Published Date: 2006-10-05 00:00:00
Subject: PRO/EDR> E. coli O157 outbreaks - UK (England)
Archive Number: 20061005.2849
E. COLI O157 OUTBREAKS - UK (ENGLAND)
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases
Date: Thu, 28 Sep 2006
From: ProMED-mail <email@example.com>
Source: Communicable Disease Report UK [edited]
Two large outbreaks of Vero cytotoxin-producing _E. coli_ (VTEC) O157
occurred in short succession in South East London in Jun and Jul 2006.
On 26 Jun 2006, the South East London HPU (SELHPU) was informed that over
20 children in a large primary school were reported absent with
gastrointestinal symptoms, including hospital admission of 1 child and 1
adult with bloody diarrhea.
Standard immediate outbreak control measures were implemented by SELHPU,
yet initial investigations did not reveal a clear source or causal
organism. After identification of a presumptive VTEC O157 isolated from a
stool sample from 1 child on 28 Jun 2006, the outbreak control team (OCT)
agreed the following control measures:
1. To close the school with immediate effect to prevent further transmission;
2. To screen all pupils and staff attending the school (over 700 people);
3. To deep-clean the school;
4. To allow pupils and staff to re-attend the reopened school only after
confirmed negative result.
Presumptive _E. coli_ O157 from 43 people (41 children aged from 3 to 11
years, and 2 adults) was confirmed by the HPA Laboratory of Enteric
Pathogens (LEP). Isolates belonged to phage type (PT) 21/28 and were
positive for Vero cytotoxin 2 (VT2) genes, and negative for VT1. Onset
dates for cases ranged from 19 Jun to 2 Jul 2006 with some clustering
around the 22/23 Jun 2006, suggesting a common point source (figure 1 [for
figure, see original URL - Mod.LL]).
There were a number of secondary cases in households, and spread to a
sibling led to one case in a local nursery. There were 24 cases and 19
asymptomatic carriers. 1 child was admitted to hospital with haemolytic
uremic syndrome (HUS). SELHPU and the local environmental health department
continue investigations to determine the source of the outbreak.
A total of 11 isolates were examined by LEP using pulsed field gel
electrophoresis (PGFE). 10 isolates had indistinguishable profiles and 1
strain had a variant profile that was clearly related to the others.
On 14 Jul 2006, SELHPU was notified of a presumptive _E. coli_ O157 in a
2-year-old child. No links could be established with the other ongoing
outbreak in Bromley. On 19 Jul 2006 a 2nd child was reported having
attended a local A&E [Accident and Emergency - Mod.LL] department with
bloody diarrhea. Both children attended the toddler group in the same nursery.
The control measures implemented by the OCT were similar to those described
above. Including the 2 initial cases, a total of 16 children (aged 11
months to 8 years) and 3 adults tested positive for presumptive _E. coli_
O157 PT 21/28.
Strain typing and fingerprinting in LEP showed that this outbreak was also
caused by a strain of PT 21/28 with genes for VT2. However, the PFGE
profile of this strain differed in at least 3 fragment positions from that
associated with the Bromley school. Onset dates ranged from 6 to 27 Jul
2006, and the epidemic curve suggests person-to-person transmission (figure
2 [for figure, see original URL - Mod.LL]).
Telephone-completed questionnaires with all cases did not reveal any
epidemiological links with the other outbreak. No source could be
identified. 2 further cases of VTEC O157, PT21/28, VT2 were identified in
siblings, 1 of whom attended the nursery. PFGE showed that the strain was
different from both the Bexley and Bromley outbreak strains.
Outbreaks of VTEC O157 have been uncommon in London. These 2 outbreaks
occurred within a few miles of each other, closely one after the other, and
in similar settings. Phage type 21/28 is the most common phage type of VTEC
O157 in the UK (1) and causes general and household outbreaks and sporadic
infections. Strains can be differentiated by PFGE profile. While profiles
within each outbreak were largely indistinguishable, there were clear
differences in profiles between the outbreaks. This supports the
epidemiological findings indicating that both outbreaks were not linked.
1. HPA: Vero cytotoxin-producing Escherichia coli O157: 2005. Commun Dis
Rep CDR Wkly 2006; 16(28): news. Available at:
[PFGE was needed to distinguish the 2 outbreaks, which might otherwise be
thought to be linked. It is interesting that in the Bromley cluster there
were almost as many cases of asymptomatic infection as there were overt
cases. A similar breakdown in the Bexley cluster is not stated. Both
strains had genes for Stx2. As previous noted in a ProMED 4 Oct 2006 post
(20061004.2840), with some genotypes of Stx2, the lack of production of the
mucus-activated Stx2d-activatable or the production of Stx2D or Stx2e are
associated with strains with a much higher propensity towards the
asymptomatic state or only mild diarrhea.
The locations of Bromley and Bexley in southeast London can be seen at
<http://www.islington.gov.uk/maps/images/map1_08.jpg>. - Mod.LL]