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Introduction: USA300 is the most common community-acquired methicillin-resistant Staphylococcus aureus (MRSA) strain. Sequence type (ST) 764 MRSA is a new local variant of the ST 5 lineage. The objective of this study was to determine the clinical characteristics of USA300 and ST 764 infections among outpatients in Japan., Methods: We obtained MRSA isolates from 132 outpatients who visited our hospital from January 2016 to December 2017 and compared USA300 infection group to ST 764 infection group. Molecular analysis, including that of various toxins and other virulence factors, of the MRSA isolates were performed. In particular, we investigated the relationships among PCR-based open reading frame typing (POT) scores, MRSA clones, and virulence factors., Results: Twenty-seven USA300 isolates (20.5%) and 16 ST 764 isolates (12.1%) were identified. Although USA300 and ST 764 had lower rates of risk factors, their infection rates were higher. USA300-infected patients had higher rates of deep skin and soft tissue infections compared with the non-USA300 CA-MRSA-infected patients. Notably, the USA300 and ST 764 isolates had unique POT scores., Conclusions: Our results indicated that USA300 MRSA was spreading in an area 120 km west of Tokyo, Japan. We observed multiple cases of ST 764 MRSA infection, raising concerns about the antimicrobial resistance of ST 764, as it limits the choices of antibiotics to treat infection. The POT score can predict the presence of toxins and virulence factors, as well as the clone identity of MRSA with high accuracy., Competing Interests: Declaration of competing interest None declared., (Copyright © 2020 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

The 2-year prognosis of malignant mammary tumors seen in 175 bitches in the Tokyo metropolitan area was assessed based on their TNM clinical staging and histological classification. The larger the tumor size became (T category), the poorer was the clinical prognosis. The 2-year survival rates of the animals with regional lymph node metastasis of tumor cells (N1, N2 category) and/or distant metastasis (M1 category) were markedly lower than those of the animals without such involvement. As the grade of TNM staging increased, the prognosis was poorer, however, there were no significant differences in survival rates among subtypes of adenocarcinomas (tubular, papillary and papillary cystic) determined by WHO histological classification. It was also noticed that animals having carcinomas without tubular formation or myoepithelial cell proliferation had a lower survival rate than animals having carcinomas with those characteristics; and invasive carcinomas into adjacent skin or lymphatic/vascular vessels implied a poorer prognosis than non-invasive ones. The results suggest that a combined practice of TNM system and our evaluation on the above-mentioned 4 histologic features could be useful for prognostic determination of canine mammary cancers.