Isoniazid- and rifampin-resistant tuberculosis in San Diego County, California, United States, 1993-2002

A local tuberculosis (TB) control program.

To measure trends in isoniazid (INH) and rifampin (RMP) resistance and identify associated factors.

Retrospective review.

Of 2883 isolates obtained from TB patients reported between 1993 and 2002, 287 (10%) were resistant to INH, 11 (< 1%) were resistant to RMP, and 40 (1%) were resistant to both (multidrug resistance [MDR]). There were no linear trends over time. Eighty-one per cent of patients with INH resistance and 85% with MDR were born outside the United States. Sixty-three per cent of patients with drug resistance and prior TB treatment were treated outside the US. INH resistance was associated with race/ethnicity and prior treatment, RMP resistance with human immunodeficiency virus (HIV) infection, and MDR with non-US birth and prior treatment. Patients with INH- and RMP-susceptible or INH-resistant TB had higher percentages of treatment completion and sputum culture conversion than patients with RMP-resistant or MDR-TB.

INH and RMP resistance remained stable between 1993 and 2002. Because most patients with drug resistance were infected or initially treated outside the US, future reductions in drug resistance will depend not only on local and national efforts, but also on the success of global interventions.