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Mannose-binding lectin (MBL) is a serum lectin that mediates phagocytosis and activates complement. Its deficiency has been associated with increased susceptibility to infectious diseases, mainly in childhood. However, non-producer mbl-2 alleles are common in most populations, suggesting a selective advantage of these alleles. We have analysed the association of mbl-2 structural and promoter polymorphisms with HIV infection and tuberculosis (TBC) in a white Spanish population, including 615 HIV patients with and without TBC, 127 no-HIV TBC patients, 142 TBC household contacts and 344 controls. The frequency of low or non-producer mbl-2 genotypes was lower in HIV patients than in controls. HIV-TBC patients presented lower frequencies of low or non-producer alleles and genotypes than HIV no-TBC patients and controls. Additionally, we found a significantly positive correlation between the incidence of TBC and the frequency of non-producer mbl-2 alleles in Western Europe. Therefore, MBL deficiency may be associated with a lower risk of HIV infection, and also of active TBC, at least in HIV patients. The protective role of low-producer mbl-2 genotypes against TBC together with the positive correlation observed between non-producer mbl-2 alleles and TBC incidence, suggest a balancing selection: in spite of an increased susceptibility to respiratory infections associated with MBL deficiency, mbl-2 deficient alleles would have been selected along different populations as a consequence of its selective advantage against intracellular pathogens, such as M. tuberculosis.

To evaluate the performance of the Amplified Mycobacterium tuberculosis Direct Test 2- Gen Probe (AMTD- 2) for direct detection of Mycobacterium tuberculosis in smear-negative samples.From January to December 1999, 683 specimens, 333 respiratory and 350 non-respiratory ones collected from 457 patients, were included in the study. All the samples of HIV-positive patients, the respiratory samples from patients suspected of having pulmonary tuberculosis (at least two by patient) and all non-respiratory samples were included. As diagnosis method of reference, the culture isolation was considered. Clinical data were analyzed in case of discrepant results and clinical diagnosis was considered the reference criteria. The technique was performed once a week.The sensitivity, specificity, and positive and negative predictive values of this assay were 58.9%, 93.9%, 37.1% and 97.4% respectively related to the standard culture. When referred to clinical diagnosis of active tuberculosis, these values improved to 70.4%, 97.7%, 73.1% and 96.8% respectively (in respiratory samples were 67.6%, 98.6%, 86.2% and 95.9% and in nonrespiratory ones 76.5%, 96.9%, 56.5% and 98.7% respectively). The mean time of diagnosis by culture and by AMTD-2 were 20.3 days (range 10-63) and 5.7 days (range 2-20) respectively.It is concluded that AMTD-2 is a rapid diagnosis method when clinical data are sugestive with active tuberculosis. However, due to the low positive predictive value, it would be convenient to obtain successive samples to confirm the result in patients without clinical evidence of tuberculosis.