The pathogenicity island-like DNA segment associated with Chinese outbreak strain of Streptococcus suis serotype 2 is absent in the United States isolates.

To determine if the 2005 Chinese outbreak strain of Streptococcus suis is circulating in the United States, three different PCR primer-pairs derived from the nucleotide sequences surrounding and internal to the unique pathogenicity island -like DNA segment of the Chinese outbreak strain (strain 05ZYH33) were used to screen 290 swine isolates of S. suis obtained from different locations. The first primer pair amplified an approximately 1000-bp fragment from 47 (16%) of the United States isolates and the second amplified an 1800-bp fragment from 23 (8%) of the isolates. Nucleotide sequences of the amplicons shared identity with those of strain 05ZYH33. The third primer pair amplified a 716-bp amplicon from the DNA of strain 05ZYH33 only. These observations demonstrated that the PAI homologue of strain 05ZYH33 is absent in the United States isolates tested and suggested that the PCR method may be useful for active surveillance to monitor possible spread of the highly invasive strain.