[2 strains of pneumococci with reduced penicillin sensitivity in Switzerland].

There are numerous reports on resistance or decreased susceptibility of pneumococci to penicillin. Recently, two strains of Streptococcus pneumoniae were isolated for the first time in Zurich with minimal inhibitory concentrations of 0.25 and 1.0 mg penicillin G per liter, respectively. One strain was also resistant to chloramphenicol and tetracycline; both isolates were resistant to sulfamethoxazole/trimethoprim. In view of this emergent resistance, routine susceptibility testing of clinically significant pneumococci is to be recommended. However, in the agar diffusion test the use of a penicillin disk may produce false-susceptible results, and therefore the susceptibility test should be performed with a disk containing oxacillin.