Proposal for effective treatment of Shiga toxin-producing Escherichia coli infection in mice.

Previously, we reported that minocycline, kanamycin and norfloxacin improved the survival rate in the E32511 model that we developed (FEMS Immunol Med Microbiol 26, 101-108, 1999), but fosfomycin did not. In this study, we investigated the effectiveness of azithromycin (AZM) against Stx2d-producing EHEC O91:H21 strain B2F1 or Stx2c-producing Escherichia coli strain E32511 treated with mitomycin C in vivo. Recently, we reported the effectiveness of AZM in our model and AZM strongly inhibited the release of Stx2c from E32511 in vitro (PLOS ONE e58959, 2013). However, it was very difficult to completely eliminate E32511 in the mouse feces by treatment with AZM alone. In this report, only AZM or Daio effectively promoted survival of mice infected with B2F1 compared to untreated mice. Furthermore, Daio inhibited the colonization of GFP-expressing B2F1 in the mouse intestine. Similarly, a combination of AZM and Daio in the E32511-infected mice reduced E32511 in the mouse feces and significantly improved survival.

Pathogenicity of Bordetella bronchiseptica isolated from apparently healthy rabbits in guinea pig, rat, and mouse.

Bordetella bronchiseptica (B. bronchiseptica) is associated with respiratory tract infections in laboratory animals. In our laboratory animal facility, B. bronchiseptica was isolated from 21 of 27 apparently healthy rabbits obtained from a breeding farm contaminated with B. bronchiseptica. Restriction fragment length polymorphism (RFLP) analysis showed that the flagellin genotype of isolates from the laboratory animal facility and breeding farm was type A, which is seen relatively frequently in rabbits in Europe. To examine its pathogenicity, guinea pigs, rats, and mice were inoculated intranasally with a representative strain isolated in the laboratory animal facility. Following inoculation of 107 colony forming unit (cfu), severe inflammation was observed in the lungs of guinea pig and mice, although the inflammation was less severe in rats. The strain was recovered from the trachea and lungs of these species after inoculation with lower dose such as 103 or 104 cfu. These results suggest that the isolated strain causes respiratory tract infection in guinea pigs, rats, and mice, and that its pathogenicity higher in mice than in rats. This study extends our knowledge of interpreting the microbiologic status of laboratory animals, which will contribute to the development of reliable and reproducible animal experiments.

Investigation of encephalopathy caused by Shiga toxin 2c-producing Escherichia coli infection in mice.

A large outbreak of Shiga toxin (Stx)-producing enteroaggregative Escherichia coli (EAEC) O104:H4 occurred in northern Germany. From this outbreak, at least 900 patients developed hemolytic uremic syndrome (HUS), resulting in more than 50 deaths. Thirty percent of the HUS patients showed encephalopathy. We previously established a mouse model with encephalopathy associated with blood brain barrier (BBB) damage after oral infection with the Shiga toxin (Stx) 2c-producing Escherichia coli O157: H- strain E32511 (E32511). In this model, we detected high expression of the Stx receptor synthase enzyme, glycosphingolipid globotriaosylceramide (Gb3) synthase, in endothelial cells (ECs) and neurons in the reticular formation of the medulla oblongata by in situ hybridization. Caspase-3 was activated in neurons in the reticular formation of the medulla oblongata and the anterior horn of the spinal cord. Astrocytes (ASTs) were activated in the medulla oblongata and spinal cord, and a decrease in aquaporin 4 around the ECs suggested that BBB integrity was compromised directly by Stx2c or through the activation of ASTs. We also report the effectiveness of azithromycin (AZM) in our model. Moreover, AZM strongly inhibited the release of Stx2c from E32511 in vitro.