An explosive increase of CPC isolated from rectal swabs of patients during weekly routine screening led to the declaration of an outbreak. A hospital-wide prevalence screening was initiated as well as screening of all patients on admission and before transfer to another ward, and canteen staff, patient rooms, medical and kitchen inventory and food. Swabs were streaked out on selective plates. All CPC isolates were analysed by mass spectrometry and selected isolates by whole-genome sequencing.
In total, 76 mostly unrelated cases in different wards were identified. The CPC was isolated from retained samples of prepared vegetable salads and puddings and from a mixing machine used to prepare them only after an overnight culture. The immediate ban on serving potential source food resulted in a sharp decline and finally disappearance of novel cases. Repeated testing of pre-sliced vegetables showed a high degree of contamination with C. freundii without a carbapenemase, indicating a possible source.
This report demonstrates that an explosive increase in carbapenemase-expressing Enterobacteriaceae contamination may be caused by a foodborne source, and suggests that pre-sliced vegetables have to be taken into account as a putative pathogen repository. It also underlines the importance of appropriate cooling, transport, re-heating and distribution of meals and indicates that probing of non-organic surfaces is limited by low sensitivity, which may be increased by additional overnight cultivation in appropriate media.
A nosocomial foodborne outbreak of a VIM carbapenemase-expressing Citrobacter freundii
The outbreak was short lived and the numbers of cases returned to expected seasonal levels within a month of the first cases being reported. Most of those affected had a mild to moderate form of illness and there were no deaths associated with the outbreak.
During the investigation, the initial link was found between illness and pre-cut spinach. When specific retailers were included in the analysis, the strongest association with infection was found to be with consumption of ready to eat pre-cut mixed salad leaves from a major supermarket chain.
In this analysis, exposure to pre-cut spinach only reached conventional levels of significance for one retailer – a second major supermarket chain. A link to spinach from a number of other retailers was also suggested but these were not statistically significant. Together these findings suggest that one or more types of salad vegetables could have been contaminated.
Dr Stephen Morton, regional director of the HPA’s Yorkshire and the Humber region and head of the multi-agency Outbreak Control Team, said, “Our findings suggest that eating mixed leaf bagged salad was the most likely cause of illness. It is however often difficult to identify the source of short lived outbreaks of this type as by the time that the outbreak can be investigated, the affected food and much of the microbiological evidence may no longer be available.
Dr Alison Gleadle, director of food safety at the FSA, took the opportunity to further confuse consumers, stating, “We’d like to remind everyone of our usual advice to wash all fruits and vegetables, including salad, before you eat them, unless they are labeled ready-to-eat.”
But wasn’t this outbreak linked to ready-to-eat salads? How is that advice of any use? Could have offered some details, like, additional washing of ready-to-eat products is largely ineffective. FSA is refocusing its efforts on farm management to limit such contamination, before it happens.
A spokesthingy for retailer Morrisons said, rather defensively, “Morrisons is not the source of this outbreak. We have received no complaints of illness and no Morrisons products have tested positive for Cryptosporidia.
“The HPA’s claim is based solely on statistics, not testing. The very same statistics also implicated products from other retailers that the HPA recognize as ‘implausible’.”
Why doesn’t Morrison’s say what they do to enhance the safety of products they sell rather than trash epidemiology?
As the Spongebob cone of news silence dims any publicly available information about the romaine lettuce-linked E. coli O145 outbreak that has sickened more than 50 people, journalists find related stories to fill the void.
A common theme is – what can consumers do?
As I told CNN last week, the answer is, not much; fresh produce purchases are faith-based exercises in food safety.
Ask Douglas Powell, food safety expert and keeper of barfblog, whether he’d consider a salad of fresh romaine for dinner tonight.
If it’s lettuce from a grocery store, Powell’s answer is yes.
He bought some Wednesday, the day the Centers for Disease Control and Prevention expanded to four states a current outbreak of potentially deadly food-borne illness linked to tainted lettuce.
