起炎菌の抗生剤感受性と臨床効果の不一致に関する基礎的ならびに臨床的研究

抄録

The present studies were undertaken to investigate some causes of discrepancy between sensitivity of a causative organism to the antibacterial agent, with which the patient is being treated, and clinical response. The following result were obtained.
1) The analysis of 542 cases with bacillary dysentery showed that there were many cases with poor or no response to the antibiotic given, to which the causative organisms were sensitive, among seriously ill and/or infant or aged patients and that, in contrast, there were many cases with good response to the antibiotic given, to which the causative organisms were resistant, among mildly ill and/or younger patients. These findings suggest an importance role of defence mechanism of the host.
2) Of various factors for discrepancy, the infecting bacteria, population of which may consist of resistant as well as sensitive cells, has to be taken into account. In view of this consideration, a new method to determine sensitivity distribution of the population was worked out. Reliability of the method was confirmed by testing the experimentally mixed culture of resistant and sensitive strains, and at the same time, the sensitivity of this experimentally mixed strain was tested by the ordinary sensitivity test procedures. By the one-concentration disk methods imcomplete inhibitory zone, indicating the presence of resistant and sensitive cells, was obtained, while by the agar dilution methods the presence of sensitive and resistant cells in the mixed strains mixture could sometimes be presumed by comparing the minimum inhibitory concentrations obtained both in large and small inoculum amount. However, both of these were not reliable.
According to the data obtained by the same procedure for the organisms isolated from lesions, sensitivity of single cells fell in narrow range, in comparison with the experimentally mixed culture, and the distribution pattern varied considerably by spieces and by antibiotics. It was particularly so in the case of tetracycline where sensitivity of each single cells fluctuated considerably in wide range. It was entirely impossible by either the disk nor agar dilution method to detect the coexistance of resistant and sensitive cells in the case of clinically isolated organisms.
These findings suggest that it is impossible by ordinary laboratory tests, except the case that double ringed inhibitory zone in the disk method is observed, to point out the coexistance of cells with various degree of sensitivity.
It is, therefore, advisable to think of the fact that the strains tested consist of both the sensitive and resistant cells, together with other possible factors, in case in which the discrepancy between data of sensitivity test and clinical effect is observed.