TUBERCULOSIS SUSCEPTIBILITY PATTERNS, PREDICTORS OF MULTIDRUG-RESISTANCE, AND IMPLICATIONS FOR INITIAL THERAPEUTIC REGIMENS AT A NEW-YORK-CITY HOSPITAL

Background: Multidrug resistance has complicated tuberculosis therapy. We studied antibiotic susceptibilities of Mycobacterium tuberculosis and predictors of multidrug resistance to assist in determining initia l drug regimens. Methods: We conducted a case-control study based on c hart review of patients with and without multidrug resistant tuberculo sis, including outpatients and inpatients with culture-proved tubercul osis seen at a large New York, NY, hospital during 1991 and 1992. Pati ent characteristics studied included serologic findings for human immu nodeficiency virus and the presence of the acquired immunodeficiency s yndrome. Descriptive analysis considered potential initial drug regime ns. A theoretically effective regimen was assumed to contain at least two drugs to which an isolate was susceptible. Results: For 172 patien ts, 28.5% of isolates were resistant to isoniazid, at least 20.9% to r ifampin, 15.7% to ethambutol, 8.1% to pyrazinamide, 18.6% to streptomy cin, 9.9% to ethionamide, 8.1%preomycin, cycloserine, and ciprofloxaci n; 18.6% were resistant to both isoniazid and rifampin. Chart review o f 159 patients showed that acquired immunodeficiency syndrome, human i mmunodeficiency virus seropositivity, female gender, residence in the Bronx, and race were associated with multidrug resistance. The four-dr ug regimen of isoniazid, rifampin, ethambutol, and pyrazinamide was th eoretically effective for 81% to 85% of patients. No subset of patient s would have a markedly better theoretical benefit from that regimen. Only five- or six-drug regimens that used the combinations of capreomy cin plus ciprofloxacin, capreomycin plus cycloserine, ciprofloxacin pl us cycloserine, or all three drugs together theoretically offered sign ificantly higher effectiveness. Conclusions: Tuberculosis isolates at our hospital have a high frequency of multidrug resistance. Only five- or six-drug regimens are theoretically adequate as initial therapy fo r our patients. to kanamycin, and none to ca