TABLE 1.
Susceptibility of L. monocytogenesis isolates collected from 1955 to 1997a
| Antimicrobial agent | No. of isolates | No. (%) of susceptible strains | No. (%) of nonsusceptible strains |
|---|---|---|---|
| Penicillin | 84 | 82 (97.6) | 2 (2.3) |
| Ampicillin | 65 | 59 (90.7) | 6 (9.2) |
| Oxacillin | 47 | 31 (55.9) | 16 (34) |
| Methicillin | 29 | 19 (65.5) | 10 (34.4) |
| Timentin | 26 | 25 (96.2) | 1 (3.8) |
| Cefazolin | 21 | 21 (100) | 0 |
| Cephalothin | 67 | 67 (100) | 0 |
| Cefuroxime | 26 | 5 (19.2) | 21 (80.8) |
| Cefotaxime | 21 | 7 (33.3) | 14 (66.6) |
| Ceftriaxone | 21 | 5 (23.8) | 16 (76.1) |
| Clindamycin | 26 | 1 (3.8) | 25 (96.2) |
| Erythromycin | 84 | 83 (98.8) | 1 (1.9) |
| Tetracycline | 66 | 64 (96.9) | 2 (3) |
| Chloramphenicol | 54 | 47 (87) | 7 (12.9) |
| Gentamicin | 52 | 51 (98) | 1 (2) |
| Amikacin | 23 | 23 (100) | 0 |
| Streptomycin | 18 | 12 (66.6) | 6 (33.3) |
| Kanamycin | 35 | 34 (97.1) | 1 (2.8) |
| Rifampin | 21 | 21 (100) | 0 |
| Nitrofurantoin | 21 | 10 (47.6) | 11 (52.3) |
| TMP-SMX | 26 | 26 (100) | 0 |
| Vancomycin | 26 | 26 (100) | 0 |
| Ciprofloxacin | 21 | 21 (100) | 0 |
| Norfloxacin | 21 | 19 (90.4) | 2 (9.5) |
| Imipenem | 21 | 21 (100) | 0 |
a
Timentin, ticarcillin-clavulanate. Antimicrobial susceptibility breakpoints during 1955 to 1979 were determined by the agar plate drug diffusion method; MIC breakpoints for agar plate drug diffusion are described elsewhere (13). Microdilution technique was used to determined antimicrobial susceptibility during 1991 to 1997. Nonsusceptible strains included intermediate and resistant L. monocytogenes isolates.