First Reported Case of Human Infection with Chromobacterium Violaceum in Gabon: Antibiotic Susceptibility Patterns and Treatment Outcome

Background:Mostly found in soil and still water in the subtropics and tropics, Chromobacterium violaceum is a Gram-negative bacillus that rarely infects humans. Nevertheless, when Chromobacterium violaceum infections do occur, they result in great distress because they are unrecognized and poorly addressed. The aim here is to describe what appears to be the first human case of Chromobacterium violaceum infection in Gabon.

Case presentation: A 12-month-old female was admitted to the paediatric ward of the Centre Regional Hospital Amissa Bongo of Franceville in Gabon with a fever that had been lingering for a week. The child was first put on antimalarial treatment for 3 days (following a positive thick blood smear for Plasmodium falciparum) combined with a 10-day prophylactic course of antibiotics (association of 500mg Ceftriaxone and Tobramycine).

Subsequently, a post-treatment cytobacteriological examination of urine (CBEU) was performed: a urine dipstick (UD) was carried out and then the urine was plated on Cystine-lactose-electrolyte-deficient (CLED) agar medium and incubated for 24 hours at 37°C.

Isolated bacterial colonies were identified with the Vitek 2 system (bioMerieux, France). Antibiotic susceptibility tests were run based on the Kirby-Bauer method (interpretation based on the breaking points given by the CLSI for Escherichia coli).

The UD revealed leukocyturia (30.103μL-1) and greyish non-pigmented bacterial colonies (positive for catalase and oxidase) found on CLED (DGU=104UFC.mL-1) were identified as Chromobacterium violaceum.

Antibiotic susceptibility tests exhibited resistance to beta-lactams (Ticarcillin, Ertapenem, Cefotaxime, Ceftazidime and Ceftriaxone), aminoglycosides (Gentamicin and Tobramycin), urinary quinolones (Nalidixic acid) and sulphonamides (Trimethoprim/Sulfamethoxazole).

Patient outcome: The infectious syndrome disappeared after the probabilistic treatment was adjusted post-CBEU and switched to Cefaclor 125 mg/5ml at a dosage of 25 mg/kg/day.

Conclusion: Chromobacterium violaceum seems to be a severe emerging human pathogen that requires prompt, adequate and lab results antibiotic-based treatment to prevent fatal outcomes.

Keywords:

Chromobacterium violaceum