Drug resistant tuberculosis in sub-Saharan Africa: an estimation of incidence and cost for the year 2000.

SETTING: Rwanda. OBJECTIVES: To evaluate the tuberculosis (TB) drug resistance in Rwanda on smear positive sputa, collected prospectively at the start of the National TB programme, before the start of any treatment or retreatment. To adapt the scenarios of Schulzer et al (1992) to the data from Rwanda, in order to obtain an estimation of the number of drug resistant and multi-drug resistant (MDR) TB cases expected by the year 2000. DESIGN: A total of 298 specimens (236 randomly selected new cases and 62 retreated cases), collected between January 1991 and June 1993, were sent to Belgium in 1% cetylpyridinium chloride. Drug resistance was determined using the proportion method. RESULTS: MDR, i.e. resistance to at least rifampicin (R) and isoniazid (H), was observed in 3 (1.3%) out of 236 new cases and in 4 (6.5%) out of 62 treated cases. For new cases, single drug resistance to H, R and ethambutol (E) was 3%, 0.4% respectively; for treated cases it was 14.5%, 1.6% and 6.5 respectively. Based on the estimate of the size of the TB problem in sub-Saharan Africa by the year of 2000 (Schulzer), we calculated that the region should expect between 15,543 and 223, 417 cases of MDR, all forms combined (between 2.3 and 32.7 per 100,000 inhabitants), by the end of the century. CONCLUSION: The results from Rwanda during the period studied do not appear dramatic. However, for some other developing countries, they may just represent the tip of the iceberg. Rapid recognition of resistance to the major antituberculosis agents is essential for control of TB. Integration of an MDR increase factor into the TB budget would not dramatically increase the total TB budget. Our data urgently point the the need for drug resistance surveys, followed by continuous drug resistance monitoring in high TB prevalence areas.

Design and evaluation of new, highly sensitive and specific primers for polymerase chain reaction detection of HIV-1 infected primary lymphocytes.

Primer pairs in the HIV-1 POL and ENV genes were evaluated by performing a PCR on lysed peripheral blood mononuclear cells (PBMCs) from 96 HIV-1 seropositive and 40 seronegative individuals originating from 16 different geographical localities in Africa, Europe and Haiti. A single PCR using primer pairs to the LTR, GAG and ENV regions and detection by radioactively labelled oligonucleotide probes was compared to a nested PCR scheme using newly designed POL and ENV primers which used ethidium-bromide staining of the amplified product on agarose gel. The newly designed POL nested primer pair was shown to be highly sensitive (93%) and specific (100%) for the detection of HIV-1 proviral DNA of very diverse geographical and genetic origin, including highly aberrant HIV-1 isolates. The sensitivity of the newly designed ENV primers was 68.7%, which does not differ significantly from the sensitivity of the classical primers, SK 68/69. Both ENV primers were unable to amplify two SIVcpz isolates from naturally infected chimpanzees.

HIV screening and confirmation: a simplified and less expensive testing algorithm.

In this study we investigated the performance of fourteen different assays capable of simultaneously detecting antibodies to HIV-1 and HIV-2, referred to as combined screening assays (CSAs), on a panel of 371 sera, with a prevalence of 51.5% and 1.3% for HIV-1 and HIV-2 antibodies respectively. The geographic distribution of the sera was as follows; Europe (121), Africa (203) and Latin America (47). These sera were collected from different clinical groups of patients; Asymptomatic (36), AIDS-Related Complex/AIDS patients (18), infected individuals with generalised lymphadenopathy (12), blood donors (149), and subjects with unknown clinical status (156). The Dupont Western blot (WB) kit for detection of HTLV-III antibodies and the Pasteur new Lav-Blot II kit were used for the confirmation of HIV-1 and HIV-2 infection respectively. Of the 14 tests studied, 9 were enzyme linked immunosorbent assays (ELISAs), and 5 were non-Elisa tests requiring visual reading. An alternative approach for HIV antibody testing was studied restrospectively, whereby sera positive in an initial CSA (A) were retested on a second CSA (B), that was different from the first. The use of WB was limited to sera that gave discrepant (A+B-) results in the two CSAs. A positive result in both CSAs was reported as anti-HIV positive. A negative result in the first CSA was reported anti-HIV negative. Sensitivity, specificity, cost, and the delta (delta) values (delta values of the ELISA assays) were taken into consideration when selecting suitable pairs of assays. All the ELISAs scored 100% sensitivity, but for the non-ELISAs, the sensitivity ranged from 96.0% to 100%. The specificity for the ELISAs and non-ELISAs varied from 87.4% to 100% and from 51.4% to 100% respectively. Delta (delta) values for the ELISAs ranged from 3.82 to 136.68 and from -1.15 to -3.08 for the anti-HIV positive and anti-HIV negative populations respectively. Of the 121 test combinations studied, 9 (7.4%) pairs yielded 100% sensitivity and specificity and 61 (50.4%) pairs of CSAs required further testing on WB. This implies 100% positive predictive value, at a cost that was on average 6 times less, and a testing time that was 5 times faster than the conventional algorithm. We conclude that there are several combinations of pairs of CSAs that can be used in the alternative algorithm that can provide accurate results at a much lower cost than the conventional algorithm requiring confirmation by WB of all initially reactive CSA results.(ABSTRACT TRUNCATED AT 400 WORDS)

[Comparison of 2 culture media for the isolation of Mycobacterium tuberculosis]. / Comparaison de deux milieux de culture pour l'isolement de mycobactéries tuberculeuses.

In Kinshasa, Zaire, 392 positive cultures were used to compare the isolation of mycobacteria on two different culture media (Löwenstein-Jensen and Ogawa (1%) with egg yolk). Although the Ogawa medium is reknown for being well adapted to the growth of atypical mycobacteria, we did not isolate more atypical mycobacteria from the tuberculous population of Kinshasa on Ogawa than were isolated in the previous years on Löwenstein-Jensen. However, significantly more M. tuberculosis were isolated on Ogawa (95% versus 88.4% on Löwenstein-Jensen). Other factors permitting, the use of the Ogawa medium is recommended.