MIC to penicillin depended on serogroup: using serogroup B and rare serogroups (e.g. A, Z, X, 29E) as reference category with a mean MIC of 0.056 mg/L, serogroups C, W-135, and Y showed significant deviations with MICs of 0.074, 0.107, and 0.067 mg/L, respectively.