Surveillance of Mycobacterium tuberculosis drug resistance in Hong Kong, 1986-1999, after the implementation of directly observed treatment.
OBJECTIVE
To study changing trends in TB epidemiology with emphasis on drug resistance rates in various age groups from 1986-1999.


METHODS
Laboratory-based data on drug susceptibility testing against streptomycin (SM), isoniazid (NH), rifampicin (RMP) and ethambutol (EMB) had been collected continuously in a centralised TB laboratory in Hong Kong. Epidemiological parameters such as sex, age and drug resistance rates in new and retreatment cases were measured and analysed for longitudinal trends.


RESULTS
Of 48 924 non-duplicate isolates from new TB cases, 7045 (14.4%) were resistant to one or more drugs, 5773 (11.8%) were resistant to SM and/or INH while 881 (1.8%) were multidrug-resistant (MDR-TB). Of 3857 isolates from retreatment patients, 1176 (30.5%) were resistant to one or more drugs, 616 (16.0%) were resistant to SM and/or [NH, and 467 (12.1%) were MDR-TB. For isolates from new cases, significant declines were observed in the resistance rates against any drug, SM alone, INH alone, SM+INH and INH+RMP. For retreatment isolates, significant declines were also observed in resistance to any drug and INH+RMP. In both new and retreatment cases, isolates from patients aged over 65 years showed significantly lower drug resistance (any drug and INH+RMP) compared with other age groups (16-34 years and 35-65 years).


CONCLUSIONS
With successful implementation of DOTS over a 14-year period, laboratory-based surveillance data showed significant declines in drug resistance, including MDR-TB. This has occurred amidst demographic changes associated with a generally ageing population as well as highly mobile sectors that are in constant exchange with highly endemic areas.
Kam
K M
KM
Tuberculosis Reference Laboratory, Yung Fung Shee Memorial Center, Department of Health, Kwun Tong, Kowloon, Hong Kong. kmkam@asiaonline.net
Yip
C W
CW
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000995:Antitubercular Agents / Q000627:therapeutic use*; D023801:Directly Observed Therapy; D004977:Ethambutol / Q000627:therapeutic use*; D005260:Female; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D007538:Isoniazid / Q000627:therapeutic use*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000302:isolation & purification*; D011159:Population Surveillance; D015995:Prevalence; D012189:Retrospective Studies; D012293:Rifampin / Q000627:therapeutic use*; D017678:Sex Distribution; D013307:Streptomycin / Q000627:therapeutic use*; D013997:Time Factors; D018088:Tuberculosis, Multidrug-Resistant / Q000188:drug therapy* / Q000453:epidemiology*
D000995:Antitubercular Agents; D004977:Ethambutol; D007538:Isoniazid; D012293:Rifampin; D013307:Streptomycin