猩紅熱患者分離A群溶血レンサ球菌の薬剤感受性の変遷 (1956～1978年)

Abstract

Among the group A streptococci isolated during the period 1956 to 1978 from the pharynx and the nostril of the scarlet fever patients quarantined in the Tokyo Metropolitan Toshima Hospital within 1 week of hospitalization, 1,586 strains of types 4, 6 and 12, the most prevalent serotypes, were estimated for their sensitivities to various antibiotics. Among the sensitivities, those to tetracycline (TC), chloramphenicol (CP) and erythromycin (EM), these being in close relation to prevalent serotypes, are to be reported. The first appearance of TC-resistant strain was seen in one strain (type 6) isolated in 1959, and, in 1964, the resistant strain increased in proportion in accordance with the prevalence of type 4. The resistant strain decreased a little in 1968 and in 1969, increased again from 1970, exceeded over 90% from 1973, and reached 100% in 1978. The first appearance of CP-resistant strain was seen in one strain (type 4) isolated in 1969, and then the resistant strain increased year by year along with the prevalence of type 12. The first appearance of EM-resistant strain was seen in 30 strains (type 12) isolated in 1972, and then, similarly to the case of CP-resistance, the resistant strain increased year by year together with the prevalence of type 12. Meanwhile, among the 1,586 strains isolated at the time of hospitalization and estimated of their minimum inhibitory concentrations (MIC), 932 strains (58.8%), 452 strains (28.5%), and 574 strains (36.2%) showed resistance to TC, CP, and EM, respectively. Variations of drug-resistance by serotypes were as follows: TC-resistant strains increased in accordance with the prevalence of type 4 in 1964; CP- and EM-resistant strains increased in accordance with the prevalence of type 12 in 1972; and type 6 strains were low in the rate of resistant strain to any of the three drugs. So far, prevalence of a serotype of group A streptococci has been considered to be caused by the accumulation of the subjects non-immune to the serotype. In the present study, a phenomenon was observed that prevalence of a serotype was effected by the state of resistance-acquisition to commonly used drugs. It would be clear that the resistance-acquisition plays, in addition to the immune state, a great role in evoking prevalence of a serotype.