Algae -- a poor man's HAART?

Drawing inferences from epidemiologic studies of HIV/AIDS and in vivo and in vitro HIV inhibition by algae, we propose algal consumption as one unifying characteristic of countries with anomalously low rates. HIV/AIDS incidence and prevalence in Eastern Asia ( approximately 1/10000 adults in Japan and Korea), compared to Africa ( approximately 1/10 adults), strongly suggest that differences in IV drug use and sexual behavior are insufficient to explain the 1000-fold variation. Even in Africa, AIDS/HIV rates vary. Chad has consistently reported low rates of HIV/AIDS (2-4/100). Possibly not coincidentally, most people in Japan and Korea eat seaweed daily and the Kanemba, one of the major tribal groups in Chad, eat a blue green alga (Spirulina) daily. Average daily algae consumption in Asia and Africa ranges between 1 and 2 tablespoons (3-13 g). Regular consumption of dietary algae might help prevent HIV infection and suppress viral load among those infected.     

AIDS mortality in a tertiary health institution: A four-year review

Africa contains 70% of adults and 80% of children living with AIDS in the world and has buried 75% of the 21.8 million worldwide who have died of AIDS since the epidemic began. Nigeria, the most populous country in Africa, has 5.8% of her adult population having HIV infection at the end of 2003. We reviewed the causes of death among AIDS patients in Aminu Kano Teaching Hospital Kano, Nigeria over four years. Four-hundred-fifty-five (9.9%) of the 4,574 adult medical admissions were due to HIV/AIDS-related diagnosis. HIV/AIDS admissions increased progressively from 45 cases in 2001 to 174 in 2004. HIV/AIDS caused 176 deaths over the period giving an HIV-related mortality of 38.7%. This also showed a gradual increase from 24 deaths in 2001 to 61 deaths in 2004. The most common causes of death were tuberculosis (33.4%), septicemia (23.8%), advanced HIV disease (9.1%), meningitis (7.4%), other pulmonary infections (5.1%) and Kaposi's sarcoma (4.5%). The present dismal situation of patients living with HIV/AIDS calls for enhanced strategies to decrease the mortality trend observed. With the introduction of affordable highly active antiretroviral therapy (HAART) in several centers in Nigeria, it is hoped that infected patients can be made to live longer.     

Transmission permeability of tuberculosis involving immigrants, revealed by a multicentre analysis of clusters

In recent years, the number of cases of tuberculosis (TB) among immigrants in Spain has increased markedly, and led to this analysis of the recent transmission patterns of TB in the immigrant population in Madrid. The countries from which the highest number of immigrant cases have been reported were Ecuador (21%), Romania (16%), Morocco (12%), Peru (11%) and Bolivia (9%). Fifty-one per cent of the cases were from South America. In a multicentre study (2004–2006), IS 6110 restriction fragment length polymorphism and spoligotyping were used to genotype the Mycobacterium tuberculosis isolates from 632 immigrant cases from 47 countries. A total of 183 cases (29%) were grouped into 59 clusters, which are markers of potential transmission events. Most of the clusters (81%) included patients living in different healthcare districts, and 54% of the clusters were multinational. When a sample of 478 autochthonous cases was included, 53% of the clusters involving immigrants also included autochthonous cases. This study revealed marked transmission permeability among nationalities and between the immigrant and the autochthonous populations.     

Diagnosing mycobacterial lymphadenitis in children using fine needle aspiration biopsy: cytomorphology, ZN staining and autofluorescence -- making more of less

Although the incidence of TB has stabilized or declined in most world regions, it is increasing in Africa, Southeast Asia, and the Eastern Mediterranean, fuelled by the HIV pandemic. More than 4,000 people died daily from TB-related illnesses in 2005. TB is a major cause of childhood morbidity and mortality in these developing countries, and there is an urgent need for rapid and definitive modalities for mycobacterial diagnosis in children. This prospective study in Tygerberg Hospital, Cape Town, South Africa, evaluates the ability of fine needle aspiration biopsy (FNAB) to diagnose mycobacterial lymphadenitis in children, using cytomorphology, autofluorescence on Papanicolaou stained smears, Ziehl-Nielsen (ZN) staining and/or culture. FNABs were performed on 200 children, and 25 (12.5%) aspirates were inadequate. Cultures were positive in 79/175 (45%); Mycobacterium tuberculosis was identified in 61 and Mycobacterium bovis BCG in 18 cases. Using culture as the gold standard, the concordance of the different techniques was as follows: cytomorphology 70%, ZN staining 73%, and autofluorescence 68%. Using an alternative gold standard (culture positive and/or suggestive cytomorphology plus positive autofluorescence or ZN smear), the "true" diagnostic performance of the various techniques was as follows: cytomorphology-sensitivity 78%, specificity 91%, positive predictive value (PPV) 93%, ZN staining - sensitivity 62%%, specificity 97%, PPV 97%; autofluorescence-sensitivity 67%, specificity 97%, PPV 97%; and culture-sensitivity 75%, specificity 100%, and PPV 100%. FNAB was shown to provide a rapid and definitive diagnosis in the majority of cases of suspected tuberculous lymphadenitis in children, based on cytomorphology and identification of the organism.     

