The first report of submandibular lymph node infection with Flavobacterium ceti in a horse and its complete genome sequence.

The article characterizes the full genomic sequence of the Flavobacterium ceti bacteria from a lymph node infection in a horse, an unprecedented finding that has broad implications for equine health.

Introduction

• This research study is a maiden report that has successfully isolated and sequenced the genome of Flavobacterium ceti (F. ceti IJFC025) from a draining submandibular lymph node abscess in a mixed-breed horse.
• This bacteria is an uncommon pathogen that causes health problems in horses.
• The horse from which the bacteria was isolated was a 6-year-old mare from Jeju, South Korea.

Findings

• The entire genome sequence of the isolated F. ceti IJFC025 consists of a 3,144,426-bp chromosome.
• The G + C content of the genome is 35.6% which is a representation of the percentage of guanine and cytosine nucleotides in the DNA molecule.
• In the mapped genome, 2909 coding sequences (CDSs), 74 tRNAs, and five rRNAs were identified.
• When compared with another strain of F. ceti (CECT7184), the genome revealed a 98.6 %-98.8 % nucleotide identity, indicating a high level of genomic similarity.

Virulence Genes and Potential Infectivity

• Four virulence genes, potentially responsible for infections in horses, were identified in the F. ceti IJFC025 genome through a software tool called PathogenFinder.
• Comparative genomic analysis between F. ceti IJFC025 and F. ceti CECT7184 revealed that the former lacks three specific genes encoded by the latter. These missing genes are responsible for encoding propionyl-CoA carboxylase, 3-oxoacid CoA-transferase A subunit, and the translation initiation factor IF-1.
• On the other hand, F. ceti IJFC025 contains genes that encode deoxyhypusine synthase, which is absent in the F. ceti CECT7184 strain.

Antimicrobial Resistance

• The F. ceti IJFC025 isolate showed resistance to multiple antibiotics including gentamicin, ceftazidime, nalidixic acid, ciprofloxacin, and colistin.
• Surprisingly, no genes that could explain this resistance were found in the genomic sequence.

Implications of Findings

• The similarity of the clinical signs of F. ceti IJFC025 infection and strangles makes it essential to consider this bacteria for the differential diagnosis of submandibular lymphadenopathy in horses.
• This finding needs to be taken into account for the continued understanding of equine health and antimicrobial resistance.