Meningitis caused by Chromobacterium haemolyticum suspected to be derived from a canal in Japan: a case report

Abstract

Background: The genus Chromobacterium, of which 12 species have been recognized, comprises bacteria that reside in tropical and subtropical environments. Of these species, Chromobacterium violaceum and Chromobacterium haemolyticum are known to cause infections in humans. There have been few reports of infections caused by Chromobacterium haemolyticum.

Case presentation: Chromobacterium haemolyticum was detected in spinal fluid and blood samples isolated from a 73-year-old Japanese male patient who fell into a canal in Kyoto City, Japan and developed bacteremia and meningitis. Although meropenem and vancomycin were administered, this patient died 9 days after admission. Although the infection was misidentified as being caused by Chromobacterium violaceum by conventional identification methods, average nucleotide identity analysis revealed that the causative pathogen was Chromobacterium haemolyticum. The same bacteria were also detected in the canal in which the accident occurred. Phylogenetic analysis of the strain isolated from the patient and the strain isolated from the canal suggested that the two strains were very closely related.

Conclusions: Chromobacterium haemolyticum can be misidentified as Chromobacterium violaceum by conventional identification methods and tends to be more resistant to β-lactams than Chromobacterium violaceum. Pigment production and β-hemolysis on blood sheep agar can provide clues for the early identification of Chromobacterium haemolyticum.

Keywords: Case report; Chromobacterium haemolyticum; Chromobacterium violaceum; Meningitis; Misidentification.

Fig. 1

Microbiological results. A The spinal fluid specimen appeared cloudy. B Numerous Gram-negative rods were present in the spinal fluid along with inflammatory findings with increasing numbers of neutrophils (Gram stain, ×1000 original magnification). C Results of assessments of Chromobacterium haemolyticum colonies on TSA II 5% sheep blood agar after a 48-h culture at 37 °C, showing yellow colonies with clear β-hemolysis, D Presence of lactose nondegradable colonies on BTB lactose-added agar, E Presence of transparent microcolonies on MacConkey II agar