Unusually high incidence of tuberculosis among boys with haemophilia during an outbreak of the disease in hospital.

Of 30 children with bleeding disorders exposed to an index tuberculosis case, six developed primary pulmonary tuberculosis and two others became positive skin reactors. There was a significant correlation between the amount of replacement treatment received and the development of evidence of tuberculous infection. Only two of those who developed evidence of tuberculosis had antibodies to the human T cell lymphotropic virus. These two boys showed much later Mantoux positive conversion than the six others.     

The role of histopathology in establishing the diagnosis of tuberculous pericardial effusions in the presence of HIV

AIMS: To establish the influence of human immunodeficiency virus (HIV) infection on the histopathological features of patients presenting with tuberculous pericarditis. METHODS AND RESULTS: A prospective study was carried out at Tygerberg Academic Hospital, South Africa; 36 patients with large pericardial effusions had open pericardial biopsies under general anaesthesia and were included in the study. Patients underwent pericardiocentesis, followed by daily intermittent catheter drainage; a comprehensive diagnostic work-up (including histopathology of the pericardial tissue) was also performed. Histological tuberculous pericarditis was diagnosed according to predetermined criteria. Tuberculous pericarditis was identified in 25 patients, five of whom were HIV+. The presence of granulomatous inflammation (with or without necrosis) and/or Ziehl-Neelsen positivity yielded the best test results (sensitivity 64%, specificity 100% and diagnostic efficiency 75%). CONCLUSIONS: Co-infection with HIV impacts on the histopathological features of pericardial tuberculosis and leads to a decrease in the sensitivity of the test. In areas which have a high prevalence of tuberculosis, the combination of a sensitive test such as adenosine deaminase, chest X-ray and clinical features has a higher diagnostic efficiency than pericardial biopsy in diagnosing tuberculous pericarditis.     

Evaluation of the Tuberculin Gamma Interferon Assay: Potential To Replace the Mantoux Skin Test

We evaluated an in vitro test of cell-mediated immunity, the tuberculin gamma interferon assay, QuantiFERON-TB (QIFN), in 455 individuals from three groups: group I, 237 immigrants from high-risk countries; group II, 127 health care workers undergoing Mantoux testing; group III, 91 patients being investigated for possible active tuberculosis (79 patients) or Mycobacterium avium-Mycobacterium intracellulare complex infection (12 patients). The QIFN results were compared either to those of the Mantoux test or to microbiological and clinical diagnosis, as appropriate. In each group the correlation between the diameter of induration for the skin test and the magnitude of QIFN response was significant and of moderate strength (Spearman's rank correlation coefficient; rho = 0.59 to 0.61; P < 0.001). For group I, the agreement between QIFN and Mantoux results was 89% for Mantoux-negative and 64% for Mantoux-positive individuals. For group II, when >/=10-mm-diameter induration was taken as positive, the agreement was 81% for Mantoux-negative and 67% for Mantoux-positive individuals. For group III, agreement was 81% for Mantoux-negative and 86% for Mantoux-positive patients. For patients being evaluated for active tuberculosis, the performance of the Mantoux test was not statistically different from that of the QIFN assay. In patients with active tuberculosis, the assay had a sensitivity of 77%, not significantly higher for extrapulmonary than pulmonary cases (83% versus 74%). QIFN sensitivity was not significantly different for smear-negative or smear-positive cases (80% versus 71%). The QIFN assay is a potential replacement for the Mantoux test. The acceptability of these performance values and those of similar evaluations will determine the place this test will have in detecting evidence of mycobacterial infection.     

