Clustering and Source Association of Clinical and Nonclinical Listeria monocytogenes Isolates, New York, USA, 2000-20211.

We analyzed whole-genome sequencing data for 1,046 human clinical and 1,332 nonclinical Listeria monocytogenes isolates collected across New York, USA, during 2000-2021. Several hypervirulent clonal complexes (CCs) were significantly associated with clinical isolates, and several hypovirulent CCs were associated with nonclinical isolates. Specific CCs also showed association with specific food categories (e.g., processed meat); specific genetic markers (e.g., inlA premature stop codons) were also significantly associated with processed meat isolates. Analysis of clusters that contained food isolates, as well as subsequently identified clinical isolates, showed that time of isolation between food isolates and clinical isolates was significantly shorter for produce isolates than for isolates from meat, dairy, or fish. This finding suggests unique transmission pathways for produce, which might reflect short shelf life or limited L. monocytogenes persistence (e.g., in agricultural environments). This study highlights new opportunities for use of whole-genome sequencing to improve outbreak investigations and source attribution.