Should bagged salads be washed again?

No. Prewashed bagged salads should not be washed again at foodservice or at home.

At least that’s what a panel of scientists with expertise in microbial safety of fresh produce concluded after reviewing recent research.

A paper published in the current issue of Food Protection Trends, published by the International Association for Food Protection presents guidelines developed by the panel, together with materials reviewed by the panel to develop the guidelines concluded that,

"leafy green salad in sealed bags labeled “washed” or “ready-to-eat” that are produced in a facility inspected by a regulatory authority and operated under cGMPs, does not need additional washing at the time of use unless specifically directed on the label. The panel also advised that additional washing of ready-to-eat green salads is not likely to enhance safety. The risk of cross contamination from food handlers and food contact surfaces used during washing may outweigh any safety benefit that further washing may confer."

Meanwhile, Eurosurveillance reported last week that

"Early in October 2007, an increase in notifications of human cases infected with Shiga toxin (Stx)-producing Escherichia coli (STEC) O157 was seen in the Netherlands. All cases reported diarrhoea, and most also had bloody diarrhoea. No cases developed haemolytic uraemic syndrome (HUS). The onset of illness for the first cases was in mid-September.

"STEC O157 strains that contained both stx1 and stx2 genes were isolated from 36 patients. Subtyping of these isolates by pulse-field gel electrophoresis (PFGE) showed, for 33 cases, an identical pattern not previously observed in the Netherlands. One further isolate was nearly identical to the 33. The two remaining isolates, which were isolated from the siblings of a confirmed case, have not yet been typed.

:The PFGE pattern was compared to the pattern found in Iceland, which appeared to be identical. The Iceland outbreak of STEC O157 is described in an accompanying article. …

"The Dutch Food and Safety Authority (FSA) is investigating the distribution channels of packed fresh vegetables and the individual ingredients. Samples of lettuce and other raw vegetables are being taken, as well as environmental samples at vegetable growers and shredding plants that may be involved. One shredding company for fresh vegetables also cuts and packs lettuce products for Iceland. …

"Five cases had consumed lettuce packaged and imported from the Netherlands, as verified either by questionnaire (three cases) or by supermarket purchase records (two cases). Intensified surveillance in lettuce with increased sampling began in mid-October and is ongoing. Culture results have so far been negative.

The strain that caused the outbreak in Iceland was identified by the Laboratory of Enteric Pathogens at the Health Protection Agency in the United Kingdom as STEC O157, phagetype 8, carrying the stx1 and stx2 shigatoxin genes. The PFGE pattern of all nine Icelandic isolates was identical to the strain that caused the current STEC O157 outbreak in the Netherlands."

Washing probably wouldn’t have done much. When it comes to fresh produce, food safety begins on the farm. And don’t eat poop.