Experiences on the application of the polymerase chain reaction in a diagnostic laboratory.

Double polymerase chain reaction (PCR) assays with nested primers have been applied in a routine laboratory for the diagnosis of herpes-, pesti- and retroviral infections of animals. Various methods and tools have been tested to prevent and to eliminate false positive results as well as to visualize the PCR products (amplicons). The u.v. and DNase treatments proved to be unsuitable for decontamination of PCR mixtures contaminated with amplicons shorter than 380 bp. By constructing special tube-holders and openers, and by applying a simple technique of pipetting, the false-positive PCR results were eliminated. The PCR products were visualized by three simple methods. The solid phase colorimetric method termed 'Detect Immobilized Amplified DNA' (DIANA) has been adapted to microplate. The other method, termed 'Colorimetric Detection Assay on Filter' (CODAF), proved to be very rapid. However, despite these advantages of DIANA and CODAF, henceforward the nucleic acid hybridization methods were found most reliable for safe identification of PCR amplicons. In order to simplify the hybridization, various non-radioactive labelling methods of oligonucleotide probes were compared. Biotinylation at the 5' end by means of oligonucleotide synthesis was the most simple and practical labelling method in this laboratory. The routine applicability of hybridization was further simplified by constructing a robot device, which automatically performs filter-hybridization and subsequently develops the signals derived from the biotinylated hybrids.