The epidemiology of multidrug-resistant tuberculosis in the United States

Epidemiology of Tuberculosis in the United States

Although considerable progress has been made in reducing US tuberculosis incidence, the goal of eliminating the disease from the United States remains elusive. A continued focus on preventing new tuberculosis infections while also identifying and treating persons with existing tuberculosis infection is needed. Continued vigilance to ensure ongoing control of tuberculosis transmission remains key.

Primary and acquired drug resistance patterns of Mycobacterium tuberculosis isolates in India: a multicenter study

Tuberculosis is the most prevalent infection worldwide. The emergence of drug-resistant Mycobacterium tuberculosis (M. tuberculosis) isolates emphasizes that it is necessary to monitor drug resistance of the organism against anti-tubercular drugs. We analyzed 327 M. tuberculosis isolates from patients who were cared for at three different health care centers, hereinafter known as study areas (SAs), in North India. Of the 327 total M. tuberculosis isolates, 255 were from a tertiary health care center (Varanasi, Uttar Pradesh [SA-1]), 48 were from a District tuberculosis center (Sawai Madhopur, Rajasthan [SA-2]), and 24 were from a different District tuberculosis center (Buxar, Bihar [SA-3]). Drug susceptibility testing against first-line antibiotics (viz. isoniazid, rifampicin, streptomycin, and ethambutol) was conducted for all the isolates using 1% proportional method. We found that the rates of acquired resistance were consistently higher than the rates of initial drug resistance. In new, untreated cases, a higher degree of MDR-TB was observed at SA-1 (13.3%) and SA-3 (25.0%), whereas it was observed in only 7.1% of the isolates at SA-2. In previously treated patients, MDR cases were found in 35.7% of the isolates from SA-1, 66.6% of the isolates from SA-2, and 43.8% of the isolates from SA-3. Resistance to a single drug was found at a much lower rate, ranging from 0.0 to 6.3% in new cases as well as previously treated cases. In conclusion, the primary resistance of M. tuberculosis is low, but acquired drug resistance is slightly higher in North India.

False-negative results obtained with the Gen-Probe Amplified Mycobacterium tuberculosis direct test caused by unrecognized inhibition of the amplification reaction

The Gen-Probe Amplified Mycobacterium tuberculosis direct test is widely used in the diagnosis of tuberculosis. Specimens may contain amplification inhibitors, potentially leading to false-negative results if unrecognized. We report a failure to detect inhibition, despite adherence to the inhibition testing guidelines provided on the label, and recommend changes.

Barriers to care seeking in directly observed therapy short-course (DOTS) clinics and tuberculosis control in southern Nigeria: a qualitative analysis

An understanding of the socioeconomic and cultural realities of persons infected with tuberculosis (TB) in communities is important to re-strategizing control programs because these realities often come as constraints to the use of the directly observed therapy short-course (DOTS) in Nigeria. In-depth interviews and focus group discussion were used to study barriers to attendance at DOTS clinics for both prompt diagnosis and treatment of smear positive cases in Nigerian communities. A number of common and interrelated factors form barriers to use of DOTS clinics. These include perceived causes of the infection, for example witchcraft, that mitigate against an orthodox solution to TB and thereby affect perceived efficacy of DOTS. Another factor is perceived high cost in resource poor settings. Facility staff were noted to have demanded money from patients in spite of the fact that DOTS is advertised as free treatment. Furthermore, community members complain of the hostile attitude of health staff toward poor people as a barrier to community use of the facilities. It follows, therefore, that the attitude of health workers must be addressed if community members will use the DOTS clinics.

Laboratory investigation of a nosocomial transmission of tuberculosis at a district general hospital

BACKGROUND/PURPOSE

Nosocomial outbreak of tuberculosis (TB) is rarely documented and the transmission is usually difficult to confirm because of the long incubation period of the mycobacterial infection. In this report, we demonstrated the use of molecular genotyping methods together with contact tracing to identify the source case, the causative outbreak strain and transmission dynamics of Mycobacterium tuberculosis, and for the definite confirmation of a suspected outbreak.

METHODS

M. tuberculosis strains were genotyped with IS6110 restriction fragment length polymorphism, spacer oligonucleotide typing and minisatellite interspersed repetitive unit-variable number tandem repeat methods. Clinical data and contact tracing results were collected from medical records and the National TB Registry.

RESULTS

In this episode, 66 health care workers (HCWs) were notified as TB cases. A total of 18 M. tuberculosis isolates from HCWs and patients were collected. IS6110 RFLP results revealed that 9 out of 10 HCWs' and 7 out of 8 patients' isolates shared the same genotype. The causative isolate was identified as the Beijing genotype. The index case was a hospitalized respirator-dependent patient.

CONCLUSION

Thorough collection along with molecular diagnosis and genotyping of all M. tuberculosis isolates are recommended for the confirmation of any suspected nosocomial TB outbreak.

