Tuberculosis and the acquired immune deficiency syndrome

Spatial patterns of tuberculosis incidence in Cologne (Germany)

In many European countries, the decline of tuberculosis notification rates levelled off in the mid 1980s. Germany has been facing only a very modest resurgence of tuberculosis (TB) in the early 1990s, but until now, the notification rate does not yet fulfil the WHO definition of a low incidence country. Mainly immigration from high incidence countries is held responsible for the delayed decline and temporary increase of TB. This paper seeks to investigate the inner-urban strength of association between tuberculosis and several potential risk factors in the city of Cologne using geographical and statistical methods within a small-area division based, GIS-supported ecological study, which never before has been conducted for a German city. Standardised annual TB incidence rates for 78 urban subdistricts between 1986 and 1997, disaggregated by age, have been analysed. Twelve independent variables representing contemporary ethnic and socioeconomic conditions are used to calculate Poisson regression models. For the entire population and for the <60 age group, a strong positive association was found between tuberculosis incidence and share of immigrants. Interestingly enough the share of German-origin immigrants from eastern Europe was seen not to be instrumental in increasing TB rates. Reflecting strong ecological correlations between variables depicting economic conditions and TB as well as immigration variables, the deprivation of certain ethnicities rather than high prevalence immigration background is inferred to be significant to TB level. As for the 60 + age group regression analysis fails to model the TB incidence patterns sufficiently it seems reasonable to assume an autonomous, spatially disaggregated TB epidemic of the elderly, echoing a severe post-war epidemic by reactivation, only marginally associated with contemporary living conditions, but contributing substantially to the current TB incidence level. This assumption is reinforced by further results of the statistical analysis (deviance of regression null models, testing for Normal distribution, time trends). It could be shown that in Cologne the HIV/AIDS epidemic is not significantly influencing the TB incidence rate of men aged 30-49 being the most AIDS-afflicted population subgroup.

Ocular manifestations of tuberculosis

OBJECTIVE

To present the clinical and histopathologic findings in five cases of tuberculosis (TB) with various ocular manifestations.

DESIGN

Observational case series.

METHODS

Retrospective review of clinical findings, course, and treatment of five patients. Diagnostic techniques, including biomicroscopic, histopathologic, and molecular biologic test results, are presented.

MAIN OUTCOME MEASURES

Visual acuity, slit-lamp biomicroscopy, indirect ophthalmoscopy, and fluorescein angiography results.

RESULTS

The ocular manifestations of TB in our patients included panophthalmitis, endophthalmitis, posterior uveitis with choroidal tubercles, keratitis, and a lid mass. Mycobacterium tuberculosis was identified in four cases in ocular specimens using acid-fast bacilli microscopy and in three cases by culture. Rapid diagnosis using polymerase chain reaction was obtained in one case. Extraocular foci of TB were identified in three cases with an intraocular infection at presentation. No patients had the human immunodeficiency virus (HIV) and none were immunocompromised. Two eyes could not be saved using antituberculous treatment because of delayed diagnosis and treatment.

CONCLUSIONS

In this age of the HIV pandemic, TB is becoming more common. Because it is curable, heightened awareness and better understanding of the disease's ocular manifestations should be of concern to all ophthalmologists.

Tuberculosis mortality in England and Wales during 1982-1992: its association with poverty, ethnicity and AIDS

This paper seeks to establish the strength of association between contemporary tuberculosis (TB) in England and Wales and several potential aetiological factors. It presents an ecological analysis of standardised annual TB mortality rates for the 403 local authority districts between 1982 and 1992, disaggregated by age and sex. Social, demographic and ethnicity measures from the 1981 and 1991 censuses and standardised annual AIDS-related mortality rates for young men are used to calculate Poisson regression models. A strong association was found between all TB mortality groups and overcrowding at the household level. For women, no other measures improved the explanatory power of the models. In multiple regressions, both poverty and AIDS-related mortality explained additional variation in the model for younger men. The link between ethnicity and tuberculosis notifications was not reflected in this analysis of mortality. For all groups no evidence of a positive relationship with ethnicity was found, once overcrowding had been accounted for. The significance of household as opposed to district level crowding suggests that prolonged contact is required for disease transmission. Regression analysis indicates that it is the overcrowding and poverty among ethnic populations that is significant for their tuberculosis mortality. The fact that the relationship between AIDS and TB is confined to the group most typical of AIDS patients provides evidence that AIDS has little influence on the level of tuberculosis mortality in the wider population. Explanations for the observed relationship include preferential certification, migration for treatment and shortcomings in health care provision.

