An extracellular protease of a mutant of strain 8325N of Staphylococcus aureus, was isolated by a three-step procedure involving stepwise chromatography on DEAE-cellulose, gradient chromatography on hydroxyapatite and gel filtration on Sephadex G-150. The enzyme was purified 250 times to homogeneity with a recovery of 20-30°/,.The protease has a molecular weight of about 29000 and consists of a single polypeptide chain as shown by gel filtration of native enzyme on calibrated columns of Sephadex G-150 as well as gel filtration of denaturated enzyme on Sepharose 6-B in 6 M guanidine-HC1 and dodecylsulfatepolyacrylamide gel electrophoresis. Peptide maps also suggest a molecular weight around 30000.

Two mutants with increased protease production were isolated after nitrosoguanidine treatment of Staphylococcus aureus 8325N. The wild type produces low amounts of extracellular proteolytic activity. The enzyme was inducible and could only be detected if casein or preferably skim milk powder was used as inducer. The optimal pH, salt concentration, and media for enzyme production were determined. The mutants differed from the wild type in several phenotypic characters. The pattern of extracellular deoxyribonuclease and alkaline phosphatase differed between the mutants and the wild type. Several carbohydrates such as lactose, galactose, and mannitol were not utilized by the mutants, probably owing to a block in the uptake. Glucose could, however, be utilized by the mutants. Reversion frequency to wild type with regard to carbohydrate utilization was spontaneously high, and all revertants regained the parental pattern irrespective of the carbohydrate used for selection. The results suggest that a single locus may control the excretion of extracellular enzymes and carbohydrate uptake in S. aureus.

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SUMMARY Men with non-gonococcal urethritis (NGU) were divided into two groups and treated with either lymecycline or tinidazole; anaerobic cultures were performed before and after treatment. Neither treatment affected the anaerobic flora. However, the men treated with lymecycline were relieved of symptoms and signs, while those treated with tinidazole were not. The anaerobic bacteria found are considered normal inhabitants of the attiology of NGU.

13 patients with Bacteroides fragilis infections were studied for antibody response against the infecting strain using indirect immunofluorescence (IFL), passive hemagglutination (HA) and tube agglutination (TA). With indirect IFL significant titre changes in IgG were found in 12/13 cases, in IgA in 8/13 and in IgM in 4/13 cases. With passive HA significant titre changes were found in 11/13 cases and with TA in 6/11 cases. The rise in antibody titre was fast and persisted for a long time in most cases. Of the methods used the indirect IFL was the most convenient for clinical use.