SMJ
2002; 47(5): 110-112
A.M.
Cadwgan*, R.B.S. Laing, L. Dargie, M. Beadsworth,
A.R. Mackenzie, J.G. Douglas.
Infection
Unit, Aberdeen Royal Infirmary, Aberdeen.
Key
Words:
*Author
For Correspondence
The
Infection Unit
Aberdeen
Royal Infirmary
Foresterhill
Aberdeen
AB25
2ZN
tony.cadwgan@arh.grampian.scot.nhs.uk
Aims:
To describe the epidemiology, clinical features, treatment and outcomes of
adults with E. coli O157 infection presenting to Aberdeen Royal Infirmary over a
three year period.
Methods:
A retrospective casenote review.
Results:
Thirty-two confirmed cases of E. coli O157
infection were admitted between 1997 and 2000. The median age was 58 years
(range 16-93). Ten patients (31%) were from the city of Aberdeen and 22 (69%)
from surrounding rural areas. Twenty-seven patients (85%) presented between May
and October. The source of infection was unknown or unconfirmed in all cases.
Bloody diarrhoea was present in 30 (94%). Leucocytosis was present in 18 (63%)
but only four patients (13%) had a fever. Six of the 32 patients (19%) developed
Haemolytic-Uraemic Syndrome (HUS) of whom 2 died. Ten patients received
antibiotics of whom two developed HUS. Twenty-seven of the 32 (85%) had made a
full recovery by time of discharge, three (9%) had impaired renal function and
two (6%) died in hospital.
Conclusion:
E. coli O157 infection tends to occur sporadically in rural areas in North
East Scotland. It is not usually associated with fever. Infection occurs more
commonly in the summer and autumn. HUS complicates infection in almost one fifth
of patients.
First recognised as a human pathogen in 19821-4, human
infection with E. coli O157 has now been reported in over 30 countries - most
commonly the United Kingdom, Canada and the United States5. Within
the U.K., Scotland has consistently had the highest incidence since 19876.
In a recent report from Grampian 16% of patients admitted to the Regional
Infection Unit with proven bacterial gastroenteritis had E. coli O157 isolated7.
As well as consumption of contaminated food, transmission of E. coli O157
is known to be associated with contaminated water supplies and direct
person-to-person contact5. Contact with animals or farms has been
shown to be a highly significant risk factor for infection8.
In light of the significant number of cases of E. coli O157 being admitted
to the Regional Infection Unit and other adult wards in Aberdeen Royal
Infirmary, we decided to review of our experience of this condition.
Information was collected from a retrospective case note review of all
adult patients (16 years and over) admitted to all wards in Aberdeen Royal
Infirmary between 1997 and 2000 who were microbiologically confirmed as having
E. coli O157 infection. Fever was defined as a temperature >37.5C on at least
one occasion. Haemolytic Uraemic Syndrome was said to have developed if the
patient had evidence of red cell haemolysis, thrombocytopenia and acute renal
impairment.
Thirty-two
confirmed cases of E. coli O157
infection were admitted to hospital over the three year study period from
January 1997 to December 2000. Ten
patients (31%) were from Aberdeen City and 22 (69%) from surrounding rural
areas. Nineteen were admitted to the Regional Infection unit, seven to the
Gastroenterology Unit, two to General Medical and three to General Surgical
wards.
The
median age of the cases was 48 years and the range was 16 to 93. Sex ratio was
17 male and 15 female cases. The duration of admission ranged from 2 to 44 days
with a median of 5 days. A seasonal variation was evident with 27 patients (85%)
presenting between May and October.
The
source of infection was unknown or unconfirmed in all cases. Twenty-six of the
32 had no contacts with E. coli O157
infection. Three patients had family contacts with E.
coli O157 infection and one each had a contact in school, at work or with a
friend. Four out of the 32 (13%) were farm workers.
The
clinical and laboratory features on admission are shown in Table
I and Table II. Six of the
32 patients (19%) developed HUS, of whom two died. The age of those who
developed HUS ranged from 16 to 70 years with a median age of 41. Of the six who
developed HUS four (66%) had a co-morbid illness: two hypertension, one
cerebrovascular disease, one epilepsy. All six patients had a raised white cell
count on admission. Thirteen of the 26 patients (50%) who did not develop HUS
had a co-morbid illness. Comparison between those with and without HUS is made
in Table 3.
