Edwardsiella piscicida: A versatile emerging pathogen of fish

Abstract

Edwardsiella piscicida is an Enterobacteriaceae that is abundant in water and causes food and waterborne infections in fish, animals, and humans. The bacterium causes Edwardsiellosis in farmed fish and can lead to severe economic losses in aquaculture worldwide. E. piscicida is an intracellular pathogen that can also cause systemic infection. Type III and type VI secretion systems are the bacterium's most lethal weapons against host defenses. It also possesses multi-antibiotic resistant genes and is selected and enriched in the environment due to the overuse of antibiotics. Therefore, the bacterium has great potential to contribute to the evolution of the resistome. All these properties have made this bacterium a perfect model to study bacteria virulence mechanisms and the spread of antimicrobial genes in the environment. We summarize recent advance in E. piscicida biology and provide insights into future research in virulence mechanisms, vaccine development and novel therapeutics.

Keywords: T3SS/T6SS and effectors; intracellular and systemic infection; resistome; virulence mechanisms.

Figure 1.

Caco-2 cells showing successful internalization of E. piscicida PPD130/91. Caco-2 cells were infected with wild type PPD130/91 for 6 h at 35°C. Edwardsiella-containing vacuoles (ECVs) with internalized bacteria are clearly visible under phase microscopy. Scale bar = 10 μm.

Figure 2.

Virulence regulators and crosstalk among the different regulators in E. piscicida. Two-component systems and other global regulators control the delivery of the effectors of T3SS and T6SS, and other virulent factors in response to external environmental stimuli. Green lines indicate activation and red lines indicate inhibition.