European E. coli outbreak — experts respond

The outbreak of Escheria coli infection in Germany appears to be worse than anticipated, with health experts suspecting that current strain of the bacterium is more virulent than usual.

Below are comments on the unfolding situation from experts. Please feel free to use these in your stories. Previous expert commentary is available here.

SciBlogs contributor Dr Siouxsie Wiles recently posted this article regarding E. coli infection.

To talk to a local expert please contact the New Zealand Science Media Centre.

Professor Kurt L. Krause, Head of the Department of Biochemistry, University of Otago:

Based on the reports in the media there are at least 3 potentially unique qualities to this outbreak. The first would be its high degree of contagiousness, the second quality would be the reduced antibiotic sensitivity of this strain and the third the fact that this is reportedly a new strain of E. coli. However as new E. coli strains do appear with some frequency this is not too surprising, and further the CDC reported today that this strain although rare has been seen clinically before. What’s potentially more important is the degree of pathogenicity displayed by this strain. We’ll know more about this in the next few weeks, especially if we begin to see a wave of secondary infections. If the outbreak dies out after this wave of primary infections, as would be expected, that would be reassuring. The final point refers to the degree of antibiotic resistance and media reports to date have been incomplete about this aspect. Most E. coli are still very sensitive to antibiotics, while major centres worldwide are reporting more resistance especially to certain classes of drugs like fluoroquinolones, but in some cases more highly resistant strains have arisen. This issue is important as it speaks to the ability to treat infections with this organism effectively.

Collected by our colleagues at the UK SMC

A few key points from Stephen Smith, Lecturer in Clinical Microbiology at Trinity College, Dublin:

New technology identifies the culprit at breakneck speed Two teams based in Germany and China have already deciphered the gene sequence of this novel E. coli pathogen in just three days using cutting edge Ion Torrent sequencing. By comparison, a harmless E. coli was sequenced 5 years ago but this took 3 years not 3 days to do!

A mongrel bacterium. This strain is a chimaera and appears to be a hybrid of two different E. coli types which are nasty themselves. It is very similar to enteroaggregative E. coli which has been associated with outbreaks of watery diarrhoea in developing nations since the 1970. However, this bacterium has been become recognized as a cause of diarrhoea in industrialized nations and has caused outbreaks in the USA, Sweden, Britain and Germany.
The hybrid strain also contains the Shiga-like toxin from Enterohaemorrhagic E. coli. This toxin binds to and damages cells of the kidney. This leads to the potential fatal Haemolytic Ureamic Syndrome.

E. coli sticks to plant material Scientists in Birmingham and London have shown that the enteroaggregative strain binds to salad leaves ( Environmental Microbiology Reports (2009) 1(4), 234-239). Thus, it would be very wise to avoid raw leaves. NOTE – There are some nice photos of the bacterium sticking to leaves in that article.
The drugs don’t work! The gene sequence has also revealed that this strain is resistant to many common antibiotics. Indeed, antibiotics would have no effect against the toxin produced by this bacterium.

Younger women mainly affected. It appears that younger women are mainly affected. I spoke to my mainly female research team here, they suggest that it may be reflective of their healthier lifestyle – i.e. consuming more salad vegetables.

Dr Paul Wigley, from the University of Liverpool’s School of Veterinary Science, said:

“E.coli that cause human disease are often classified by the type of disease that they cause or the toxins they produce. The most serious are the VTEC also known as EHEC and STEC. These acronyms stand for Verocytoxin (VT), Enterohaemorrhagic (EH) or Shiga-Toxin (ST) E. coli (EC) – hence VTEC, EHEC etc. These bugs are able to cause disease through a combination of toxins called Verocytotoxins or Shiga-like toxins and a bacterial machine called a Type III secretion system that allows the bug to attach to the intestines. There is some indication that this outbreak may caused another type of E. coli called EAEC (entero-aggregative E. coli) that also causes diarrhea, which has acquired the toxins from VTEC. EAEC survives well in food and so represents a particular problem.

“In the lab E .coli are typed by antibodies that recognize features on the surface of the bacteria. The most important of these is the ‘O’ antigen or lipopolysaccharide which forms a large component of the bacterial surface. So serotype O1 has a Type 1 ‘O’ antigen, serotype O104 a type 104 ‘O’ antigen.”