The epidemiology of tuberculosis in the United States

After a dramatic increase in the incidence of TB in the United States from 1985 to 1992, the epidemiology of TB changed, with both the number of cases and the incidence of TB decreasing since 1992. The decreases have been focal, however, affecting only certain geographic areas (e.g., New York, California, and New Jersey) and certain populations (e.g., 25-44 year age group and people born in the United States). The factors responsible for the decrease in those areas and populations are multiple but the most important are thought to be improvements in TB control and treatment programs in communities serving populations at greatest risk for TB. Despite the overall decline in TB cases, the numbers of foreign-born people with TB continue to increase. Factors contributing to the increase in TB among foreign-born people include the prevalence of TB in the country of origin, duration of residence in the United States after immigration, inadequate screening for or treatment of TB before entering the United States, and inadequate follow-up of those who have entered the United States with noninfectious TB (i.e., abnormal chest radiograph with negative sputum smears). Control of TB among the foreign-born population is essential if the current downward trend in reported TB cases in the United States is to be maintained. The HIV epidemic had a significant impact on the increase in TB incidence in the United States in the late 1980s but improvements in measures to control transmission of TB appear to have been effective in reversing that trend. The current national decrease trend in TB morbidity can be sustained through organized efforts by federal and private agencies and state and local health departments to ensure that all people with TB are identified and treated promptly. Such efforts must be aimed at areas and populations identified as high risk for TB, especially foreign-born people and people who are infected with HIV.

Comparison of A60 and three glycolipid antigens in an ELISA test for tuberculosis

OBJECTIVES: To compare the diagnostic usefulness in tuberculosis of the serodiagnostic enzyme-linked immunosorbent assay (ELISA) kit A60 (Anda Biologicals, Strasbourg, France) and of our domestic ELISA based on three purified cell wall glycolipid antigens. METHODS: The presence and concentrations of IgG and IgM anti-A60 antibodies and anti-LOS, anti-DAT and anti-PGLTb1 antibodies against the glycolipid antigens were determined by ELISA in 50 HIV-seronegative and 46 HIV-seropositive patients, with documented active tuberculosis. The specificity of these ELISAs was determined with use of sera from 50 healthy blood donors, 29 patients with non-mycobacterial pulmonary diseases and 24 HIV-positive patients with disseminated Mycobacterium avium infection. RESULTS: With a calculated cut-off for each antigen and immunoglobulin that gave a specificity higher than or equal to 98%, the cumulative ELISA results showed that only 36.5% of the patients with tuberculosis had a positive response in the A60 test, as compared with 84.4% who showed a response to the three glycolipid antigens (p<0.001). This striking difference persisted when the cumulative sensitivities were calculated according to the HIV status of the patients and the localization of tuberculosis. The anti-A60 antibody (IgG and IgM) levels and the degree of sensitivity of the ELISA for detection of A60 antigen were always lower in HIV-positive patients with pulmonary and extrapulmonary tuberculosis than in HIV-negative patients with tuberculosis. The sensitivity of A60 ELISA was further decreased in HIV-positive patients with low CD4+ lymphocytes counts, in contrast to the results with the three glycolipid antigens. CONCLUSIONS: These results show the limitations of the A60 ELISA, and confirm the potencies of the glycolipid antigens in serodiagnosis of tuberculosis in HIV-positive and HIV-negative patients.

