Faucicola mancuniensis isolated from human respiratory tract and its genomic characteristicstics.

Background: Faucicola mancuniensis (F. mancuniensis), a Gram-negative bacterium within the Moraxellaceae family, has been isolated from the human respiratory tract. Genomic characteristics, antibiotic resistance profiles, and pathogenic potential of this rarely reported species remain largely unexplored. This study aimed to isolate F. mancuniensis from the human respiratory tract, characterize its genome, functional potential, and antimicrobial susceptibility, and assess its public health significance.

Methods: F. mancuniensis strain HZ006 was isolated from a human respiratory specimen in Guizhou, China. Taxonomic identification was confirmed using 16S rRNA gene sequencing. Morphology and physiological biochemistry were characterized. Whole-genome sequencing was performed using second- and third-generation technologies. Genomic functional annotation utilized GO, KEGG, VFDB, CARD, and four additional databases. Antimicrobial susceptibility against 29 antibiotics was determined phenotypically.

Results: 16S rRNA sequencing confirmed strain HZ006 as F. mancuniensis (99.58% identity). HZ006 is an aerobic, Gram-negative coccobacillus (observed via electron microscopy), lacking flagella and spores. Optimal growth occurred at 18-37°C on blood agar, forming smooth, moist, circular colonies (~ 1.0 mm diameter). The complete genome is 2,740,046 bp with a G + C content of 40.38 mol%, encoding 2594 predicted genes. Annotation revealed 104 putative virulence factors (VFDB) and 27 antibiotic resistance genes (CARD), indicating potential pathogenicity and resistance mechanisms. Phenotypic testing, however, showed HZ006 was susceptible to all 29 antibiotics tested.

Conclusion: This study reports the first isolation and complete genome sequence of F. mancuniensis (HZ006) from a human specimen in China. Comprehensive genomic annotation and phenotypic characterization, including electron microscopy, provide foundational data on this species. While genomic analysis suggests potential pathogenicity and resistance mechanisms, the observed phenotypic susceptibility to all tested antibiotics informs potential treatment strategies. These findings significantly enhance our understanding of F. mancuniensis and its public health relevance.