cohort study was conducted of all patients 18 years and older admitted to respiratory isolation during 3 separate time periods before and after opening of an 26-bed AII unit in a 1000-bed, public, university-affiliated, innercity hospital.

RESULTS

A total of 879 patients were admitted during the 3 study periods. Most were black and males (87%, 72%, respectively). The median age was 42 years, and 70% of patients included in the study were HIV positive. Among patients who "ruled out," ie, TB was excluded by having 3 negative AFB smears of respiratory specimens for TB, there was a significant decrease in time from 5.0 days in period I to 3.3 days in period III (P < .0001). In period III, patients who were admitted to rule out TB in areas outside of the AII unit in other wards of the hospital required a significantly longer period to have TB excluded: 5.9 days compared with 3.5 on the AII unit (P = .0015).

CONCLUSION

The decrease in isolation time after the opening of the dedicated AII unit demonstrates that a concerted effort to rule patients out by having nurses and respiratory therapists trained in tuberculosis control is efficacious and efficient and results in significant cost savings.

Prevalence and incidence of Mycobacterium tuberculosis infection in nursing students in Vitória, Espírito Santo

This prospective study evaluated the incidence of Mycobacterium tuberculosis infection among nursing students at the Federal University of Espírito Santo, using the purified protein derivative test. In parallel, we evaluated whether knowledge on tuberculosis transmission mechanisms had any impact on nursing students' attitudes in relation to the risk of tuberculosis infection. The incidence of tuberculin conversion was 10.5% per year (p=0.035, 95% CI = 3.63-17.43), whereas the expected conversion rate in the overall population in Brazil is 0.5% per year. These results indicate nursing students as a group at risk for TB infection. Among the risk factors studied only the use of NIOSH95 masks was associated with protection against infection (RR=0.2). Furthermore there was no statistical difference among students that PPD converted and those who remained negative regarding disease knowledge and the existence of adequate facilities for patient hospitalization. Our data reinforces the need for implementing special biosafety programs targeting this professional group.

Fast ligation-mediated PCR, a fast and reliable method for IS6110-based typing of Mycobacterium tuberculosis complex

IS6110 restriction fragment length polymorphism (RFLP) analysis is the most widely applied method for strain differentiation of Mycobacterium tuberculosis complex. We have previously described mixed-linker PCR, an IS6110-based PCR method that favorably compared with other typing methods for M. tuberculosis complex according to reproducibility and ability to differentiate between strains. Here we report the further development of this method, called fast ligation-mediated PCR (FLiP), which allows analysis of strains within one working day and starting from less than 1 ng of mycobacterial DNA or a crude cell lysate. Blinded analysis of a standard set of 131 M. tuberculosis complex and nontuberculous isolates showed the ability to differentiate 81 types among 90 M. tuberculosis complex isolates with 84 different IS6110 RFLP fingerprint patterns and detected 97% of the 31 duplicate samples. We suggest that FLiP can serve to rapidly detect chains of transmission prior to starting high-throughput analysis or standard IS6110 RFLP. It may as well serve as a secondary typing technique for other, non-IS6110-based methods.

American Thoracic Society/Centers for Disease Control and Prevention/Infectious Diseases Society of America: Controlling Tuberculosis in the United States

During 1993-2003, incidence of tuberculosis (TB) in the United States decreased 44% and is now occurring at a historic low level (14,874 cases in 2003). The Advisory Council for the Elimination of Tuberculosis has called for a renewed commitment to eliminating TB in the United States, and the Institute of Medicine has published a detailed plan for achieving that goal. In this statement, the American Thoracic Society (ATS), Centers for Disease Control and Prevention (CDC), and the Infectious Diseases Society of America (IDSA) propose recommendations to improve the control and prevention of TB in the United States and to progress toward its elimination. This statement is one in a series issued periodically by the sponsoring organizations to guide the diagnosis, treatment, control, and prevention of TB. This statement supersedes the previous statement by ATS and CDC, which was also supported by IDSA and the American Academy of Pediatrics (AAP). This statement was drafted, after an evidence-based review of the subject, by a panel of representatives of the three sponsoring organizations. AAP, the National Tuberculosis Controllers Association, and the Canadian Thoracic Society were also represented on the panel. This statement integrates recent scientific advances with current epidemiologic data, other recent guidelines from this series, and other sources into a coherent and practical approach to the control of TB in the United States. Although drafted to apply to TB-control activities in the United States, this statement might be of use in other countries in which persons with TB generally have access to medical and public health services and resources necessary to make a precise diagnosis of the disease; achieve curative medical treatment; and otherwise provide substantial science-based protection of the population against TB. This statement is aimed at all persons who advocate, plan, and work at controlling and preventing TB in the United States, including persons who formulate public health policy and make decisions about allocation of resources for disease control and health maintenance and directors and staff members of state, county, and local public health agencies throughout the United States charged with control of TB. The audience also includes the full range of medical practitioners, organizations, and institutions involved in the health care of persons in the United States who are at risk for TB.