The epidemiology of Mycobacterium bovis infections in animals and man: a review

Tuberculosis is primarily a respiratory disease and transmission of infection within and between species is mainly by the airborne route. Mycobacterium bovis, the cause of bovine-type tuberculosis, has an exceptionally wide host range. Susceptible species include cattle, humans, non-human primates, goats, cats dogs, pigs, buffalo, badgers, possums, deer and bison. Many susceptible species, including man, are spillover hosts in which infection is not self-maintaining. In countries where there is transmission of infection from endemically infected wildlife populations to cattle or other farmed animals, eradication is not feasible and control measures must be applied indefinitely. Possible methods of limiting spread of infection from wildlife to cattle including the use of vaccines are outlined. The usefulness of DNA fingerprinting of M. bovis strains as an epidemiological tool and of BCG vaccination of humans and cattle as a control measure are reviewed. The factors determining susceptibility to infection and clinical disease, and the infectiousness of infected hosts and transmission of infection, are detailed. Reports of the epidemiology of M. bovis infections in man and a variety of animal species are reviewed. M. bovis infection was recognised as a major public health problem when this organism was transmitted to man via milk from infected cows. The introduction of pasteurization helped eliminate this problem. Those occupational groups working with M. bovis infected cattle or deer, on the farm or in the slaughter house, are more likely to develop pulmonary disease than alimentary disease. In recent years, tuberculosis in farmed cervidae has become a disease of economic as well as public health importance in several countries. Nowadays, the human immunodeficiency virus (HIV) is associated with a greatly increased risk of overt disease in humans infected with Myobacterium tuberculosis. It is believed this increased risk also occurs in the case of M. bovis infections in humans.

Zoonotic aspects of Mycobacterium bovis infection

The bovine tuberculosis eradication campaigns in many industrially developed countries have led to a huge reduction in the incidence of human tuberculosis caused by Mycobacterium bovis. Overt disease in man may, however, manifest decades after the initial infection and the occurrence of such disease raises several important questions. In particular, it is important to determine whether man-to-man transmission occurs, thereby rendering man a continuing reservoir of infection, and whether, if this is the case, man develops infectious forms of tuberculosis that enable M. bovis to be transmitted back to cattle. Epidemiological studies in South East England indicate that human tuberculosis due to M. bovis is rare and that the incidence is declining. In contrast to earlier days, the lung is now involved in many cases, raising the possibility of transmission of bacilli to other human beings and to cattle by the aerogenous route. No direct evidence of man-to-man transmission of overt disease was found but it is possible that inapparent primary pulmonary infections are occurring and these may proceed to overt post-primary disease in the future. The genito-urinary tract is now the most prevalent site of non-pulmonary lesions and there is firm evidence that this form of tuberculosis poses a hazard to cattle. Though uncommon, human tuberculosis due to M. bovis is still a public health problem of concern to both the medical and veterinary professions and there is a need to maintain careful bacteriological surveillance.

Isolation of mycobacteria from patients seropositive for the human immunodeficiency virus (HIV) in south east England: 1984-92

BACKGROUND

Tuberculosis and other mycobacterial infections are well recognised complications of HIV infection and surveillance is thus required.

METHODS

All mycobacteria isolated from HIV positive subjects and referred to the Public Health Laboratory Service South East Regional Tuberculosis Centre (SERTC) from the first such case in 1984 until the end of 1992 were reviewed.

RESULTS

A total of 803 mycobacteria isolated from 727 HIV positive subjects were referred to the SERTC during the study period. A single species was isolated from 660 patients: 150 members of the tuberculosis complex (146 M tuberculosis, two M bovis, and two M africanum), 356 M avium-intracellulare (MAI), and 154 other environmental mycobacteria. More than one mycobacterium was isolated from 67 patients. In 12 cases M tuberculosis and MAI were isolated from the same patient, almost always in that sequence, with an interval of 8-41 months between isolations. Most of the 407 isolates of MAI (74%) were considered to be clinically significant and often caused disseminated disease. In other cases single isolates of MAI were obtained from sputum or faeces and occasionally such isolates preceded disseminated disease by several months. Only 33 (14%) of the 229 isolates of environmental mycobacteria other than MAI were considered clinically significant.

CONCLUSIONS

HIV related mycobacterial disease is increasing in incidence in south east England. Further studies are required to determine the significance of single isolates of MAI and other environmental mycobacteria as a guide to the need for preventive chemotherapy or immunotherapy.

