J Med Microbiol 57 (2008), 1141-1146; DOI: 10.1099/jmm.0.2008/001362-0
© 2008 Society for General Microbiology
ISSN 1473-5644
Enteroaggregative Escherichia coli associated with a foodborne outbreak of gastroenteritis
Gaia Scavia1,
Monica Staffolani2,
Stefano Fisichella2,
Gianluca Striano2,
Stefano Colletta3,
Giovanni Ferri3,
Martina Escher1,
Fabio Minelli1 and
Alfredo Caprioli1
1 Dipartimento di Sanità Pubblica Veterinaria e Sicurezza Alimentare, Istituto Superiore di Sanità, Viale Regina Elena, 299, 00161 Rome, Italy
2 Istituto Zooprofilattico Sperimentale dell'Umbria e delle Marche, Macerata, Italy
3 Azienda Sanitaria Unica Regionale, Civitanova Marche, Italy
Correspondence
Gaia Scavia
gaia.scavia{at}iss.it
Received 20 February 2008
Accepted 1 June 2008
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 106 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.
Abbreviations: 95 % CI, 95 % confidence interval; EAEC, enteroaggregative Escherichia coli; ISS Istituto Superiore di Sanità; OB1/2, outbreak 1/2; VT, verocytotoxin.
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