RESUMEN
A collection of 307 pneumococcal isolates form 84 children and 223 adults admitted to Siriraj Hospital were separated into two groups, penicillin-susceptible (PSSP) and penicillin-nonsusceptible (PNSP). Each group was tested for susceptibilities to 12 drugs (cefuroxime, amoxicillin, chloramphenicol, tetracycline, cefotaxime, ceftriaxone, imipenem, meropenem, ciprofloxacin, ofloxacin, erythromycin and co-trimoxazole). PSSP were susceptible to cefuroxime (87.5%), amoxicillin (100%), chloramphenicol (84.7%), tetracycline (45.8%), cefotaxime (99%), ceftriaxone (99%), imipenem (99%), meropenem (100%), ciprofloxacin (76%), ofloxacin (99%), erythromycin (94.8%) and co-trimoxazole (61.5%). PNSP were resistant to most drugs, except for amoxicillin (99%), ofloxacin (99%) and ciprofloxacin (86.3%). Twenty-two pneumococcal isolates belonging to the three most common serotypes (6, 19, 23) were randomly selected for studies of the pbp2b gene with RFLP. There were 7 distinct pbp2b RFLP patterns. RFLP pattern 1 was the most predominant resistant pattern. The RFLP pattern 2 was found only in PSSP.