A-Z Index × Submit A-Z Index × Submit A-Z Index Search Dropdown × Submit Facebook Twitter LinkedIn Syndicate Emerging Infectious Disease journal ISSN: 1080-6059 Disclaimer: Early release articles are not considered as final versions. Any changes will be reflected in the online version in the month the article is officially released.
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.
Listeria monocytogenes is a leading cause of foodborne illness–related deaths in the United States; an estimated 1,250 human illnesses and 172 deaths occurred annually during 2016–2019 ( 1 ). L. monocytogenes is frequently isolated from dairy, ready-to-eat meats, seafood, fruits, and vegetables, and it can persist in food processing environments ( 2 ), leading to recurrent contamination of finished products. Hence, robust surveillance is critical for protecting vulnerable populations and rapid detection of contamination sources.
Multilocus sequence typing (MLST) is widely used to classify L. monocytogenes into clonal complexes (CCs), and certain CCs are suggested as presenting higher and lower virulence ( 3 ). CC1, CC4, and CC6 are considered hypervirulent and are frequently associated with human listeriosis cases ( 4 ). Conversely, CC9 and CC121 are frequently isolated from food or food-processing environments and are considered hypovirulent CCs ( 4 , 5 ). Hypovirulent CCs often carry adaptations that promote environmental persistence (e.g., stress tolerance genes) but might have reduced ability to cause invasive disease ( 6 ). Characterizing the distribution of CCs across clinical and nonclinical isolates is key for identifying contamination reservoirs and understanding the public health relevance of isolates found in foods. Distinguishing hypervirulent strains from those mainly associated with the environment can help prioritize risk management and improve listeriosis prevention strategies ( 7 ). In this study, we analyzed 2,371 clinical and nonclinical L. monocytogenes isolates collected across the state of New York (NY), USA, during 2000–2021 to compare the CC distributions among clinical and nonclinical isolates, examine associations between CCs and food categories, and evaluate the time between food isolate collection and subsequent detection of a genetically-related clinical isolate using single-nucleotide polymorphism (SNP)–based thresholds. The Wadsworth Center and Cornell Uni…