H. Traore

Analysis of the population structure of Mycobacterium tuberculosis strains from the People's Republic of China showed that the vast majority belong to a genetically closely related group. These strains shared the majority of their IS6110 DNA-containing restriction fragments, and also, the DNA polymorphism associated with other repetitive DNA elements, like the polymorphic GC-rich sequence and the direct repeat, was very limited. Because the majority of these strains originated from the province of Beijing, we designated this grouping the "Beijing family" of M. tuberculosis strains. Strains of this family were also found to dominate in neighboring countries such as Mongolia, South Korea, and Thailand, whereas a low prevalence of such strains was observed in countries on other continents. These data indicate that strains of the Beijing family recently expanded from a single ancestor which had a selective advantage. It is speculated that long-term Mycobacterium bovis BCG vaccination may be one of the selective forces implicated in the successful spread of the Beijing genotype.

Mycobacterium tuberculosis resistance to rifampin results from nucleotide changes in the gene encoding the beta-subunit of the RNA polymerase (rpoB). We developed a reverse hybridization-based line probe assay (LiPA; the INNO-LiPA Rif. TB) carrying one oligonucleotide probe for the detection of M. tuberculosis complex strains and nine probes designed to detect nucleotide changes in the relevant part of rpoB. This assay was evaluated with 107 M. tuberculosis isolates with known rpoB sequences, 52 non-M. tuberculosis complex strains, and 61 and 203 clinical isolates found to be sensitive and resistant, respectively, by in vitro testing. The results indicated that (i) the M. tuberculosis complex probe was 100% specific, (ii) when compared to the results of nucleotide sequencing, no discrepancies with the results of INNO-LiPA Rif. TB were observed, (iii) all strains sensitive by in vitro susceptibility testing were correctly identified, and (iv) among the strains resistant by in vitro susceptibility testing, only 4 (2%) yielded conflicting results. The INNO-LiPA Rif. TB is therefore a reliable and widely applicable assay and a valuable tool for routine diagnostic use, given its simplicity and rapid performance.

The line probe assay (LiPA), a rapid molecular method for detecting rifampicin resistance (RMPr) in Mycobacterium tuberculosis, correctly identified all 145 rifampicin-sensitive (RMPs) and 262 (98.5%) of 266 RMPr strains among 411 isolates collected from diverse countries. If used as a marker of multidrug-resistant tuberculosis (MDR-TB), detection of RMPr by LiPA would have detected 236 of the 240 MDR strains in this study but would have wrongly suggested the presence of MDR in 26 RMP-monoresistant isolates (sensitivity 98.3%, specificity 84.8%). Hence, the reliability of using LiPA (or any other rapid RMPr-detection method) as a surrogate marker of MDR-TB largely depends on the prevalence of RMP-monoresistance in the study population. This approach must therefore be validated in each local situation.

Eighteen patients hospitalized with intestinal parasitic infections associated with diarrhea and dehydration completed a study of nitazoxanide in the treatment of Cryptosporidium parvum and other intestinal parasitic infections. Seventeen of the 18 patients were positive for human immunodeficiency virus. Twelve patients were diagnosed with clinical Stage 4 acquired immunodeficiency syndrome (AIDS) according to the 1990 World Health Organization proposed clinical classification system and cryptosporidiosis. Nitazoxanide (500 mg tablets) were administered orally, one tablet twice a day for seven consecutive days. Cryptosporidium parvum oocysts were eradicated or reduced by more than 95% in seven of the 12 Stage 4 AIDS patients who completed the study based upon two post-treatment fecal examinations conducted on days 7 and 14 following the initiation of treatment. The elimination or reduction of C. parvum oocysts was associated with a complete resolution of diarrhea in four of the seven patients. The test drug was also effective against cases of Isospora belli, Entamoeba histolytica, Giardia lamblia, Ascaris lumbricoides, Enterobius vermicularis, Hymenolepis nana, and Dicrocoelium dentriticum. Treatment with nitazoxanide was well tolerated by the patients. There were no abnormalities in blood chemistry or hematology data that were considered to be attributable to nitazoxanide therapy. Transient episodes of vomiting were observed in four patients, all with Stage 4 AIDS and cryptosporidiosis, which resolved spontaneously without discontinuation of treatment and were not considered to be related to administration of nitazoxanide.