Tubercle最新文献

Non-BCG-vaccinated preschool children (4 or 5 years of age) were simultaneously tested on separate arms with a 2 IU PPD RT23 and 0.1 μg Mycobacterium avium sensitin RS10 or 0.1 μg Mycobacterium scrofulaceum sensitin RS95. None of the 762 children had any known exposure to tuberculosis. A total of 8.8% reacted with an induration (⩾ 3 mm to PPD RT23 while 2% reacted with ⩾ 6 mm. Half the children were tested with M. avium sensitin: 18.9 and 7.8% reacted when 3 and 6 mm cut-off points, respectively, were taken. The remaining children were tested with M. scrofulaceum sensitin: 18.4 and 6.3%, respectively, reacted.

In a previous study of schoolchildren aged 8 or 9 years, reactions to sensitins were considerably more frequent. Thus, sensitisation by atypical mycobacteria seems to increase from the preschool to the early school age. This finding probably reflects a continuous exposure of the children to atypical mycobacteria from various sources.

The preschool children with a reaction to PPD RT23 ⩾ 6 mm were examined and chest X-rays were performed. All children were healthy but one child had enlarged lymph nodes in the mediastinum and abdomen. It cannot be excluded that these pathological findings were caused by atypical mycobacteria.

The epidemiology of mycobacterial infections was studied in a wide cross-section of the Jeddah population over 2 years (1987–1989). Saudis, non-Saudis and patients from a stable population attending National Guard King Khalid Hospital (NGKKH) were compared. The ratio of Saudi to non-Saudi was 1:2 and males accounted for 65% of the total. The incidence was highest among young adults although the peak varied slightly between Saudi and non-Saudi patients. Extra-pulmonary tuberculosis was also preponderant among young adults, particularly females. Variants of Mycobacterium tuberculosis were investigated for the first time in Saudi Arabia. African and Asian variants were isolated from both Saudi and non-Saudi patients, the former being more numerous. Extra-pulmonary tuberculosis, particularly lymphadenopathy, accounted for a large proportion of mycobacterial infections, 59% at NGKKH. Mycobacterial species other than M. tuberculosis were fully identified and accounted for 9% of the isolates, Mycobacterium fortuitum and Mycobacterium chelonei being the two most prevalent.

A polymerase chain reaction for the specific detection of Mycobacterium tuberculosis has been developed and evaluated for clinical applicability. Primers were designed to amplify a 240 base pair region in the MPB 64 protein coding gene (nts 460–700). From among 15 different DNA templates tested (including 10 species of mycobacteria) PCR amplified the DNA from M. tuberculosis complex only, demonstrating its exquisite specificity. Sensitivity studies using serial ten-fold dilutions of M. tuberculosis bacilli determined the limit of detectability to be 10 organisms.

A total of 143 clinical specimens were analysed. This consisted of 26 known non-tuberculous specimens (control group) and 117 specimens received at the Tuberculosis Diagnostic Service of AIIMS (test group). None of the specimens in the control group was positive by PCR. Out of 117 specimens in the test group, 19 were culture positive for mycobacteria and 17 of these isolates were identified as M. tuberculosis. All the specimens from which M. tuberculosis was grown were also PCR positive. The remaining two isolates were identified as mycobacteria other than M. tuberculosis and these two specimens were PCR negative. An additional 14 culture negative specimens were PCR positive yielding an overall M. tuberculosis positivity rate of 26.5% (31/117) compared to 14.5% (17/117) by culture. The superior sensitivity of PCR over culture was more evident in non-pulmonary cases where PCR picked up 10 cases in addition to three culture positives out of 69 specimens. On the other hand, out of 48 pulmonary specimens only four cases in addition to 14 culture positives were picked up by PCR.

Non-BCG-vaccinated schoolchildren (8 or 9 years of age) were simultaneously tested on separate arms with 2 IU PPD RT23 and 0.1 pg Mycobacterium avium sensitin RS10 or 0.1 Fig Mycobacterium scrofulaceum sensitin RS95. None of the 2819 analysed children had any known exposure to tuberculosis. A total of 3.4% reacted with an induration ⩾ 6 mm to PPD RT23. Half the number of children were tested with M. avium sensitin and 25.4% reacted while the remaining were tested with M. scrofulaceum sensitin and 32.4% reacted when the cut-off was 6 mm. For about 90% of the children the sensitin reaction was larger than or equal to the tuberculin (PPD RT23) reaction. Correlation analyses showed that moderate and high PPD RT23 values were combined with still higher sensitin values, indicating that the tuberculin reactions were mainly cross-reactions due to the antigenic similarity between tuberculin and sensitins. The presence of birds, dogs and cats in the homes was combined with an increased frequency of children reacting to the sensitins used. The children with reactions to PPD RT23 ⩾6 mm were examined and chest X-rays were performed. None of them showed any signs or symptoms of mycobacterial disease. In non-BCG-vaccinated Swedish schoolchildren without clinical signs of tuberculosis and without known contact with a contagious tuberculous person, indurations less than 12 to 14 mm on tuberculin testing are probably caused by atypical mycobacteria. In such cases sensitin tests should be performed to verify the suspicion.

Two cases of tuberculous meningitis complicated by spread to the spinal cord and nerve roots are described. Recognition of impending paraplegia by a rising cerebrospinal fluid protein content and manometric block should prompt steroid therapy as this may prevent irreversible neurological deficit.