In 1993 and 1994, 10 microbiological laboratories in Switzerland collected 351 strains of Streptococcus pneumoniae from invasive infections. Susceptibilities to the main representatives of the chemical classes were as follows: penicillin, 93%; chloramphenicol, 92%; erythromycin, 94%; sulfamethoxazole-trimethoprim, 86%; tetracycline, 92%; vancomycin, 100%. Forty-three strains showed resistance to one agent, and 35 strains showed resistance to two or more antimicrobial agents simultaneously;

more »

... 22% of the strains were resistant to at least one antimicrobial agent. Four strains (1%) were fully resistant to penicillin, whereas 21 strains (6%) showed reduced susceptibility. Of these 25 strains not fully susceptible to penicillin, 10 were resistant to one, 3 were resistant to two, and 8 were resistant to three additional antimicrobial agents. Of the quinolones, sparfloxacin was the most active substance, with an MIC at which 90% of the strains are inhibited of 0.5 mg/liter. The most common serotypes were types 6 (13.6% of isolates), 7 (10.5%), 19 (10.5%), 14 (9.1%), and 1 (8.5%) as well as 3 and 23 (8.0% each). Reduced susceptibility to penicillin was found mainly among serotypes 6, 14, 19, and 23. The currently available 23-valent pneumococcal vaccine covers 320 (91%) of the pneumococci isolated. Regional differences within Switzerland with regard to serotypes and antimicrobial resistance were not observed.