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Laboratoire de Bacteriologie-Virologie, Hpital de la Timone, CNRS UMR 6020, IFR48, 264 rue Saint-Pierre, 13385 Marseille, Cedex 05, France
ABSTRACT
We present the first report on the characterization of Clostridium celerecrescens isolated from liquid drained via abscess puncture from a 45-year-old man. The organism was identified by sequence comparison of 16S rRNA genes.
CASE REPORT
A 45-year-old man was admitted to the intensive care unit in August 2003 because of a metaphysis interior open fracture of the left thigh bone following a fall. On admission, the patient presented heart arrhythmia and chronic bronchitis. Antibiotic therapy (amoxicillin in combination with clavulanic acid) and pain-relieving treatment (morphine) were given. Surgical intervention with bone synthesis was performed. Ten days later, an abscess evacuation operation was performed on his left thigh. Hyperthermia (38°C) and shivers were noted.
Examination of a blood sample revealed leukocytosis (14.85 x 109 cells/liter), low hemoglobin level (4.9 mmol/liter), and hyperthrombocytosis (1,310 x 109 platelets/liter). Inflammatory markers were elevated; the erythrocyte sedimentation rate and the C-reactive protein level were 94 mm/h and 11.7 mg/liter, respectively. Grave heart metabolism disturbances were also noted: alanine aminotransferase was 138 UI/liter and lactate dehydrogenase was 557 IU/liter. Before abscess evacuation, three blood samples were performed for bacterial culture, but none of them was positive. An Enterobacter cloacae strain was isolated from the wound. Antimicrobial treatment included ciprofloxacin (500 mg three times/day) and ceftriaxone (2 g/day intravenous). Two weeks later, the patient left the hospital. One month after the accident, during medical consultation, inflammatory signs were noted again and an abscess was identified by computerized axial tomography examination. It was drained, and a gram-positive spore-forming bacillus grew from the puncture liquid. It was identified as Eubacterium limosum at 78.2% using API 20A strips (BioMerieux, France) and was unidentified using API 32A strips (BioMerieux). In view of the insufficiency of this identification, 16S rRNA gene sequence comparisons were performed (Service of Bacteriology, Hospital La Timone, Marseille, France), and the isolated bacterium was identified as Clostridium celerecrescens (99% identity from a 1,449-nt fragment). The biochemical characteristics of the isolate were compared to those of the original species description. Only two differences were noted. Gelatinase production and mannitol fermentation were found to be positive in the original species description but were found to be negative in this study.
Oral antibiotic therapy was given with a combination of sulfamethoxazole (800 mg six times/day), trimethoprim (160 mg six times/day), clindamycin (600 mg two times/day), and metronidazole (250 mg two times/day). After 3 weeks of treatment, the absence of pain and inflammation symptoms was noted at the examination, but antibiotic therapy was continued for 6 months.
The genus Clostridium includes obligately anaerobic, endospore-forming, gram-positive bacteria, which are not able to carry out dissimilatory sulfate reduction (4). This genus comprises more than 100 species and thus represents a wide heterogeneous group of organisms. Clostridial species are ubiquitous and can be found in soil, decaying vegetation, marine sediment, and the intestinal tracts of humans, other vertebrates, and insects (2). Human contamination by Clostridium can occur by different ways, such as wounds and food. We describe the first case of Clostridium celerecrescens isolation from liquid drained from an abscess. The first isolation of this microorganism from methanogenic cellulose-enriched culture was described by Palop et al. (7). Phylogenetically, C. celerecrescens is a member of the low-G+C-content gram-positive branch as defined by Collins et al. (4). Later, other authors proposed to group C. celerecrescens with Clostridium aerotolerans and Clostridium xylanolyticum in view of their common ability to reduce m- and p-methoxycinnamic and p-methylcinnamic acids to their corresponding 3-phenylpropionic acid derivates (3). Moreover, these organisms (with Clostridium sphenoides and the new species Clostridium methoxybenzovorans) exhibit high levels of 16S rRNA gene sequence relatedness (mean similarity of 98%) (6). Figure 1 presents the phylogenetic relationships between our isolate and other representatives of this genus.
Potential clinical implications of species closely related to C. celerecrescens have not been described. Two cases of C. sphenoides infections were published. The first case was severe diarrhea (8), and the second case was primary osteomyelitis (5). Thus, only one species closely related to Clostridium celerecrescens has been implicated in human infection.
Clostridial strains may be present in a variety of clinical samples from different compartments of the human gastrointestinal tract, the female genital tract, the skin surface, and the mouth. In the case of septicemia, these strains can be isolated from blood culture and also from punctured-abscess liquid (2). However, the isolation of Clostridium celerecrescens from a human sample has not been previously described. This may be explained by the fact that this microorganism is not represented in the commercial biochemical kits due to its relatively recent discovery and unknown clinical implications.
The question about potential ways of bacterial penetration remains open. It is known that nontoxigenic clostridial species can penetrate into the general circulatory system through the stomach wall and can be isolated from blood samples. As clostridial species require low oxygen tension in tissue for growth, poor vascular supply to local tissue likely explains the increased risk in patients with diabetes or peripheral vascular disease (1). However, C. celerecrescens has never been found in the human intestine. So its presence in a deep abscess was probably due to environmental contamination.
Routine phenotypic laboratory methods are often insufficient for correct identification of bacterial species that are uncommonly implicated in clinical manifestations. In these cases, the molecular identification approach may be recommended as a valuable and reliable method.
In conclusion, the case of a thigh abscess due to Clostridium celerecrescens presented in this report is the first one and highlights the organism's pathogenicity. Accurate identification, pathogenesis, and potential risk factors of this bacterium will require further investigations.
ACKNOWLEDGMENTS
We are grateful to Vijay A. K. B. Gundi for reviewing the manuscript.
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