The object of this study is to investigate the characterization of equine neonatal actinobacillosis by retrospective analysis, epidemiological studies and antimicrobial susceptibility testing. In Hidaka District, Hokkaido, from 2009 to 2015, we investigated 26 cases diagnosed with actinobacillosis in 284 neonatal foals that died within 5 days after birth. The investigation discovered that the body weight of these foals is lower than that of healthy foals. Half of the foals were weak due to failure to receive the passive transfer of immunoglobulin. Around 70% of them died within 2 days after birth. Nine of the 12 isolates obtained from the diseased foals were Actinobacillus equuli (AE) subsp. equuli (AEE), and 3 isolates were AE subsp. haemolyticus (AEH). In the necropsy, legions from AEE infection were associated with septicemia, whereas that by AEH infection were associated with pneumonia. All strains were susceptible to antimicrobial agents tested here. Molecular analysis by polymorphic DNA analysis of the isolates suggests high diversity of the isolates.

Escherichia albertii is recognized as an emerging gastrointestinal pathogen in humans and several foodborne outbreaks have been reported in Japan. However, it is difficult to differentiate this organism from entero-pathogenic Escherichia coli (EPEC) and entero-hemorrhagic E. coli (EHEC) due to its poorly defined biochemical characteristics. We have isolated and identified an isolate as E. albertii from the feces of a healthy domestic dog. The isolate harbored the intimin gene (eae ) and cytolethal distending toxin gene (cdt ), but lacked the Shiga toxin gene (stx2f ). Moreover, the isolate was resistant to penicillin, ampicillin, and erythromycin, as reported elsewhere. The current study suggests that domestic dogs may act as a reservoir for this organism, transmitting it to humans.