Rapid susceptibility testing of Mycobacterium tuberculosis by the Mycobacteria Growth Indicator Tube (MGIT AST SIRE).

OBJECTIVE: To evaluate the reliability of the Mycobacteria Growth Indicator Tube (MGIT AST) for susceptibility testing of Mycobacterium tuberculosis. METHODS: Seventy strains of M. tuberculosis were tested for susceptibility to streptomycin, isoniazid, rifampicin and ethambutol by comparing MGIT AST results to those obtained by the method of proportion (MOP) on Lowenstein-Jensen (LJ) and Middlebrook 7H10 media. The 7H10 MOP was considered the method of reference. RESULTS: The turnaround time for MGIT AST was 6.2 days (5-10 days) and for MOP it was 18-21 days. With rifampicin, MGIT AST agreed for all isolates with both MOP. For streptomycin, MGIT AST and 7H10 MOP agreed for 64 isolates (91.4%); 61 were susceptible and three resistant. LJ MOP and 7H10 MOP agreed for 64 isolates (92.2%); 62 were susceptible and three resistant. With isoniazid, both MOP agreed for all isolates, while MGIT AST and 7H10 MOP had two discrepancies. For ethambutol, MGIT AST and 7H10 MOP were concordant for 66 isolates; 65 were susceptible and one resistant. Both MOP were concordant for 67 isolates; 66 were susceptible and one resistant. CONCLUSIONS: Based on these results, MGIT AST is a time-saving method and can be used as an alternative to the BACTEC System. MGIT AST is reliable as far as rifampicin and isoniazid are concerned; however, additional studies are needed for streptomycin and ethambutol.

[Improvement of tuberculosis diagnosis by the Mycobacteria Growth Indicator Tube (MGIT) in a developing country laboratory]. / Amélioration du diagnostic de la tuberculose par le Mycobacteria Growth Indicator tube (MGIT) dans un laboratoire de pays en développement.

In order to improve tuberculosis diagnosis in a developing country (Senegal), we evaluated a new liquid-based medium and nonradioactive system, Mycobacteria Growth Indicator Tube (MGIT), with individual clinical specimens collected in Dakar. The main purpose was to compare the time to detection and the rate of recovery of Mycobacterium tuberculosis complex and to determine its importance with respect to Lowenstein-Jensen (LJ), a liquid-based-medium for isolation of M. tuberculosis complex. 531 specimens were processed with Mycoprep kit containing NaOH-N-acetyl L-cystein and inoculated on both LJ and MGIT and incubated at 37 degrees C for 60 days. For each medium, the recovery rate and the time to detection were recorded. Among the 531 specimens, of which 121 smears were positive, 32.5% (173/531) grew the M. tuberculosis complex. Of these, 103 were smear positive (S+) and 70 smear negative (S-). LJ recovered 54.9% (95/173) and MGIT recovered 91.9% (159/173). Disagreements were observed with 92 isolates, LJ failed to recover 78 while MGIT failed to recover 14. The overall mean time to detection was 20.1 days for LJ and 10.5 days for MGIT. MGIT has shown a better sensitivity in isolation with significant reduction in reporting culture for M. tuberculosis complex. As a simple and a nonradiometric system, it could be used in conjunction with egg-based media in developing countries laboratories.

[Micromethod for identification of enterobacteria]. / Microméthodes d'identification des Enterobactéries.

The aim of this study was to set accurate and reliable methods in the identification of Enterobacteriaceae. In Micro CSB Entero each of a strip with 20 cupules containing dehydrated substrates for biochemical identification of bacterial species. Strips were inoculated with 100 microliters per cupule and incubated. After 18 hours, reagents were added. Baye's theorem was used to validate tests. Reactions from Micro CSB were cleared and easily read. 102 strains of Enterobacteriaceae were identified by MicroCSB--89.3% were correctly identified. 0.9% were identified with other tests 9.8% were incorrectly identified MicroCSB gives many advantages: This method save time, space and is less expensive than the other methods and it gives security for identifying species belonging to the different genera.

[Micromethod for the identification of streptococcal, enterococcal and staphylococcal species]. / Microméthodes d'identification des Streptocoques, Enterocoques et des Staphylocoques.

The aim of this study was to set accurate and reliable methods in the identification of streptococcal, enterococcal and staphylococcal species. Micro CSB Strep and Staph system consists each of a strip with cupules containing dehydrated substrates for biochemical identification of bacterial species. Baye's theorem was used to validate tests. Reactions from micromethods were clear and easily read. Identification of 229 strains of streptococci and enterococci was correct for most species with 98.7% species with 99.3% sensitivity. 41 strains of staphylococci were also correctly identified with 85.2% of specificity and 97.68% of sensitivity.

Use of reverse transcriptase PCR in early diagnosis of Rift Valley fever.

Reverse transcriptase PCR (RT-PCR) for diagnosis of Rift Valley fever (RVF) was evaluated by using 293 human and animal sera sampled during an RVF outbreak in Mauritania in 1998. Results of the RT-PCR diagnostic method were compared with those of virus isolation (VI) and detection of immunoglobulin M (IgM) antibodies. Our results showed that RT-PCR is a specific, sensitive tool for RVF diagnosis in the early phase of the disease and that its results do not differ significantly from those obtained by VI. Moreover, the combined results of RT-PCR and IgM antibody detection were in 100% concordance with the results of VI.