Prevalence, antibiotic resistance and genetic diversity of Listeria monocytogenes isolated from retail ready-to-eat foods in China

Abstract Listeria monocytogenes is a major foodborne pathogen that is well known as high mortality rate upon infected. This study aimed to investigate the prevalence of L. monocytogenes isolates from retail ready-to-eat (RTE) foods in China and characterize the isolates of L. monocytogenes by antibiotic resistance, serotyping, ERIC-PCR and REP-PCR subtyping analyses. From September 2012 to January 2014, a total of 364 retail RTE foods were obtained. Using the qualitative and quantitative methods, 25 samples (6.87%) were positive for L. monocytogenes . The identity of isolates of L. monocytogenes was confirmed by PCR. All 80 isolates in this survey were sensitive to penicillin and mezlocillin, the highest resistance is clindamycin (51.25%), followed by cephalothin (23.75%) and ampicillin (12.5%). Twenty-seven isolates were susceptible to all 14 tested antibiotics; seventeen isolates were resistant to more than two antibiotics, including six multiresistent strains resist to more than 10 antibiotics. L. monocytogenes isolates belonged to serovar types 1/2a (3a), 4b (4d, 4e), 1/2b (3b, 7) and 1/2c (3c). 29 L. monocytogenes isolates were selected by serotyping. At the relative similarity coefficient of 0.80, it grouped 29 isolates and 5 reference strains into 2 clusters and 3 singletons, 4 clusters and 1 singleton by ERIC-PCR and REP-PCR, respectively. Our study reflects the potential risk of L. monocytogenes infection in China. We also provide a comprehensive surveillance on its incidence on the RTE foods of L. monocytogenes and ensure more accurate treatment of human listeriosis with effective antibiotics.