Molecular epidemiology of tuberculosis in Guadeloupe from 1994 to 2000

In Guadeloupe, the incidence of tuberculosis decreased between 1994 and 2000. The rate of resistance to at least one antibiotic remained constant at 11%, whereas the rate of multiple-drug resistance increased from 0.9 to 2.4% in 2000. The proportion of patients of foreign origin (mainly from Haiti and the Dominican Republic) increased whereas the number of French patients decreased. These results show that the epidemiology of tuberculosis in Guadeloupe is similar to industrialized countries as older people, foreigners from countries where TB is endemic, and HIV+ patients are at a higher risk to declare tuberculosis disease. Molecular typing realized by spoligotyping showed the importance of previous successive colonizations and migrations as characterized by the presence of major phylogenetic families originating essentially from Northern Europe (Haarlem), Latin America and Mediterranean (LAM) and from Anglo-Saxon countries (X). The sub-typing of clustered strains by IS6110-RFLP and by a PCR method based on the variable number of tandem DNA repeats (VNTR), highlighted 29 clusters, corresponding to 44.8% of clustered strains, and allowed to estimate the rate of recent transmission at 32.2%. The epidemiologic data associated with fingerprinting results underlined the importance of reactivation cases among older people, a significant number of imported TB cases without evident links, and casual contacts.     

艾滋病流行病学

1　概述艾滋病是严重危害人群健康的疾病之一 ,其病死率极高。自 1981年美国首次报道艾滋病以来 ,艾滋病以传播迅速、病势凶险 ,预后差及危害严重而震惊世界。目前艾滋病已在全球广泛流行 ,严重危害着人类的健康。1 1　全球流行形势联合国艾滋病规划署和世界卫生组织最新报告显示 ,截至 1999年底全球ＨＩＶ感染者总数已超过5310万人 ,死于ＡＩＤＳ的人数已达 1880万人 (其中成人 150 0万、儿童 380万 )。 1999年全球新增加ＨＩＶ/ＡＩＤＳ 540万人 ,因艾滋病死亡 2 80万 ,平均每天新增加ＨＩＶ感染者 1 5万人。而且 95%以上的感染者集中在发…     

Tuberculous lymphadenitis associated with human immunodeficiency virus (HIV) in Uganda.

Sixteen adults presented with lymphadenopathy which was tuberculous on biopsy; they were all seropositive for human immunodeficiency virus (HIV-1), but none had the clinical criteria of the acquired immunodeficiency syndrome (AIDS). The biopsy specimen showed caseating tuberculosis, with scanty or no visible acid fast bacilli in seven cases; the remaining nine had a poor cellular reactivity with numerous bacilli. Antituberculous chemotherapy for two months reduced the lymphadenopathy. Two patients subsequently developed AIDS. Mycobacterial cultures were not performed, but the infection was almost certainly Mycobacterium tuberculosis. The space-time clustering of tuberculous lymphadenitis now seen in Kampala, and the unusual non-reactive histopathology, are typical of the impairment of cellular immunity induced by HIV infection.     

Relapse of pulmonary tuberculosis in the context of tuberculosis-HIV co-infection in Abidjan (Côte d'Ivoire). Short note

A cohort study was carried out from October 2001 to March 2002, in order to analyze the main characteristics of 53 adults patients (38 HIV-positive and 15 HIV-negative), who had a relapse of pulmonary tuberculosis. The observance in the first period of the treatment of tuberculosis was regular in 79% of tuberculous patients infected by the HIV (30/38) and in 87% of tuberculous patients who where HIV-negative (13/15) (p = 0.7). The relapse occurred before one year after recovery in 74% among the HIV-positive (28/38) and in 33% among the HIV-negative patients (5/15) (p = 0.00). Most of the HIV-positive patients (74%) had CD4 counts under 200/mm3 and 80% of the HIV-negative patients had more than 500 CD4 counts/mm3 (p = 0.00). After two months of retreatment following the relapse diagnosis, the rate of improvement in patients was about 16% in HIV infected (6/38) and about 67% in HIV-negative patients (10/15) (p = 0.00).     

Identification of B- and T-cell epitopes within the MTP40 protein of Mycobacterium tuberculosis and their correlation with the disease course.