[Epidemiological survey of a suspected nosocomial case of tuberculosis by spoligotyping]

Transmission of tuberculosis within hospitals has been increasingly recognized as a hazard for patients and health care workers. A case of pulmonary tuberculosis was detected in September 2003 in a nursing auxiliary working at Avicenne's Hospital. This 49 year-old woman was considered infected since April 2003. During this 6 months period, she worked in 23 distinct hospital units and could have contaminated patients and hospital staffs. The epidemiological survey was comprised for 1735 individuals (701 hospital staffs and 1034 patients). It encompassed clinical, para-clinical investigations and bacteriological investigations. Furthermore, between January 2003 and September 2004, a systematic comparison of 62 Mycobacterium tuberculosis strains isolated in the hospital was conducted by spoligotyping, a molecular typing method in order to access an eventual transmission. The nursing auxiliary's strain clearly showed a distinct spoligotype from the other investigated strains. This spoligotype was unique in the international spoligotype database. In this large epidemiological survey of a case of suspected nosocomial of tuberculosis, spoligotyping appeared as an interesting, easy and rapid method of molecular typing. It allowed to demonstrate that the nursing auxiliary tuberculosis case was unrelated to the others cases of tuberculosis diagnosed in the hospital during this period.

Risk of tuberculous infection among healthcare workers in a tertiary-care hospital in Ankara, Turkey

OBJECTIVE

To determine risk factors for tuberculin skin test (TST) positivity among healthcare workers (HCWs).

DESIGN

Two-step TST was performed in 2002.

SETTING

Tertiary-care hospital in Ankara, Turkey.

PARTICIPANTS

A sample of 491 hospital HCWs were included. Information related to demographics, profession, work duration, department, and individual and family history of tuberculosis (TB) was obtained by a structured questionnaire.

RESULTS

Four hundred eight (83%) had two-step TST positivity. On multivariate analysis, male physicians (relative risk [RR], 1.5; 95% confidence interval [CI95], 1.23-1.69; P = .001), nurses (RR, 1.5; CI95, 1.29-1.66; P = .005), radiology technicians (RR, 1.7; CI95, 1.35-1.73; P = .002), laboratory technicians (RR, 1.6; CI95, 1.3-1.74; P = .007), and male housekeepers (RR, 1.6; (HCWs). CI95, 1.38-1.7; P < .001) had a higher risk than did female physicians. Among laboratory technicians, radiology technicians had the highest TST positivity (85%). HCWs working for less than 1 year (RR, 0.8; CI95, 0.72-0.98; P = .027) had a lower risk of infection. The HCWs having bacille Calmette-Guerin vaccination (RR, 1.12; CI95, 1.08-1.45) had higher TST positivity.

CONCLUSION

Male physicians, nurses, and laboratory technicians had increased risk of Mycobacterium tuberculosis infection in this setting, but community exposure likely accounted for most infections.

Factors influencing health care workers' adherence to work site tuberculosis screening and treatment policies

BACKGROUND

Despite the known risk of tuberculosis (TB) to health care workers (HCWs), research suggests that many are not fully adherent with local TB infection control policies. The objective of this exploratory study was to identify factors influencing HCWs' adherence to policies for routine tuberculin skin tests (TSTs) and treatment of latent TB infection (LTBI).

