Two hundred four strains of Streptococcus pneumoniae isolated in Hong Kong from January 1993 to May 1995 were analyzed for their antibiotic susceptibilities and epidemiological patterns. The ages of the patients from whom the strains were isolated ranged from 1 month to 93 years (median, 53 years); the male-to-female ratio was 2.8, with a predominance of males in the pediatric group. Fifty-nine (28.9%) strains showed reduced penicillin susceptibility, including 40 (19.6%) with frank penicillin resistance (MIC > 1 g/ml). Tetracycline resistance alone was found in 28.4% of strains. Isolates with reduced penicillin susceptibility were more common in children than adults (40 versus 23.9%; P ‫؍‬ 0.02), and penicillin resistance rates were significantly higher in hospitalized patients than in outpatients (39.5 versus 12.5%; P < 0.001). Penicillin resistance was significantly associated with resistance to ceftriaxone, erythromycin, and tetracycline (P < 0.01) but not with ofloxacin or vancomycin (P ‫؍‬ 0.5). Among eight different patterns of resistance to three or more antibiotics, the commonest one (14.2%) was multiple resistance to penicillin, chloramphenicol, ceftriaxone, erythromycin, and tetracycline. Emergence of multiple-antibiotic-resistant S. pneumoniae reflects recent changes in the pneumococcus itself and the general indiscriminate use of antibiotics in treatment of respiratory infections in Hong Kong.Despite the prompt use of antibiotic treatment, the pneumococci persist as a significant cause of morbidity and mortality in humans (5,7,8,30,31). The number of pneumococcal strains found to be resistant to different antimicrobial drugs is increasing worldwide (2). In the Southeast Asian region, the recent report of a penicillin resistance rate of 70% in Korea was one of the highest reported to date (15,17). In Hong Kong, earlier case reports have indicated the possible spread of penicillin-resistant pneumococci in the community (29). Prompted by an earlier pilot study (18), we embarked on a comprehensive survey to assess the extent of the problem. We describe here the results of our study on the antibiotic susceptibilities and epidemiology of the multiple-antibiotic-resistant pneumococci in Hong Kong. MATERIALS AND METHODSBacterial strains. Strains of Streptococcus pneumoniae were collected from four public hospital and two outpatient clinic laboratories from January 1993 to May 1995. These laboratories were scattered over most urban districts of Hong Kong. Isolates were transported in screw-cap bottles with cooked-meat medium and subcultured on 5% horse blood agar plates with 5% CO 2 on arrival. Identification was performed by colonial morphology on blood agar, Gram stain, optochin susceptibility, bile solubility, and API 20S tests (bioMerieux, Marcy l'Etoile, France). After identity was confirmed, strains were lyophilized and stored at room temperature before further examination.Antibiotic susceptibility tests. The broth microdilution method as described by the National Committee for Clinical Laboratory Stan...