Dual inhibition of mycobacterial fatty acid biosynthesis and degradation by 2-alkynoic acids

2-Hexadecynoic acid and 2-octadecynoic acid have cidal activity against Mycobacterium smegmatis and Mycobacterium bovis BCG. At subinhibitory concentrations, M. smegmatis rapidly transformed [1-(14)C]-2-hexadecynoic acid into endogenous fatty acids and elongated them into mycolic acids. Toxic concentrations of 2-hexadecynoic acid resulted in accumulation of 3-ketohexadecanoic acid, which blocked fatty acid biosynthesis, and 3-hexadecynoic acid, an inhibitor of fatty acid degradation. The combination of these two metabolites is necessary to achieve the inhibition of M. smegmatis. We conclude that 2- and 3-hexa/octadecynoic acids inhibit mycolic acid biosynthesis, fatty acid biosynthesis, and fatty acid degradation, pathways of significant importance for mycobacteria.

Evaluation of efficacy of community-based vs. institutional-based direct observed short-course treatment for the control of tuberculosis in Kilombero district, Tanzania

Tuberculosis (TB) has reappeared as a serious public health problem. Non-compliance to antituber-culous drug treatment is cited as one of the major obstacles to the containment of the epidemic. Compliance may be optimized by Directly Observed Treatment (DOT) and short-course treatment regimens. Since 1986, Tanzanian TB patients have received daily DOT at health facilities for the first 2 months of the treatment course. However, adherence and cure rates have been falling as the number of TB cases continues to increase and the burden on already stretched health facilities threatens to become unmanageable. We used an open cluster randomized controlled trial to compare community-based DOT (CBDOT) using a short-course drug regimen with institutional-based DOT (IBDOT). A total of 522 (301 IBDOT and 221 CBDOT) patients with sputum-positive TB were recruited. Overall, there was no significant difference in conversion and cure rates between the two strategies [M-H pooled odds ratio (OR) 0.62; 95% confidence interval (CI) 0.23, 1.71 and OR = 1.58; 95% CI 0.32, 7.88, respectively] suggesting that CBDOT may be a viable alternative to IBDOT. CBDOT may be particularly useful in parts of the country where people live far from health facilities.

Antituberculosis drug resistance patterns in two regions of Turkey: a retrospective analysis

BACKGROUND

The emergence of Mycobacterium tuberculosis strains resistant to antituberculosis agents has recently received increased attention owing largely to the dramatic outbreaks of multi drug resistance tuberculosis (MDR-TB).

METHODS

Patients residing in Zonguldak and Kayseri provinces of Turkey with, pulmonary tuberculosis diagnosed between 1972 and 1999 were retrospectively identified. Drug susceptibility tests had been performed for isoniazid (INH), rifampin (RIF), streptomycin (SM), ethambutol (EMB) and thiacetasone (TH) after isolation by using the resistance proportion method.

RESULTS

Total 3718 patients were retrospectively studied. In 1972-1981, resistance rates for to SM and INH were found to be 14.8% and 9.8% respectively (n: 2172). In 1982-1991 period, resistance rates for INH, SM, RIF, EMB and TH were 14.2%, 14.4%, 10.5%, 2.7% and 2.9% (n: 683), while in 1992-1999 period 14.4%, 21.1%, 10.6%, 2.4% and 3.7% respectively (n: 863). Resistance rates were highest for SM and INH in three periods. MDR-TB patients constituted 7.3% and 6.6% of 1982-1991 and 1992-1999 periods (p > 0.05).

CONCLUSION

This study demonstrates the importance of resistance rates for TB. Continued surveillance and immediate therapeutic decisions should be undertaken in order to prevent the dissemination of such resistant strains.

Limited transmission of multidrug-resistant tuberculosis despite a high proportion of infectious cases in Los Angeles County, California

Preventing transmission of multidrug-resistant tuberculosis is critical because of treatment toxicity, cost, and the lack of effective therapy for latent infection. We attempted to determine the extent of transmission in Los Angeles County by comparing relatedness of multidrug-resistant tuberculosis cases using restriction fragment length polymorphism and by cross-matching contact information to the Tuberculosis Registry. Strain typing was done on isolates of 102 pulmonary multidrug-resistant cases identified between August 1993 and 1998. Seventy-one (70%) of the cases had cavitary lesions on chest radiograph, and 94 (92%) had sputa smear-positive for acid fast bacilli. Fifteen (15%) of the cases were known to be infected with human immunodeficiency virus. Four molecular clusters of two cases each and one closely related pair were identified among the 102 cases; contact investigation successfully identified all clusters but one. Among 946 contacts identified and cross-matched with the county's Tuberculosis Registry, one secondary case due to drug-resistant Mycobacterium bovis was found. To summarize, a very high proportion of pulmonary multidrug-resistant tuberculosis cases in Los Angeles County were infectious. Molecular strain typing indicated limited spread of disease, although it underestimated transmission compared with contact investigation. We believe aggressive surveillance and case management were critical to limiting the spread of multidrug- resistant tuberculosis.