METHODS

Sixteen focus groups were conducted with clinical and nonclinical staff at 2 hospitals and 2 health departments. Participants were segmented by adherence to TST or LTBI treatment policies. In-depth, qualitative analysis was conducted to identify facilitators and barriers to adherence.

RESULTS

Among all focus groups, common themes included the perception that the TST was mandatory, the belief that conducting TSTs at the work site facilitated adherence, and a general misunderstanding about TB epidemiology and pathogenesis. Adherent groups more commonly mentioned facilitators, such as the perception that periodic tuberculin skin testing was protective and the employee health (EH) provision of support services. Barriers, such as the logistic difficulty in obtaining the TST, the perception that LTBI treatment was harmful, and a distrust of EH, emerged consistently in nonadherent groups.

CONCLUSIONS

This information may be used to develop more effective interventions for promoting HCW adherence to TB prevention policies. Informed efforts can be implemented in coordination with reevaluations of infection control and EH programs that may be prompted by the publication of the revised TB infection control guidelines issued by the Centers for Disease Control and Prevention in 2005.

Characterization of rifampicin-resistant Mycobacterium tuberculosis in Taiwan

Sixty-three rifampicin-resistant (Rif(r)) isolates of Mycobacterium tuberculosis from Kaohsiung, Taiwan, were analysed for mutations in the core region (69 bp, codons 511-533) of the rpoB gene. Some 84.1 % (53/63) of the resistant isolates showed mutations in this region, especially in codons 531 (41.5 %), 526 (18.9 %), 516 (15.1 %) and 533 (7.5 %). Five novel alleles of a total of 16 different types of mutations were identified in Rif(r) isolates. Ten Rif(r) isolates (15.9 %) exhibited no mutations in the core region of rpoB. Also, they did not show mutations in another 365 bp fragment (codons 99-220) of rpoB. The agar proportion method was used to determine the relationship between the degree of rifampicin resistance and alterations in the core region of rpoB. The results revealed that the mean MIC was 92.38 micro g ml(-1) for the 53 isolates with a mutation in the core region, whereas the mean MIC of the other 10 isolates without mutations was only 24.8 micro g ml(-1). This indicates that the isolates with mutations in the core region had higher levels of resistance than those without mutations in this region. IS6110 restriction fragment length polymorphism (RFLP) was used for typing of 55 Rif(r) M. tuberculosis isolates. Isolates contained two to 19 copies of IS6110, with sizes ranging from 600 to 16 000 bp. The majority (85 %) contained six to 16 copies. No strains lacking IS6110 were found. A total of 54 of 55 RFLP types were defined at the 90 % similarity level. The observation of varied IS6110-associated banding patterns indicates that an outbreak of drug-resistant tuberculosis did not occur in this area.

Risk of tuberculin skin test conversion among health care workers: occupational versus community exposure and infection

A prospective observational cohort study to assess rates of and risk factors for tuberculin skin test (TST) conversion among health care workers (HCWs) was conducted at an urban hospital located in a high tuberculosis-incidence area in 1994-1998. All hospital employees undergoing required testing every 6 months were included. A total of 69 (1.2%) of 5773 susceptible employees had a documented TST conversion (overall rate, 0.38 per 100 person-years worked). No significant difference existed in conversion rates among employees with frequent, limited, or no patient contact. HCWs with a TST conversion lived in zip codes with higher tuberculosis case rates (P< or =.05). In multivariate analysis, TST conversion was associated with history of bacille Calmette-Guérin vaccination (relative risk [RR], 11.63), annual salary <$20,000 (RR, 3.67), and increasing age. In the setting of an effective tuberculosis infection-control program, TST conversion rates were low, and risk of conversion among HCWs was associated most strongly with nonoccupational factors.

Tuberculin skin test conversion among medical students at a teaching hospital in Rio de Janeiro, Brazil

OBJECTIVE

To describe the cumulative incidence of and risk factors for tuberculosis (TB) infection among medical students.

DESIGN

In 1999, a cohort study of medical students with negative results (induration < 10 mm) on tuberculin skin test (TST) was performed. Students who had undergone two-step testing in 1998 were retested.

SETTINGS

University and teaching hospital and referral center for TB and acquired immunodeficiency syndrome, and the Health Sciences Building of the Medical School of the Federal University of Rio de Janeiro, Brazil.

