POSTANTIBIOTIC EFFECT OF SANFETRINEM COMPARED WITH THOSE OF 6 OTHER AGENTS AGAINST 12 PENICILLIN-SUSCEPTIBLE AND PENICILLIN-RESISTANT PNEUMOCOCCI

The postantibiotic effect (PAE) and postantibiotic sub-MIG effect (PAE -SME) of sanfetrinem mere compared to those of penicillin G, amoxicill in, cefpodoxime, ceftriaxone, inipenem, and clarithromycin against fou r penicillin-susceptible, four intermediately susceptible, and four re sistant pneumococci. The MICs of imipenem were the lowest against all of the strains (0.03 to 0.5 mu g/ml), followed by those of sanfetrinem (0.016 to 1.0 mu g/ml), amoxicillin and ceftriaxone (0.016 to 2.0 mu g/ml), and cefpodoxime (0.03 to 8.0 mu g/ml). High-level resistance to clarithromycin (MIC, > 64.0 mu g/ml) was seen in three selected strai ns. The PAEs of all of the oral beta-lactams tested were similar for a ll of the strains, ranging from 1 to 6.5 h. The PAEs of ceftriaxone an d imipenem ranged from 1 to 8 h, and those of clarithromycin ranged fr om 1 to 7 h. The mean PAEs of all of the beta-lactams and clarithromyc in were 2.8 to 4.3 and 2.5 h, respectively. PAE SMEs could not be dete rmined for all of the strains due to complete killing, especially at h igh subinhibitory concentrations. However, the overall pattern with al l of the compounds tested was that PAE-SMEs were longer than PAEs. Mea surable PAE-SMEs of sanfetrinem at the three subinhibitory concentrati ons (0.125, 0.25, and 0.5 times the MIC) were 2 to 7, 2 to 7, and 3 to 6 h, while those of amoxicillin and cefpodoxime were 1 to 7.5, 2 to 4 , and 4 to 9 and 2 to 7, 4 to 7, and 4 to 6 h, respectively. Measurabl e PAE SMEs of ceftriaxone and imipenem were 1 to 6.5, 2 to 9, and 2 to 9 and 1.5 to 6, 2 to 5.8, and 4 to 7.7 h, respectively. Measurable cl arithromycin PAE-SMEs were 1 to 5, 1 to 5, and 1 to 6 h at the three c oncentrations.