Sadao Miyamura

Classification of Rickettsia tsutsugamushi in a new genus, Orientia gen. nov., as Orientia tsutsugamushi comb. nov.

Recent studies of Rickettsia tsutsugamushi have demonstrated clearly the phenotypic and genotypic differences between this microorganism and other species belonging to the genus Rickettsia. Therefore, classification of R. tsutsugamushi in a new genus, Orientia gen. nov., is proposed.

Isolation of Rickettsia tsutsugamushi Antigenically Different from Kato, Karp, and Gilliam Strains from Patients

Rickettsia tsutsugamushi strains from three recent patients of Tsutsugamushi disease in Niigata Prefecture were isolated primarily in mice and then in L cell cultures. By this procedure, low virulent strains to mice, as well as high virulent ones, could be isolated and cultivated serially in L cell cultures, suggesting the usefulness of L cells for isolation of this species of rickettsia. Each newly isolated strain was identified as a member of R. tsutsugamushi from the results of cross immunological tests and morphological observation. On the other hand, it was recognized that one of these rickettsiae showed immunological properties distinguishable from the prototype strains of Kato, Karp, and Gilliam by the cross complement fixation test, and also had low virulence in mice.

Resistance Mechanism of Chloramphenicol in Streptococcus haemolyticus, Streptococcus pneumoniae and Streptococcus faecalis

The chloramphenicol resistance of Streptococcus haemolyticus, Streptococcus pneumoniae and Streptococcus faecalis isolated from clinical materials was proved to be due to an inactivating enzyme produced by these bacteria. The inactivated products of chloramphenicol were identified as 1‐acetoxy, 3‐acetoxy and 1,3‐diacetoxy derivatives by thin‐layer chromatography and infrared spectroscopy. The responsible enzyme was thus confirmed to be chloramphenicol acetyltransferase. The enzyme was inducible. It was partially purified by ammonium sulfate precipitation, DEAE‐cellulose chromatography and gel filtration on Sephadex G‐150. The enzymes obtained from S. haemolyticus, S. pneumoniae and S. faecalis have been compared with the conclusion that they are identical with respect to molecular weight (approximately 75,000–80,000), optimum pH and heat stability.