Inconsistencies in drug susceptibility testing of Mycobacterium tuberculosis: current riddles and recommendations

Drug susceptibility testing [DST] of Mycobacterium tuberculosis is a crucial procedure to determine the effective drug regimen for patients' treatment. Reporting of erroneous DST results to the treating physician has adulterous effects on patients. As a first study of its type, the inconsistencies in reporting DST results of rifampicin and isoniazid from Saudi Arabia were assessed. An automated liquid culture-based DST and a molecular mutation detection technique were used. Performance of first-line drug susceptibility testing of 1904 clinical isolates showed 44 inconsistent results. The majority of the cases reported as MDR-TB from the referral laboratories could not reproduce the same results at a different site [Mycobacteriology Research Section]. Of the 44 cases, 16 [36.3%] showed false resistance to isoniazid and rifampicin and on the other hand, 14 [31.8%] cases showed false susceptibility to the same drugs. The possible causes for the inconsistencies and recommendations to overcome the biases based on this experience are discussed

emergence of beijing genotype of mycobacterium tuberculosis in the Kingdom of Saudi Arabia

To investigate the prevalence of Beijing genotype strains of Mycobacterium tuberculosis in the Kingdom of Saudi Arabia. We analyzed the available data on a total of 1505 strains isolated during 2002-2005. Spoligotyping results revealed that Beijing family isolates represented 4.5% of all the isolates. Existence of Beijing clade is alarming as this family is known to be multi-drug resistant and transmissible. This study showed that the occurrence of Beijing genotype is associated with young age and drug resistance. The Beijing strains affected both Saudi nationals as well as migrants originating in Asia. The Beijing clade could be responsible for the ongoing transmission of tuberculosis within the community