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Author: search.filters.author.Srisapoome, P.

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    Molecular serotyping, virulence gene profiling and pathogenicity of Streptococcus agalactiae isolated from tilapia farms in Thailand by multiplex PCR
    (2017-06-01)
    Kannika, K.
    ;
    Pisuttharachai, D.
    ;
    Srisapoome, P.
    ;
    Wongtavatchai, J.
    ;
    Kondo, H.
    Aims: This study aimed to biotype Streptococcus agalactiae isolated from tilapia farms in Thailand based on molecular biotyping methods and to determine the correlation between the serotype and virulence of bacteria. In addition to a biotyping (serotyping) technique based on multiplex PCR of cps genes, in this study, we developed multiplex PCR typing of Group B streptococcus (GBS) virulence genes to examine three clusters of virulence genes and their correlation with the pathogenicity of S. agalactiae. The epidemiology of S. agalactiae in Thailand was analysed to provide bacterial genetic information towards a future rational vaccine strategy for tilapia culture systems. Methods and Results: Streptococcus agalactiae were isolated from diseased tilapia from different areas of Thailand. A total of 124 S. agalactiae isolates were identified by phenotypic analysis and confirmed by 16S rRNA PCR. Bacterial genotyping was conducted based on (i) molecular serotyping of the capsular polysaccharide (cps) gene cluster and (ii) virulence gene profiling using multiplex PCR analysis of 14 virulence genes (lmb, scpB, pavA, cspA, spb1, cyl, bca, rib, fbsA, fbsB, cfb, hylB, bac and pbp1A/ponA). Only serotypes Ia and III were found in this study; serotype Ia lacks the lmb, scpB and spb1 genes, whereas serotype III lacks only the bac gene. Virulence tests in juvenile Nile tilapia demonstrated a correlation between the pathogenicity of the bacteria and their virulence gene profile, with serotype III showing higher virulence than serotype Ia. Epidemiological analysis showed an almost equal distribution in all regions of Thailand, except serotype III was found predominantly in the southern areas. Conclusions: Only two serotypes of S. agalactiae were isolated from diseased tilapia in Thailand. Serotype Ia showed fewer virulence genes and lower virulence than serotype III. Both serotypes showed a similar distribution throughout Thailand. Significance and Impact of the Study: We identified two major serotypes of S. agalactiae isolates associated with the outbreak in tilapia culture in Thailand. We developed multiplex PCR assays for 14 virulence genes, which may be used to predict the pathogenicity of the isolates and track future infections. Multiplex PCR typing of the GBS virulence genes was developed and might be further used to predict the pathogenicity of S. agalactiae.
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    Waterborne and cannibalism-mediated transmission of the Yellow head virus in Penaeus monodon
    (2015-02-01)
    Hamano, K.
    ;
    Miyoshi, T.
    ;
    Aue-umneoy, D.
    ;
    Srisapoome, P.
    ;
    Maeno, Y.
    Disease outbreaks caused by yellow head virus (YHV) can result in significant economic losses for shrimp aquaculture; however, little is known about how YHV is transmitted. Here we evaluate the role of direct and indirect contact with YHV among Penaeus monodon. One in 3 specimens released into 5 experimental tanks was inoculated with the virus, and 100. μm-filtered water from each tank was allowed to circulate through another tank containing an additional set of 3 naive P. monodon. All of the injected shrimps died within 4. d; 9 of the 10 shrimps cohabitating with them died within 10. d. Only 5 of the 15 shrimps in the water-exposed tanks died within 14. d. As determined by RT-nested PCR, YHV infection was also lower among shrimp exposed to water. To assess the potential of moribund shrimp to transmit disease, gill samples from individuals inoculated with YHV at either 12. h or 24. h after the onset of the first obvious signs of morbidity were injected into naïve P. monodon housed in individual tanks. Over a 30-d period following inoculation, the mortality rate was higher among shrimps injected with 12. h gill extracts than in those injected with 24. h gill extracts. Taken together, these data suggest that cannibalism of moribund shrimps presents a far greater potential to transmit the yellow head disease than does water exposure alone. Removing moribund shrimps as soon as morbidity becomes evident could represent an efficient measure to reduce YHV transmission and disease outbreaks.
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