Departments of 1 Medical Microbiology and 2 Renal Medicine Manchester Royal Infirmary UK
Case
In July 1997, a 64-year-old Afro-Caribbean woman with chronic renal failure (CRF) managed by peritoneal dialysis presented with abdominal discomfort, weight loss, poor appetite, nausea, vomiting and pruritis. She had had chronic joint pain for many years which was treated with anti-inflammatory drugs, extensive and prolonged use of which was thought to have led to development of CRF. She described a 68 year history of vague abdominal pains which became subacute on occasion. Previous investigations, however, had not identified a cause. On this occasion her blood urea was high and this was thought to account for her symptoms and, as conservative management of her CRF had become increasingly difficult, she was switched to haemodialysis.
Over the next 2 years, although the renal failure was adequately managed by haemodialysis, the clinical course worsened with low-grade pyrexia, episodes of coffee ground vomiting and confusion. On one occasion, the haemoglobin level was 9.8 g/dl, total leucocyte count 15.1x109/l, eosinophil count 1.96x109/l (normal range; 0.040.44) and platelet count 379x109/l. CT scan and CSF were normal. Upper gastrointestinal endoscopy showed haemorrhagic gastritis presumed to be secondary to aspirin, diclofenac and heparin. Her aspirin and diclofenac were stopped and she was treated with ranitidine, sucralfate and omeprazole which led to an improvement. However, at haemodialysis review she had recurrent pyrexia and persistent abdominal discomfort. In March 1999, blood culture from the Hickman line yielded Xanthomonas maltophilia which was effectively treated by line removal. However, a few days later, a repeat blood culture grew a sensitive Escherichia coli which was effectively treated with cefuroxime and gentamicin to which it was susceptible. Over the subsequent 6 months in response to a persistent pyrexia, blood cultures were taken in the out-patient department on 11 different occasions each separated by 26 weeks. Escherichia coli was cultured from the Hickman line and peripheral blood simultaneously. On each occasion, the patient was treated with antibiotics to which the respective organism was sensitive, and on each occasion this treatment led to a temporary resolution. The Hickman line was suspected as the source of these infective episodes and was replaced on a number of occasions. However, despite this the problem persisted. It was not until March 2000, that microscopy of urine and faeces revealed the organism shown in Figure 1 that the diagnosis became clear.
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Although culture of E. coli from the blood of this patient on many separate occasions did account for acute illness which responded to appropriate antibiotic therapy, this organism was not responsible for the underlying problem. Microscopy of urine and faeces showed rhabditiform larvae of Strongyloides stercoralis (Figure 1). Two courses of thiabendazole at 5 mg/kg in intervals of 2 weeks led to a cure with disappearance of all symptoms and signs.
Strongyloides stercoralis is a nematode, causing parasitic infestation which is endemic in tropical and subtropical areas of the world [1]. It is more prevalent in adults and is common in institutionalized groups such as mental hospitals in warm, moist climates [1,2]. Strongyloides stercoralis infection is frequently chronic and asymptomatic. Persistence is facilitated by its ability to autoinfect the human host directly through the bowel wall or through perianal skin [3]. Asymptomatic infection is associated with a small parasite burden, but this may lead to hyperinfection with the onset of immunosuppression. Hyperinfection is the term used for a marked increase in the parasite burden. Development of this phenomenon following immunosuppression implies the existence of immune control of this infection in the immunocompetent, but this mechanism has not been elucidated. The intensified parasitic infection frequently leads to bacterial complications which may occur late in the disease process or may be the presenting problem. In the present case, the parasitic infection was diagnosed in response to investigation of recurrent bacteraemia which in effect was the presenting problem. However, it is likely that the parasitic infection was longstanding in this lady as there were abdominal symptoms for many years.
Persistent or recurrent bacteraemia despite appropriate antibiotic treatment associated with disseminated S. stercoralis infection has been reported previously [1,2,4,5]. Such cases are usually compromized hosts with haematological malignancies, renal transplant patients, patients with acquired immune deficiency syndrome (AIDS), or with miscellaneous diseases associated with immunosuppression. In one series, five of 32 patients with S. stercoralis hyperinfection suffered from CRF [6], a phenomenon thought to be due to depressed cell-mediated immunity secondary to uraemia.
It is thought that the pathogenesis of bacteraemia involves the accelerated infection with consequent ulceration of the intestinal wall which may be transmural, thus providing access to the intestinal bacteria. It has also been suggested that the bacteria ride on the back of the worms in their path of migration. It has been shown that in rabbits, injection of Sphaerophorus necrophorus alone causes only localized infection but that in the presence of Strongyloides papillosus larvae, the bacteria reach the lungs along with the larvae [7].
The diagnosis of systemic S. stercoralis may be delayed when it occurs in association with unusual conditions like CRF with no clear evidence of immune suppression. Early diagnosis is further hampered by frequent atypical presentation [8,9] and unfamiliarity of medical staff with this disease entity in temperate regions where it is rare. Acute and chronic gastritis in association with disseminated S. stercoralis infection has been reported [10] suggesting that the episode of haemorrhagic gastritis in the present case may have been due to S. stercoralis infection.
In conclusion, we report a case of chronic infection with S. stercoralis presenting as recurrent E. coli bacteraemia in a patient with CRF and recommend that recurrent bacteraemia associated with CRF should prompt testing for S. stercoralis as for other cases of immunosuppression even in the absence of overt evidence of immunosuppression.
Notes
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References