Antimicrobial susceptibilities of amoxycillin-non-susceptible and susceptible isolates among penicillin-non-susceptible Streptococcus pneumoniae

Antimicrobial susceptibilities of 244 amoxycillin-non-susceptible and 81 amoxycillin-susceptible pneumococcal isolates from 15 Spanish hospitals were determined and clonal relationships were investigated by pulsed-field gel electrophoresis after SmaI restriction. Amoxycillin-non-susceptible isolates exhibited higher rates of resistance to cefuroxime, cefixime, cefpodoxime and clarithromycin, but not to levofloxacin and cefotaxime. Cefditoren exhibited MIC90 values one dilution lower than those of cefotaxime. Higher numbers of the Spain14-5 and Spain6B-2 clones, but not the Spain9V-3 and Spain23F-1 clones, were found among amoxycillin-non-susceptible isolates. Spain14-5 was the most problematic clone in terms of antibiotic resistance.