Eight hundred Erysipelothrix strains isolated between 1992 and 2002 from swine with erysipelas in Japan were serotyped. Thirty-seven, 47, 73, and 643 strains were isolated from animals with acute septicemia, urticaria, chronic endocarditis, and chronic arthritis, respectively, of which 381, 146, 254, and 19 isolates belonged to serotypes 1a, 1b, and 2b and other serotypes, respectively. All serotype 1a isolates were further examined for acriflavine resistance and their genotypes to discriminate them from the attenuated live vaccine strain, defined as serotype 1a, which is resistant to 0.02% acriflavine and which shows low levels of pathogenicity in mice. Of the serotype 1a isolates, 64.6% were acriflavine resistant, with 98.4% of these acriflavine-resistant strains having been isolated from animals with chronic arthritis. By randomly amplified polymorphic DNA (RAPD) analysis, almost all the acriflavine-resistant serotype 1a strains showed the 253-bp band characteristic of vaccine strains and were easily discriminated from all 113 strains of acriflavine-sensitive serotype 1a strains from animals with acute and subacute swine erysipelas. The incidence of acriflavine-resistant strains of the distinctive RAPD type 1-2 was markedly higher than that of the other RAPD types and serotypes. RAPD type 1-2 strains also included a specific group identifiable by restriction fragment length polymorphism DNA analysis. Furthermore, the pathogenicities of 29 isolates of RAPD type 1-2 for mice were lower than those of the 21 isolates of other RAPD types. Our results indicate that RAPD type 1-2 strains are live vaccine strains and that 37% of the cases of chronic swine erysipelas detected in the past 11 years in Japan have occurred as a side effect of live vaccine use.

ABSTRACT. In August 2007, an outbreak of equine influenza occurred among vaccinated racehorses with Japanese commercial equine influenza vaccine at Kanazawa Racecourse in Ishikawa prefecture in Japan. Apparent symptoms were pyrexia (38.2-41.0°C) and nasal discharge with or without coughing, although approximately half of the infected horses were subclinical. All horses had been shot with a vaccine that contained two inactivated H3N8 influenza virus strains [A/equine/La Plata/93 (La Plata/93) of American lineage and A/ equine/Avesta/93 (Avesta/93) of European lineage] and an H7N7 strain (A/equine/Newmarket/1/77). Influenza virus, A/equine/ Kanazawa/1/2007 (H3N8) (Kanazawa/07), was isolated from one of the nasal swab samples of diseased horses. Phylogenetic analysis indicated that Kanazawa/07 was classified into the American sublineage Florida. In addition, four amino acid substitutions were found in the antigenic sites B and E in the HA1 subunit protein of Kanazawa/07 in comparison with that of La Plata/93. Hemagglutinationinhibition (HI) test using 16 serum samples from recovering horses revealed that 1.4-to 8-fold difference in titers between Kanazawa/ 07 and either of the vaccine strains. The present findings suggest that Japanese commercial inactivated vaccine contributed to reducing the morbidity rate and manifestation of the clinical signs of horses infected with Kanazawa/07 that may be antigenically different from the vaccine strains. KEY WORDS: antigenic analysis, equine influenza virus, genetic analysis, Japan, racehorses.

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Aims:  To investigate the clonality of Staphylococcus aureus isolates, it is important to identify their clonal complexes (CCs) with multilocus sequence typing (MLST). However, it is expensive to carry out MLST analyses for many isolates. The aim of this study, therefore, was to develop a cost‐effective method to identify CCs by determining the conservation pattern of ‘small genomic islets’ (SGIs). SGIs are nonconserved regions between strains and have single or multiple open‐reading frames (ORFs). Methods and Results:  The whole‐genome sequences of nine strains were compared in order to select 16 SGIs. The conservation patterns of the 16 SGIs (islet patterns) were investigated in 136 S. aureus isolates, which were classified into 21 CCs. The islet patterns (IPs) exhibited a one‐to‐one correspondence with the CCs, except for isolates belonging to CC1, CC5 and CC8. The IPs typical of strains belonging to CC1, CC5 and CC8 differed between those of sequence type 1 (ST1) and ST188 (CC1), ST5 and ST6 (CC5) and ST8 and ST239 (CC8). Significance and Impact of the Study:  The CCs of many isolates can be identified in an easy and inexpensive manner by detecting these 16 SGIs. Emergent clones, particularly methicillin‐resistant ones, can be identified by examining numerous islets by IP analysis.