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Open AccessArticle

Aeromonas hydrophila, an Emerging Causative Agent of Freshwater-Farmed Whiteleg shrimp Litopenaeus vannamei

by Huihua Zhou 1,†, Chunlei Gai 2,†, Guifang Ye 1, Jian An 3, Kai Liu 4, La Xu 2 and Haipeng Cao 1,*
National Pathogen Collection Center for Aquatic Animals, Shanghai Collaborative Innovation for Aquatic Animal Genetics and Breeding, Shanghai Engineering Research Center of Aquaculture, Shanghai Ocean University, Shanghai 201306, China
Marine Biology Institute of Shandong, Qingdao 266104, China
Lianyungang Marine and Fisheries Development Promotion Center, Lianyungang 222000, China
Institute of Fishery Science, Hangzhou Academy of Agricultural Sciences, Hangzhou 310024, China
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Microorganisms 2019, 7(10), 450;
Received: 7 August 2019 / Revised: 30 September 2019 / Accepted: 12 October 2019 / Published: 14 October 2019
(This article belongs to the Special Issue An Update on Aeromonas)
Aeromonas hydrophila is a well-known bacterial pathogen associated with mass mortalities in aquaculture. Yet, few reports are available on whiteleg shrimp-pathogenic A. hydrophila. In the present study, a virulent isolate WS05 was confirmed as a causative agent of diseased freshwater-cultured whiteleg shrimp and showed a mean lethal dose (LD50) value of 4.8 × 104 CFU mL−1. It was identified phenotypically and molecularly as an A. hydrophila strain, and exhibited susceptibility to several veterinary antibiotics extensively used in aquaculture, including cotrimoxazole, doxycycline, florfenicol, neomycin, and tetracycline. In view of the strongest inhibition zone of florfenicol against isolate WS05, the synergistic effect of the combinations of florfenicol and herb extracts was further evaluated, and the result indicated that Punica granatum extract was a potential synergist of florfenicol against isolate WS05 and the fractional inhibitory concentration index (FICI) for the florfenicol-P. granatum extract was calculated as 0.31. When combined with 7.81 mg mL−1 P. granatum extract, the minimum inhibitory concentration (MIC) of florfenicol against isolate WS05 was reduced from 0.50 to 0.03 mg L−1, and its activity against isolate WS05 was also enhanced with a significant reduction of ≥3.61 log in cell density after 24 h of treatment compared with that in the single drug treatment. In addition, the protective effect was potentiated by the combination of florfenicol and P. granatum extract, with a cumulative mortality of 36.66% (p < 0.05) and 33.33% (p < 0.05) lower than that in the single treatment with florfenicol and P. granatum extract after the challenge with isolate WS05 for seven days. As far as we know, this is the first study to describe whiteleg shrimp-pathogenic A. hydrophila and suggest P. granatum extract as a potential synergist of florfenicol against the A. hydrophila pathogen. View Full-Text
Keywords: Aeromonas hydrophila; Litopenaeus vannamei; Punica granatum; florfenicol; synergist Aeromonas hydrophila; Litopenaeus vannamei; Punica granatum; florfenicol; synergist
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Zhou, H.; Gai, C.; Ye, G.; An, J.; Liu, K.; Xu, L.; Cao, H. Aeromonas hydrophila, an Emerging Causative Agent of Freshwater-Farmed Whiteleg shrimp Litopenaeus vannamei. Microorganisms 2019, 7, 450.

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