Pyonephrosis caused by Salmonella sp. in a patient with polycystic kidney disease undergoing hemodialysis

AIMS: This article reports a case of pyonephrosis caused by Salmonella sp. in a patient with polycystic kidney disease undergoing hemodialysis treatment. CASE DESCRIPTION: An elderly male patient previously diagnosed with polycystic kidney disease undergoing standard hemodyalitic treatment presented uronephrosis, evolving to pyonephrosis caused by Salmonella sp., and was successfully treated with ciprofloxacin. CONCLUSIONS: The polycystic kidney disease may have contributed to the bacteria’s attachment to the kidney, due to increase of permeability of the intestinal mucosa, easier bacterial translocation to bloodstream and its subsequent accommodation in the infected organ.


INTRODUCTION
Salmonella sp. is a gram-negative bacillus responsible for outbreaks of food-borne infections worldwide, as well as high rates of morbidity and mortality, especially in developing countries [1,2].There is a great variety of Salmonella spp.serotypes pathogenic to human beings, the most common clinical disease being gastroenteritis [1,3].Nevertheless, infections may occur in other sites out of the gastrointestinal tract, as well as may cause a septicemia [3].Obstructions to urine drainage, like those caused by calculi, may lead to complications such as pyonephrosis, when urine becomes infected.In such cases the combination of prompt drainage associated with antibiotic therapy is imperative [4,5].
This study aimed to report the isolation of Salmonella sp. from secretion drained from the surgical site of nephrostomy in a patient with chronic kidney disease admitted to a tertiary public hospital.The report was approved by the Research Ethics Committee of Universidade Federal de Santa Maria under the registration number 0285.0.243.000-09.

CASE REPORT
An 83-year-old male patient was admitted with a two month history of nausea, occasional vomiting, epigastric pain, prostration, fever, weight loss, lower limbs edema and oliguria.He was on chronic hemodialytic treatment, over the last three years, through an arteriovenous fistula in the left upper limb.His past medical history included chronic renal failure due to polycystic kidney disease (PKD), systemic arterial hypertension, benign prostatic hyperplasia, secondary hyperparathyroidism and an ischemic stroke two years before.
A computed tomography showed marked dilation of the left pyelocalyceal system and ureter until the intramural urinary bladder segment, which was filled in by a dense fluid.Both kidneys presented exophytic cysts of varying sizes.The largest cyst measured 6.4 cm at its longest axis and had a thin wall (Figure 1).The patient was diagnosed with uronephrosis evolving to pyonephrosis, and was submitted to a nephrostomy.During the surgery, 30 ml of purulent secretion were drained, from which Salmonella sp. was isolated.Blood cultures were negative.Antibacterial therapy with ceftriaxone was started.Antibiogram showed sensitivity to ampicillin, ampicillin/sulbactam, piperacillin/tazobactam, ceftazidime, ceftriaxone, cefepime, ertapenem, imipenem, meropenem, ciprofloxacin, tigecycline, and colistin, and resistance to cefuroxime, cefuroxime/axetil, amikacin, and gentamicin.Empiric antibiotic therapy with ceftriaxone was started and further replaced by ciprofloxacin after the sensitivity result.The patient was discharged six days after the nephrostomy and scheduled for 14 days of antibiotic therapy.

DISCUSSION
The genus Salmonella sp. may be divided into typhoid serotypes, which include Salmonella enterica var.typhi, Salmonella enterica var.paratyphi A, and hundreds of serotypes of non-typhoid Salmonella.The first group is responsible for typhoid fever and systemic infections, and the second is commonly associated to limited diarrheal episodes in developed countries, and septicemia in developing countries [1,6].Infections involving Salmonella spp. in humans may present different clinical manifestations such as 3/4 enteric fever, septicemia, focal disease (associated to bacteremia or not), gastroenteritis, and chronic carrier state [7].Patients with gallbladder diseases are more prone to chronic colonization by this microorganism, which may remain in the reticuloendothelial system, from where it is continuously disseminated [1].
Complications resulting from infections in patients with PKD, especially those who are on chronic hemodialysis, are recurrent, tend to relapse and are life-threatening [8].The cysts raise the intra-abdominal pressure and increase the permeability of the intestinal mucosa due to reduction of the blood flow in the microcirculation, therefore favouring bacterial passage through the intestinal wall [9,10].
Patients who undergo hemodialysis are more prone to bacterial translocation, due to predisposing factors such as slow intestinal transit and heart failure [8].The patient in this case was immunocompromised due to chronic kidney disease, a group of increased risk for this occurrence.Escherichia coli, Klebsiella spp., Proteus spp.and Pseudomonas spp.are frequently isolated from nephrostomy cultures, but Salmonella spp.are rarely found [1].
Due to virulence factors which enable multiresistance, the Clinical and Laboratory Standards Institute [11] advises that sensitivity tests should be performed for Salmonella spp.regarding the antimicrobials ciprofloxacin, levofloxacin, ofloxacin, pefloxacin, nalidixic acid, and azithromycin for S. typhi.In this report, the patient was treated with ciprofloxacin.However, there are reports of bacteria resistance to fluoroquinolones in developing countries.For this reason, treatment with third generation cephalosporins is an adequate alternative in these cases [3,12].
A case similar to this was reported in 2011, in a 40 years old male patient with autosomal dominant PKD, hospitalized with fever and flank pain after diarrhea.Salmonella enteritidis was isolated from coproculture and blood culture.Magnetic resonance and tomography identified kidney cysts, which were aspirated and from which the same microorganism was isolated, but no urinary obstruction was reported.The patient was successfully treated with ciprofloxacin.Those researchers supposed that bacterial translocation from the gastrointestinal tract caused bacteremia and may be responsible for infection of the renal cysts [13].
As the patient in this case report had PKD and was on chronic hemodialysis, we suppose that the infection was favoured by the bacterial translocation in a immunocompromised host.To the best of our knowledge, this is the first report of isolation of Salmonella sp. of pyonephrosis in the referred hospital.

Figure 1 .
Figure 1.Computed tomography of the abdomen showing dilatation of the left pyelocalyceal system and ureter, and kidneys with exophytic cysts.