1978 Volume 26 Issue 4 Pages 499-507
A 14-month old boy with pulmonary cyst complicated by empyema thoracis due to H. influenzae was treated. In spite of administration of mezlocillin to which the causative organisms seemed sensitive, the course was prolonged and relapsed.
Then, examinations were made to investigate the effects of penicillins through the observations of growth curves and morphological changes of the organisms after treated with various antibiotics.
The characteristic finding was filament formation in response to mezlocillin and apalcillin (PC-904) in wide range of drug concentration around MIC, which had been recently developed and more effective than ampicillin in terms of MIC.
The bactericidal effects of these penicillins, moreover, were weaker than that of ampicillin. The above phenomenon in vitro seemed to cause a prolongation of the course and relapse.