Influence of Mycobacterium bovis bacillus Calmette Guérin on in vitro induction of CD1 molecules in human adherent mononuclear cells

Nonpeptide antigens (including glycolipids of microbial origin) can be presented to T cells by CD1 molecules expressed on monocyte-derived dendritic cells. These HLA unrestricted responses appear to play a role in host immunity against Mycobacterium tuberculosis and other pathogenic bacteria. It is known that vaccination with Mycobacterium bovis bacillus Calmette-Guérin (BCG) has limited efficacy in many clinical settings, although the reasons for its inadequacy remain unclear. Here we have investigated the influence of BCG on the induction of CD1b on human monocytes by granulocyte-macrophage colony-stimulating factor (GM-CSF), which is believed to be the principal inducer of this antigen-presenting molecule. Although BCG alone led to a slight induction of CD1b expression, this agent reduced markedly the ability of GM-CSF to induce high levels of CD1b that were typically observed in uninfected cells. Inhibition of CD1b expression in BCG-infected monocytes was apparent at both the mRNA transcript and CD1b protein levels. Down-regulation of CD1b expression by BCG was mediated, at least in part, by one or more soluble factors and could not be reversed with high concentrations of GM-CSF or a variety of other cytokines. The present results suggest that BCG could diminish the efficiency of CD1-restricted T-cell responses against nonpeptide mycobacterial antigens by reducing CD1 expression on antigen-presenting cells. These findings have potential implications for understanding the nature of the immune response elicited by BCG in humans and suggest potential strategies that could be important for the development of better vaccines for the prevention of tuberculosis.

Drug-resistant tuberculosis in a tertiary referral teaching hospital of Korea

BACKGROUND

Resistance of Mycobacterium tuberculosis strains is an increasing problem worldwide. Our purpose was to determine the prevalence of drug resistance (DR) and risk factors of DR in patients with tuberculosis and to assess the clinical characteristics and socioeconomic status of patients with drug-resistant tuberculosis.

METHODS

We retrospectively studied drug susceptibility tests and clinical and socioeconomic records for 308 cases of culture-positive Mycobacterium tuberculosis infection, diagnosed at Mokdong Hospital, Ewha Womans University from March, 1995 to February, 2000.

RESULTS

DR to at least one drug was identified in 75 (24.4%); the rate of primary DR, 18.7% and acquired DR, 39.3%. Multi-drug resistance (MDR) was identified in 31 (10.1%); primary MDR, 7.0% and acquired MDR, 21.4%. The risk factors of DR were previous TB treatment, pulmonary involvement and associated medical illness. DR group showed lesser adherence to treatment than the drug-sensitive group. DR group showed more frequent self-interruption of medication, lower completion rate of treatment and higher failure rate of follow-up than the drug-sensitive group. In previously treated tuberculosis patients, higher rate of overall DR and MDR, larger number of resistant drugs and more frequent self-interruption of medication were observed than newly diagnosed patients. Among DR group, acquired DR (ADR) group was older, less educated and treated for longer duration and had more advanced disease than primary DR group.

CONCLUSION

Previously treated tuberculosis is a most important risk factor for DR. DR group, especially ADR, showed less compliance with treatment. More proper education and attention to prevent self-interruption should be given to a previously treated group. In TB prevalent areas, it should be considered to obtain initial drug susceptibility testing in high risk of DR.

Tuberculosis and drug resistance among patients seen at an AIDS Reference Center in São Paulo, Brazil

OBJECTIVES

To assess the frequency of resistance of Mycobacterium tuberculosis to antituberculosis drugs and the factors associated with it among patients with tuberculosis (TB) and acquired immunodeficiency syndrome (AIDS).

MATERIALS AND METHODS

The medical records of TB and AIDS cases diagnosed from 1992 to 1997 in a public service for AIDS care were reviewed.

RESULTS

Resistance was diagnosed in 82 (19%) of 431 cases. The mean and median values between the diagnosis of AIDS and the diagnosis of TB were 214.8 days and 70.5 days, respectively. Multidrug-resistant TB (MDR TB) occurred in 11.3% of cases. Of the 186 patients with no previous treatment, 13 (6.9%) presented primary MDR TB. Of the 90 cases with previous treatment, six (6.7%) presented monoresistance to rifampin and 27 (30%) presented MDR TB. The distribution of cases with sensitive and resistant M. tuberculosis strains was homogeneous in terms of the following variables: gender, age, category of exposure to human immunodeficiency virus (HIV), alcoholism, and homelessness. Multivariate analysis showed an association between resistance and the two following variables: previous treatment and duration of AIDS prior to TB exceeding 71 days. The rates of primary multiresistance and of monoresistance to rifampin were higher than those detected in HIV-negative patients in Brazil.

CONCLUSIONS

In this patient series, M. tuberculosis resistance was predominantly of the acquired type, and resistance was independently associated with previous treatment for TB and with duration of AIDS prior to TB exceeding 71 days.

