Enterovirulent E. Coli (EEC) (cont.)

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A new EEC group? (E. coli 0104:H4)

As an update to this article, the addition of the newest EEC E. strain will be presented. It recently arose in Germany in early 2011 and has now been documented in 11 European countries; at least four people who traveled to Germany and returned to the US have been infected with this strain. In most people, the exposure to the infection source occurred while people were visiting Germany, most likely through contaminated food (salads).

The strain has been identified as E. coli 0104:H4 (also termed STEC 0104:H4). It is presented in this section because as stated in the previous paragraph, there are unfortunate overlaps in ECC caused disease and this new strain seems to exhibit some of the worst overlap features of the ECC group members. For example, E. coli 0104:H4 is reported to contain about 93% of the genome of EHEC and produces the Shiga (Vero) toxin; however, it also seems to have the ability like EAEC strains to attach well to gastrointestinal cells.

The outbreak in Germany was the third largest ever reported for E. coli (about 4320 infected people) and the most lethal (at least 82 dead). In addition, most strains isolated are resistant to multiple antibiotics (aminoglycosides, macrolides and Beta-lactams). The source of the infection may be contaminated bean sprouts grown organically and then shipped to many German restaurants. One major difference in E. coli 0104:H4 from other E. coli that cause hemolytic uremic syndrome or HUS (mainly E. coli 0157:H7) is that the organism is causing HUS in young adult females and other adults. Often, HUS caused by E. coli 0157:H7 is seen in children and the elderly, not relatively healthy adults. This outbreak had 850 people develop HUS. This new strain had three disease causing (pathogenic) mechanisms; 1) Shiga toxin, 2) adherent fimbriae (pili), and 3) EXPEC (extra-intestinal pathogenic E. coli). E. coli 0104:H4 may constitute a new group as yet unnamed.

The CDC suggested the following guidelines for E. coli 0104:H4. It is not recommended to give antibiotics to individuals with suspected STEC infections until complete diagnostic testing can be performed and STEC infection is ruled out. Some studies have shown that administering antibiotics in people with STEC infections might increase their risk of developing HUS. However, clinical decision making must be tailored to each affected individual. There may be indications for antibiotics in those with severe intestinal inflammation if perforation is of concern. Of note, isolates of STEC O104:H4 from patients in Germany have demonstrated resistance to multiple antibiotics.

CDC guidelines to ensure as complete as possible detection and characterization of STEC infections include the following:

  • All stools submitted for testing from patients with acute community-acquired diarrhea should be cultured for STEC O157:H7. These stools should be simultaneously assayed for non-O157 STEC with a test that detects the Shiga toxins or the genes encoding these toxins.
  • Clinical laboratories should report and send E. coli O157:H7 isolates and Shiga toxin-positive samples to state or local public health laboratories as soon as possible for additional characterization.
  • Specimens or enrichment broths in which Shiga toxin or STEC are detected, but from which O157:H7 STEC isolates are not recovered, should be forwarded as soon as possible to a state or local public health laboratory so that non-O157:H7 STEC can be isolated.
  • It is often difficult to isolate STEC in stool by the time a patient presents with HUS. Immunomagnetic separation (IMS) has been shown to increase recovery of STEC from HUS patients. For any patient with HUS without a culture-confirmed STEC infection, stool can be sent to a public health laboratory that performs IMS or to the CDC (through a state public health laboratory). In addition, serum can be sent to CDC (through a state public health laboratory) for serologic testing of common STEC serogroups.

The benefits of adhering to the recommended testing strategy include early diagnosis, improved patient outcome, and detection of all STEC serotypes.

All patients with Shiga toxin-positive diarrheal illness or HUS should be reported to health departments, regardless of a travel history to Germany.

Medically Reviewed by a Doctor on 4/4/2014

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