Chromobacterium violaceum: An uncommon source of urinary tract infection – A case study with review of literature

Case report

A 22-year old unmarried female presented as an outpatient with fever and burning micturition associated with increased urinary frequency. She did not have any other comorbidity. Her full blood count was unremarkable (Hb: 142 g/L; red blood cells: 5.4x10⁹/L; platelets: 316x10⁹/L) except for a mild leucocytosis (12.6x109/L), and other tests were normal. Urine testing showed numerous pus cells with scanty red blood cells.

The urine sample was cultured on 5% Sheep blood agar and MacConkey agar and placed in an aerobic incubator at 37°C for 24 h. The following day, smooth, round, convex, butyrous, violet-colored colonies on both plates were observed. On the blood agar plate, there weredeep violet colonies displaying ß-haemolysis (Fig. 1).

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Figure 1.

(A, B) Purple colonies of Chromobacterium violaceum isolated from the overnight subcultures in 5% sheep blood agar and (C) MacConkey agar of a positive urine culture bottle.

The micro-organism was identified as a facultatively anaerobic, motile, Gram-negative rod, testing positive for catalase and oxidase. In terms of biochemical tests, it yielded negative results for indole, methyl red, and Voges-Proskauer. A repeat culture also showed the same pathogen. The micro-organism was ultimately identified as Chromobacterium violaceum (CV) based on its biochemical profile.

An antibiogram using Kirby Bauer's disc diffusion susceptibility testing (Fig. 2) displayed susceptibility to ciprofloxacin, cotrimoxazole, and piperacillin-tazobactam but resistance to fosfomycin and cefotaxime.

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Figure 2.

Antibiogram of Chromobacterium violaceum using the disc diffusion method.

We treated our patient with oral ciprofloxacin 500 mg bd for 3 weeks, and she responded well. Her symptoms improved, and the repeat urine culture after the antibiotic therapy was sterile.

Discussion

CV is an important bacterium characterised by the features of a high degree of sepsis, frequent metastasis to distant organs, and a high mortality rate. This bacterium is endemic to tropical and subtropical regions as an environmental pathogen. In recent years, it has been considered an emergent pathogen with geographical areas beyond the tropics, believed to be because of global climate change. ¹ The pigment violacein is responsible for its virulence. ²

So far, 200 cases of CV infection have been reported in the literature. A variety of clinical manifestations are reported, including pneumonia, meningitis, brain abscess, cutaneous manifestations including vesiculobullous eruptions, ³ fulminant sepsis multiple abscesses, and otitis media. Infections are usually found in immunocompromised individuals. CV-causing urinary tract infection, especially in immuno-competent individuals, is extremely rare. CV-causing urinary tract infections in a chronic kidney patient ⁴ and a healthy 19-year old boy have been reported. The urine may turn bluish (rather than violet)

A degree of mortality of 53% of infected cases is reported. ⁵ Ciprofloxacin is the most active drug against CV and a prolonged treatment course up to six weeks may be necessary due to the risk of relapse. ⁴

Conclusion

CV-causing urinary tract infection in an immunocompetent infection is a rare event with only a handful of cases reported in the literature. Prompt diagnosis with a urinary culture and appropriate antibiotic therapy is recommended. The patients should be kept on strict monitoring as there is a high probability of serious complications.