Progressive rise of Mycobacterium tuberculosis resistance to rifampicin and streptomycin in Riyadh, Saudi Arabia

The aim of this study was to investigate, for the first time, the factors associated with resistance to antituberculous drugs in Saudi Arabia, and to follow the long-term trends in drug resistance.

A retrospective study of patients with positive Mycobacterium tuberculosis recorded at the Riyadh Tuberculosis Center in 1990 was undertaken. The resistance figures from the same centre for the period July 1996 to June 1997 were reviewed for comparison.

Resistance was significantly higher in those previously treated (71%) than in those who denied previous treatment (34%). There was a trend towards association of resistance with cavitatory, multilobar, and acid fast bacilli-positive cases. Nationality (Saudis, Yemenis, others) had no significant effect on resistance. The Riyadh Region now has the same high prevalence of rifampicin resistance as previously reported in the Western Region of the Kingdom. The figures on resistance for the years 1986-88, 1990, and 1996-97 were: isoniazid 19.5/13.8/11.1%, rifampicin 10/20.7/24.6%, streptomycin 5/22/27.4%, ethambutol 3.7/3.9/1.8%, respectively. The reduction in isoniazid and ethambutol resistance coincided with a rise in resistance to rifampicin and streptomycin. We speculate that this resulted from the fact that isoniazid and ethambutol are restricted only to the treatment of tuberculosis and cannot, by law, be dispensed by general practitioners or private pharmacies. Rifampicin and streptomycin, however, are widely used for brucellosis; an endemic disease in Saudi Arabia where up to 12 weeks of rifampicin therapy is recommended.

There has been a significant increase in rifampicin and streptomycin resistance in Saudi Arabia over the last 10 years. Possible causes include poor compliance and wide use of these two drugs for non-tuberculosis conditions. These findings could jeopardize the benefits of the directly observed therapy short course policy which is being implemented in Saudi Arabia. Consideration should be given to prohibiting the routine use of rifampicin for the treatment of brucellosis.