Dr Anthony C. Hilton, Reader in Microbiology at Aston University, said:

“The pattern of infection in this outbreak is unusual in the proportion of adults presenting with Haemolytic Uremic Syndrome (HUS) which is normally observed in children, and the bias towards females. We could very well be looking at a new virulent strain of E. coli.

“E. coli O104 is uncommon and that may actually help in the investigation to determine the origin and routes of transmission of this strain. Nevertheless it may be some time, if at all, that we are able to pinpoint this with any certainty.

“If the current strain is indeed a novel virulent type it will be important to determine if this is simply surface contamination of vegetables or if the organism has developed a mechanism of intracellular invasion and persistence, as that will greatly influence the effectiveness of the simple washing of vegetables intended to be eaten raw as a means of reducing the risk of infection.”

Dr Douglas Noble, a Public Health Doctor and Lecturer in the Centre for Primary Care and Public Health at Queen Mary, University London said:

“This is obviously a very serious outbreak of a rare strain of E coli with the exact source of contamination remaining undetermined. The UK has in recent years been very strong in its response to such threats to human health, and this episode particularly highlights the need for a joined up public health response across Europe.”

Dr Paul Wigley, from the University of Liverpool’s School of Veterinary Science, said:

“The E. coli outbreak associated with cucumbers and other vegetables in Germany has been caused by a type of the bug called 0104. This is part of the group of E .coli bacteria called VTEC or verocytotoxin producing E. coli which includes the more common O157 form that were responsible for fatal disease outbreaks in Wales and Scotland and with the outbreak at Godstone Farm, Surrey in 2009.

“VTEC normally infect people directly through animal faeces, or more usually through poorly cooked meat contaminated with the bacteria. Whilst most strains of E. coli do not cause disease, VTEC are able to attach to the wall of the intestines very tightly and produces toxins. It is these toxins that cause damage to the gut leading to bloody diarrhoea and may cause damage throughout the body including the kidneys.

“The most serious consequence of infection is Haemolytic Uraemic Syndrome (HUS) that frequently leads to kidney failure resulting in the need for kidney dialysis or sometimes death. Animals, and in particular cattle, may carry VTEC in their intestines without disease which may lead to the bacterium being shed in their faeces.

“It is most likely that the use of manure as a fertilizer in organic salad vegetable production has lead to contamination of cucumbers and other vegetables. Although E. coli infection is most commonly associated with meat, there have been previous reports of the disease being contracted from raw vegetables.

“Consumers should follow the advice of the Heath Protection Agency and ensure good hygiene practice in the kitchen and thoroughly wash all salad vegetables and fruit before eating.”

Q&A with Professor Brendan Wren, from the London School of Hygiene and Tropical Medicine:

Q: What is the testing process for EHEC and the different strains; how difficult it is to narrow down which strain is responsible for the outbreak?

To definitively link the patients EHEC to the source of infection, the modern method is to compare the whole genome DNA sequence of the “suspect” and the “offending” strain. These should be near identical. Thus rather like the way we use DNA fingerprinting for crime investigation and paternity claims, we can apply this to bacteria. A few specialised labs are able to do this.

Q: Is there any reason cucumbers would be more likely to carry EHEC than other fresh produce?

No, in fact I have never heard of cucumbers being a source of food poisoning before. I doubt it is the source; EHEC is usually caught from the consumption of meat products (particularly beef). You would have to compare directly the “suspect” and the “offending” strains before being confident, and I don’t think that this has been done in Germany. Also it is peculiar that the outbreak is localised in Northern Germany (or people who have visited the region). The Spanish fresh produce would have been transported to many places in Europe and there have not been outbreaks elsewhere.

Q: Is EHEC normally in the environment and on vegetables, but perhaps milder strains?

EHEC is found in the gut microflora of humans and mammals (livestock). Improper water/sewage disposal and slurry procedures can contaminate fresh produce (which isn’t cooked, so therefore does not kill adherent bacteria). No – EHEC is not normally in the environment, but some manuring or slurry practises can be a source to cross-contaminate fresh produce

Q: Will this testing be able to definitively identify what sparked the outbreak?

Yes – by whole genome DNA sequencing, but of course you need to have the real suspect to be sure. It is unlikely to be cucumber and as in many food borne disease outbreaks, the real culprit may never be identified and the epidemic just fades away.

ENDS

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