The
time from admission to development of HUS ranged from 0 to 5 days with a median
of 0.5 days. Time from onset of symptoms to HUS ranged from 4 to 8 days, with a
median of 8 days. Three patients received haemodialysis; three patients received
therapeutic plasma exchange (TPE); two patients received both dialysis and TPE,
both of whom died.
Ten
patients were treated with antimicrobials - oral or intravenous ciprofloxacin in
six patients and intravenous cefotaxime plus metronidazole in four. With one
exception all these anti-microbials were started in other units for presumed
intra abdominal sepsis prior to confirmation of E.coli
O157 infection. Two of the patients who received antimicrobials (20%) developed
HUS.
Four
of those with HUS developed neurological features, one transient limbweakness,
one seizures and two intracerebral haemorrhage both of whom died. Twenty-seven
patients had made a full recovery by time of discharge, three had impaired renal
function on discharge and two died in hospital. 29 out of the remaining 30
patients had made a complete recovery at six months leaving one impaired renal
function.
Awareness
of the pathogenic potential of E. coli O157 in humans was increased by the
Lanarkshire outbreak of 19969. In 1998, the incidence of infection
was estimated at 4.2 cases per 100,00 in Scotland and 1.7 per 100,000 in England
and Wales8. In this three year study, only adults who were
sufficiently unwell to warrant hospital admission were included. None of the
cases occurred as part of an outbreak.
Seasonal variation was identified with most patients
presenting in the warmer months, between May and October. It might be speculated
that this is due to more people taking part in outdoor/rural pursuits during
these months and there is also evidence that faecal shedding of E. coli O157 by
cattle increases in the summer10. A Scottish study of patients under
15 years of age found the rate of infection was highest between June and
September11 but seasonal variation in adults has not been previously
reported in the region.
Most
cases of E. coli O157
infection (69%) arose in patients from outwith Aberdeen in rural areas. In such
areas the farming of cattle and sheep is a main industry and many houses receive
a private water supply. In an outbreak in the Grampian village of Tarves, the
local drinking water supply was implicated12. In this study, 4 out of
32 patients (13%) worked in the farming industry. By comparison, less than 4% of
the Grampian population works in agriculture13.
Attempts
to look for a food source of infection were not undertaken in any of the cases
reported here. This is usually performed in the outbreak setting.
The
clinical features described in this study are comparable to those previously
published14,15. Most patients had diarrhoea initially with stools
becoming bloody one or two days later. Abdominal pain and tenderness were
prominent features. Leucocytosis was present in the majority of admission
bloods. Fever was not commonly reported, this contrasts with the majority of our
patients with bacterial gastroenteritis in whom fever is present on admission in
65%7.
In
a large American study, clinical signs and symptoms independently associated
with E. coli O157 compared with
campylobacter, salmonella or shigella included reported bloody diarrhoea,
visibly bloody stool samples, a peripheral leucocyte count greater than 10 and
abdominal tenderness. At least three of these features were present in 65.4% of
patients with E. coli O157 infection in contrast they were present in 18.5 % of
those who had infection with campylobacter, salmonella or shigella15.
Our experience would suggest that the absence of fever should be added to those
aforementioned criteria in deciding the likelihood of E. coli O157 infection.
Ten
out of the 32 patients were treated with antibiotics on initial presentation. A
body of literature has, for several years, supported an association between use
of antibiotics and progression to HUS16. A prospective cohort study
has confirmed that giving antibiotics to children with E.coli O157 infection
increases their risk of developing HUS17. No similar study exists in
adults. In this review of 32 cases we found no association between antibiotic
use and HUS but the small numbers may be relevant to this negative finding.
Three
patients in this study were treated with Therapeutic Plasma Exchange. Although
this form of therapy has not been proven to be effective in randomised trials, a
general consensus supports it's use in adults with idiopathic HUS18.
Experience from the 1996 Lanarkshire outbreak suggested that treatment was
promising in patients with HUS secondary to E. coli O157 infection9.
Age less than four years or more than 65 years is perceived as a risk factor for the development of HUS subsequent to infection with E. coli O157 infection19. The median age of those who developed HUS in this study was 41 years, all were adults and only three were aged over 65 years. Although the numbers are small, these patients affected by HUS tended to be younger than described in previous studies and may suggest that serious the clinical sequelae associated with this infection are not confined to the extremes of age.
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