a b s t r a c t
Article history:
Received 21 February 2015
Received in revised form 13 May 2015
Accepted 15 May 2015
Available online 29 May 2015
Keywords:
Streptococcus suis
Pork
LAMP
We here developed a novel loop-mediated isothermal amplification (LAMP) method to detect Streptococcus suis in
raw pork meat. This method, designated LAMPSS, targeted the recombination/repair protein (recN) gene of S. suis
and detected all serotypes of S. suis, except those taxonomically removed from authentic S. suis, i.e., serotypes 20,
22, 26, 32, 33, and 34. The specificity of LAMPSS was confirmed and its detection limit was 5.4 cfu/reaction.
Among the 966 raw pork meat samples examined, including sliced pork, minced pork, and the liver, tongue,
heart, and small intestine, 255 samples tested positive with LAMPSS. The rate of contaminationwas higher in the organs
than in pork. No significant difference was observed in the total bacterial count between LAMPSS-positive and
-negative samples. The number of shops that provided LAMPSS-positive pork was slightly higher in those that sold
swine organs and pork than in those that sold only pork, suggesting that cross contamination occurred from the organs
to pork. Among the 255 which tested positive for LAMPSS, only 47 samples tested positive for the previously
described LAMP specific for S. suis serotype 2. Two isolates of S. suis serotype 2, belonging to sequence type 28,
which is potentially hazardous to humans, as well as those of some other serotypes were obtained from 19 out of
47 samples by combining LAMP with a replica plating method. These results suggest that LAMPSS will be a useful
tool for the surveillance of raw pork meat in the retail market