Risk factors for drug-resistant Mycobacterium tuberculosis in Saudi Arabia

OBJECTIVE: To identify rates of primary and secondary drug-resistant Mycobacterium tuberculosis and their risk factors from a tertiary-care center in the Kingdom of Saudi Arabia.

METHODS: Review of microbiological and clinical data of all patients with positive isolates of Mycobacterium tuberculosis between 1995 and 2000 at King Faisal Specialist Hospital and Research Centre, Riyadh, Kingdom of Saudi Arabia.

RESULTS: Susceptibility to antituberculosis agents was tested in 320 isolates from 320 patients. The median age was 50 years. Pulmonary tuberculosis was diagnosed in 106 (33%) patients, extrapulmonary in 183 (57%), and both in 31 (10%) patients. Two hundred forty-six isolates were sensitive to all 5 first line agents. Resistance to at least one of the first line agents was documented in 36 (11.3%) isolates. For the year 2000, resistance rates increased to 17.6%. Monoresistance was noted in 20 isolates (6.3%) and polyresistance in 16 isolates (5.0%) including 9 multidrug-resistant Mycobacterium tuberculosis isolates (2.8%). Resistance rates for antituberculosis agents are: Isoniazid, 9.1%; Rifampin, 2.8%; Ethambutol, 1.6%; Streptomycin, 5%; Pyrazinamide, 3.6%. Seventy-eight percent of the resistant isolates are considered primary resistance. History of antituberculosis therapy was the only risk factor associated with drug resistant Mycobacterium tuberculosis, odds ratio 19.9 (P< 0.00001). The mean age of patients with resistant isolates was 42 years compared to 49 years in patients with susceptible isolates (P= 0.047).

CONCLUSION: In a population of mostly Saudi patients, primary and secondary drug-resistant Mycobacterium tuberculosis is relatively low but has increased lately. Previous history of antituberculosis chemotherapy and young age are risk factors identified.