An elderly female patient with an uncomplicated urinary tract infection from Salmonella newport is presented. Radiological and laboratory studies were performed because of her systemic and exposure risk factors as well as prior urinary tract abnormalities. While this patient was successfully treated as an outpatient with oral antibiotics, complications and recurrence are common and deserve close follow-up with repeat urine cultures at a minimum. Further laboratory and radiological testing should be guided by patient gender, risk factors and recurrence.
Non-typhoidal Salmonella is a rare cause of urinary tract infections in children and adults. 1–5 It is often not associated with enteritis symptoms or positive stool cultures and can be fraught with complications of recurrence even after multiple prolonged antibiotic treatment regimens. 2 3 5–7 Owing to the importance of underlying structural genitourinary abnormalities, a radiological workup is often necessary, as well as a search for other risk factors associated with this disease entity. 3 5–7
A 73-year-old Caucasian woman presented with ‘another urine infection’. Two weeks earlier, she had been evaluated at our office for symptoms of dysuria and nocturia. At that time, a urinalysis with microscopy revealed moderate blood with positive leucocyte esterase on a midstream collection, however, a urine culture was not performed. She was treated empirically with a 7-day course of macrodantin, which she had finished, but her symptoms had not improved. Her genitourinary (GU) history was negative for gross haematuria or renal lithiasis but positive for dysuria, nocturia and stress incontinence. Her review of systems was negative for fever, nausea, abdominal pain, emesis or diarrhoea. The patient's medical history was significant for frequent urinary tract infections, renal insufficiency without hypertension, gastroesophageal reflux disease, significant osteoarthritis of her knees and hips and depression with insomnia. Prior pertinent surgeries included a cystocele and rectocele repair in the 1980s, which was complicated by left hydronephrosis and a non-functioning kidney. This led to a subsequent left nephrectomy in 2005, related to an infection in the left ureteral tract. She also had a prior cholecystectomy following an episode of gallstone pancreatitis. Her physical examination showed vitals of temperature 98.1° F, blood pressure 160/84, 88 bpm, 16 breaths/min and weight of 281 with body mass index of 50. The rest of her physical examination was otherwise normal.
Haematology and basic chemistry panels were normal apart from a baseline creatinine of 1.54. Urinalysis with microscopy was again positive for many WCC's and bacteria seen, but no casts or crystals. Her urine culture reported out 2 days later and grew >100 000 colony forming units/mL of a Salmonella species sensitive to ampicillin, ceftriaxone and trimethoprim/sulfamethoxazole. This was further typed as Salmonella newport by our state health department. A review of her prior UTIs, showed no history of Salmonella by urine culture but only isolated urinary infections of Klebsiella pneumonia, Citrobacter freundii and Escherichia coli, respectively, in the years since her nephrectomy.
Stool cultures were not ordered as she reported no gastrointestinal (GI) symptoms of diarrhoea or hematochezia and had already started the empiric treatment of trimethroprim/sulfamethoxazole at the time of the urinary culture result. Owing to her history of left nephrectomy, the patient underwent abdominal ultrasonography which showed a 1.2 cm hyperechoeic region on the lower pole of the right kidney concerning for an angiomyolipoma and discreet small pancreatic pseudocysts. Further imaging with CT of the abdomen and pelvis showed a subcentimeter renal cyst in the lower pole of the right kidney with overlying calcification of the renal fat, a pseudocyst of the pancreas with fatty infiltration and a mildly enlarged spleen. No hydronephrosis or renal or bladder stones were seen in either study.
The patient was treated with trimethoprim/sulfamethoxazole twice daily for 14 days and referred to our local infectious disease consultant.
The patient did well following her single oral antibiotic regimen but required 14 days, compared to typical UTI regimens, appropriate to her Salmonella aetiology. 2 6–9 Stool studies were not performed at the time of her infectious disease visit, 6 weeks later, as the patient had already completed her trimethroprim/sulfamethoxazole regimen prior to this appointment and was asymptomatic of both urinary and GI symptoms at that evaluation. She did report to the specialist, however, a weeklong period of diarrhoea 3–4 weeks prior to the UTI symptoms, but without fever, hematochezia or mucous in the stool. Her exposure risk factors included farm animals of goats and pigs on her property but she had no direct contact with them and no exotic pets. She recalled eating some questionable spoiled shrimp during that time frame but this did not concern her as it was self-limited, and she occasionally experienced similar episodes of loose stool since her cholecystectomy. After 14 days of trimethoprim/sulfamethoxazole follow-up urine cultures were negative for Salmonella. She has had several UTI's since then with different bacterial species identified by urine culture (E. coli and K. pneumonia) and was referred back to her urologist for further evaluation and consideration of antibiotic prophylaxis. Imaging with postvoid residual ultrasonography revealed 0 mL of urine remaining in the bladder. Treatment with daily prophylactic antibiotics was initiated by her urologist, and the patient has been asymptomatic since that time.
