Pathogenic Mechanisms of Aeromonas Species in Aquatic Systems

Aeromonas species are ubiquitous Gram-negative bacteria in freshwater and brackish environments, recognised for their capacity to infect a wide range of hosts including fish, amphibians and occasionally humans. Their pathogenicity reflects a multifactorial strategy that combines potent toxins, sophisticated secretion systems and adhesive structures. Key toxins such as aerolysin and haemolysin induce pore formation and cell lysis, while enterotoxins and cytotonic factors disrupt intestinal integrity. Secretion systems of types II, III and VI enable targeted delivery of virulence effectors, modulating host immunity and promoting intracellular survival. Adhesion and colonisation are mediated by surface appendages including lateral flagella and type IV pili, which also underpin biofilm formation and environmental persistence. Genomic analyses have revealed extensive lateral gene transfer events that have disseminated virulence islands, metabolic operons and antibiotic-resistance determinants, driving the emergence of hypervirulent clonal lineages that pose significant threats to aquaculture and public health.

Research from Nature Portfolio

Comparative genomic analysis of epidemic Aeromonas hydrophila ST251 clones has revealed that canonical secretion systems such as type III and VI are not solely responsible for high virulence. Instead, conserved metabolic pathways for utilisation of myo-inositol, sialic acid and L-fucose appear to underpin the epidemic potential of this clonal group. This seminal work has delineated a high-risk lineage characterised by distinct metabolic operons, lateral flagellar genes and unique toxin profiles, offering new targets for surveillance and intervention in aquaculture settings.

Pathogenic Mechanisms of Aeromonas Species in Aquatic Systems publication trend

The graph below shows the total number of articles in pathogenic mechanisms of aeromonas species in aquatic systems across all publications each year (not limited to Nature Index journals).

Technical terms

Type II/III/VI secretion system (T2SS/T3SS/T6SS): Protein complexes that export bacterial effectors into the extracellular environment or directly into host cells, crucial for toxin delivery and immune modulation.

Aerolysin: A beta-pore-forming toxin secreted by Aeromonas that inserts into host membranes, causing ion imbalance and cell death.

Biofilm: A structured community of bacterial cells embedded in a self-produced matrix, conferring protection against environmental stressors and antimicrobials.

Type IV pili (T4P): Hair-like appendages on the bacterial surface that mediate attachment to biotic and abiotic surfaces and facilitate microcolony formation.

Operon: A cluster of functionally related genes transcribed under the control of a single promoter, such as the Tad operon involved in pilus biogenesis.

References

1. Novel insights into the pathogenicity of epidemic Aeromonas hydrophila ST251 clones from comparative genomics. Scientific Reports (2015).
2. Tad pili contribute to the virulence and biofilm formation of virulent Aeromonas hydrophila. Frontiers in Cellular and Infection Microbiology (2024).
3. Effect of Purslane (Portulaca oleracea L.) on Intestinal Morphology, Digestion Activity and Microbiome of Chinese Pond Turtle (Mauremys reevesii) during Aeromonas hydrophila Infection. International Journal of Molecular Sciences (2023).
4. A review on pathogenicity of Aeromonas hydrophila and their mitigation through medicinal herbs in aquaculture. Heliyon (2023).