Correlation Study Of L.Monocytogenes Contamination Among Environment,Insects And Raw Meat In Retail Market

Listeria monocytogenes can contaminate various foods via food processing environments and contaminated raw materials.To better understand whether retail environments and insects acted as risk factor for raw meat contamination of L.monocytogenes,we investigated the prevalence of L.monocytogenes isolated from retail environments and insects in a retail market in Beijing,China.A total of 2789 samples were collected from 64 stalls once a month for six months(March 2016-August 2016).Samples include raw neat,retail environments(chopping boards and knives,the inner and outer surfaces of chest freezers,meat mincers,floors and walls)and insects(flies and cockroaches).The L.monocytogenes isolates were analyzed by serotyping,multilocus sequence typing(MLST)and pulsed-field gel electrophoresis(PFGE)to detect the characteristics and relevance of raw meat,retail environments and insets.For 2789 samples collected from pork retail market,overall,424(15.20%)of the samples were positive for L.monocytogenes.Among that,the prevalence rates of L.monocytogenes were 29.21,16.31,3.9 and 19.76%respectively from raw meat,MCS(meat contact surface),NMCS(nonmeat contact surface)and insects.Raw meat and MCS has high levels and NMCS has a relatively low rate of L.monocytogen.es contamination.Insects were also found to have a high carriage of L.monocytogenes.Overall,all isolates were divided into three serotypes including 1/2c(71.70%),l/2a(17.45%)and 3a(10.85%),and 26 PFGE types including PT4(52.83%),followed by PT16(10.61%),PT279(9.67%),and 9 sequence types(STs)including ST9(71.75%),followed by ST155(12.74%)and ST121(8.96%).It is likely that the retail environments,in particular the MCS and insects in retail markets act as high risk factors to transmit L.monocytogenes to raw meat.Persistence of L.monocytogenes in the retail market was the main cause for raw meat contamination.These findings will be useful to develop more effective strategies to reduce the risk of retail meat L.monocytogenes contamination and prevent and control foodbome human listeriosis.