Synthetic peptides derived from the amino acid sequence of MTP40, a recently characterized Mycobacterium tuberculosis protein, were tested by two different immunological assays in 91 individuals. For the purposes of this study, the population was distributed in four groups: active tuberculosis (TBC) patients with elevated bacillus loads (BK+), active TBC patients with low bacillus loads (BK-), healthy individuals living in the same household with tuberculous patients (HH), and normal individuals, who had presumably never been in contact with the bacilli (control). We found that T cells of individuals belonging to the HH group showed the highest and most frequent recognition of these peptides in a T-cell proliferation assay, while their antibodies showed the lowest recognition of these peptides when tested by enzyme-linked immunosorbent assay. In contrast, TBC patients revealed an inverse pattern of immune response. Interestingly, one of these peptides (P7) was recognized by T cells of 64% of the HH individuals and by 4.5% of normal donors. Another peptide (P4) was recognized by 55% of sera from BK+ patients and by 5.5% of normal donors. The results presented here indicate the existence of T- and B-cell epitopes within the MTP40 protein. Given the particular recognition pattern of this protein, added to the fact that it appears to be a species-specific antigen of M. tuberculosis, a detailed study of the immune response to it may be useful in the design of more accurate diagnostic tests and an improved vaccine against human TBC.     

Molecular epidemiology and drug resistance of Mycobacterium tuberculosis isolates from Ethiopian pulmonary tuberculosis patients with and without human immunodeficiency virus infection

We have analyzed the molecular epidemiology and drug resistance of 121 Mycobacterium tuberculosis isolates from consecutive patients with culture-positive pulmonary tuberculosis attending a university hospital outpatient department in Addis Ababa, Ethiopia. Restriction fragment length polymorphism analysis and spoligotyping were used to analyze the DNA fingerprinting patterns. Fifty-one (41.2%) of the isolates were found in 13 clusters with two or more identical DNA patterns. Two such clusters contained 49.0% of all clustered isolates. In a multivariate logistic regression model, human immunodeficiency virus (HIV)-positive serostatus was significantly associated with clustering of isolates for patients of both sexes (odds ratio [OR], 2.55; 95% confidence interval [CI], 1.17 to 5.80). There was a trend toward increased clustering of isolates from tuberculous women residing in Addis Ababa (OR, 2.10; 95% CI, 0.85 to 5.25). In total, 17 of 121 isolates (14.0%) were resistant to one or more of the antituberculosis drugs isoniazid (8.3%), streptomycin (7.4%), rifampin (2.5%), and ethambutol (1.7%). The high rate of drug-resistant isolates (29.6%) coincided with the peak prevalence of HIV infection (77.8%) in patients 35 to 44 years old. The majority (62.5%) of resistant isolates in this group were found within clusters. The simultaneous accumulation of certain bacterial clones in a patient population likely reflects recent transmission. Hence, we conclude that tuberculosis is commonly caused by recent infection with M. tuberculosis in HIV-positive Ethiopian patients. Furthermore, with the rapidly increasing prevalence of HIV infection in Ethiopia, the burden of tuberculosis, including drug-resistant tuberculosis, is likely to increase. Strengthening of classical tuberculosis control measures by promoting active case finding among HIV-positive adults with tuberculosis is warranted to reduce rates of transmission.     

Tuberculous meningitis in patients infected with the human immunodeficiency virus.

BACKGROUND AND METHODS. Tuberculosis is a frequent complication of human immunodeficiency virus (HIV) infection. We describe the clinical manifestations and outcomes of tuberculous meningitis in patients with HIV infection, and compare them with those in non-HIV-infected patients. We reviewed the records from 1985 through 1990 at two large referral hospitals in Madrid for patients who had Mycobacterium tuberculosis isolated from cerebrospinal fluid. RESULTS. Of 2205 patients with tuberculosis, 455 (21 percent) also had HIV infection, of whom 45 had M. tuberculosis isolated from the cerebrospinal fluid. Of the 37 HIV-infected patients with tuberculous meningitis for whom records were available, 24 (65 percent) had clinical or radiologic evidence of extrameningeal tuberculosis at the time of admission. In 18 of 26 patients (69 percent), a CT scan of the head was abnormal. In most patients, analysis of cerebrospinal fluid showed pleocytosis (median white-cell count, 0.234 x 10(9) per liter) and hypoglycorrhachia (median glucose level, 1.3 mmol per liter), but in 43 percent (15 of 35), the level of protein in cerebrospinal fluid was normal. In four patients with HIV infection, tuberculosis was only discovered after their deaths. Of the 33 patients who received antituberculous treatment, 7 died (in-hospital mortality, 21 percent). Illness lasting more than 14 days before admission and a CD4+ cell count of less than 0.2 x 10(9) per liter (200 per cubic millimeter) were associated with a poor prognosis. Comparison with tuberculous meningitis in patients without HIV infection showed that the presentation, clinical manifestations, cerebrospinal fluid findings, and mortality were generally similar in the two groups. However, of the 1750 patients without HIV infection, only 2 percent (38 patients) had tuberculous meningitis, as compared with 10 percent of the HIV-infected patients (P less than 0.001). CONCLUSIONS. HIV-infected patients with tuberculosis are at increased risk for meningitis, but infection with HIV does not appear to change the clinical manifestations or the outcome of tuberculous meningitis.     