PARTICIPANTS

A sample of 618 consecutive medical students with negative TST results who had been tested 12 months before were approached. Information about sociodemographic characteristics, bacille Calmette-Guérin vaccination history, and potential exposures to TB was obtained using a standardized questionnaire. Four hundred fourteen (67%) students completed the study. Students were at two different levels of their training programs (juniors = no contact with patients; seniors = intensive contact with patients).

RESULTS

Of 414 participants, 16 (3.9%; 95% confidence interval, 1.06% to 12.1%) had converted to a positive reaction after 1 year. In a multivariate logistic regression analysis, higher level of clinical training was confirmed to be an independent factor associated with TST conversion (odds ratio, 4.77; 95% confidence interval, 1.01 to 22.46; P= .048).

CONCLUSION

Senior medical students are at increased risk of Mycobacterium tuberculosis infection in this setting. Therefore, a program of routine tuberculin skin testing and specific TB infection control guidelines are needed for this population.

Historical risks of tuberculin skin test conversion among non-physician staff at a large urban hospital

BACKGROUND

Nosocomial transmission of Mycobacterium tuberculosis among workers at a 1000-bed inner-city hospital led to an extensive evaluation of this risk among workers with potential exposure to TB patients or laboratory specimens.

METHODS

Retrospective cohort study to determine the incidence and risk of tuberculin skin test (TST) conversions among workers employed 1/1/90 to 9/30/92.

RESULTS

Personal, community, and occupational risk factors were evaluated in 2,362 workers with potential M. tuberculosis exposure and 886 workers with no known exposure. The 33-month cumulative rate of TST conversion was 5.8% for potentially exposed workers and 2.0% for controls (RR 3.6; 95% CI; 2.2-5.8). Among workers with potential M. tuberculosis exposure, statistically significantly elevated risks were found for nurses, laboratory technicians, pharmacy workers, phlebotomists, housekeepers, clerks, emergency room workers, and emergency responders.

CONCLUSIONS

Workers with patient contact and those employed in certain occupational groups were at increased risk for occupational M. tuberculosis infection.

Tuberculin skin testing surveillance of health care personnel

To estimate the incidence of and assess risk factors for occupational Mycobacterium tuberculosis transmission to health care personnel (HCP) in 5 New York City and Boston health care facilities, performance of prospective tuberculin skin tests (TSTs) was conducted from April 1994 through October 1995. Two-step testing was used at the enrollment of 2198 HCP with negative TST results. Follow-up visits were scheduled for every 6 months. Thirty (1.5%) of 1960 HCP with >/=1 follow-up evaluation had TST conversion (that is, an increase in TST induration of >/=10 mm). Independent risk factors for TST conversion were entering the United States after 1991 and inclusion in a tuberculosis-contact investigation in the workplace. These findings suggest that occupational transmission of M. tuberculosis occurred, as well as possible nonoccupational transmission or late boosting among foreign-born HCP who recently entered the United States. These results demonstrate the difficulty in interpreting TST results and estimating conversion rates among HCP, especially when large proportions of foreign-born HCP are included in surveillance.

Tuberculin skin testing of physicians at a midwestern teaching hospital: a 6-year prospective study

The epidemiology of tuberculin reactivity among physicians practicing in regions of moderate tuberculosis prevalence is unknown. We prospectively assessed the epidemiology of tuberculin skin test (TST) reactivity among physicians in training in St. Louis between 1992 and 1998. Of 1574 physicians who were tested, 267 (17%) had positive TST results. Older age, birth outside of the United States, prior bacille Calmette-Guérin (BCG) vaccination, and practice in the fields of medicine, anesthesiology, or psychiatry were associated with a positive TST result. Among physicians born in the United States, 63 (5.7%) had positive TST results. Among physicians with > or = 2 documented TSTs, 12 had conversion to a positive TST (1.6%; 1.03 conversions per 100 person-years). Physicians in this study had a high rate of tuberculin reactivity, despite a low conversion rate. The relationship between TST conversion and birth outside of the United States and BCG vaccination suggests a booster phenomenon rather than true new TST conversions.

