1978 Volume 26 Issue 2 Pages 167-174
MICs against respiratory pathogenic H. influenzae were measured by the agar plate dilution method. The inoculum size 106/ml was easier to evaluate the growth of the organisms than in the case of the inoculum size 108/ml. The treatment in accordance with the results obtained by the former method was reasonable from the clinical standpoint.
Regarding the stability and transparency of the medium plate in the measurement of MICs against H. influenzae, the modified FILDES agar plate was superior to blood agar plate and chocolate agar plate. MIC values of 20 antibiotics against 80 to 83 strains of respiratory pathogenic H. influenzae were measured. The comparison of the MIC value against H. influenzae was as follows : Piperacillin<Ampicillin≤Amoxycillin, Carbenicillin, Ticarcillin, Apalcillin, Sulbenicillin<Chloramphenicol≤Thiamphenicol≅Doxycycline, Minocycline≅Gentamicin≅Nalidixic acid≤Erythromycin<Cephalothin<Clindamycin≅Cefatrizine≤Cefazolin≅Cephalexin≅Flucloxacillin.
Six strains of H. influenzae from England resistant to Ampicillin showed rapid increase of MIC values by the increase of inoculum size. On the other hand, recently isolated 3 strains moderately resistant to Ampicillin did not show such a phenomenon, but they revealed a decrease of MIC value by the repetition of generation.
Most of 84 strains were defined to be nontypable in serotype.
H. influenzae could survive for more than 3 weeks either at room temperature or at 4°C in the deep blood agar.
