Molecular serogrouping and virulence of Listeria monocytogenes from local dairy cattle farms and imported beef in Jordan

Listeria monocytogenes is a significant foodborne pathogen with numerous serogroups which vary in their virulence and distribution across countries. This study aimed to determine the serogroups and virulence genes of L. monocytogenes isolated from bulk tank milk, dairy cow feces and imported beef in Jordan. To achieve this aim, multiplex PCR assays were utilized to serogroup and determine the virulence genes of 70 L. monocytogenes isolates from dairy ruminants (n = 28) and imported beef (n = 42). Results identified that the L. monocytogenes isolates from these sources were in five serogroups. The majority of isolates (55.7%) belonged to serogroup 1/2a (3a), followed by serogroup 1/2b (22.9%), serogroup 4b (d, e) (14.3%), serogroup IV (serotypes 1/2c and 3c) (5.7%), and serogroup 4a/c (1.4%). Forty-six (65.7%) of the isolates carried both the InlA and InlC genes, specifically 53.6% of dairy and 73.8% of beef isolates. Four isolates also carried the inlC gene, specifically, two dairy isolates and two beef isolates. These findings recommend the implementation of improved sanitation procedures at slaughterhouses and dairy operations in Jordan to reduce the public health risk of L. monocytogenes.