Aeromonas haianensis, Sp. Nov., from Eels and Humans

Ten strains of unidentified bacteria were isolated from diseased eels and patients with diarrhea in Haian County, Jiangsu Province. All isolates were Gram-negative motile rods growing in non-salt peptone medium at 37 C. They were oxidase positive, glucose fermenting and produced a brown pigment. The bacteria were resistant to O/129. The bacteria were identified as belonging to Aeromonas; some phenotype characteristics were different from these of the reported Aeromonas species. DNA-DNA hybridization studies showed that DNA of strain CCTCC AB97026 was 93 and 89% similar to that of strain 95-72, 96-109 and showed 63% relatedness to Aeromonas veronii, which is below the cut-off value for species differentiation. The determination of mol% G+C, DNA-DNA hybridization and 16S rRNA gene sequencing and fatty acids analysis indicated that these bacteria constitute a new Aeromonas species. These bacteria were susceptible to norfloxacin, furazolidone, nutgall and rhubarb and resisted to penicillin and SMZ. The LD50 for mice and eel is 3.9 106 and 1.2 105 cfu, respectively. The bacterium had some virulence factors, such as type IV pilli, HEC toxin and extracellular proteinase. All the above data and the epidemiological information indicated that the new bacterium was pathogenic to eel and humans. For the new species, the name of Aeromonas haianensis has been proposed because the bacteria were all isolated from Haian County, Jiangsu Province, China. The type strain is CCTCC AB97026T (=IFO16641=strain95-173).