Hospitals in England are failing to follow guidance for tuberculosis infection control - results of a National Survey

Tuberculosis outbreaks can occur in hospitals if adequate infection control is not in place. UK guidelines on the prevention of tuberculosis transmission have recently been published. A national survey of acute NHS Trusts in England was conducted to evaluate whether tuberculosis infection control in hospitals is consistent with the new guidance. There was a 72% response rate (144 NHS Trusts). Sixty percent of Trusts had updated their tuberculosis infection control plans since the new guidance was published. Even trusts with updated plans failed to meet guidance in many areas. Thirty-five percent of Trusts had negative pressure facilities for the isolation of infectious tuberculosis patients. Depending on the risk category of the patient, 45-67% of Trusts met guidelines for isolation of infectious patients. Patients frequently left isolation for non-medical reasons. Only a minority of Trusts complied with guidance for respiratory protection of staff and visitors. These findings suggest that many Trusts remain at risk of outbreaks of tuberculosis and therefore need to re-examine infection control procedures and the availability of isolation facilities.

Predictors of tuberculosis transmission in prisons: an analysis using conventional and molecular methods

OBJECTIVE

To determine the tuberculosis (TB) transmission patterns within the prison system in Catalonia, conventional epidemiological techniques were combined with DNA fingerprinting of Mycobacterium tuberculosis.

METHODS

IS6110- and polymorphic GC-rich repeat sequence (PGRS)-based restriction fragment length polymorphism (RFLP) were combined with epidemiological studies to assess the relatedness of isolates from all patients with confirmed TB at five prisons in the province of Barcelona (Catalonia, Spain), between 1 July 1994 and 31 December 1996. Risk factors for transmission were analysed to a logistic regression. The extent of drug-resistant TB was also assessed.

RESULTS

The incidence of TB during the study period was 2775 cases per 100,000 inmate years. Of the 247 culture-positive cases, 126 (51%) appeared to have active TB as a result of recent transmission. Using conventional epidemiological methods, 14 active chains of transmission were identified in prison involving 65 isolates (52% of clustered patients). A lengthy history of imprisonment [odds ratio (OR) 2.8, 95% confidence interval (CI) 1.52-5.11] and pulmonary TB (OR 2.36, 95% CI 1.17-4.75) were independently associated with clustering. Low rates of both initial (2.9%) and acquired drug resistance (5.8%) were identified and there was no evidence of the transmission of drug-resistant TB.

CONCLUSION

In the prison system studied, the recent transmission of TB contributes substantially to the overall incidence of the disease. Both lengthy incarcerations and delays in identifying inmates with pulmonary symptoms play a key role in this recent transmission. Directly observed therapy (DOT) is a critical control strategy for reducing the emergence of drug resistance and for avoiding the transmission of resistant organisms.

Evaluation of a western blot test as a potential screening tool for occupational exposure to Mycobacterium tuberculosis in health care workers

Health care workers (HCWs) have a higher than average risk for contracting Mycobacterium tuberculosis (MTB) infection and tuberculosis (TB). No markers of MTB-exposure are available, and TB risk assessment is performed by tuberculin screening, identifying individuals with acquired MTB infection. This study evaluated a western blot (WB) anti-M. bovis A60 complex antibody as a MTB-exposure marker. WB reactivity was evaluated on 127 exposed and 28 non-exposed HCWs from four divisions of the Policlinico Hospital of Modena, and 140 non-exposed bacille Calmette-Guérin-vaccinated controls. Excess of occupational TB risk according to the Occupational Safety and Health Administration (OSHA) was calculated in each division. WB-positivity (%) was: (1) significantly higher in exposed HCWs compared with non-exposed (72% vs 25%, P < 0.00001), (2) highly related (r = 0.99) to OSHA risk excess in all divisions, (3) higher than non-exposed in HCWs with short (< 5 years) MTB-exposure (purified protein derivative [PPD], P > 0.18; WB, P < 0.04). PPD-positivity (%) was higher than controls only in HCWs with longer (> 5 years) MTB-exposure. The study suggests that the WB antibody might represent a more sensitive biological marker of MTB contact among exposed HCWs, related to the level of TB risk and detectable earlier than the PPD skin test, thus providing new tools for TB risk assessment in health care facilities.