But would Powell put the green stuff on his plate at a salad bar? Absolutely not.
That’s because a current recall of romaine lettuce involves companies that distribute to wholesale and food service outlets. And because "salad bars in general have the potential for lots more contact with lots of hands and people."
Let me clarify. The romaine lettuce I bought was in a bag. And I ate from a salad bar the next night.
Lettuce is overrated, and I prefer my own variation of a Greek salad without the lettuce – red pepper, olives, garlic, herbs, feta cheese, cucumber, tomatoes and whatever else may be around, marinated in olive oil and red wine vinegar. I also eat the greens, grow some of my own (which will be ready for harvest in about three days) and buy the bagged stuff.
Mike Doyle, a microbiologist who directs the Center for Food Safety at the University of Georgia, told CNN.com, if you want to reduce risks, "buy whole lettuce and cut it yourself."
Often, the bacteria lurk in the outer leaves. Nothing is foolproof, he said, but safety goes up when you toss the outer leaves and wash your hands properly.
Food safety lawyer Bill Marler said consumers should not give up eating a good thing out of fear. He also suggested that whole lettuce was a safer option than the bagged variety.
"Mass-produced lettuce is big business. The public wants it. But think hard whether the convenience is worth the risk."
I’m not sure I buy the higher-risk with bagged greens argument. I get that cross-contamination can happen when leaves are thrown in the same dump (wash) tank, but really, how hard is it to use a chlorine monitor and keep the water clean so the leaves aren’t washed in a muck?
The Washington Post reported this week it is difficult to judge whether pre-cut produce has been linked to more outbreaks than whole vegetables because state and federal health officials don’t always specify whether the leafy greens associated with an outbreak were bagged or whole. But several multi-state outbreaks involving pre-cut produce in the last five years have raised concerns, most notably the 2006 outbreak of E. coli O157:H7 associated with Dole bagged spinach that sickened 238 people and caused five deaths.
James Gorny, senior adviser for produce safety at the Food and Drug Administration, said bagged greens represent a disproportionate number of recalls, chiefly because they’re easier to identify than whole produce.
"When you buy a whole head of lettuce, you have no idea what the brand name is, or who the grower is. So tracing it back is that much harder."
But, he said, pre-cut produce is not inherently riskier than whole vegetables.
Dr. Doyle told the Post,
"I’ve been avoiding bagged lettuce for years. I’ve been concerned about this for some time."
Most processors of fresh-cut produce remove the outer leaves and core the heads of lettuce in the field, where cutting utensils can come into contact with soil and spread contamination from the dirt to the crop, Doyle said. In farming areas, especially in a region near cattle farms, it is not unusual to find E. coli in the soil.
In a study published last year in the Journal of Food Protection, Doyle and several colleagues contaminated coring devices with soil that contained E. coli O157:H7 — the most common E. coli strain associated with human illness — and showed how the bacteria spread from the coring equipment to heads of lettuce.
Washing the cored lettuce with a chlorine spray, a standard step, did not kill enough of the bacteria, the researchers found.
"In a processing plant, you’d have to have walls and clean floors. But here, they’re starting it right out in the dirt. It’s a very hazardous practice."
Once the bacteria attach to a lettuce leaf, "it’s very difficult to remove them," said Robert Gravani, a microbiologist at Cornell University. "We certainly want to increase our consumption of fresh fruits and vegetables, but we really have to address some of these issues."
What I told CNN was, production practices, harvesting, packing, processing and food handling have all been linked to illnesses associated with leafy greens. E. coli can get into food through manure, contaminated water used during growing or harvesting, or improper food handling at a store, restaurant or home. It’s best to ask a lot of questions of the people who sell you the green stuff. Was the irrigation water tested? Do the pickers know to properly wash their hands?
Beyond that, the only way to kill bacteria is to cook it. But who wants to eat mushy romaine?