Bacillus Calmette-Guerin down-regulates CD1b induction by granulocyte-macrophage colony stimulating factor in human peripheral blood monocytes

Non-peptide antigens (e.g. glycolipids of microbial origin) presented by monocyte-associated CD1 molecules to T cells appear to play an important role in host immunity against tuberculosis and other pathogenic bacteria. Since vaccination with Bacillus Calmette-Guerin (BCG) has limited efficacy, the influence of viable BCG organisms on the induction of CD1b antigen by granulocyte macrophage-colony stimulating factor (GM-CSF) has been tested in adherent mononuclear cells obtained from peripheral blood of healthy donors. The results indicate that the vaccine reduces substantially CD1b induction by GM-CSF. On the other hand, BCG was found to promote a slight increase in the expression of this molecule on target cells not exposed to GM-CSF. Attempts to reverse the antagonistic effects of BCG on GM-CSF with high concentrations of GM-CSF, alone, or associated with IL-4, were unsuccessful. Moreover, mycobacteria suppression by 10 microg/ml of rifampin, did not affect BCG influence on CD1b induction. The present results suggest that mycobacterium-induced impairment of the CD1 system could play a role in the unsatisfactory results obtained with BCG vaccination.

Increasing drug resistance of Mycobacterium tuberculosis isolates in Ontario, Canada, 1987-1998

We examined trends in resistance to first-line antituberculous agents for Mycobacterium tuberculosis strains isolated in Ontario, Canada from 1987 through 1998 (n=8069). The proportions resistant were as follows: isoniazid, 9.6%; rifampin, 1.9%; streptomycin, 4. 9%; ethambutol, 1.3%; and pyrazinamide, 1.7%. Resistance to isoniazid has increased markedly since 1990, whereas resistance to streptomycin, ethambutol, and pyrazinamide increased from 1997 through 1998. Resistance to both isoniazid and rifampin did not increase. The incidence of persistence and reactivation (early or late treatment failure) was 1-2 per 100 person-years (PY) in the first 7-12 months and 0.3-0.9 per 100 PY from 13 months to 5 years thereafter. For initially susceptible strains, the incidence of resistance to isoniazid was 0.11 per 100 PY and for and rifampin was 0.06 per 100 PY in the first year and negligible thereafter, with an overall risk of 0.14% for isoniazid and 0.10% for rifampin. Resistance of M. tuberculosis to antituberculous agents, and in particular to isoniazid, is a growing problem in Ontario and is higher than elsewhere in Canada.

Improving naltrexone response: an intervention for medical practitioners to enhance medication compliance in alcohol dependent patients

The effectiveness of naltrexone, a FDA-approved medication for alcohol dependence, can be improved if we support and help patients to consistently take their medication. We illustrate how patient noncompliance with treatment negatively affects outcome, and, we describe a new intervention to enhance medication compliance. Outcome was evaluated for 196 alcohol dependent outpatients who were treated with 50 mg/day naltrexone or placebo for 12 weeks. For patients who adhered to the prescribed treatment, relapse rates were lower with naltrexone than placebo (10% vs. 38.6%, p < 0.001). For noncompliant patients, relapse rates were high and comparable between naltrexone- and placebo-treated patients (42.9% vs. 40%). In a second study of 100 alcohol dependent outpatients, we introduced an intervention that resulted in better medication compliance rates compared to a previous naltrexone study of patients who did not receive the intervention (77.0% vs. 60.8%, p < 0.01). This provided some support for the use of an intervention that targets medication compliance when prescribing naltrexone.

Epidemiology and ethnic distribution of multidrug-resistant tuberculosis in southern Israel, 1992-1997: the impact of immigration

STUDY OBJECTIVES

To assess the incidence of tuberculosis in the native and immigrant populations of southern Israel in the period between 1992 and 1997, and to study the prevalence of drug resistance overall and among these subpopulations in the region in order to create guidelines for empirical antituberculous treatment in this region.

DESIGN

A retrospective population-based study.

SETTING

The southern district of the country and its tertiary-care hospital.

PATIENTS

All new culture-proven tuberculosis cases diagnosed in adults residing in the Negev region during the study period. Patients were classified into four groups according to ethnic origin and immigration date.

RESULTS

During the study period, 249 new cases involving 249 patients were recorded. Immigrants from the former Soviet Union (IFSU) were significantly younger and of male gender, and the incidence among this group rose sharply. IFSU had higher rates of resistance to any drug or drug combination. Isoniazid resistance rates were 16% overall and 32% among IFSU. Resistance to any drug was observed in 29% overall and 50% of isolates among IFSU. Multidrug-resistant tuberculosis was observed in 8.5% and 17%, respectively.

CONCLUSIONS

The population of southern Israel carries very high rates of drug-resistant tuberculosis, mandating quadruple empiric treatment. IFSU should be regarded as having multidrug-resistant tuberculosis until proven otherwise, and empiric therapy with at least five drugs should be considered. This report demonstrates the influence of immigration on the incidence of tuberculosis, and the great value of local surveillance of population-specific resistance rates in an immigrant society, in order to optimize drug treatment and prevent the dissemination of resistant strains.

