Enterobacter cloacae: A probable etiological agent associated with slow growth in the giant freshwater prawn Macrobrachium rosenbergii

Abstract

Macrobrachium rosenbergii, the giant freshwater prawn, is an economically crucial freshwater shrimp that has been severely affected by slowing growth in recent years. In Gaoyou County, Jiangsu Province, China, Enterobacter cloacae infection frequently occurs in M. rosenbergii hatcheries, and E. cloacae has been detected with high prevalence in slow-growing prawns. In this study, the growth of prawns was found to be significantly reduced after E. cloacae infection. In addition, under co-culture of healthy and slow-growing prawns, slow-growing prawns were infectious and able to cause the slow growth of healthy prawns. The expression of growth-related genes after E. cloacae infection was analyzed, and differential expression of growth-related genes between slow-growing and healthy prawns was investigated. The results showed that the expression of CHIT3, Cat, JHEH, EcR, and RXR was downregulated after E. cloacae infection and that of EcR was upregulated after E. cloacae infection. Similarly, the expression of CHIT3, Cat, JHEH, EcR, and RXR was downregulated in slow-growing prawns compared to that in healthy prawns, and that of EcR was upregulated in slow-growing prawns compared to that in healthy prawns. The present results reveal a high prevalence of E. cloacae in slow-growing M. rosenbergii and suggest that this pathogen is the probable cause of the slow growth in M. rosenbergii.