HIV/AIDS and its implications for the control of animal tuberculosis

The HIV/AIDS pandemic is associated with a number of opportunist mycobacterial infections, principally tuberculosis and disease due to the avian tubercle bacillus, Mycobacterium avium. Tuberculosis occurring early in the course of HIV infection is usually caused by M. tuberculosis. However some cases are due to the bovine tubercle bacillus, M. bovis, which, in turn, is transmissible from man to animals, principally by the aerogenous route although the majority of cases in man are non-pulmonary. These two mycobacterial species may be differentiated by means of a set of simple tests. The quality and quantity of information on the world-wide distribution and prevalence of bovine and human tuberculosis due to M. bovis is not uniform. There is a notable paucity of information from the tropics but available reports suggest that there are significant levels of bovine tuberculosis. If correct, this information has serious public health implications in the light of the current HIV/AIDS epidemic. Urgent investigation is required so that appropriate control measures can be instituted where indicated and possible. The avian tubercle bacillus is a very common opportunistic pathogen in the late stage of AIDS but infection leading to disease is extremely rare in healthy, HIV-negative persons. Because of its widespread environmental distribution, infection by this pathogen cannot be prevented.

A bacteriological survey of tuberculosis due to the human tubercle bacillus (Mycobacterium tuberculosis) in south-east England: 1984-91

The occurrence and nature of bacteriologically confirmed tuberculosis due to Mycobacterium tuberculosis in South-East England in the period 1984-91 is reported and compared with the results of a study for 1977-83. Registered new cases reached a low of 1028 in 1988 but increased to 1252 in 1991. This appeared to be due to a halt in the previous decline in new cases of European patients, a small increase in the number of Indian subcontinent (ISC) patients and an increase in patients from Africa. A total of 122 patients, mostly of European ethnic origin, were known to be HIV positive. As in the 1977-83 study, disease in the ISC group affected younger patients than in the European group, tubercle bacilli were more frequently isolated from a non-pulmonary site in the ISC group (45%) than in the European group (19%) and there was a higher incidence of the South Indian variant of M. tuberculosis in the former group (17%) than in the latter (9%). The overall incidence of drug resistance has not altered significantly since the 1977-83 study but 46 strains resistant to 3 or more drugs were isolated from 4099 ISC patients, compared with 3 of 4594 strains from European patients. Six of the 122 isolates from HIV positive patients were drug-resistant but none was multi-drug resistant. The slight rise in registered bacteriologically proven cases of tuberculosis, the presence of multi-drug resistant strains, the occurrence of HIV-related tuberculosis and reports of the emergence of multi-drug-resistant HIV-related tuberculosis in other countries strongly indicate the need for continued careful surveillance.

Isolation of a fastidious Mycobacterium species from two AIDS patients

Two strains of fastidious mycobacteria were isolated from two patients with AIDS and clinical disease suggestive of Mycobacterium avium complex infection. Acid-fast bacilli were isolated from blood and bone marrow of both patients in BACTEC 12B and/or 13A media. The acid-fast bacilli failed to grow on subculture to routine Löwenstein-Jensen medium containing pyruvate and egg yolk agar. After several attempts, the strain from one patient was finally cultured on Middlebrook 7H9 medium with agar, charcoal, and yeast extract 13 months after the initial specimens were received in the laboratory. The second patient's strain was cultured on the same medium 6 weeks postinoculation with fresh BACTEC fluid and 5 months after specimen collection. Routine biochemical and growth tests were performed on these isolates but failed to give definitive identifications. 16S rRNA gene sequencing suggested that the organisms share at least 98.9% homology with M. simiae. Even greater homology (99.86%) was found with the recently described species "M. genavense." Recognition of the fastidious nature of some mycobacteria that infect AIDS patients is important in the treatment of infections in these patients and in understanding the epidemiology of atypical mycobacterial infections. It is suggested that a liquid culture medium such as BACTEC be employed for primary isolation of mycobacteria from AIDS patients and that subculture to the charcoal medium described here be carried out for those organisms that fail to grow on subculture to routine media.

Slow bacterial infections or autoimmunity?

In this article, Graham Rook and John Stanford propose that a group of idiopathic diseases that are often associated with a degree of autoimmunity and arthritis, including rheumatoid arthritis, inflammatory bowel disease, sarcoidosis and psoriasis, are caused by extremely slow-growing bacteria. They suggest that these diseases are one end of a continuous spectrum caused by related slow-growing genera, which ranges from rheumatoid arthritis, through Takayasu's arteritis and Whipple's disease, to reach the conventional mycobacterioses such as tuberculosis and leprosy.