Escherichia coli, biotype EAggEC, strain O104:H4, cultivated on ESBL agar (Bio Merieux). The red (burgundy) colour of the colonies indicates that this strain has an extended spectrum of betalactamase (ESBL), which means that it is resistant to different penicillins and many cefalosporins. The image is published with permission from Dr. Beutin.
The recent outbreak of VTEC (verotoxin producing E. coli) O104 infections in Europe, leading in some cases to the serious complication HUS (hemolytic uremic syndrome), was first suspected to be caused by consumption of vegetables contaminated by Escherichia coli of the biotype EHEC (enterohaemorragic E. coli). However, it seemed to be a new variant of EHEC, because it was unusually aggressive. It has now been reported from two different European National Reference Laboratories for Escherichia coli (in Rome and Berlin) that this new variant, in addition to the gene for Verotoxin 2, also has the aggR gene, which helps this bacterium to adhere to the host cells. According to the National Reference Laboratories for Escherichia coli at the National Veterinary Institute in Sweden, this E. coli should, therefore, not be regarded as beeing of biotype EHEC, but rather of bioype EAggEC (enteroaggregative E. coli), because it has the aggR gene. Furthermore, this particular E. coli strain was neither found in samples from the vegetables that were suspected to be contaminated, nor from environmental samples although hundreds of samples have been investigated.
More information about biotypes of E. coli, can be found at the website of Dr. Lothar Beutin, at the website of VetBact and in a Ph.D. thesis of Dr. Erik Eriksson at the National Veterinary Institute, Sweden.
Note that it is not allowed to use the image without permission from Dr. Beutin (Natl. Ref. Lab. for E. coli, Federal Institute for Risk Assessment, Diedersdorfer Weg 1, D-12277 Berlin, Germany).