Salmonella is an enteroinvasive bacterium primarily responsible for gastroenteritis and commonly isolated from stool specimens. However, it may also be recovered from blood, urine, or deep-seated infections [1]. UTIs caused by Salmonella spp. are rare and usually occur in patients with comorbidities or urological abnormalities [2]. UTIs due to non-typhoidal Salmonellaenterica are uncommon and infrequently reported in the literature [3]. The association with Shigellasonnei carriage is exceptionally reported. These infections usually occur in patients with comorbidities or predisposing factors. We reported a case of Salmonella spp. UTI associated with intestinal carriage of Shigellasonnei in a patient attending the Urology Department of the Peace Hospital in Ziguinchor and referred to the bacteriology laboratory for urine culture. This case highlights the need for comprehensive investigations, including digestive screening, in atypical UTIs.

A 58-year-old male patient with benign prostatic hyperplasia complicated by bilateral ureterohydronephrosis and recurrent UTIs was admitted for management. He also had hypertension and chronic renal failure. Clinical symptoms included nocturia (5 - 6 episodes), dysuria, and burning micturition. A urine sample collected on 18 February 2025 underwent cytobacteriological examination. The cytobacteriological analysis revealed significant leukocyturia (>10⁴ leukocytes/mL) associated with significant bacteriuria (>10⁵ CFU/mL), supporting the diagnosis of a true urinary tract infection rather than contamination or colonization. Culture on CLED agar yielded Gram-negative bacilli. Identification using API 20E and VITEK 2 confirmed Salmonella spp. The isolate was identified as non-typhoidal Salmonella enterica based on biochemical profile using VITEK 2 (probability 99%). However, serotyping was not performed due to limited laboratory resources, and the identification remained at the species level. Given the unusual nature of this pathogen in UTIs, a second urine sample and a stool specimen were collected on 21 February 2025 to confirm the urinary isolation and investigate intestinal carriage. Stool samples were cultured on Salmonella-Shigella (SS) and Hektoen agars. Identification and antimicrobial susceptibility testing were performed using the VITEK 2 system (GN card).

Blood cultures were not performed as the patient did not present with systemic signs such as fever or sepsis.

The first urine culture confirmed a UTI caused by Salmonella spp. The second urine culture and stool culture allowed further characterisation. On SS agar, colonies typical of H₂S-producing enterobacteria were observed. API 20E biochemical identification suggested Salmonella spp., which was confirmed by VITEK 2 with a 99% probability and excellent reliability, consistent with non-typhoidal Salmonella enterica.

Antimicrobial susceptibility testing showed preserved susceptibility to most beta-lactams (ampicillin, amoxicillin/clavulanic acid, third- and fourth-generation cephalosporins), carbapenems (ertapenem, imipenem), and fluoroquinolones (ciprofloxacin, levofloxacin). Resistance to amikacin and gentamicin was observed.

Stool culture revealed non-H₂S-producing colonies on SS agar. Identification by VITEK 2 confirmed asymptomatic intestinal carriage of Shigellasonnei. The isolation was susceptible to all tested beta-lactams, carbapenems, fluoroquinolones, and aminoglycosides. Resistance was observed only to trimethoprim-sulfamethoxazole (MIC = 20 mg/L).

Clinical management consisted of targeted antibiotic therapy with a third-generation cephalosporin for 10 days. The patient showed clinical improvement with resolution of urinary symptoms. A follow-up urine culture was negative. No urinary catheter was in place during management.

UTIs caused by Salmonella spp. are rare and were first described in 1946 [4][5], accounting for less than 1% of bacterial UTIs [6][7]. Two competing mechanisms may explain the infection: 1) ascending infection via perineal contamination, particularly in the context of intestinal carriage, and 2) hematogenous spread following intestinal translocation [8].

In this case, several recognised predisposing factors were present, including benign prostatic hyperplasia complicated by bilateral ureterohydronephrosis and chronic renal failure, all contributing to urinary stasis and persistent bacterial colonisation [9]. In this patient, the absence of fever and systemic signs, as well as the lack of blood culture positivity, supports the hypothesis of an ascending infection [10][11]. However, the presence of intestinal carriage suggests that translocation cannot be completely excluded. The concomitant intestinal carriage of Shigellasonnei may reflect altered gut barrier integrity, facilitating bacterial translocation [12]-[14]. The association betweenSalmonella UTI andShigella carriage remains poorly documented in sub-Saharan Africa [7].

The antimicrobial susceptibility profile of the Salmonella isolate was favourable, consistent with African data where fluoroquinolone resistance remains moderate [15].Shigellasonnei also showed preserved susceptibility, contrasting with global trends of increasing multidrug resistance involving fluoroquinolones, azithromycin, and ESBL-producing strains [16][17]. This may reflect limited circulation of resistant clones locally.

Stool culture was performed because of the unusual isolation of Salmonella in urine. The identification of Shigellasonnei did not modify antibiotic treatment but prompted reinforcement of hygiene measures and patient education to prevent fecal-perineal contamination.

This case highlights the rarity of Salmonella UTIs in patients with predisposing conditions and the exceptional association with asymptomatic intestinal carriage of Shigellasonnei. The favorable antimicrobial susceptibility profile contrasts with global resistance trends. This observation underscores the value of extended microbiological investigations in atypical UTIs and contributes valuable data from sub-Saharan Africa on these uncommon infections.