First Comparative Analysis of Clostridium septicum Genomes Provides Insights Into the Taxonomy, Species Genetic Diversity, and Virulence Related to Gas Gangrene

Clostridium septicum is a Gram-positive, toxin-producing, and spore-forming bacterium that is recognized, together with C. perfringens, as the most important etiologic agent of progressive gas gangrene. Clostridium septicum infections are almost always fatal in humans and animals. Despite its clinical and agricultural relevance, there is currently limited knowledge of the diversity and genome structure of C. septicum. This study presents the complete genome sequence of C. septicum DSM 7534T type strain as well as the first comparative analysis of five C. septicum genomes. The taxonomy of C. septicum, as revealed by 16S rRNA analysis as well as by genomic wide indices such as protein-based phylogeny, average nucleotide identity, and digital DNA–DNA hybridization indicates a stable clade. The composition and presence of prophages, CRISPR elements and accessory genetic material was variable in the investigated genomes. This is in contrast to the limited genetic variability described for the phylogenetically and phenotypically related species Clostridium chauvoei. The restriction-modification (RM) systems between two C. septicum genomes were heterogeneous for the RM types they encoded. C. septicum has an open pangenome with 2,311 genes representing the core genes and 1,429 accessory genes. The core genome SNP divergence between genome pairs varied up to 4,886 pairwise SNPs. A vast arsenal of potential virulence genes was detected in the genomes studied. Sequence analysis of these genes revealed that sialidase, hemolysin, and collagenase genes are conserved compared to the α-toxin and hyaluronidase genes. In addition, a conserved gene found in all C. septicum genomes was predicted to encode a leucocidin homolog (beta-channel forming cytolysin) similar (71.10% protein identity) to Clostridium chauvoei toxin A (CctA), which is a potent toxin. In conclusion, our results provide first, valuable insights into strain relatedness and genomic plasticity of C. septicum and contribute to our understanding of the virulence mechanisms of this important human and animal pathogen.

Clostridium septicum-induced gangrene in the right lower extremity complicating pneumatosis in the right ventricle and the pulmonary artery and occlusion of right femoral artery: a case report

Background Gas gangrene is usually manifested as myonecrosis and subcutaneous gas accumulation, but rarely manifested as arterial occlusion or pneumatosis in the right ventricle and the pulmonary artery. Case presentation We report a case of gas gangrene caused by Clostridium septicum. The patient developed gas gangrene after being pecked by a chicken but turned for the better following antibiotic treatment and debriment. Imaging test revealed a rare occlusion of the right femoral artery and pneumatosis in the right ventricle and the main pulmonary artery. Conclusions In the presence of gas gangrene, special care must be taken to prevent against the formation of circulatory air embolism. The gas gangrene-induced gangrene in the limb of this patient might be attributed to the combined action of infection and arterial occlusion. MDT (Multidisciplinary team)-Green Channel mode is conductive to treatment success of gas gangrene.

Emergency amputation necessitated within 24 hours by a human bite: a case report

We herein review and analyze the diagnosis, treatment, and outcome of a severe infection caused by a human bite. A 68-year-old man was bitten on the forearm by a 3-year-old child. Rapid progression of infection, severe local and systemic poisoning, and diverse clinical manifestations were observed at presentation. Based on the medical history, physical signs, imaging examinations (X-ray films, color Doppler ultrasound, and computed tomography), laboratory examinations, and multidisciplinary consultation, the patient was diagnosed with gas gangrene or gas gangrene-like changes. Twenty-four hours after the injury, an emergency amputation was performed (open amputation with wound closure after 1 week). After the operation, the patient was sent to the intensive care unit for isolation and further anti-infection and anti-shock treatments. His condition gradually improved after treatment and he was discharged without further complications. Bacteriological and pathological examinations indicated Aeromonas hydrophila infection leading to extensive necrotizing fasciitis of the limb and severe systemic poisoning. In addition, pre-existing myelodysplastic syndrome progressing to acute myeloid leukemia was identified as a possible predisposing factor. Human bites can cause serious infections requiring timely treatment, particularly in patients with predisposing comorbidities.