ATP-induced killing of virulent Mycobacterium tuberculosis within human macrophages requires phospholipase D

The global dissemination of antibiotic-resistant Mycobacterium tuberculosis has underscored the urgent need to understand the molecular mechanisms of immunity to this pathogen. Use of biological immunomodulatory compounds to enhance antituberculous therapy has been hampered by the limited efficacy of these agents toward infected human macrophages and lack of information regarding their mechanisms of activity. We tested the hypotheses that extracellular ATP (ATPe) promotes killing of virulent M. tuberculosis within human macrophages, and that activation of a specific macrophage enzyme, phospholipase D (PLD), functions in this response. ATPe treatment of infected monocyte-derived macrophages resulted in 3.5-log reduction in the viability of three different virulent strains of M. tuberculosis. Stimulation of macrophage P2X7 purinergic receptors was necessary, but not sufficient, for maximal killing by primary macrophages or human THP-1 promonocytes differentiated to a macrophage phenotype. Induction of tuberculocidal activity by ATPe was accompanied by marked stimulation of PLD activity, and two mechanistically distinct inhibitors of PLD produced dose-dependent reductions in ATPe-induced killing of intracellular bacilli. Purified PLD restored control levels of mycobacterial killing to inhibitor-treated cells, and potentiated ATPe-dependent tuberculocidal activity in control macrophages. These results demonstrate that ATPe promotes killing of virulent M. tuberculosis within infected human macrophages and strongly suggest that activation of PLD plays a key role in this process.

Tuberculosis and pericarditis in children

With the rapid spread of tuberculosis (TB) in Zimbabwe the disease is becoming a major paediatric health problem. Children are at high risk of TB, are prone to disseminated disease and the diagnosis of paediatric TB may be difficult, since complaints often are unspecific and contacts may not been known. Data from 265 children, aged between 2 weeks and 12 years, being treated for TB in Gweru Hospital in 1995, are analysed. In 72% pericardial effusion was found as a sign of early dissemination. Cultures of gastric aspirates for Mycobacterium tuberculosis were positive in 31%. In optimal circumstances the yield for isolates of M. tuberculosis is less than 50%, and these results under limited conditions are acceptable, and may reflect the true incidence. Given the epidemiology of TB in Zimbabwe, pericardial effusions should be considered indicative of TB until proven otherwise.

Multicenter comparison of ESP Culture System II with BACTEC 460TB and with Lowenstein-Jensen medium for recovery of mycobacteria from different clinical specimens, including blood

The recently developed ESP Culture System II (AccuMed, Chicago, Ill.) was compared with radiometric BACTEC 460TB (Becton Dickinson, Towson, Md.) and with Lowenstein-Jensen medium for recovery of mycobacteria from over 2,500 clinical specimens both of respiratory and nonrespiratory origin, including blood. The majority of the 219 mycobacterial isolates (129) belonged to the Mycobacterium tuberculosis complex, followed by 37 isolates of the Mycobacterium avium complex (MAC) and 53 isolates of eight other mycobacterial species. Rates of recovery obtained with BACTEC, ESP, and Lowenstein-Jensen medium were 89, 79, and 64%, respectively, with such differences being statistically significant. Different media and systems appeared to behave differently when the more frequently detected organisms were considered: M. tuberculosis complex isolates grew better with BACTEC, and MAC isolates grew better with ESP. An analysis of the combinations of Lowenstein-Jensen medium with BACTEC and with ESP did not reveal significant differences in recovery rates. With regard to the times needed for the detection of positive cultures, they were significantly longer on Lowenstein-Jensen medium (average, 28 days) than with the remaining two systems, between which there was no difference (average, 18 days). We conclude, therefore, that the ESP system, when used in combination with a solid medium, performs as well as the thoroughly validated radiometric BACTEC system and offers the advantages of full automation and absence of radioisotopes.

Knowledge, Perceptions, and Practice of Nurses Toward HIV+/AIDS Patients Diagnosed With Tuberculosis

BACKGROUND

Tuberculosis (TB) continues to be a major health problem in the United States. Nurses may be exposed to TB and not realize their risks for becoming infected. The presentation of HIV-associated TB is somewhat different from "standard TB."

PURPOSE

The purpose of this study was to determine if an educational program could improve nurses' attitudes, level of knowledge, and compliance with infection control standards for HIV/AIDS patients diagnosed with TB.

METHOD

Participants included 50 staff nurses. The experimental group (35) and control group (15) completed a knowledge test and an attitude survey. Researchers observed participants for compliance with infection control standards pretest and posttest.

RESULTS

Following an educational program, the experimental group demonstrated a greater knowledge of TB than the control group who did not participate in the educational program (F [1.47] = 14.43, p = .000). In addition, the experimental group had a greater improvement in their Nursing Intervention Observation Tool adherence to respiratory isolation and universal precaution protocols scores as compared to the control group (F [1.47] = 8.95, p = .004). However, there was not a tangible increase in knowledge level of AIDS, attitudes or concerns about caring for these patients.

