An outbreak of multiple genotypes of Listeria monocytogenes in New Zealand linked to contaminated ready-to-eat meats—a retrospective analysis using whole-genome sequencing

Abstract

Four cases of listeriosis in a hospital (A) in New Zealand were identified in 2012. Pulsed‐field gel electrophoresis (PFGE) used at the time identified four pulsotypes amongst the clinical isolates. Two of the pulsotypes matched to Listeria monocytogenes isolates obtained from ready‐to‐eat (RTE) meat samples from a RTE producer tested during a nationwide microbiological survey the month prior. The outbreak investigation confirmed that the RTE producer had supplied product to the hospital and additional testing confirmed the presence of L. monocytogenes in RTE meats from the hospital kitchen. Two further listeriosis cases presented in another hospital (B) with one clinical isolate identified as the same pulsotype as identified for one case in hospital A, but the epidemiology information concluded that the clinical cases from hospital B were not linked to the outbreak. Retrospective whole‐genome sequencing confirmed that epidemiologically linked isolates belonging to three different genotypes for clinical cases from hospital A and RTE meats samples from the hospital kitchen differed by 0‐1 core‐genome locus or single nucleotide polymorphisms (SNP). The use of core‐genome multilocus sequence typing and SNP analysis provided a greater degree of discrimination between isolates compared to PFGE. Significance and Impact of the Study This study describes a listeriosis outbreak associated with a hospital in New Zealand and attributed to contaminated ready‐to‐eat (RTE) meat supplied to the hospital by a single producer. Retrospective whole‐genome sequence analysis of outbreak isolates was found to provide a greater degree of discrimination between isolates compared to pulsed‐field gel electrophoresis and supported the conclusions made at the time of the outbreak. The multiple genotypes identified from clinical cases and the RTE meats obtained during the outbreak highlight the importance of epidemiological concordance alongside genotyping.

Prevalence and Genetic Diversity of Listeria monocytogenes Isolated From Retail Pork in Wuhan, China

“…Genome sequencing has been gradually used to reveal the detailed characteristics of typing, virulent, and antibioticresistant genes and has become a useful investigation tool to support public health (Halbedel et al, 2018;Allard et al, 2019). The cgMLST and SNP have the advantage of high discriminatory power and are widely used for surveillance by appropriate public health analysts and epidemiologists (Hurley et al, 2019;Jagadeesan et al, 2019;Rivas et al, 2019;Papić et al, 2020), whereas CRISPR subtyping is rarely used for Listeria molecular epidemic investigations. In the present study, based on isolates from raw pork meat, WGS was applied to obtain information on cgMLST, SNP, and the CRISPR-Cas system.…”

Quality and safety of pork meat after cooling and treatment with lactic starters

“…The storage of the pork in a chilled condition for 1 day contributed to a decrease (p ≤0.05) in the total half-carcass weight of control group 1 by 2.27%, control group 2 -by 1.65%, experimental group 1 -by 1.61%, and experimental group 2 -by 1.25%, in comparison with the output of the paired carcasses (Figure 2 On the 4 th day of storage of the pork in a chilled condition, the shrinkage of the pork half-carcasses of control group 1 was 2.93%, control group 2 -2.50%, experimental group 1 -2.22%, and experimental group 2 -1.87%, in comparison with similar indicators of the paired carcasses (Figure 2-5). Such difference (p ≤0.05) in the moisture loss of the pork half-carcasses is due to the accelerated cooling with the use of stiving and the decrease in the intensity of the moisture evaporation [42].…”