An Outbreak of Human Listeriosis in England between 2010 and 2012 Associated with the Consumption of Pork Pies

Abstract

An outbreak of listeriosis in England affecting 14 people between 2010 and 2012 and linked to the consumption of pork pies was investigated. All 14 individuals were older than 55 years, 12 were men, and 10 reported the presence of an underlying condition. All were resident in or had visited either of two English regions and were infected with the same strain of Listeria monocytogenes. In interviews with 12 patients, 9 reported eating pork pies, and individuals that consumed pork pies were significantly more likely to be infected with an outbreak strain than were individuals with sporadic cases of listeriosis infections in England from 2010 to 2012. Pork pies were purchased from seven retailers in South Yorkshire or the East Midlands, and the outbreak strain was recovered from pork pies supplied by only the producer in South Yorkshire. The outbreak strain was also recovered from samples of finished product and from environmental samples collected from the manufacturer. The likely source of contamination was environmental sites within the manufacturing environment, and the contamination was associated with the process of adding gelatin to the pies after cooking. Inadequate temperature control and poor hygienic practices at one of the retailers were also identified as possible contributory factors allowing growth of the pathogen. Following improvements in manufacturing practices and implementation of additional control measures at the retailers' premises, L. monocytogenes was not recovered from subsequent food and environmental samples, and the outbreak strain was not detected in further individuals with listeriosis in England.

An assessment of the microbiological quality of liver-based pâté in England 2012–13: comparison of samples collected at retail and from catering businesses

“…The epidemiological and subtyping analysis did not allow the identification of links between consumption of pâté and cases of listeriosis. However, the present surveillance strategies now include whole genome sequencing for the characterisation of L. monocytogenes isolates and this will provide the potential for improved identification of associations between infected patients and contaminated foods as well as better recognition of foodborne outbreaks [29].…”

An Assessment of Different Genomic Approaches for Inferring Phylogeny of Listeria monocytogenes

“…The choice of the reference genome is fundamental for SNP calling (Pightling et al, 2014 ). The SNP approach is currently used in Denmark (Agasan et al, 2013 ; Wingstrand et al, 2015 ; Jensen et al, 2016 ) and UK (Awofisayo-Okuyelu et al, 2016 ), as well as for regulatory purposes by the US Food & Drug Administration (FDA). An additional approach consists in inference of categorical data based on presence or absence of predicted proteins.…”

Design Elements of Listeria Environmental Monitoring Programs in Food Processing Facilities: A Scoping Review of Research and Guidance Materials

“…As such, the objective of EM will inform the timing and frequency of sampling. For example, nine outbreak investigations from years 1989 to 2016 reported focused and detailed sampling investigations of food processing facilities, taking between 19 and 282 samples when production was stopped in order to find the source of Lm associated with cases of human listeriosis (Acciari et al., ; Awofisayo‐Okuyelu et al., ; Dalton et al., ; Gaul et al., ; Jacks et al., ; McLauchlin, Greenwood, & Pini, ; Salvat, Toquin, Michel, & Colin, ; Wenger et al., ; Winter et al., ). On the other hand, studies evaluating the efficacy of interventions conducted sampling immediately before and after the intervention, but may also have followed up after months or years of production to determine the long‐term effect of plant‐specific interventions, such as employee training, equipment disassembly during sanitation, or a new disinfectant compound or procedure (Eglezos, Thygesen, Huang, & Dykes, ; Lappi et al., ; Lappi et al., ; Ortiz, Lopez‐Alonso, Rodriguez, & Martinez‐Suarez, ).…”

“…The use of multiple typing methods or multiple enzymes (for example, for ribotyping) may increase discriminatory power and provide additional information on contamination patterns (Norton et al., ). Whole genome sequencing (WGS) was adopted by US regulatory agencies in 2013 and is routinely used in public health surveillance and outbreak investigations in the US and selected other countries (Awofisayo‐Okuyelu et al., ; Center for Food Safety and Applied Nutrition (CFSAN),; FDA, ). WGS provides for improved discrimination of isolates and is rapidly replacing PGFE as the “gold standard” for subtyping of Lm.…”