Non-typhoidal Salmonella (NTS) urinary tract infections were found to represent only 0.63% of all Salmonella infections in large retrospective reviews. 1 2 The overall incidence of Salmonella positive urine cultures has been estimated to be between 0.015% and 0.118%. 5 Human salmonellosis most commonly presents with acute gastroenteritis symptoms and only occasionally bacteraemia or focal infections. An asymptomatic carrier state of the urinary, biliary or intestinal tracts can potentially be present for months to years after the initial onset of acute disease symptoms. 2 5 6 9
The finding of a focal Salmonella UTI is not believed to merely be contamination of a urine sample from the stool of a patient with acute gastroenteritis or carrier state. 2–5 8 10 11 Most recent case series report patients with only urinary tract symptoms and Salmonella isolated on urine culture but negative stool cultures for Salmonella species. 2 3 5–7 11 The pathophysiology of Salmonella UTIs results from either haematogeneous spread or direct ascending invasion of the GU tract. 1 3 5–7 9–11 An ascending route of infection is favoured in this patient due to the mild diarrhoeal illness she reported prior to her presentation and her risk factors of recurrent urinary infections. Her exposure to farm animals and potentially contaminated food is also consistent with NTS infections, such as S. newport.
Risk factors for Salmonella UTI include exposure to exotic reptiles, recent Salmonella gastroenteritis and patients with chronic illnesses such as cardiopulmonary or liver disease, gastric resection, duodenal ulcers, sickle cell disease, diabetes mellitus and haemodialysis. As well, immunosuppression is a risk factor in patients with renal transplant, HIV/AIDS, rheumatological diseases such as systemic lupus erythematosus and haematological or solid tumour cancers. 3–6 10 Urological predispositions such as prior surgery, renal allograft, neoplasm, duplicating collection system, indwelling catheter, enteric fistula, uncircumcised state and urinary stasis due to pregnancy, stones, stricture, cystocele, vesicoureteral reflux or an enlarged prostate are reported to be risk factors and must be considered in the work up of patients who are found to have Salmonella UTIs. 3 5–7 9–12 Paterson et al suggests a urological work up in all male patients. They further contend that the isolated finding of NTS in the urine of women most commonly represents uncomplicated cystitis without the need for further investigation. 12 In this non-immunocompromised patient, the risk factors of recurrent UTIs and prior nephrectomy were believed to warrant an ultrasound to rule out another genitourinary anatomic risk factor or complication.
Complications of Salmonella UTIs include pyelonephritis, renal insufficiency, nephrotic syndrome, renal lithiasis, genitourinary abscesses, recurrence and chronic bacteriuria. 1 3 6 7 11 As in all Salmonella infections, bacteraemia and death can occur, although the later appears to be rare in UTI-reported cases. 1 3 5 6 10
Finally, some case reviews of patients with Salmonella UTIs report the need for prolonged antibiotic therapy of 2 weeks or longer. 3 5–7 This increased duration is due to potential bacteraemia during the course of the disease, the risk for recurrent or chronic asymptomatic bacteriuria as a Salmonella carrier with shorter treatment regimens, and concern for antibiotic resistance of carriers in spite of appropriate treatment from in vitro sensitivity data of isolated cultures. 2 3 5–7 11
Prolonged antibiotic therapy (2 weeks or longer) and follow-up urinary cultures are necessary due to recurrence or chronic asymptomatic bacteriuria.
Salmonella UTIs are frequently associated with chronic diseases, immunosuppression or structural abnormalities of the genitourinary tract. A focused history and relevant physical examination are always warranted.
Special thanks to Dr Anne Mounsey at the University of North Carolina, Chapel Hill for her editorial help and guidance in the preparation of this manuscript.
Competing interests: None.
Patient consent: Obtained.
Provenance and peer review: Not commissioned; externally peer reviewed.
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