Isolation and identification of Enterobacteriaceae from raw horsemeat intended for human consumption (Basashi)

The status of Enterobacteriaceae contamination was investigated in a total of 131 samples of raw horsemeat (Basashi) intended for human consumption purchased from a general meat shop or by mail-order from October 2012 to December 2013. The bacteria were isolated from 105 of the 112 samples (93.8%). Prominent differences in the isolation rate due to the place of manufacture/sale or by the cut of the meat were not observed. Moreover, in a comparison between domestic (92.6%) and imported (100%) samples, the isolation rate was slightly higher in the imported samples. When Enterobacteriaceae isolated from raw horsemeat was identified, it was highly diverse, with 14 species identified in total. From among these species, Hafnia alvei was the most common, with 33 strains (19.8%),followed by 27 strains (16.2%) of Klebsiella pneumoniae and 26 strains (15.6%) of Enterobacter cloacae, indicating that these three species were dominant. A trend was observed, with the dominant strain differing depending on the place of manufacture/sale or the cut of the meat. H. alvei was isolated at an especially high frequency from imported samples. An investigation was carried out regarding raw horsemeat intended for human consumption from Yamanashi Prefecture and Canada, regularly purchased from one store in Kanagawa Prefecture. Enterobacteriaceae were isolated during five of nine (55.6%） trials, in which the isolated bacteria were H. alvei, K. pneumoniae, etc. Moreover, they were isolated at a very high isolation rate of seven among 10 trials for the Canadian meat, and H. alvei was the most commonly isolated bacteria. Accordingly, when an investigation was carried out regarding the differences in the strain level in the six isolates of H. alvei periodically isolated from raw horsemeat from Canada by the pulsed-field gel electrophoresis (PFGE) pattern using a restriction enzyme, SfiI, there was a possibility that these were the same H-38 strain (November 2013) and H-64 strain (April 2014) as well as the same H-104 strain (July 2014) and H-131 strain (December 2014). As mentioned above, it has been demonstrated that a variety of Enterobacteriaceae were isolated from raw horsemeat (Basashi) intended for human consumption, and at a high frequency. Moreover, based on the fact that the same species or strain was chronologically isolated, the possibility of contamination by the same contamination source at different times was suggested.