2000 Volume 35 Issue 4 Pages 223-228
Distribution of Pseudomonas plecoglossicida in tissues of ayu (Plecoglossus altivelis) challenged by immersion was studied by real-time quantitative polymerase chain reaction (Q-PCR). Fish were immersed in 107 CFU/mL of P. plecoglossicida suspension for 15 min. The fish were sampled at 1, 3, 6, 12, 24, 48, 72 h post-infection (p.i.) and the skin, gills, liver, spleen, kidney and blood were tested by Q-PCR. The skin and gills are likely to be portals of entry for the bacterium since P. plecoglossicida was found as early as 1 and 3 h p.i., respectively. The bacteria became concentrated in the liver, spleen and kidney at 6 h p.i., indicating that P. plecoglossicida can successfully invade ayu within 6 h p.i. Septicemia occurred at 48 h p.i., because high concentrations of the target DNA were abruptly found in the blood of infected fish. The sensitivity of QPCR used here was slightly higher than the culture method to identify subclinically infected fish by P. plecoglossicida. High throughput and turnover time of this assay is useful for monitoring large number of samples and rapid detection.