Adult non-viral lymphocytic meningitis in Abidjan (Côte d'Ivoire)

Our prospective and longitudinal study aimed to analyse the aetiologies, clinical features and prognostic of non viral lymphocytes meningitis (NVLM). We recruited 131 patients, 77 males (59%) and 54 females (41%) sex-ratio 1.4. The mean age was 35 years [15-67]. 117 patients were HIV positive (89%) and 14 (11%) were HIV negative. Feverish meningoencephalitis was present in 85% of cases, with 7 days for mean delay of admission into hospital. 80 germs were found in the C.S.F. 70 Cryptococcus neoformans, 4 Mycobacterium tuberculosis, 3 Streptococcus pneumoniae, 1 Candida albicans, 1 Neisseria meningitis and 1 Trypanosoma gambiense. 63 aetiologies were linked to lymphocytes meningitis by indirect deduction: 41 cases of tuberculous meningitis with lung X-ray anomalies and M. tuberculosis in sputum (11 times), 11 cases of cerebral malaria with Plasmodium falciparum in blood, 11 cases of cerebral toxoplasmosis by significant features with cerebral tomodensitometry. Letality was 53%, 35% of patients improved and 12% were lost to follow-up. Our study shows the difficulties in the management of the NVLM, due to the delay of diagnosis, particularly for tuberculous meningitis.     

Molecular epidemiology of Mycobacterium tuberculosis strains isolated during a 3-year period (1993 to 1995) in Seville, Spain.

The genetic polymorphism of Mycobacterium tuberculosis strains isolated in Seville, Spain, was studied by using computer-assisted analysis of the IS6110 fingerprint in order to determine the current situation and to evaluate the human-to-human transmission of this pathogen. One hundred seventy-six isolates from 175 patients among the 205 patients diagnosed with tuberculosis (TB) during a 3-year period (1993 to 1995) were cultured and analyzed. One hundred nine patients (62%) were infected with genetically different isolates, and 67 isolates (38%) were grouped into 19 clusters. These results demonstrate that the level of clustering of strains in Seville is intermediate between those in developed and developing countries. Epidemiological relatedness was shown for isolates from only 10 of these clusters. Active and high transmission rates exist in children and in human immunodeficiency virus (HIV)-infected adults, while in non-HIV-infected adults this transmission rate is moderate. Although transmission from children to adults is uncommon, the probability of transmission from HIV-infected patients to young adults not infected with HIV may be higher. On the basis of these observations, we predict a constant rise in the rate of TB transmission among HIV-infected patients and probably in young adult patients not infected with HIV if measures for the effective prevention of TB among the HIV-infected population are not implemented.     

Presentation and outcome of tuberculous meningitis among children: experiences from a tertiary children's hospital

Background

Diagnosis of tuberculous meningitis (TBM) is complicated and outcome is poor especially in resource limited settings. Early diagnosis and prompt treatment are vital in effective treatment. We set out to describe experiences in the management and immediate outcome of TBM a tertiary-level children''s hospital in a high HIV and tuberculosis co-infection setting.

Methods

This retrospective study included children who were diagnosed with TBM in the year 2009. A pre-coded questionnaire was used to extract data on presentation, diagnostics, treatment and outcome at the time of hospital discharge. Data was analyzed using STATA statistical package (StataCorp, Version 11).

Results

Of the 40 children diagnosed with TBM, 6 (15%) had definitive TBM, 17 (42.5%) had probable TBM and 17 (42.5%) had possible TBM. The cerebrospinal fluid (CSF) chemistry and cells were abnormal in 39/40 (98%). Mantoux test was reactive in 16/29 (55%) and 17/30 (57%) had Chest X-rays suggestive of tuberculosis. Only 3/21 (14%) had positive sputum tuberculosis culture and 89% (32/36) had neuro-imaging abnormalities. Outcome at discharge was; 8% died, 49% improved with neurological sequelae and 43% improved without sequelae. Having TBM stage 3 at admission was associated with mortality (p=0.001).