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.

Tuberculosis in the inner city: impact of a continuing epidemic in the 1990s

Tuberculosis cases have recently declined in the United States, renewing interest in disease elimination. We examined the epidemiology of tuberculosis from 1991 through 1997 at an inner-city public hospital and assessed population-based tuberculosis rates by ZIP code in the 8 metropolitan Atlanta counties. During the 7 years, 1378 new patients had tuberculosis diagnosed at our hospital (mean, 197 patients/year), accounting for 25% of tuberculosis cases in Georgia. Coinfection with human immunodeficiency virus (HIV) was common, but a significant decrease in the proportion of HIV-infected patients with tuberculosis was noted over time. Most patients were members of a minority group (93%) and were born in the United States (96%). Two inner-city ZIP code areas had annual tuberculosis rates >120 cases per 100,000 persons, and 8 ZIP code areas had annual rates of 47-88 cases per 100,000 persons between 1993 and 1997, compared with the annual national average of 8.7 cases per 100,000 persons. Our hospital continues to care for large numbers of tuberculosis patients, and rates of tuberculosis remain high in the inner city. These data mandate a concentration of efforts and resources in urban locations if tuberculosis control and elimination is to be achieved in the United States.

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.

A simulation model for occupational tuberculosis transmission

A simulation model of tuberculosis (TB) transmission among hospital employees is described. A hypothetical cohort of 1000 workers was divided into low-, medium-, and high-risk groups. The number of TB patients admitted daily was treated as a Poisson random variable. A patient imparted a daily infection risk that was identical for all workers within a risk group but that varied between risk groups. In some scenarios, infected employees were assigned a daily risk of developing TB disease. If disease developed, the individual remained on the job for 3 calendar weeks and imparted a substantial infection risk to 25 close contacts. Simulations were run over 5-year intervals. Cumulative infection incidence increased over time and with more TB patients admitted. Given a scenario in which there were 600, 300, and 100 susceptibles in the low-, medium-, and high risk groups, respectively, 50 TB patients admitted annually and accounting for disease among infected employees, at 5 years there were approximately 100 primary infections (due to infection by patients), 40 secondary infections (due to infection by diseased coworkers), five primary disease cases, and two secondary disease cases. The input parameter values and simulation outcomes were reasonably consistent with the sparse information reported in the literature.

Prevention of nosocomial transmission of Mycobacterium tuberculosis

The recent resurgence of TB together with the ongoing HIV epidemic has resulted in a larger number of infectious TB patients being admitted to US health care facilities. These patients have become a source for both nosocomial (patient-to-patient) and occupational (patient-to-health care worker) M. tuberculosis transmission. Infectious MDR-TB patients serve as even greater potential infectious sources because they often remain AFB smear and culture positive for months to years. The keys to the prevention of nosocomial and occupational transmission of M. tuberculosis is conducting a risk assessment for each area of the facility and instituting appropriate control measures, having a high index of suspicion by clinicians for infectious TB in those who present with consistent signs and symptoms, rapid triage of such patients to isolation areas and their appropriate clinical work-up, and the institution of effective antituberculous therapy. Infection control personnel should ensure that infectious TB patients are isolated in appropriate isolation rooms (i.e., negative pressure, greater than or equal to 6 ACH, and direct external exhaust of the room air). Health care workers with infectious TB patient contact should be instructed in the epidemiology of M. tuberculosis transmission, the role of respirators in protecting the health care worker from airborne inoculation, and the importance of periodic health care worker TST. The nosocomial TB outbreaks in the 1980s and 1990s document that M. tuberculosis can be transmitted to both patients and health care workers in US health care facilities when appropriate infection control measures are not fully implemented. Follow-up studies at some of these institutions, however, document that when infection control measures similar to the 1990 or 1994 CDC TB Guidelines are fully implemented, M. tuberculosis transmission to both patients and health care workers can be reduced or eliminated. Protection of both patients and health care workers from M. tuberculosis infection is dependent on an understanding and full implementation of the 1994 CDC TB Guidelines.

