E.coli O157 outbreak investigation analysed
Researchers described the illnesses which affected Limburg in 2012 by performing a case-control study, a trace back/forward investigation and comparing strains isolated from human cases and food samples.
It involved 24 cases from 17 different households. Seventeen were laboratory-confirmed and the meat products were traced back to a slaughterhouse.
Outbreak affected
The mean age was 31 years (range: 6-84 years), 13 cases were female, eleven male.
Fifteen were hospitalized for an average of seven days and five patients developed Hemolytic Uremic Syndrome (HUS), three children and two adults.
From 1994 to 2011, between 47 and 103 Enterohaemorrhagic E. coli (EHEC) cases were registered yearly in Belgium.
Pulsed Field Gel Electrophoresis (PFGE) and insertion sequence 629-printing (IS 629-printing) proved that beef products, sold at different supermarkets, were the source of the EHEC O157:H7 outbreak.
A case in the case-control study was defined as anyone with a laboratory-confirmed E. coli O157:H7 infection in the North-East Limburg region from May 30 2012 until June 14 2012.
Out of 13 laboratory-confirmed cases known by the start of the case-control study, the researchers selected eleven and invited them to an electronic survey.
“As the exploratory interviews, conducted by the start of the case-control study, pointed towards meat products, we shortened this survey by excluding specific questions about dairy, vegetable and fruit consumption,” they said.
“The final survey included 13 meat products, three dairy products (including ice-cream) and six other food products (vegetables and sprouts).”
Sampling efforts
Beef meat was traceable back and forward through the unique “Sanitel numbers” and data in a computerized management system.
Food samples were taken at the butcheries of five different supermarkets, a meat establishment, a cutting plant and a slaughterhouse.
On June 14, the National Reference Laboratory for Foodborne Outbreaks (NRL-FBO) confirmed the presence of vtx1a vtx2a eae ehxA positive E. coli O157 in two samples of raw beef meat and “steak tartare” collected on June 8.
A total of 73 samples were analyzed and three vtx1a vtx2a eae ehxA positive E.coli O157 and one vtx1a vtx2c eae ehxA positive E. coli O157 were isolated.
Ten other samples were suspected of having the epidemic strain at the screening level but the strain could not be isolated due to a high number of background flora.
Detecting an outbreak as fast as possible and reporting results to all concerned are the greatest challenges towards significantly improving outbreak management, said the researchers.
“A lot of different authorities, institutes and laboratories, each with its own mandate, are involved in outbreak investigation and management,” they said.
“Our main recommendations are the facilitation and acceleration of the outbreak detection and the development of a communication plan to reaches all persons at risk.”
Source: Archives of Public Health 2014, 72:44
Online ahead of print, DOI: 10.1186/2049-3258-72-44
“Lessons learned from a textbook outbreak: EHEC-O157:H7 infections associated with the consumption of raw meat products, June 2012, Limburg, Belgium”
Authors: Toon Braeye, Sarah Denayer, Klara De Rauw, Anmarie Forier, Jurgen Verluyten, Ludo Fourie, Katelijne Dierick, Nadine Botteldoorn, Sophie Quoilin, Pascale Cosse, Jeannine Noyen and Denis Pierard
