Abstract
Six kinds of ELISA procedures consisting of the direct (including double-sandwich method that uses antibodies labelled with alkaline phosphatase) and the indirect method using the avidin-biotin complex system (ABC-ELISA) were compared for the highly sensitive detection of Pseudomonas cepacia (Pc). When bacterial cells were applied directly to the microplates both direct and indirect ELISA were found to be equally sensitive for the detection of Pc and enabled to detect cell suspensions containing ca. 104cfu/ml. Only 22 strains of Pc reacted specifically among the 151 bacterial species tested in direct ELISA using alkaline phosphatase conjugates which were prepared from glutaraldehyde-fixed Pc cells (F), while some of the related species of bacteria reacted in the indirect ELISA. By using the direct ELISA, Pc was detected at a concentration below 104cfu/g soil in 3 kinds of soils which were artificially co-inoculated with either P. solanacearum or Erwinia carotovora subsp. carotovora at the concentration of ca. 105-109cfu/g soil. Furthermore, both the reaction sensitivity and minimum detection level were increased by heating samples at 100°C for 15min and Pc in the soil was detected at the level of ca. 102cfu/g.