The changing face of the epidemiology of tuberculosis due to molecular strain typing--a review

About one third of the world population is infected with tubercle bacilli, causing eight million new cases of tuberculosis (TB) and three million deaths each year. After years of lack of interest in the disease, World Health Organization recently declared TB a global emergency and it is clear that there is need for more efficient national TB programs and newly defined research priorities. A more complete epidemiology of tuberculosis will lead to a better identification of index cases and to a more efficient treatment of the disease. Recently, new molecular tools became available for the identification of strains of Mycobacterium tuberculosis (M. tuberculosis), allowing a better recognition of transmission routes of defined strains. Both a standardized restriction-fragment-length-polymorphism-based methodology for epidemiological studies on a large scale and deoxyribonucleic acids (DNA) amplification-based methods that allow rapid detection of outbreaks with multidrug-resistant (MDR) strains, often characterized by high mortality rates, have been developed. This review comments on the existing methods of DNA-based recognition of M. tuberculosis strains and their peculiarities. It also summarizes literature data on the application of molecular fingerprinting for detection of outbreaks of M. tuberculosis, for identification of index cases, for study of interaction between TB and infection with the human immuno-deficiency virus, for analysis of the behavior of MDR strains, for a better understanding of risk factors for transmission of TB within communities and for population-based studies of TB transmission within and between countries.

Hospital infection control practices for tuberculosis

Although completely eliminating the risk for transmission of M. tuberculosis in all health-care facilities may not be possible, adherence to the principles outlined in the CDC guidelines should reduce the risk to persons in such settings. The guidelines are designed to help health-care facilities develop an infection-control plan tailored to the individual circumstances and risk in each facility. The key to maintaining an effective TB infection control plan is periodic evaluation of the plan, with reassessment of risk and revision of the plan accordingly.

Current perspectives on multidrug-resistant bacteria. Epidemiology and control

Antimicrobial resistance in bacteria has diminished the availability of effective antimicrobial agents. Knowledge of epidemiology, mechanisms of resistance, and new diagnostic modalities can help to identify and treat patients at risk for infection by these organisms. Limited or nonexistent effective microbial therapy underscores the importance of effective preventive and containment measures.

U.S. hospital mycobacteriology laboratories: status and comparison with state public health department laboratories

In response to the resurgence of tuberculosis, the Centers for Disease Control and Prevention recommended the use of certain mycobacteriology laboratory methods to improve the accuracy of diagnosis and/or minimize times to complete specimen processing. A study to determine the extent to which these recommended methods were being used in hospital laboratories was needed. In 1992, a survey was mailed to infection control and laboratory personnel at 1,076 hospitals with > or = 100 beds to determine the mycobacterial laboratory services being performed, the methods being used, the number of specimens being processed, and the times to completion during 1991. In 1995, a 20% sample of hospital laboratories that responded to the initial questionnaire was resurveyed. Responses to the 1992 survey were received from personnel at 756 (70%) hospitals representing 750 laboratories. Among laboratories performing the services, the use of recommended methods was as follows: fluorochrome stain for acid-fast bacillus microscopy (47%); radiometric methods for primary culture (29%); rapid (radiometric methods, use of nucleic acid probes, high-performance liquid chromatography, or gas-liquid chromatography) methods for identification of Mycobacterium tuberculosis (59%); and radiometric methods for drug susceptibility testing (55%). Reported times to complete specimen processing were shortest for laboratories that used recommended methods and longest for hospitals that referred specimens to outside laboratories. Only 46% of surveyed laboratories performed at least the minimal number of mycobacterial cultures (20/week) deemed necessary to maintain competence. Among 145 laboratories that performed the services and were resurveyed in 1995, use of recommended techniques increased from 44 to 73% for acid-fast bacillus microscopy, from 27 to 37% for primary culture, from 59 to 88% for M. tuberculosis identification, and from 55 to 75% for drug susceptibility testing. These changes were associated with reductions in reported specimen turnaround times. Use of the methods recommended by the Centers for Disease Control and Prevention increased at the resurveyed hospital mycobacteriology laboratories between 1991 and 1995. However, continued efforts are needed to increase the use of recommended methods at moderate- and high-volume laboratories, encourage referral of specimens from low-volume laboratories, and transmit results rapidly from all laboratories.