we studied 53 mdr m. tuberculosis strains isolated from different patients between 1993 and 2001 at the bangui pasteur institute .
fourteen of these patients were hiv positive , 30 were hiv negative , and 9 were of undetermined status .
a non - mdr , nonbiased control group , which included 263 m. tuberculosis and 2 m. bovis strains , was also studied .
all 318 isolates were typed by using the spoligotyping method previously described ( 13 ) .
spoligotypes were obtained for 283 ( 53 mdr and 230 non - mdr strains ) of the 318 isolates and were analyzed with bionumerics software ( applied maths , kortrijk , belgium ) .
dendrograms were constructed according to degree of similarity ( dice coefficient ) and comparison with known spoligotypes .
seventy - nine different spoligotypes were identified : 55 included only a single strain , and 24 included 256 strains .
twenty - five ( 47.2% ) of 53 clustered in type e , which has characteristics of the t family ( ancient m. tuberculosis strains with numerous spacers ) .
the 230 spoligotype patterns of non - mdr strains were grouped into 22 clusters , and spoligotype e was not a major cluster ( figure , panel b ) .
its spoligotype is identical to the db3 pattern st47 characteristic of the haarlem family ( 15 ) .
spoligotypes 97%99% identical with profiles characteristic of the haarlem family of strains represent 155 strains .
strain distribution into various clusters observed among 53 spoligotyped multidrug - resistant ( mdr ) strains ( a ) and 230 spoligotyped non - mdr strains ( b ) .
the clustering of mdr strains suggested an mdr outbreak ; therefore , we looked for other characteristics in cluster e isolates .
first , we tested for diversity in the rpob region , which was likely to be responsible for rifampin resistance .
five variants were found among the 26 mdr strains that constituted clusters e and f ( table ) : 9 had a ser-531 ( tcg ) to leu ( ttg ) substitution ; 8 and 5 strains contained a substitution of his-526 ( cac ) with tyr ( tac ) and arg ( cgc ) , respectively ; 3 had an asp-516 ( gac ) to val ( gtc ) variant ; and 1 a leu-533 ( ctg ) to pro ( ccg ) substitution .
all these variations are in the rifampin resistance - determining region frequently encountered in strains with a rifampin - resistant phenotype ( 8) . these variants probably determine rifampin resistance and may have occurred independently , not necessarily corresponding to mdrtb transmission , even for strains of the same cluster with the same change in rpob .
indeed , sociodemographic and epidemiologic characterization of the patients did not show any links between these mdrtb cases .
therefore , rifampin resistance seems to have been acquired independently and repeatedly by cluster e and f strains . to find a way to reduce the dissemination of such strains
likely to generate mdr isolates , we characterized strains of cluster e and f. in particular , we looked for single nucleotide polymorphisms ( snps ) in the putative genes mutt1 , mutt2 , mutt3 , rv3908 , muty , mutm , ada / alka , and ogt .
sequencing was performed as previously described ( 11 ) . with reference to published m. tuberculosis sequences
, we found 1 synonymous snp in mutt1 corresponding to val 265 ( gtc ) to val ( gta ) .
this snp is only present in strains of cluster e and strains 27 ( cluster f ) , 28 , and 29 and is absent from all strains in other clusters .
therefore , these mdr strains are characterized by a spoligotype pattern ( st 52  spacer 11 or 12 to 15 and st 107 ) and the presence of the mutt1 snp 265 .
* atb , antibiogram results , indicates strains resistant to rifampin ( r ) , isoniazid ( i ) , ethambutol ( e ) , and streptomycin ( s ) ; nd , not determined .
mdr strains of clusters e and f and strains 28 and 29 ( a single difference in spacers between e and f , strain 28 or 29 ) corresponded to 9 new cases and 19 patients who had received previous treatment .
mdr strains in other clusters corresponded to 9 new cases , 15 previously treated patients , and 1 case for which no history was available ( 3 ) .
we used 2 types of markers to study the genetic diversity of mdr m. tuberculosis strains isolated in bangui : spoligotyping and snps in a series of putative dna repair genes .
many mdr strains were clustered in 1 spoligotype and carried the same snp in the anti - mutator gene mutt1 . indeed , 25 of the 53 mdr strains were in cluster e. thirty - two percent of these mdr strains were from new cases of infection , and 40% were from hiv - infected patients .
this cluster was not a major cluster among the 265 non - mdr isolates collected during a 5-month period .
the same snp was found in all strains of cluster e and f tested and in 2 strains that differed by 1 spacer .
these strains carry variants of rpob that confer rifampin resistance , which implies that these strains do not correspond to an mdr - tb outbreak . however , this finding is consistent with the possibility that these strains represent an mdr - prone family , members of which are often associated with mdr phenotypes in bangui .
detection of strains characterized by the t family spoligotype and mutt1 snp 265 may be useful to identify patients at risk of developing mdr - tb .
 we investigated multidrug - resistant ( mdr ) mycobacterium tuberculosis strains in bangui , central african republic . 
 we found 39.6% with the same spoligotype and synonymous single nucleotide polymorphism in the mutt1 gene . 
 however , strains had different rpob mutations responsible for rifampin resistance . 
 mdr strains in bangui may emerge preferentially from a single , mdr - prone family . 
The Study
Conclusions