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Chromobacterium haemolyticum-induced bacteremia in a healthy young man
© Okada et al.; licensee BioMed Central Ltd. 2013
Received: 3 April 2013
Accepted: 28 August 2013
Published: 3 September 2013
The genus Chromobacterium consists of 7 recognized species. Among those, only C. violaceum, commonly found in the soil and water of tropical and subtropical regions, has been shown to cause human infection. Although human infection is rare, C. violaceum can cause life-threatening sepsis, with metastatic abscesses, most frequently infecting those who are young and healthy.
We recently identified a case of severe bacteremia caused by Chromobacterium haemolyticum infection in a healthy young patient following trauma and exposure to river water, in Japan. The patient developed necrotizing fasciitis that was successfully treated with a fasciotomy and intravenous ciprofloxacin and gentamicin.
C. haemolyticum should be considered in the differential diagnosis of skin lesions that progressively worsen after trauma involving exposure to river or lake water, even in temperate regions. Second, early blood cultures for the isolation and identification of the causative organism were important for initiating proper antimicrobial therapy.
The genus Chromobacterium consists of 7 recognized species: C. violaceum, C. subtsugae, C. aquaticum, C. haemolyticum, C. pseudoviolaceum, C. piscinae, and C. vaccinii. Of these species, only C. violaceum, commonly found in the soil and water of tropical and subtropical regions, has been shown to cause human infection. Although human infection is rare, C. violaceum can cause life-threatening sepsis, with metastatic abscesses, most frequently infecting those who are young and healthy .
We describe, here, clinical evidence for another species, C. haemolyticum, which caused an infection in a healthy, young patient. This bacterium should be considered in the differential diagnosis of skin lesions that quickly worsen after trauma associated with exposure to river or lake water. This is particularly important because of the species’ resistance to antimicrobials, particularly β-lactams.
A healthy, 26-year-old Japanese man was admitted to our hospital with pain in his left shoulder and leg caused by a road accident; he was hit by a car and thrown into a river. The outside air and water temperatures at the time of the injury were 20°C. He had no family history of any particular condition.
Upon admission, his temperature was 36.6°C; pulse rate, 66 beats/min; blood pressure, 143/99 mmHg; respiratory rate, 15/min; oxygen saturation, 100% (10-L reservoir mask); and Glasgow Coma Scale score, E4V5M6. A physical examination showed only bruising, not open wounds, on the left side of his face and shoulder and tenderness in his left leg. His height, weight, and body mass index were 175 cm, 67 kg, and 21.9 kg/m2, respectively. Laboratory tests showed mild inflammation (white blood cell [WBC] count, 13,500/μL; and C-reactive protein [CRP], 0.9 mg/L [normal range: < 2.0 mg/L]). A radiograph showed fractures of the fibula shaft and scapula.
Before the recognition of C. haemolyticum in 2011, less than 140 proven cases of human infection with C. violaceum had been reported . Among the few reports of infections caused by non-pigmented, β-hemolytic strains of C. violaceum, identification of C. haemolyticum strain MDA0585T by 16S rRNA gene sequencing has not been previously reported. Thus, we present the first clinical evidence for C. haemolyticum infection.
C. haemolyticum, strain MDA0585T, is a gram-negative bacillus, and has been isolated from a clinical sample  and from lake water . C. violaceum and C. haemolyticum are closely related, phylogenetically, making them impossible to distinguish based on results of biochemical tests (i.e., the Vitek GNI + card and the API 20 NE test). However, the lack of violet pigmentation, hemolysis of sheep blood, and positive oxidase test results allow an accurate identification. Hence, as shown in the current report, these features can be used to differentiate between these 2 bacterial species in a clinical setting.
Growth, biochemical reactions, and results of antibiotic susceptibility tests for C. haemolyticum isolates
Xan et al.
Growth on agar (37°C, 5% CO2, 24 h):
2.3 mm, β-hemolysis
2 mm, β-hemolysis
2 mm, no hemolysis
Buffered charcoal yeast extract
2 mm, flat, dull
2 mm, raised, shiny
0.2 mm, pinpoint
0.2 mm, pinpoint
Indole production (tryptophanase)
Antimicrobial susceptibility (MIC, μg/mL)
In the present report, the patient was found to have necrotizing fasciitis on day 6 based on his clinical presentation. In terms of antibiotic therapy for necrotizing fasciitis, currently acceptable regimens include the admin-istration of a carbapenem or β-lactam/β-lactamase inhibitor, together with clindamycin, in addition to an agent with activity against methicillin-resistant S. aureus. In addition, the Gram stain showed the bacteria to be gram-negative. Hence, without the results of the blood culture taken on day 4, we would likely have concluded that the infection was caused by Burkholderia spp., Aeromonas spp., or Pseudomonas spp. , and would have administrated antibiotics according to the therapy for general necrotizing fasciitis. However, C. haemolyticum has been found to be extremely resistant to beta-lactams. Therefore, as our initial findings suggested an infection with either C. haemolyticum or the closely related C. violaceum, we provided long-term ciprofloxacin. According to a study by Aldridge et al., ciprofloxacin was the most active drug in combatting C. violaceum, and several studies have reported successful treatment with this therapy.
The most common symptoms of C. violaceum infections are fever and pain over the infected site, in association with various skin lesions . To our knowledge, only 1 case of necrotizing fasciitis involving C. violaceum has been reported . According to the pathology results, the patient in the current report had necrotizing fasciitis. Chattopadhyay et al. have recommended aggressive debridement for cases of C. violaceum infection .
C. haemolyticum should be considered in the differential diagnosis of skin lesions that progressively worsen after trauma involving exposure to river or lake water, even in temperate regions. Second, early blood cultures for isolation and identification are important for initiating proper antimicrobial therapy.
Written informed consent was obtained from the patient for publication of this case report and the accompanying images. A copy of the written consent is available for review by the Editor of this journal.
We would like to acknowledge Takako Sakamaki and Toshiko Ooishi for their assistance, and Katsuhiko Hashimoto, Itaru Saito, Fumihito Ito, Yoshibumi Kumada, and Hideyuki Yokoyama for their assistance with patient management.
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