Aeromonas Infections in African Sharptooth Catfish

Abstract

The aim of this study was to investigate the dominant species of Aeromonas in naturally infected African Sharptooth catfish, Clarias gariepinus, in Qena, Egypt and the distribution of two virulence genes among the isolates to assess their pathogenicity. Twenty-five isolates of Aeromonas were recovered from infected fish showing signs of septicemia. Restriction-fragment-length-polymorphism (RFLP) analysis of the 16S-rDNA amplified products demonstrated that the specie isolated were Aeromonas hydrophila (56%) and Aeromonas veronii (44%). Isolates were screened for the cytotoxic enterotoxin, act, and aerolysin, aerA, genes. The act gene was detected only in A. hydrophila, while the aerA gene was more frequently found among all isolates. Catfish challenged with an A. hydrophila isolate that have both the act and aerA genes showed higher mortalities (80.9%) and more severe signs of septicemia than those challenged with an isolate that lacks both genes studied.