Public Health Investigation of Two Outbreaks of Shiga Toxin-Producing Escherichia coli O157 Associated with Consumption of Watercress

Abstract

f An increase in the number of cases of Shiga toxin-producing Escherichia coli (STEC) O157 phage type 2 (PT2) in England in September 2013 was epidemiologically linked to watercress consumption. Whole-genome sequencing (WGS) identified a phylogenetically related cluster of 22 cases (outbreak 1). The isolates comprising this cluster were not closely related to any other United Kingdom strain in the Public Health England WGS database, suggesting a possible imported source. A second outbreak of STEC O157 PT2 (outbreak 2) was identified epidemiologically following the detection of outbreak 1. Isolates associated with outbreak 2 were phylogenetically distinct from those in outbreak 1. Epidemiologically unrelated isolates on the same branch as the outbreak 2 cluster included those from human cases in England with domestically acquired infection and United Kingdom domestic cattle. Environmental sampling using PCR resulted in the isolation of STEC O157 PT2 from irrigation water at one implicated watercress farm, and WGS showed this isolate belonged to the same phylogenetic cluster as outbreak 2 isolates. Cattle were in close proximity to the watercress bed and were potentially the source of the second outbreak. Transfer of STEC from the field to the watercress bed may have occurred through wildlife entering the watercress farm or via runoff water. During this complex outbreak investigation, epidemiological studies, comprehensive testing of environmental samples, and the use of novel molecular methods proved invaluable in demonstrating that two simultaneous outbreaks of STEC O157 PT2 were both linked to the consumption of watercress but were associated with different sources of contamination.

Human mini-guts: new insights into intestinal physiology and host–pathogen interactions

“…Even though the per patient frequency of diarrhoea is decreasing, because of the increasing population in developing countries, the number of diarrhoea cases per year is increasing or staying near constant. This problem is evidenced by deaths from outbreaks of Vibrio cholera e in Haiti 64 (with ~10,000 deaths), Shiga-toxin-producing Escherichia coli in Europe and the USA 65–67 , and the considerable increase in the numbers of Clostridium difficile cases in hospitals 68–70 . No specific FDA-approved therapies exist against these and other enteric pathogens.…”

Imported edible leaves collected at retail sale in England during 2017 with an emphasis on betel and curry leaves: microbiological quality with respect toSalmonella, Shiga-toxin-producingE. coli(STEC) and levels ofEscherichia coli

“…; Jenkins et al . ). Foods of nonanimal origin can be particularly problematic since they are often RTE or consumed after minimal cooking.…”

“…in 25 g of sample using EN/ISO 6579 method (International Organisation for Standardisation ); detection of Shiga‐toxin‐producing E. coli (STEC) in 25 g of sample based on CEN ISO TS 13136 as previously described (International Organisation for Standardisation ; Jenkins et al . ; Butcher et al . ); and enumeration of E. coli based on using a surface spread (0·5 ml of a one in 10 homogenate of the food sample was spread over the surface of an agar plate) rather than pour plate technique (International Organisation for Standardisation, ).…”

Improved traceability of Shiga-toxin-producing Escherichia coli using CRISPRs for detection and typing

“…Also, it has been suggested that VNTR may evolve too rapidly, leading to changes in repeat numbers during the course of an outbreak. More recently, the evolution of sequencing technologies has prompted the use of whole genome sequencing for typing of pathogens (EFSA 2013b), including STEC (Franz et al 2014;Joensen et al 2014;Dallman et al 2015;Jenkins et al 2015). WGS-based typing proved fast and efficient, providing an extraordinary phylogenetic accuracy.…”