Plesiomonas shigelloides

Plesiomonas shigelloides is a motile, gram-negative, facultatively anaerobic bacterium that has gained attention in agricultural science as a potential phytopathogen and a significant contaminant of fresh produce. Often associated with water-borne transmission, it poses a direct threat to leafy vegetables and hydroponic farming operations worldwide.

The host range of this pathogen primarily includes leafy greens such as lettuce, spinach, and herbs. These crops are particularly vulnerable when grown in soil-less cultures or in fields with contaminated irrigation water. The bacteria can persist in the environment for extended periods, making them difficult to eradicate once the production system is compromised.

Symptoms of Plesiomonas shigelloides infection typically involve the development of soft rot on the roots and the base of the stems. As the infection progresses, affected tissues turn necrotic, become mushy, and may emit a foul odor due to the activity of pectinolytic enzymes. Wilting is a common sign, as the damage to the root system inhibits water and nutrient uptake.

The development of this disease is highly dependent on environmental factors, with optimal growth occurring at temperatures between 25°C and 37°C. High moisture levels in the rhizosphere and stagnant water create ideal breeding grounds. The bacteria spread rapidly through irrigation systems, especially if the source water contains fecal matter or insufficient disinfection processes are in place.

Effective prevention and control measures are essential to minimize losses and ensure food safety. Growers should prioritize water sanitization, using UV treatment, ozone, or appropriate filtration for irrigation systems. Maintaining proper hygiene in greenhouses, implementing strict crop rotation, and ensuring the health of the root zone through balanced oxygen levels are critical strategies for mitigating the impact of this pathogen.