Letter to the Editor

Authors


8 October 2009

Dear Editor,

TRANSMISSION OF ESCHERICHIA COLI 0157:H7 IN CHILDREN VIA A PADDLING POOL

Haemolytic uraemic syndrome (HUS) is the commonest cause of acute kidney injury in childhood.1 The usual infectious agent is Shiga toxin-producing entero-haemorrhagic Escherichia coli (STEC), of which 0157:H7 is the most frequently identified serotype in Europe and the United States. Here we describe four cases from the same family with STEC 0157 infection, of which three developed HUS.

The affected children were two pairs of siblings who were cousins of each other. The index case was a 4-year-old female who developed self-limited bloody diarrhoea. On the day her diarrhoea started, she had been in a paddling pool with the other cases. Her stool was positive on culture for E. Coli 0157:H7, and the Health Protection Agency did not find a source for her infection.

The first child to present to the Accident & Emergency (A&E) department with bloody diarrhoea and vomiting was patient 1, a 9-year-old male cousin of the index case. He had been well prior to being in contact with his cousin while she was symptomatic. Patient 1 was admitted for rehydration and was discharged home. Renal function and blood counts during this admission had been normal (Hb 14.5 g/dL, WBC 13.4 × 109, Plts 389 × 109, urea 4.7 mmol/L, creatinine 49 µmol/L, LDH 262 IU/L). His stool, however, was positive for E. Coli 0157.

Three days later, patient 1 returned to A&E together with his 4-year-old sister (patient 2) and his 9-year-old female cousin (patient 3, sister to the index case). Patient 1's diarrhoea and vomiting had subsided, but he was complaining of abdominal pain and was jaundiced. Patient 2 presented with lethargy, decreased urine output and loss of appetite. She too had had bloody diarrhoea the week before. Patient 3 presented with vomiting, bruising and decreased urine output. She also had bloody diarrhoea which had subsided by the time of presentation to A&E. All three had microangiopathic haemolytic anaemia with schistocytes on blood film, thrombocytopenia, high lactic dehydrogenase (LDH), low haptoglobin, and non-oliguric kidney injury (Table 1). Coagulation screens were normal in all three patients. These features confirmed the diagnosis of typical HUS. None of the children had neurological symptoms.

Table 1.  Blood results at admission
Laboratory resultsPatient 1
9 years old, male
Patient 2
4 years old, female
Patient 3
9 years old, female
Haemoglobin g/dL8.97.99.2
Platelets ×109/L477318
Total WBC (Neutrophils) ×109/L10.6 (7.4)11.4 (5.7)12.1 (7.7)
Urea22.622.322.0
Creatinine208120106

E. Coli 0157 was detected in the stools samples from all three by culture.

In view of their diagnosis, blood transfusion requirements and oliguric state, all three children were transferred to a tertiary renal unit for further management. None required dialysis, they were managed with fluid balance and appropriate blood product transfusions, and were discharged home when better. A follow-up 1 month later showed they all had normal clinical examination including blood pressures, normal laboratory tests and negative urinary dipsticks (Table 2).

Table 2.  Table of blood results at 1 month follow-up
Laboratory resultsPatient 1
9 years old, male
Patient 2
4 years old, female
Patient 3
9 years old, female
Haemoglobin g/dL11.011.411.1
Platelets ×109/L353297265
Urea (mmol/L)5.44.13.6
Creatinine (µmol/L)554254

This outbreak occurred during the school holidays. Stool samples were negative for E. Coli 0157 by the time the children returned to school. No complement studies were done in these children.

The Health Protection Agency investigated the outbreak. Stool samples from relatives found three more children who had been in the paddling pool positive for E. Coli 0157. Two of these children had experienced self-limiting diarrhoea and had never presented to medical services. The third child was asymptomatic. Swabs from the paddling pool were positive for E. Coli 0157 of the same phage type detected in the patients' stool.

Discussion

In this family, six children (including the index case) were symptomatic with diarrhoea and had stool samples positive for E. Coli 0157. Three of them progressed to develop HUS (50%). It is notable that the index case did not develop HUS. The affected children all developed the classical triad of microangiopathic haemolytic anaemia, thrombocytopenia and acute kidney injury.1 The annual incidence of HUS is estimated at 1–3 per 100 000.2 Three to fifteen per cent of children who have E. Coli 0157 with diarrhoea progress to develop HUS.2

Bloody diarrhoea may occur from 3 days to more than 2 weeks prior to diagnosis of HUS.2 Patient 1 was admitted with the initial diarrhoeal illness and had a normal blood film and renal function at the time. This raises the question of whether all children who are diagnosed as having diarrhoea secondary to E. Coli 0157 should be routinely followed up for at least 2 weeks, with repeat blood films and monitoring of renal function.

It seems that the affected children acquired it from the index case in the paddling pool. HUS has been described in nursing homes, daycare centres and household contacts. When the index case is under the age of 5 years the risk of transmission is higher.3

The treatment of HUS is supportive. Fluids must include nutrition and transfusion requirements and fluid balance against losses. Electrolyte abnormalities are common, but are usually mild, including hyponatraemia, hyperchloremia and metabolic acidosis. Hyperkalaemia despite renal injury is rare. Two-thirds of children require dialysis.1 The indications for dialysis are anuria, severe metabolic acidosis, fluid overload and hyperkalaemia. Blood transfusions are required in approximately 80% of cases. Platelet transfusions are only recommended when there is active bleeding, or prior to surgical procedures. It is thought that platelet transfusions may exacerbate the development of microthrombi causing organ ischaemia,1 particularly the formation of microthrombi in the CNS leading to cerebral ischaemia and seizures.

The prognosis is generally good with almost 70% of children making a complete recovery. Bad prognostic features include: neutrophilia on admission, central nervous system (CNS) involvement, longer duration of oliguria and dialysis requirement of more than 2 weeks.4 Mortality from typical HUS has decreased significantly standing at <3–5%. The majority of deaths occur in children with severe extrarenal disease, particularly CNS involvement.1

We recommend that under similar circumstances, the index case is isolated from other children, particularly if 5 years old or younger.

Ancillary