ABSTRACT
Objective:To identify a pathogenic strain JM-1 isolated from the pus of a patient stabbed by a sea shrimp and to analyze its antibiotic susceptibility and virulence genes, aiming to provide reference for screening clinically related infections caused by Cysteiniphilum litorale as a rare pathogen and improving prognosis. Methods:Biochemical phenotype identification, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), 16S rRNA gene sequencing, analysis of average nucleotide identity (ANI) and average amino acid identity (AAI) based on the whole genome and phylogenetic analysis of the 16S rRNA gene and the whole genome were performed to accurately determine the taxonomic status of the strain JM-1. E-test was used to detect antibiotic susceptibility, and the results were interpreted according to the interpretation standards of Francisella tularensis in CLSI M45-A3. The virulence factor database (VFDB) was used for genome-wide annotation and analysis of virulence genes. Results:After culturing the strain JM-1 on the Columbia blood plate for 3 d, some grey-white, medium-sized, smooth, round and convex hemolytic colonies were observed. Gram staining result showed lightly colored Gram-negative Coccobacillus. API NH identification results suggested that the isolate JM-1 was Moraxella catarrhalis (biochemical code: 3010), while there was no identification result in Vitek2 system NH card (biochemical code: 0211002121). The EXS3000 mass spectrometer self-built database identified the isolate JM-1 as Cysteiniphilum litorale. The phylogenetic analysis based on the 16S rRNA gene and the whole genome showed that the isolate JM-1 and Cysteiniphilum litorale DSM 101832 T clustered into the same branch, and the ANI and AAI values between the two strains were 95.07% and 95.65%, respectively. The biochemical phenotype identification indicated the isolate JM-1 producing β-lactamase and penicillinase. Antibiotic susceptibility test results showed the strain was resistant to penicillin and sensitive to gentamicin, streptomycin, doxycycline, tetracycline, ciprofloxacin, levofloxacin, and chloramphenicol. Genome annotation suggested the virulence genes of the isolate JM-1 were similar to those of Francisella, including Francisella pathogenicity island (FPI), type Ⅳ fimbriae, capsule and lipopolysaccharide. Conclusions:Cysteiniphilum litorale was a rare pathogen with virulence genes similar to those of Francisella, and its antibiotic susceptibility was also similar to that of Francisella. This study confirmed a case of clinical infection caused by Cysteiniphilum litorale. The self-built MALDI-TOF MS system could be used for its rapid identification.