Vero-cytotoxin Producing Escherichia coli O104:H4 Version 1 7/6/2011
This is an update for microbiologists in the HPA, NHS and other hospitals in the UK. Please note that this briefing incorporates the changes to the testing requirements from ECDC issued on the 6/6/2011 and now includes testing specimens from patients with acute diarrhoea and a travel history to Germany. Health and Safety Advice VTEC O104 is a Hazard Group 3 pathogen and specimens from patients with relevant clinical symptoms (high index of suspicion) or which meet the definitions for specialist testing (see below) or presumptive isolates should be handled in a CL3 laboratory. All laboratories will need to review and update their risk assessments accordingly. Advice for Testing Clinical Specimens The VTEC O104:H4 is an unusual strain of non-O157 VTEC and is not easily differentiated from normal E. coli found in faecal or other clinical specimens. Currently there are no specific diagnostic tests available that routine clinical laboratories can use. We therefore ask medical microbiologists to use the following advice: NHS and HPA clinical laboratories are asked to urgently refer faecal specimens to the Reference Laboratory in the Laboratory of Gastrointestinal Pathogens (LGP) from patients with the following clinical presentations and travel history:
1. Bloody diarrhoea or acute diarrhoea with a history of travel to Germany within 14 days prior to the onset of symptoms*. 2. Haemolytic Uraemic Syndrome (HUS), Thrombotic Thrombocytopenic Purpura (TTP) regardless of the travel history*. 3. Bloody diarrhoea and no travel, follow existiand and refer specimens to the Reference laboratory if the patient has a VTEC compatible illness but O157 is not isolated. 4. Diarrhoea and no travel, perform local routine gastrointestinal tests * The local laboratory should perform routine gastrointestinal testing urgently but at the same time also send the sample to LGP, rather than waiting for the results of the local tests. All presumptive VTEC isolates should continue to be rapidly referred to the LGP for confirmation. The local laboratory should ensure that they inform the local Health Protection Unit. Serological diagnosis: Please collect a serum sample, at least 10 days after onset of symptoms, from all cases with bloody diarrhoea or acute diarrhoea and/or HUS with a history of travel to Germany whether negative or positive by culture and/or molecular tests and send to the LGP for serogroup O104 specific antibody testing. Out of normal working hours specimens can be sent to the Reference laboratory and they will be stored securely until the laboratory staff are able to processes them. Antimicrobial Treatment Current guidance produced by an expert panel in Germany representing the German Society for Infectious Diseases, the German Society of Hygiene and Microbiology the German Society of Nephrology, the Robert-Koch-Institute and the Paul-Ehrlich-Society for Chemotherapy, cautions against antimicrobial treatment for patients infected with the outbreak strain, consistent with current practice for VTEC infection. If on the basis of clinical judgment antimicrobial treatment is required for the outbreak strain or super-infecting microorganisms the guidance specifically advises against fluoroquinolones, co-trimoxazole, aminoglycosides, fosfomycin and suggests a carbapenem is the preferred choice.” The link to the origin of this information is:
Infection Control We recommend that Trusts should use the same precautions as those established for cases of VTEC O157. Microbiological Characteristics of VTEC O104:H4 Background
Single cases of E. coli O104 have been seen before and this serogroup has been associated with at least two separate outbreaks in 1994 reported in the USA. Preliminary sequencing results announced on Thursday 2nd June by WHO have suggested that a new strain of E.coli O104 may be responsible for this outbreak. The HPA is currently undertaking DNA sequencing of isolates from England. Preliminary analysis confirms that the English E.coli O104 isolate associated with this outbreak has the same highly unusual combination of virulence properties as already recognised in Germany. We agree that the strain of E.coli O104 associated with this outbreak – which we know to have a highly unusual combination of virulence properties – could be one that’s never been seen before. This strain is now designated as VTEC/STEC/EHEC O104:H4. For the purposes of the various international descriptions of this outbreak strain use of the terms VTEC, STEC and EHEC are interchangeable. Properties of the VTEC O104:H4 outbreak strain:
The cultures of this outbreak strain isolated from faecal samples in the Gastrointestinal Infections Reference Unit, Colindale have been confirmed as VTEC O104:H4 VT2 and have the following phenotypic/morphological properties:
Biochemical characteristics are typical for E. coli including:Lactose positive, Sorbitol fermenting, β- Glucuronidase positive, indole positive, H2S formation negative and does not grow on Simmons Citrate Agar.
The organisms grow well on the following differential and selective media used in the UK: Sorbitol MacConkey agar (SMAC), Cefixime Tellurite SMAC (CTSMAC) and MacConkey agar. Strains have been tested on one Chromogenic Agar (E&O Labs Scotland) and grew well giving the correct colony colouration for non-O157 E. coli
In liquid culture (static broth tubes) they form a distinct ring of clumped cells on the glass around the surface of the culture. This tendency to form a pellicle is a trait associated with enteroaggregative E. coli (EAggEC).
All the isolates confirmed so far have genes detected by PCR for vtx2 and aggR (latter found in enteroaggregative strains). They are all negative for the intimin (eae) gene that is associated with pathogenic VTEC O157.
In conclusion the UK isolates of the VTEC O104:H4 have the same characteristics as those isolated in Germany and other European countries.
Additional characteristics of the outbreak strain that have been reported:
The VTEC O104:H4 strain is multi-resistant to: Ampicillin, Cefoxitin, Cefotaxime, Cetfazidime, Streptomycin, Tetracycline, Trimethoprim/Sulfamethoxazole and Nalidixic acid. It produces an extended spectrum beta lactamase (ESBL): CTX-M 15.
It has therefore been suggested that microbiology laboratories can use ESBL culture media for the initial growth and screening of potential isolates. (See Appendix 1 for colonial morphology on selective and differential culture media).
Does not produce haemolytic colonies on enterhaemolysin-agar (Many EHEC strains produce haemolysis)
Vtx/Stx Detection The classical method to detect toxins is to use the verocytotoxin cell assay but this is only available in reference laboratories. The commercially available Rida Screen Verotoxin EIA Shiga Toxin assay has been shown to give positive results with isolates of the outbreak strain tested in Europe.
Advice for Testing of Food Samples
A testing protocol for food samples and a testing algorithm using the presence of Veroctytotoxin (vtx) genes as a screening procedure has been developed for use in the HPA’s Food, Water and Environmental Laboratories. Testing will be limited for public health purposes to samples where there is a link with a suspect case or the outbreak. Please contact your local HPA FW&E Microbiology Laboratory for details of the nearest testing site and collection and transport of samples.
Contact with the HPA
For further information on Microbiology Services matters related to this outbreak, please contact the HPA at 0208 327 6195.
The HPA will continue to update this briefing note as the situation develops.
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