CONCLUSION

This nursing research study supports the need for an ongoing educational program with continual monitoring of infection control practices to positively affect client and caregiver outcomes.

Multiple drug-resistant tuberculosis

The national and international emergence of drug-resistant M. tuberculosis has complicated both the programmatic control of the tuberculosis epidemic and the clinical management of individual cases. In the United States, the problem of MDR tuberculosis is regionalized and likely stems from multifactorial causes, including the concurrent HIV epidemic. The epidemic is propagated by two distinct entities, PDR and ADR tuberculosis, which result from different inadequacies in tuberculosis control programs. The clinical management of drug-resistant tuberculosis, MDR tuberculosis in particular, is complex, frequently results in adverse outcomes, and often necessitates consultation with a specialist in the field. Two important management principles are to always use at least two agents to which the organism is susceptible and to never add a single drug to a failing regimen. Selection of an appropriate treatment regimen and determination of the duration of therapy depend on the resistance pattern, toxicities of the drugs, and the patient's response to therapy. Measures to ensure patient adherence with therapy are of paramount importance in the setting of drug resistance. Preventive therapy should be considered in the management of close contacts to active cases of MDR tuberculosis, although there is little evidence to support this practice.

Do the homeless get a fair deal from general practitioners?

Many studies have indicated the health status of homeless people to be typically poorer than that of the general population, with various studies indicating a high prevalence of psychiatric illness, drug or alcohol misuse and associated socio-medical problems. The Bristol Primary Healthcare Project is an agency which was established to provide a local health care service tailored to the needs of people who are homeless. The present study was carried out as part of an evaluation of the service offered locally to homeless people by General Practitioners (GPs). A postal questionnaire survey of 155 general practices within the Avon FHSA area was carried out. Both fundholding and non-fundholding practices were included, within an area including inner city, urban and rural/semi-rural locations. One hundred and seventeen completed questionnaires were returned, providing a response rate of 75%. Twenty-seven percent of practices would fully register a homeless person who seeks to register at the practice, 24% would treat as immediate and necessary and 33% would treat as a temporary resident. Four percent of fundholding practices surveyed would fully register homeless persons and 55% of inner city practices would do so. Seventy-nine percent of doctors indicated that homeless patients were more difficult to treat than other patients. The most frequent problems associated with registering homeless persons were perceived to be the associated social problems (90% of respondents agreed), the lack of medical records (88% agreed), the complex health problems (79% agreed) and the associated alcohol or substance misuse (78% agreed). The study has highlighted a need for government to consider providing incentives to GPs to register homeless people without resulting in adverse effects on their contract targets. The reluctance of some practices to register these patients varied by area and type of practice with doctors at fundholding practices being the most reluctant. There is an identified need for further health education and promotion work and initiatives exemplified by the Bristol Primary Healthcare Project for people who are homeless.

Transmission between HIV-infected patients of multidrug-resistant tuberculosis caused by Mycobacterium bovis

OBJECTIVE

To investigate outbreaks of multidrug-resistant tuberculosis (TB) by using DNA fingerprint databases.

DESIGN

Investigation of two outbreaks of multidrug-resistant TB in separate hospitals in Spain by restriction fragment length polymorphism (RFLP) and spoligotyping. Outbreak strains were compared with more than 1500 RFLPs of Mycobacterium tuberculosis complex strains isolated in Spain and 6000 RFLPs from 30 different countries.

METHODS

Standardized IS6110 DNA fingerprinting and 'spoligotyping' was used to type multidrug-resistant isolates belonging to the M. tuberculosis complex amongst the outbreak cases. The DNA types were matched against DNA fingerprint databases in Spain and The Netherlands.

RESULTS

The DNA typing analysis indicated that a single multidrug-resistant Mycobacterium bovis strain was responsible for a nosocomial outbreak in a hospital in Spain involving at least 16 HIV-infected patients with non-treatable to multidrug-resistant TB. Introduction of the fingerprint type of this strain to the international database revealed a single matching strain. This strain was also isolated from an HIV-infected patient in The Netherlands who had died from multidrug-resistant TB. This patient had previously been hospitalized in Spain, where a multidrug-resistant TB nosocomial outbreak involving 20 HIV-infected patients was ongoing. The strains causing this outbreak were also identified as M. bovis with an identical DNA pattern to those strains isolated in the Spanish hospital and the patient in The Netherlands.

CONCLUSIONS

The use of centralized DNA databases can help to identify rapidly the origin and transmission routes of multidrug-resistant TB across international boundaries and the potential use of such an early warning surveillance system for investigation of nosocomial multidrug-resistant TB outbreaks between HIV-infected patients. To our knowledge this is the first report of transmission of multidrug-resistant M. bovis between hospitals.

