Characteristics of Listeria monocytogenes isolated from foods in Changping district of Beijing

Objective To understand the virulence genes,antibiotic resistances and molecular characteristics of Listeria monocytogenes. Methods A total of 22 L. monocytogenes strains isolated from 12 kinds of foods between 2010 and 2016 in Changping were used for serotyping,virulence genes detection,antibiotic susceptibility test,multi-locus sequence typing (MLST)and pulsed-field gel electrophoresis (PFGE). Results The 22 L. monocytogenes strains belonged to 5 serotypes, 1/2c and 3a were the predominant serotypes. A total of 19 virulence gene profiles (T1-T19)were found,and most strains carried 6-12 kinds of virulence genes. All the L. monocytogenes isolates were sensitive to ampicillin,penicillin,meropenem, sulfamethoxazde,vancomycin and ciprofloxacin,and a few strains were resistant to tetracycline and erythromycin. The result of MLST showed 8 different sequence types,including 7 new STs,i.e. STA1-STA7,and the predominant ST was STA3. Seventeen PFGE patterns were found with a similarity coefficient from 63.5%-100.0%,and the PT Ⅰ was predominant. Conclusion Most L. monocytogenes isolates isolated in Changping belonged to serotype 1/2c and 3a,STA3 and PT Ⅰ strains were predominant. Most strains had different virulence genes profiles. Resistance to tetracycline and erythromycin were found in a few L. monocytogenes isolates. Our data provides a reference for the study of foodborne Listeria spp.