The Epidemic Detectives: The Hunt for the Source of Germany's E. Coli Outbreak

[Ronan Kelly]

Nice backgound summary of the E. coli outbreak from Der Spiegel;

05/31/2011
The Epidemic Detectives
The Hunt for the Source of Germany's E. Coli Outbreak
By Veronika Hackenbroch, Samiha Shafy and Frank Thadeusz

The eeriest thing of all, according to Rolf Stahl, is the way patients change. "Their awareness becomes blurred, they have problems finding words and they don't quite know where they are," says Stahl. And then there is this surprising aggressiveness. "We are dealing with a completely new clinical picture," he notes.


Stahl, a 62-year-old kidney specialist, has been the head of the Third Medical Clinic and Polyclinic at the University Medical Center Hamburg-Eppendorf (UKE) for almost 18 years. "But none of us doctors has ever experienced anything quite like this," he says. His staff has been working around the clock for the last week or so. "We decide at short notice who can go and get some sleep."

The bacterium that is currently terrifying the country is an enterohemorrhagic strain of the bacterium Escherichia coli (EHEC), a close relative of harmless intestinal bacteria, but one that produces the dangerous Shiga toxin. All it takes is about 100 bacteria -- which isn't much in the world of bacteria, which are normally counted by the millions -- to become infected. After an incubation period of two to 10 days, patients experience watery or bloody diarrhea.

'The Situation Is Deteriorating Dramatically'

But Stahl only sees the most severe cases, those in which EHEC also attacks the blood, kidneys and brain. These patients suffer from a life-threatening complication known as hemolytic-uremic syndrome (HUS). About 10 days after the diarrhea begins, the red blood cells suddenly disintegrate, blood clotting stops working and the kidneys fail. In many cases patients need dialysis to stay alive.

...

complete 3 page story at;
http://www.spiegel.de/international/germany/0,1518,765777,00.html

 

[Emily]

Re: The Epidemic Detectives: The Hunt for the Source of Germany's E. Coli Outbreak

This news from Der Spiegel was interesting:

"On Tuesday, the German newspaper S?ddeutsche Zeitung reported that Karch had discovered that the O104:H4 bacteria responsible for the current outbreak is a so-called chimera that contains genetic materia[l] from various E. coli bacteria. It also contains DNA sequences from plague bacteria, which makes it particularly pathogenic. There is no risk, however, that it could cause a form of plague, Karch emphasized in remarks to the newspaper."

I haven't been able to find any previous studies finding incorporation of plague bacteria DNA into E. coli in the 'natural' environment, but found this study concerned about the opposite transfer.

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0000309

Multiple Antimicrobial Resistance in Plague: An Emerging Public Health Risk

Welch TJ, Fricke WF, McDermott PF, White DG, Rosso M-L, et al. 2007 Multiple Antimicrobial Resistance in Plague: An Emerging Public Health Risk. PLoS ONE 2(3): e309. doi:10.1371/journal.pone.0000309

"Recently there also has been a rapid worldwide emergence of MDR foodborne bacterial pathogens [6], [7]. While these resistant variants can be transferred to humans via contaminated food supplies, subsequent infections usually result in a self-limited gastroenteritis that does not require antimicrobial therapy [8]. However, since these MDR determinants are often encoded on mobile plasmids, the potential transfer of MDR phenotypes from foodborne pathogens to more virulent human pathogens, including Y. pestis, constitutes a serious public health threat.

Here we report the complete sequence and comparative analysis of three nearly identical large (>150 kb) MDR plasmids isolated from Yersinia pestis [5], Salmonella enterica ser. Newport and Yersinia ruckeri. Our findings indicate a very recent common origin for these plasmids. Moreover, we present evidence that a common plasmid backbone is prevalent among E. coli, Klebsiella sp. and multiple Salmonella serotypes isolated from retail meats in the US, and among some food animal isolates of E. coli. Our data imply that high levels of MDR in the causative agent of plague may rapidly evolve naturally, and present a vital biomedical, public health, and biodefense threat."

So far the only transfer of Y. Pestis genes to E. Coli that I could find have occurred in labs.
http://onlinelibrary.wiley.com/doi/10.1111/j.1574-695X.2007.00280.x/full

ETA:
Here's an article about bacteria evolution focusing on Yersinia and E. Coli that I think is saying that 'pathogenic islands' in the genome of a bacteria strain makes it more likely to pick up new genetic material that could potentially make it even more pathogenic.

http://www.bioupdates.co.uk/disevo.htm
The evolution of bacterial diseases

"Studies such as this, which attempt to piece together the genetic events which led to the development of diseases are relevant to current concerns about the appearance of new and unsuspected epidemics against which we have little protection. An example is Escherichia coli strain O157. This differs from more familiar less harmful, strains in causing severe diarrhea and possibly death. The complete genomes of two non-pathogenic strains of E. coli have been sequenced (5). Now the O157 sequence is being analysed and compared with the other E. coli sequences. So far the comparison has revealed the gene for shiga toxin from the diarrhea-causing bacterium Shigella (on a bacteriophage) (7), virulence genes carried on plasmids and a pathogenicity island. There is also evidence for a higher than normal mutation rate due to defective repair of mismatches in sequence between DNA strands. Such defects also make it more likely that foreign DNA will be incorporated into the chromosome. This potential for accelerated genomic change could increase the rate of acquisition of pathogenic characteristics."