• MNK
• Vibrio vulnificus
• bactericidal activity
• inflammation
• mTOR
• macrophage
• phagocytosis

• Vibrio vulnificus/metabolism
• Vibrio vulnificus/genetics
• Macrophages/microbiology
• Macrophages/immunology
• Macrophages/metabolism
• Animals
• Mice
• Mechanistic Target of Rapamycin Complex 1/metabolism
• Protein Serine-Threonine Kinases/metabolism
• Protein Serine-Threonine Kinases/genetics
• Cell Line
• Phagocytosis
• Vibrio Infections/immunology
• Vibrio Infections/microbiology
• Signal Transduction
• Cytokines/metabolism
• Tumor Necrosis Factor-alpha/metabolism
• Phosphorylation
• Intracellular Signaling Peptides and Proteins/metabolism
• Intracellular Signaling Peptides and Proteins/genetics
• Humans
• Aniline Compounds
• Purines

• 2021YFC2300302 The National key research and development program
• LY22H190002 The natural science foundation of Zhejiang Province
• 2022RC045 The medical health science and technology project of Zhejiang provincial health commission
• Y2020217 Wenzhou science and technology plan project
• 220604408244731, 220604408241341 The industry school cooperation collaborative education project of Ministry of Education of China
• 31400764 The National Natural Science Foundation of China

• CRISPR/Cas
• Conjugation
• Electroporation
• Molecular methods
• Natural competency
• Shuttle plasmid

• Bacteria/genetics
• Bacteria/metabolism
• Plasmids/genetics
• Aquatic Organisms/genetics
• Transformation, Bacterial
• Electroporation
• Genetic Engineering/methods
• Conjugation, Genetic
• Escherichia coli/genetics
• Escherichia coli/metabolism
• Seawater/microbiology
• Transformation, Genetic
• CRISPR-Cas Systems

We report on a case of Vibrio vulnificus (V. vulnificus) detected by metagenomics next-generation sequencing (mNGS) in a 53-year-old male patient with polymicrobial gas gangrene and successful treatment by surgery. This report raises awareness among dermatologists that when a patient is clinically suspected of a special type of pathogenic infection, the mNGS method should be preferred to identify the patient’s pathogen infection as soon as possible and then take effective treatment in time to save patients’ lives.

A 53-year-old male who worked in the aquatic market complained of redness and swelling of the lower limbs, blisters and ulcers with fever for 3 d. We used mNGS to test the pathogens in ulcer secretions. The results were returned in 24 h and indicated: V. vulnificus, Fusobacterium necrophorum, Staphylococcus haemolyticus, Staphylococcus aureus, Streptococcus dysgalactiae and Klebsiella aerogenes. This patient was diagnosed with V. vulnificus infection. The emergency operation was performed immediately under combined lumbar and epidural anesthesia: Left leg expansion and exploration (August 10, 2021). After surgery, we continued to use piperacillin sodium tazobactam sodium 4.5 g every 8 h and levofloxacin 0.5 g for anti-infection treatment. The patient underwent further surgery under lumbar anesthesia on August 17, 2021 and August 31, 2021: Left leg deactivation and skin grafting, negative pressure closed drainage and right thigh skin removal. After treatment, the transplanted flap survived.

We could confirm the diagnosis of Vibrio vulnificus infection within 24 h through mNGS detection and then immediately performed emergency surgery.

• Metagenomics next-generation sequencing
• Vibrio vulnificus
• Polymicrobial gas gangrene
• Surgery
• Case report

Vibrio vulnificus is an opportunistic human pathogen and autochthonous inhabitant of coastal marine environments, where the bacterium is under constant predation by heterotrophic protists or protozoans. As a result of this selection pressure, genetic variants with antipredation mechanisms are selected for and persist in the environment. Such natural variants may also be pathogenic to animal or human hosts, making it important to understand these defense mechanisms. To identify antipredator strategies, 13 V. vulnificus strains of different genotypes isolated from diverse environments were exposed to predation by the ciliated protozoan Tetrahymena pyriformis, and only strain ENV1 was resistant to predation. Further investigation of the cell-free supernatant showed that ENV1 acidifies the environment by the excretion of organic acids, which are toxic to T. pyriformis. As this predation resistance was dependent on the availability of iron, transcriptomes of V. vulnificus in iron-replete and iron-deplete conditions were compared. This analysis revealed that ENV1 ferments pyruvate and the resultant acetyl-CoA leads to acetate synthesis under aerobic conditions, a hallmark of overflow metabolism. The anaerobic respiration global regulator arcA was upregulated when iron was available. An ΔarcA deletion mutant of ENV1 accumulated less acetate and, importantly, was sensitive to grazing by T. pyriformis. Based on the transcriptome response and quantification of metabolites, we conclude that ENV1 has adapted to overflow metabolism and has lost a control switch that shifts metabolism from acetate excretion to acetate assimilation, enabling it to excrete acetate continuously. We show that overflow metabolism and the acetate switch contribute to prey-predator interactions.

IMPORTANCE Bacteria in the environment, including Vibrio spp., interact with protozoan predators. To defend against predation, bacteria evolve antipredator mechanisms ranging from changing morphology, biofilm formation, and secretion of toxins or virulence factors. Some of these adaptations may result in strains that are pathogenic to humans. Therefore, it is important to study predator defense strategies of environmental bacteria. V. vulnificus thrives in coastal waters and infects humans. Very little is known about the defense mechanisms V. vulnificus expresses against predation. Here, we show that a V. vulnificus strain (ENV1) has rewired the central carbon metabolism, enabling the production of excess organic acid that is toxic to the protozoan predator T. pyriformis. This is a previously unknown mechanism of predation defense that protects against protozoan predators.