Drug resistance of Mycobacterium tuberculosis isolated from patients at a medical center in Taiwan.
BACKGROUND
The advent of bactericidal drugs has had a major impact on the treatment of pulmonary tuberculosis. However, the main reasons for continuing tuberculosis prevalence are the resistance of mycobacteria and patients' lack of endurance to undergo the long-term therapy. In Taiwan, the prevalence of tuberculosis among the population of over 20-year olds has fallen from about 5.15% in 1957, to 0.88% in 1982, but then increased to 1.29% in 1987. Although it continued decreasing to 0.65% in 1994, tuberculosis remains a potential public health problem.


METHODS
To determine the temporal status of drug resistance pattern among the Mycobacterium tuberculosis (M. tuberculosis) isolated at Veterans General Hospital (VGH)-Taipei, analysis was undertaken of the drug susceptibility data reported by the central Mycobacterial Laboratory, using conventional indirect methods, between 1990 to 1992.


RESULTS
The susceptibility pattern of 651 M. tuberculosis isolates obtained from patients admitted to VGH-Taipei during 1990 to 1992 were analyzed; 504/651 (77.4%) were sensitive to all drugs tested. Among veterans, 23.7% (95/401) had organisms resistant to one or more antituberculosis medications: 11.5% (46/401) to a single drug; 6.2% (25/401) to two drugs; 3.2% (13/401) to three drugs, and 2.7% (11/401) to four drugs. The overall resistance rates in isolates from 250 non-veterans (142 males and 108 females) were 22.5% (32/142) in male patients and 18.5% (20/108) in female patients. Among the 142 male patients, 6.3% were resistant to a single drug; 3.5% to two; 7.7% to three and 4.9% to four drugs. Among 108 female patients, 8.3% to a single drug; 1.9% to two drugs; 2.8% to three drugs, and 5.6% to four drugs. The proportion of drug-resistance was higher in the isolates from patients with a history of previous therapy (p < 0.05). Overall, of the 401 veterans with positive cultures, 4.0% had isolates resistant to only isoniazid (INH), 14.7% had isolates resistant to at least INH, and 7.5% had isolates resistant to both INH and rifampin (RIF). Of the 142 non-veteran males, 1.4% had isolates resistant to only INH, 16.9% had isolates resistant to at least INH, and 10.6% had isolates resistant to both INH and RIF. Of the 108 non-veteran females, 3.7% had isolates resistant to only INH, 12.0% had isolates resistant to at least INH, and 8.3% had isolates resistant to both INH and RIF. Among the 401 veterans, all the drug resistant isolates were found in patients older than 45 years, and of these, 66.3% (63/95) were over 65 years, whereas age was not a significant factor for predicting resistance rates among the non-veteran patients.


CONCLUSIONS
There has been a marked increase in drug-resistant tuberculosis in old aged veterans. In contrast, age was not found to be a significant factor to predict resistance rates among the non-veterans. Previously treated patients are at increased risk for drug resistance. In view of these data, it is important to identify drug susceptibility patterns accurately from all tubercle bacilli isolated from patients as this has implications for control programs as well as for patient therapy. Surveillance of drug resistance is again being considered for patients admitted to this hospital, and all physicians are urged to remain alert to drug-resistance rates and patterns in the areas where they practice.
Su
W J
WJ
Chest Department, Veterans General Hospital-Taipei, Taiwan, R.O.C.
Lee
P Y
PY
Yu
K W
KW
Perng
R P
RP
D000328:Adult; D000367:Age Factors; D000368:Aged; D004352:Drug Resistance, Microbial; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000187:drug effects*; D018088:Tuberculosis, Multidrug-Resistant / Q000188:drug therapy