Prevalence of Escherichia coli O157 : H7 and serogroups O26, O103, O111 and O145 in sheep presented for slaughter in Scotland

Abstract

Sheep have been proposed as a source of human verocytotoxigenic Escherichia coli infection on a number of occasions but few prevalence studies have focused on identifying rates of carriage of these pathogens in this species. The purpose of this work was to establish the frequency of excretion of E. coli of serogroups O157, O26, O103, O111 and O145 in sheep presented for slaughter in Scotland and to examine their carriage of known virulence determinants. The study involved microbiological isolation of E. coli from 1082 sheep presented for slaughter in four Scottish abattoirs between July 2005 and June 2006. Using faecal enrichment and immunomagnetic separation, the isolation rate from these samples was 3.4 % for E. coli serogroup O157, 5.2 % for E. coli serogroup O26, 2.3 % for E. coli serogroup O103 and 0.1 % for E. coli serogroup O145. E. coli O111 was not isolated. In the last month of testing, which coincided with sorbitol-fermenting E. coli O157 (SFO157) cases in children in Scotland, all 83 recta received were screened and tested negative for SFO157 strains. The study found no verocytotoxin-positive strains amongst the E. coli serogroup O103 or O145 isolates. Verocytotoxin-positive strains were identified amongst isolates of E. coli serotypes O157 : H7 and O26 : H11. E. coli O157 : H7 was not isolated from samples collected between January and March, a statistically significant drop (P,0.001) in mean shedding relative to other months. There was evidence (P50.003) of higher shedding of O157 in adults and hoggs than in lambs. E. coli O26 : H11 was isolated throughout the year, with a statistically significant peak in shedding in the third quarter (P50.003). The results showed that sheep presented for slaughter in Scotland may carry strains of E. coli, particularly of serogroups O157 and O26, which can be presumed to have potential to cause human infection. They did not support a hypothesis that human cases of E. coli O157 : H7 are higher in any particular Scottish region as a direct consequence of a higher rate of faecal carriage in sheep in that region. INTRODUCTIONEscherichia coli strains that produce verocytotoxins are important pathogens causing human illnesses ranging from diarrhoea to haemorrhagic colitis and haemolytic uraemic syndrome (Karmali, 1989;Riley, 1987). In the UK, North America, Japan and much of continental Europe, such disease is commonly caused by E. coli strains of serogroup O157 (Riley et al., 1983;Kleanthous et al., 1990;Willshaw et al., 2001;Kaper et al., 2004;Chase-Topping et al., 2008).A variety of infection routes, including food-borne transmission and person-to-person spread, have been described, but in the UK, human infections by E. coli O157 are also recognized arising from direct contact with animal reservoirs (Locking et al., 2001;O'Brien et al., 2001). Examples of where infection has been specifically associated with sheep include: illness linked with lambing ewes (Allison et al., 1997); sheep faeces apparently contaminating the water supply at a campsite outbreak (Licence et...

Potentially Human-Pathogenic Escherichia coli O26 in Norwegian Sheep Flocks

“…Although several surveys for E. coli O26 have been conducted, most of these studies have been limited, with small sample sizes, or have focused on isolating STEC O26 and not E. coli O26 in general. Also, most studies have been performed with cattle (9,26,40,41), and knowledge about E. coli O26 in sheep is sparse (3,18,19).…”

Veterinary Public Health Approach to Managing Pathogenic Verocytotoxigenic Escherichia coli in the Agri-Food Chain

“…Seasonal prevalence of VTEC in sheep has been reported (54,56), with incidences peaking in summer months in a similar trend to that in cattle and human infections (45). Much of the data on VTEC colonization of small ruminants relate to E. coli O157.…”

“…Some animals, particularly those that are persistently colonized, can excrete exceptionally high numbers of E. coli O157 (>10,000 CFU/g) in their feces (54,57). There is some evidence of higher shedding of O157 in adult sheep and hoggets than in lambs (56).…”

Estudio preliminar para investigar Salmonella sp. y E. Coli 0157:H7 en carne molida de res, de venta en supermercados en la ciudad de Puebla, México

“…Prácticamente, desde su descubrimiento se ha reconocido su participación en las enfermedades humanas. Habitualmente, E. coli 0157:H7 produce la colitis hemorrágica y daño renal, que requiere una baja dosis mínima infectante (10-100 células), es uno de los patógenos que mayor atención ha recibido, y hacia los cuales la industria de alimentos ha reenfocado su atención como una causa de morbilidad-mortalidad significativas (Jure y col., 2010;Evans, 2011;Vally y col., 2012;Ramoneda, 2013). La presencia de E. coli 0157:H7 en carne molida de res constituye un factor de riesgo para el consumidor (Narváez y col., 2005;Marzocca y col., 2006;Kasnowski y col., 2008;Jure y col., 2010;Phang y Bruhn, 2011;Cardozo y col., 2012).…”