Virulence gene profiling

The NTS isolates were screened by PCR for the presence of eight virulence-associated genes, including three genes involved in NTS colonization/biofilm formation: fimbrial usher (bcfC), plasmid-encoded major fimbrial subunit (pefA), and non-fimbrial adhesion (siiE) as well as five genes involved in invasion of the host, invasion protein InvE (invE), secretion system apparatus outer membrane protein SsaC (ssaC), magnesium transport protein MgtC (mgtC), enterotoxin (stn), and inositol phosphate phosphatase SopB (sopB). Three multiplex PCR reactions were used to detect: (1) mgtC/bcfC; (2) pefA/siiE; and (3) stn/sopB. Identification of remaining two virulence-associated genes, ssaC and invE, was performed individually by employing conventional PCR methods. All primer sequences used for the virulence-profiling assay were designed in this study. S. enterica serovar Enteritidis ATCC 4931 was used as a positive control and Escherichia coli O157 strain B-1 (Vidovic and Korber, 2006) was used as a negative control. PCR amplification was carried out in 50 μL using a T100™ thermal cycler (Bio-Rad, Hercules, CA). Primers for the PCR assays used in this study are presented in Table ​Table22.

Primers used for detection of eight virulence-associated genes in the population of NTS isolates.