Multicenter evaluation of mycobacteria growth indicator tube (MGIT) compared with the BACTEC radiometric method, BBL biphasic growth medium and Löwenstein---Jensen medium

OBJECTIVE: To evaluate the new BBL mycobacteria growth indicator tube (MGIT) in comparison with other media. METHODS: MGIT was evaluated in 10 Italian centers on 433 clinical samples, mainly of respiratory origin and mainly smear positive, in comparison with Löwenstein---Jensen and with one or more other methods represented, according to participating centers, by the BACTEC radiometric method or by the biphasic BBL Septi-Chek AFB system. While MGIT and Löwenstein---Jensen were used for all the samples, 285 of them were also inoculated in BACTEC vials and 274 in biphasic bottles. Of these samples, 132 were investigated with all the four methods. RESULTS: Although less rapid and sensitive than the radiometric method, the results of MGIT were equal when compared with the other two media with respect to overall isolation yield; furthermore, it allowed the detection of growth in significantly shorter times. CONCLUSIONS: The results of this study indicate the value of MGIT for the detection of mycobacteria and, thanks to its extreme simplicity of use, its suitability for small and large laboratories. Its combined use with a solid medium can substantially improve the diagnosis of mycobacterial infection.

Mycobacterial complications of HIV infection

Tuberculosis is the most common opportunistic infection worldwide and is caused by the only readily transmissible pathogen among persons with HIV infection. If treatment is initiated promptly and is supervised appropriately, cure, fortunately, is highly likely. Isoniazid preventive therapy substantially reduces the risk of tuberculosis in persons with HIV infection. Of the nontuberculous mycobacteria, Mycobacterium avium complex (MAC) is the most frequent cause of disease; however, disseminated MAC disease usually is not seen until the CD4+ cell count is less than 50 cells/L. Newer agents, such as the macrolides and rifabutin, form the nucleus of treatment regimens and also are effective in preventing the disease.

The homeless

The medical literature on homeless people tends to concentrate on their biographic characteristics or clinical problems without enough attention being given to the social and environmental contexts which they have to survive. This article summarises the literature on the role of social factors in the causation and outcome of health problems of the homeless and emphasises the importance of addressing the social context in effecting intervention. Services that deal with the social needs of the homeless will be more successful in meeting their needs and reducing their distress.

The 5-year outcome of multidrug resistant tuberculosis patients in the Cape Province of South Africa

Little is known about the outcome of multidrug resistant (MDR) tuberculosis (TB) in developing countries. In this study, 443 patients with MDR-TB, defined as resistance to two or more antituberculosis drugs, were identified over the 2-year period 1987 and 1988 in the Cape Province of South Africa. The 5-year outcome of the 343 (77%) patients that could be traced by questionnaire was evaluated retrospectively during 1992 and 1993. Of these, 240 (70%) were resistant to both isoniazid (H) and rifampicin (R) with or without resistance to other first-line antituberculosis drugs and 103 (30%) were resistant to H or R and/or other antituberculosis drugs. Mortality was 116 (48%) and 28 (27%) in these groups respectively with a significantly greater risk of death in the first group. Only 114 (33%) of all the MDR-TB patients were cured after 5 years, 50 (15%) were respiratory disabled and 44 (13%) were still bacteriology positive. Twenty-four (7%) patients were lost during follow-up. Taking into account the high costs involved in treating MDR-TB patients and the scarce resources available in developing countries, more emphasis should be placed on direct observed therapy to cure newly diagnosed infectious drug sensitive tuberculosis patients, thus preventing MDR-TB rather than treating it.

Tuberculosis: disease of the past, disease of the present

Once thought to be under control, tuberculosis is now the number one cause of infection-related death worldwide and the sixth most significant cause of death overall. Transmission occurs by inhalation of airborne droplet nuclei that can be viable for days, and is facilitated by substance abuse, poverty, overcrowding, malnutrition, and, most importantly coinfection with human immunodeficiency virus. This article describes the history and current status of tuberculosis as a growing global health problem, transmission of the disease, risk factors for the general public and health care workers, and prevention of the disease.

Evaluation of Amplicor MTB test as adjunct to smears and culture for direct detection of Mycobacterium tuberculosis in the French Caribbean