Conclusions

Most children had early diagnosis of TBM and mortality was lower than in previous studies. We recommend a larger prospective study to further understand the outcome of TBM.     

A comparison of seven tests for serological diagnosis of tuberculosis

Seven serological tests, two immunochromatographic tests, ICT Tuberculosis and RAPID TEST TB, and five enzyme-linked immunosorbent assays, TUBERCULOSIS IgA EIA, PATHOZYME-TB complex, PATHOZYME-MYCO IgG, PATHOZYME-MYCO IgA, and PATHOZYME-MYCO IgM, were evaluated simultaneously with 298 serum samples from three groups of individuals: 44 patients with active tuberculosis, 204 controls who had undergone the Mantoux test (89 Mantoux test-positive and 115 Mantoux test-negative controls), and 50 anonymous controls. The sensitivities of the tests with sera from patients with active tuberculosis were poor to modest, ranging from 16 to 57%. All the tests performed equally with sera from subgroups of those with active tuberculosis, those with pulmonary (33 patients) versus extrapulmonary (11 patients) disease, and those who were smear positive (24 patients) versus smear negative (12 patients) (P > 0.05). The specificities of the tests ranged from 80 to 97% with sera from the Mantoux test controls and 62 to 100% with sera from the anonymous controls. The TUBERCULOSIS IgA EIA had the highest sensitivity (57%) with sera from patients with active tuberculosis, with a high specificity of 93% with sera from the Mantoux test controls, but a very poor specificity of 62% with sera from the anonymous controls. Overall, ICT Tuberculosis followed by PATHOZYME-MYCO IgG had the best performance characteristics, with sensitivities of 41 and 55%, respectively, with sera from patients with active tuberculosis and specificities of 96 and 89%, respectively, with sera from the Mantoux test controls and 88 and 90%, respectively, with sera from the anonymous controls. By combining all the test results, a maximum sensitivity of 84% was obtained, with reciprocal drops in specificities to 55 and 42% for the Mantoux test controls and anonymous controls, respectively. The best combination was that of ICT Tuberculosis and PATHOZYME-MYCO IgG, with a sensitivity of 66% and a specificity of 86% for the Mantoux test controls and a sensitivity and specificity of 78% for the anonymous controls. While a negative result by any one of these tests would be useful in helping to exclude disease in a population with a low prevalence of tuberculosis, a positive result may aid in clinical decision making when applied to symptomatic patients being evaluated for active tuberculosis.     

Molecular epidemiology study of exogenous reinfection in an area with a low incidence of tuberculosis

In geographical areas with a low incidence of tuberculosis, recurrent tuberculosis is generally due to reactivation of the disease. However, the relative contribution of tuberculosis reinfection increases in parallel with the incidence of disease and is likely to depend on the epidemiological context: factors such as the spread of multidrug resistance, human immunodeficiency virus (HIV) infection, and immigration from developing countries could modify disease transmission in areas at low risk for tuberculosis. A molecular epidemiology study was performed in Lombardy, Northern Italy, where the incidence of tuberculosis is 17.5 cases per 100,000 persons. A total of 2,452 cases of culture-confirmed tuberculosis in 2,127 patients were studied. A group of 32 patients (1.5%), each of whom had two episodes of tuberculosis with cure as the outcome of the first episode and with more than 6 months between the two episodes, were studied by means of restriction fragment length polymorphism DNA fingerprinting analysis. For 5 of the 32 patients (16%), the DNA fingerprinting patterns of Mycobacterium tuberculosis strains responsible for the second episode did not match those of the corresponding isolates of the first episode, indicating exogenous reinfection. Two of these patients developed multidrug-resistant tuberculosis during the second episode, and in three cases the isolates belonged to clusters of M. tuberculosis strains spreading in the community. A fourfold-increased risk for reinfection was observed in immigrant patients compared to Italian subjects. In contrast, a higher risk of relapse rather than reinfection was evidenced in HIV-positive subjects and in patients infected with multidrug-resistant tuberculosis. Episodes of tuberculosis reinfection in areas with a low incidence of tuberculosis are rare compared to those in high-incidence geographical regions. In populations that have immigrated from high-risk areas, reinfection may represent a considerable contributor to the rate of recurrent tuberculosis. This finding emphasizes the importance of containing the spread of epidemic strains in close communities, in order to prevent changes in global tuberculosis trends for developed countries.