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Aeromonas spp., which inhabits freshwater and marine water bodies, can be responsible for the diseases and mortalities of many different cultured fishes. In this study, the antibiotic susceptibility profiles of 20 Aeromonas hydrophila strains isolated from diseased freshwater fish cultured in the Red River Delta, Vietnam were categorised as non-wild-type (non-WT) strains or were resistant to at least one antibiotic. Also, in-vitro antibacterial activities of extracts from two local plants against several antibiotic-resistant A. hydrophila strains were done to screen for potential bio-antibiotic materials. The antibiotic susceptibility results showed that 25 % of bacterial strains were resistant to 3–9 antibiotics, 35 % to 2 antibiotics, and 10 % to one antibiotic. Both plants, rose myrtle seed, Rhodomyrtus tomentosa Hassk, 1842, extract and fermented garlic, Allium sativum Linnaeus, 1753, supernatant, showed inhibitory activities against antibiotic-resistant A. hydrophila strains. Furthermore, the R. tomentosa extract and the fermented A. sativum supernatant exhibited significant antibacterial effects to several A. hydrophila strains, namely A. hydrophila CEDMA17.021, CEDMA17.002, CEDMA17.008, and CEDMA17.009 resistant to two or more antibiotics. This study demonstrated multiple resistant profiles of A. hydrophila strains to different antibiotics and the inhibitory activities of R. tomentosa extract and the fermented A. sativum supernatant against antibiotic-resistant A. hydrophila strains. Hence, this study indicates the potential use of bio-antibiotics derived from plants to manage Aeromonas-related infections. [ABSTRACT FROM AUTHOR]

The envelope protein VP28 of white spot syndrome virus ( WSSV) is considered a candidate antigen for use in a potential vaccine to this important shrimp pathogen (the cause of white spot syndrome, WSS). Here, we used spores of Bacillus subtilis to display VP28 on the spore surface. Trials were conducted to evaluate their ability to protect shrimps against WSSV infection. The gene cotB-vp28 was integrated into the chromosome of the laboratory strain B. subtilis PY79, and expression of Cot B- VP28 was detected by Western blotting and immunofluorescence. Expression of Cot B- VP28 was equivalent to 1000 molecules per spore. PY79 and Cot B- VP28 spores were mixed with pellets for feeding of whiteleg shrimps ( Litopenaeus vannamei), followed by WSSV challenge. Superoxidase dismutase ( SOD), phenoloxidase activities and mortality rates of the two shrimp groups were evaluated. Groups fed with PY79 and Cot B- VP28 spores at day 7 had increased SOD activities of 29% and increased phenoloxidase activities of 15% and 33%, respectively, compared to those of the control group. Fourteen days postchallenge, 35% of vaccinated shrimps had died compared to 49% of those fed naked spores ( PY79) and 66% untreated, unchallenged animals. These data suggest that spores expressing VP28 have potential as a prophylactic treatment of WSS. [ABSTRACT FROM AUTHOR]