INTERNATIONAL JOURNAL OF AGRICULTURAL TECHNOLOGY

Volume 14, No. 07, Month DECEMBER, Year 2018, Pages 1115 - 1128

Virulence factor gene profiles of aeromonas veronii isolated from diseased nile tilapia (oreochromis niloticus) in nakhon si thammarat province and its expression towards diurnal water temperature changes

Chirapongsatonkul, N., Srichanun, M. and U-taynapun, K.

Abstract Download PDF

Aeromonas spp. is the causing agent of motile Aeromonas septicemia (MAS) which cause a great loss in Nile tilapia (Oreochromis niloticus) farming. More than 200 bacteria were isolated from Nile tilapia exhibiting MAS disease in Nakhon Si Thammarat province, an important tilapia culturing area in Southern Thailand, since 2014–2017. Every collected isolates was Gram-negative and short rod-shaped. Three isolates of bacteria, A2014–1, A2015–8 and A2016–28, were randomly selected. Characterization based on molecular cloning indicated that all 3 isolates were A. veronii. This present study aimed to elucidate the appearance of 5 virulence factor genes considerably relevant to pathogenesis including lipase, elastase, enolase, aerolysin (aerA), and heat-labile cytotonic enterotoxin (alt) in these 3 isolates. The differences in virulence factor gene profiles were detected; lipase–/elastase+/enolase+/aerA–/alt+, lipase+/elastase+/enolase+/aerA+/alt+ and lipase–/elastase+/enolase+/aerA+/alt+ for A2014–1, A2015–8 and A2016–28, respectively. Moreover, the effects of diurnal water temperature change of 2 different patterns, which were actually recorded from the tilapia culturing pond, on the bacterial growth and the mRNA expression level of the virulence factor genes were determined. The variable paatern of the bacterial growth as well as the expression of virulence factor genes were noticed. These data preliminary suggested the diversity of bacterial genotypes especially that of virulence factor gene profiles in the Aeromonas spp. causing MAS in Southern Thailand. However, the relationship between the chage of temperature and the bacteria growth, virulence and pathogenecity will be further studied.

Keywords

motile Aeromonas septicemia (MAS), Aeromonas veronii, Oreochromis niloticus, virulence factor genes, diurnal water temperature change

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