A total of 784 specimens collected from 370 individuals between January and August 1995 were analyzed by using the Amplicor Mycobacterium tuberculosis test (Roche Diagnostic System, Basel, Switzerland), a PCR-based test for the direct detection of organisms of the M. tuberculosis complex. The PCR results were compared with standard bacteriological data, including those obtained by acid-fast microscopy, culture, and biochemical identification as well as final clinical diagnosis for each patient. Several parallel controls were used: the kit DNA positive control, 10(3) CFU of M. tuberculosis, and three negative controls for each independent assay. No false-positive PCR results were obtained, and overall, M. tuberculosis was detected in 20 of 370 individuals screened. Five additional patients during the same time were found to be infected with mycobacteria other than tubercle bacilli; their specimens gave positive smear and/or culture test results, but Amplicor tests were always negative. The sensitivity, specificity, positive predictive value, and negative predictive value for the Amplicor MTB test compared with culture per specimen were 76.7, 97.7, 66.0, and 98.6%, respectively. For resolved cases, these values were, respectively, 69.4, 100, 100, and 96.8%; however, the sensitivity and negative predictive value increased to 90.9 and 99.2%, respectively, if PCR-negative nonrespiratory specimens (gastric washings) were not considered. When only specimens from proven tuberculosis patients were considered (n = 114) and the sum of PCR-positive and/or culture-positive samples from proven tuberculosis patients was considered the total number of positive samples, PCR had a sensitivity of 83.3% compared with 71.6% for culture. Results per patient (about three samples each) yielded 100% sensitivity and 100% specificity. We conclude that the Amplicor MTB test is highly specific and rapid for routine use in a clinical laboratory. However, in order to obtain a higher degree of sensitivity, it should be run as an adjunct to smears and culture with at least three samples for each patient, and a single-sample PCR-negative results must be considered carefully because of potential false-negatives.

Changing practices in mycobacteriology: a follow-up survey of state and territorial public health laboratories

The resurgence of tuberculosis, which includes an increase in the isolation of multidrug-resistant strains of Mycobacterium tuberculosis, emphasizes the need for more rapid laboratory testing for identification of the etiological agent of the disease. In December 1991, state and territorial public health laboratories were surveyed to determine the methods that they were using for testing and reporting of M. tuberculosis. A follow-up survey was conducted in June 1994 to measure changes in the testing and reporting practices that had occurred as a result of efforts focused on the disease and on laboratory improvement. Completed questionnaires were received from 51 of 55 laboratories. Comparative data indicate that the proportion of laboratories reporting testing results within the number of days recommended by the Centers for Disease Control and Prevention has increased. Starting from the time at which the laboratory receives the specimen, the proportion of laboratories reporting the results of microscopic smear examination within the recommended 24 h has increased from 52.1 to 77.6%; the proportion reporting isolation and identification within 21 days has increased from 22.1 to 72.9%; and the proportion reporting results of isolation, identification, and drug susceptibility testing within 28 days has increased from 16.7 to 48.9%. Use of the recommended rapid testing methods has also increased: the proportion of laboratories using fluorescence staining for acid-fast microscopy has increased from 71.4 to 85.7%, the proportion using BACTEC for primary culture has increased from 27.1 to 79.6%, the proportion using rapid methods for M. tuberculosis identification has increased from 74.5 to 100.0%, and the proportion using BACTEC for primary drug susceptibility testing has increased from 26.2 to 73.3%. By implementing the recommended methods for M. tuberculosis testing and reporting, state and territorial public health laboratories are now able to transmit results to physicians more rapidly.

Views on the sustenance of resistant Mycobacterium tuberculosis in the environment

Microbial resistance to conventional as well as newly introduced drugs is a hallmark feature of several infectious diseases, notably tuberculosis. It is hypothesized that the greater the selective pressure exerted by increasingly potent drugs, the more rapidly is an organism able to adapt to a drug-containing environment. The roles of drug-containing environments, and the immunological status of the host and bacterial molecular mechanisms of development of drug resistance to Mycobacterium tuberculosis have been examined and examples cited for implementation of modified drug regimens in tuberculosis-control programmes. The views expressed, albeit restricted to Mycobacterium tuberculosis, encourage consideration of drug regimens on a disease evolution basis as well as understanding of the natural rules that govern development and sustenance of drug resistance in the microbial world.

Nurses: at special risk

Nurses are at occupational risk for many infections, but it was not until human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) was recognized that a work-acquired infection was uniformly fatal. Other work-acquired infections, including tuberculosis, rubella, measles, varicella, and the viral hepatitides, may cause morbidity for the nurse and his/her family. Although the number of nurses who acquire occupational infections is small, each has a unique personal story, and all will have their productivity affected. A few will lose their lives to infections acquired on the job. Although all occupational infections cannot be prevented, understanding the chain of infection and how to break the links can go a long way in reducing risks and maintaining health for all health care workers.

Drug-resistant tuberculosis in pediatrics

As the incidence of tuberculosis in the United States has increased over the past 10 years, the number of cases caused by drug-resistant organisms has risen dramatically. The genetic mechanisms of resistance, which could lead to better methods of diagnosis and treatment, are being determined. Treatment of drug-resistant tuberculosis is complex, requiring the use of several toxic drugs over 9 to 18 months. At present, drug resistance is fairly localized and can be avoided in most communities if appropriate public health measures are taken. Stronger attention to treatment regimens and adherence with treatment will prevent further emergence of drug-resistant tuberculosis.

When public health competes with individual needs

A case of a homeless, alcoholic man with tuberculosis is presented. This case is used to illustrate the ethical dilemmas health care providers must face when the needs of society and the actions of the patient come into conflict. In addition to discussing historical cases of conflicts between individual rights and the needs of society, two models for solving the dilemma in the current case are considered.