Aeromonas veroniiassociated with red gill disease and its induced immune response inMacrobrachium nipponense

摘要

Aeromonas veroniiis a freshwater bacterium associated with many diseases in aquatic animals. In this study, the pathogenic ofA. veroniiwas isolated from diseasedMacrobrachium nipponenseshowing signs of weakness, poor appetite and red gills in some farms in Jiangsu province, China. The pathogenicity ofA. veroniitoM. nipponensewas determined by challenge experiments. Results of artificial challenge showedA. veroniiNJ1 was pathogenic toM. nipponense, and theLD(50)was 4.5 x 10(6) CFU/ml at 7 d post infection. Detection virulence factors of theA. veroniiNJ1 showed thatA. veroniiNJ1 produced caseinase, lipase, amylase, lecithinase, gelatinase and haemolysin. Detection of virulence-related genes showed thatA. veroniiNJ1 was positive for aerolysin (aer), outer membrane protein (ompA), adhesin (aha), flagellin (flaA,flgH, flgM,flgN), lipoidase (lip), cytotonic enterotoxins (act,alt,ast), serine protease (ser), DNases (exu), haemolysin (hlyA), type IV pilus (tapA) and fimbrillin (fim). Antibiotic sensitivity testing indicatedA. veroniiNJ1 was susceptible to quinolones, but resistant to penicillins. Additionally, the immune-related gene expression inM. nipponensewas evaluated, and the results showed that anti-lipopolysaccharide factor (ALF1,ALF2,ALF3),Cusrin1,Cusrin2,Cusrin3,Haemocyanin,i-lysozymeandProphenoloxidasewere significantly upregulated from 6 to 24 hr afterA. veroniiinfection. The results of our study suggested thatA. veroniiwas an aetiological element in the mass mortalities ofM. nipponenseand this study provided preliminary insights into the diversity in the immune response ofM. nipponenseto theA. veroniiinfection.