SURVEILLANCE OF PNEUMOCOCCAL RESISTANCE IN BELGIUM DURING WINTER 1996-1997

This study tested 212 pneumococcal isolates from 9 institutions for th eir susceptibilities to penicillin, ampicillin, amoxycillin, amoxycill in/clavulanate, cefaclor, cefuroxime, cefotaxime, imipenem, tetracycli ne, erythromycin, and clarithromycin using NCCLS-standardized microdil ution. Penicillin-insusceptibility was 12.3% [5.7% intermediate (0.12- 1 mu g/ml) and 6.6% high-level (greater than or equal to 2 mu g/ml)], tetracycline-insusceptibility (greater than or equal to 4 mu g/ml) 31. 1%, and erythromycin-insusceptibility (greater than or equal to 0.5 mu g/ml) 31.1% as well. Erythromycin-insusceptible isolates showed cross -insusceptibility to clarithromycin. Penicillin-susceptible isolates w ere susceptible to all beta-lactams. MICs of all beta-lactams rose wit h those of penicillin for penicillin-insusceptible isolates. Ampicilli n and penicillin were equally potent against penicillin-insusceptible isolates, imipenem, cefotaxime, and amoxycillin +/- clavulanate were m ore potent (generally 5, 1, and 1 doubling dilution, respectively), an d cefuroxime and cefaclor less potent (generally 1 and 6 doubling dilu tions, respectively). Most penicillin-insusceptible isolates were high -level resistant to cefaclor (2 32 mu g/ml). Although MICs of all beta -lactams rose with those of penicillin, resistance to penicillin was n ot absolute in terms of cross-resistance. Most penicillin-intermediate and high-level penicillin-resistant isolates remained fully susceptib le and intermediate, respectively, to amoxycillin +/- clavulanate, cef otaxime, and imipenem, but not to cefuroxime. Penicillinin-susceptible isolates were 76.9%, 42.3%, and 34.6% co-insusceptible to tetracyclin e, erythromycin, and tetracycline plus erythromycin, respectively. Mos t penicillin-, tetracycline-, and erythromycin-insusceptible isolates were of capsular types 23 >> 6 > 19 > 32, 19 > 6 > 28 > 23, and 19 > 6 > 14 > 23, respectively. Compared to winter 1994-1995, insusceptibili ty to penicillin, tetracycline, and erythromycin rose by some 4%, 4%, and 13%, respectively.