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THE WATT GROUP REPORT
CHAPTER 2 THE SALMONELLA OUTBREAK IN THE VICTORIA INFIRMARY
Summary and Chronology
The Group, having read the Report of the Outbreak Control Team (OCT) agrees with the detailed facts of the outbreak given therein. These can be summarised as follows:
Salmonella species was isolated from Patient A (who had been admitted with diarrhoea on 27
th December 2001) on 30
th December 2001. This patient had been transferred to a medical ward before being transferred to a specialist unit in another hospital on that day.
Salmonella species was also isolated on 2
nd January 2002 from Patient B, who had been in the same medical ward since 21
st November 2001. This patient developed diarrhoea from 31
st December 2001 and a faecal sample had been taken on that date.
Patient C, being nursed in the same ward in a bed next to Patient B, had had diarrhoea since admission on 16
th November 2001 but became increasingly unwell. A stored faecal sample taken on 27
th December 2001 tested for
Salmonella spp. and reported positive on 3
rd January 2002. A faecal sample taken on 10
th December 2001 was negative.
3
rd January 2002 - at this stage 3 patients from the same ward had been confirmed as having
Salmonella spp.
On 7
th January 2002,
Salmonella species was isolated from Patient E, who had been a patient in the same ward since 27
th December 2001 and had diarrhoea from 5
th January 2002. [Stool samples from another patient, Patient D, who had been nursed next to Patients B and C but who was asymptomatic, were negative and this patient was not considered part of the outbreak.].
By 8
th January 2002, the Salmonella Reference Laboratory reported as follows:
Patient A -
Salmonella enteritidis phage type 4.
Patient B -
Salmonella enteritidis phage type 21.
Patient C -
Salmonella enteritidis phage type 21.
[Thus Patient A was not part of the outbreak.]
At this time, the laboratory reported that they had received a report from the Reference Laboratory on 7
th January 2002 that another patient, Patient F, who had been in the same ward from 21-23 December 2001, had
Salmonellaenteritidis phage type 21 present.
On 8
th January 2002 Patients B and C died.
On 10
th January 2002, the
Salmonella species isolated from Patient E was also confirmed as
Salmonella enteritidis phage type 21.
On 11
th January 2002 Patient E died.
Salmonella species were isolated from a further 2 patients: from Patient G (faecal sample on 11
th January 2002) and from Patient H (faecal sample on 18
th January 2002). The organism was identified as
Salmonella enteritidis phage type 21 on 15
th January 2002 (Patient G) and 21
st January 2002 (Patient H). Neither patient had been in the ward in which the other cases had occurred.
At this stage (23
rd January 2002) the Outbreak Control Team (OCT) implemented faecal screening of staff. Two health care workers were found to have
Salmonella enteritidis phage type 21.
After this time there were no further patients or staff identified with
Salmonella enteritidis phage type 21.
Epidemiological Conclusions
The views of the OCT are set out in their OCT Report and can be summarised as follows:
Patient F was the likely source, having acquired
Salmonella enteritidis in the community before admission to hospital.
There was no evidence that hospital food caused the outbreak (one of the patients was being fed by tube only and there was no evidence of unusual levels of diarrhoea in patients or staff).
Patients B, C and E acquired their infections by inadvertent transmission of the organism in the medical ward.
There was no link between Patients G and H or with the other patients. Food histories from these patients indicated possible acquisition of the organism in the community. This was considered by the OCT to be the likeliest explanation on the balance of probabilities.
The two health care workers identified as having
Salmonella enteritidis phage type 21 on screening were not considered to be responsible for cross-infection but rather to have acquired the organism as a result of exposure to it in the course of their duties on the medical ward.
The exact route(s) of cross-infection could not be identified.
The Review Group generally agrees with these conclusions, based as they are on the best evidence available and, where more than one possibility existed, on the balance of probability. However, the Group considers that person-to-person spread within another of the Hospital wards cannot be excluded as a factor in the latter two patients (G and H).
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