Prevalence and clonal diversity of Listeria monocytogenes strains isolated from food wastes

International audience

English. <div><p>According to EU regulations, member states must take measures to promote the recycling of household biowastes. In France, the separate collection of food wastes (FW) is therefore booming. However, there are no data on the presence of pathogenic bacteria in FW. This study aimed to estimate the prevalence of Listeria monocytogenes in FW produced in an urban area, and to investigate the genetic diversity of L. monocytogenes isolates. The presence of L. monocytogenes was examined in FW collected 4 times (once per season) from 28 sites (9 apartment buildings (ABs) that produce their own compost, 7 restaurants, 7 canteens, 5 food shops) and from composts produced by three of the nine ABs. A total of 166 isolates were classified by multiplex PCR into serogroups. According to their origin and serogroup, 43 isolates were selected for whole-genome sequencing. L. monocytogenes was present in all types of FW producers. The frequency of detection of L. monocytogenes in FW from canteens, restaurants, food shops and ABs was 8%, 19%, 42% and 53% of the samples, respectively. L. monocytogenes was also detected in the composts of two of the three ABs. Serogroups IVb (47.6% of the isolates) and IIa (34.9%) dominated, followed by serogroups IIb (9.6%) and IIc (7.8%). The 43 isolates belonged to 22 clonal complexes (CCs), mainly CC121, CC4, CC388 and CC1 (44.2% of the isolates). Most of the isolates (70%) were distributed in CCs mainly associated with strains isolated from foods or agro-industrial environments. Three CCs found in this study, CC1, CC4, CC6 (25.6% of the isolates) have been often associated with clinical infections. Due to the high prevalence of L. monocytogenes in FW from ABs, awareness should be increased among the residents especially when FW, produced and composted by apartment buildings, are recycled as agricultural fertilizers in community gardens.</p></div>