Enteroaggregative Escherichia coli associated with a foodborne outbreak of gastroenteritis

Abstract

This study investigated two foodborne outbreaks of gastroenteritis that occurred 10 days apart among individuals who had meals at the restaurant of a farm holiday resort. Mild gastrointestinal symptoms were reported and none of the patients needed hospitalization. Mean incubation times were 45 and 33 h, and the overall attack rates were 43.5 and 58.3 %, respectively. Stool sample examination was negative for common enteric pathogens in both outbreaks. Specimens from 13 people involved in the second outbreak and 3 restaurant staff were examined for diarrhoeagenic Escherichia coli. An enteroaggregative E. coli (EAEC) strain of serotype O92 : H33 was isolated from six participants and one member of staff. In particular, the EAEC strain was isolated from five of the six cases of diarrhoea examined. The strain showed an aggregative pattern of adherence to HEp-2 cells, did not produce a biofilm and possessed the virulence-related genes aat, aggR, aap and set1A, but not the astA gene. A retrospective cohort study indicated a pecorino cheese made with unpasteurized sheep milk as the possible source (P,0.001). Samples of the cheese had E. coli counts higher than 10 6 c.f.u. g "1 , but the outbreak EAEC strain was not isolated. This report confirms that EAEC infections are probably underdiagnosed because of the limited availability of laboratories capable of identifying this group of pathogenic E. coli. INTRODUCTIONEnteroaggregative Escherichia coli (EAEC) are diarrhoeagenic E. coli characterized by the ability to adhere to HEp-2 cells in a characteristic 'stacked-brick' pattern (Nataro & Kaper, 1998). This property is usually due to the presence of aggregative adherence fimbriae, whose expression is positively controlled by the aggR gene, located on a large plasmid termed pAA (Nataro, 2005). EAEC infections are usually associated with watery diarrhoea, which is often persistent (Nataro & Kaper, 1998). Illness results from a complex interaction between pathogen and host, which implicates the initial adherence of the bacteria to the epithelium of terminal ileum and colon, in the characteristic aggregative pattern, followed by damage and a subsequent inflammatory response of the intestinal mucosa (Nataro, 2005;Huang et al., 2006).EAEC are a major cause of protracted diarrhoea in children in developing countries (Nataro & Kaper, 1998;Huang et al., 2006), where they are also linked to diarrhoeal illness of travellers and human immunodeficiency virus-positive patients (Huang et al., 2006). However, they have also been found to be associated with diarrhoea in industrialized countries (Tompkins et al., 1999;Weintraub, 2007). EAEC belong to a wide range of serotypes (Wilson et al., 2001) and are considered as emerging pathogens, characterized by a varied and complex epidemiology (Huang et al., 2006). Cases of EAEC infection are reported to be sporadic, but some outbreaks, involving both children and adults, have been described. The sources of infection have rarely been identified in these episodes. In France, an outbreak due to a...

Characteristics of the enteroaggregative Shiga toxin/verotoxin-producing Escherichia coli O104:H4 strain causing the outbreak of haemolytic uraemic syndrome in Germany, May to June 2011

“…Another EAggEC outbreak was reported in a Serbian nursery in 1995 [42] in which 16 newborn babies (duration of illness 3-9 days) and three infants (18-20 days) developed diarrhoea accompanied by pyrexia and weight loss. Outbreaks have also been reported among adults in the United Kingdom [43] and a small outbreak of EAggEC serotype O92:H33 was reported in Italy in which pecorino cheese (unpasteurised milk) was epidemiologically implicated [44]. As these outbreaks suggest, EAggEC is capable of causing diarrhoea in adults and children, even in the absence of Stx/VT.…”

Ruminants are not a reservoir of enteroaggregative Escherichia coli

“…Our results extend the literature by indicating that goats are unlikely to be an EAEC reservoir either. While the available evidence suggests that ruminants are not a relevant reservoir of typical EAEC pathogenic to humans, it remains possible that EAEC can transiently colonize ruminants (Scavia et al 2008).…”

“…EAEC infection usually occurs sporadically, but some outbreaks involving both children and adults have been described (Scavia et al 2008). In addition, the large outbreak of food-borne illness in Europe in the summer of 2011 was caused by a verotoxin (VT)-producing EAEC O104:H4 strain (Bielaszewska et al 2011, EFSA 2011, Paddock et al 2013.…”

“…Nevertheless, the possibility remains that ruminants may be a reservoir of EAEC and a potential source of transmission to humans. In fact, two EAEC outbreaks of gastroenteritis in Italy have been tentatively attributed to a cheese made with unpasteurised sheep's milk (Scavia et al 2008).…”

Molecular characterization and evaluation of antimicrobial susceptibility of enteropathogenic E. coli (EPEC) isolated from minas soft cheese

“…Similar results were reported by Ahmed, Ahmed and Moustafa (1988) and Najand and Ghanbarpour (2006), who noted the presence of EPEC in handmade cheese samples. Other pathogenic E. coli strains have also been reported in this product, such as ETEC and VETEC (PANETO et al, 2007), EAEC (SCAVIA et al, 2008), and STEC (STEPHAN et al, 2008).…”