Utility of the Ribosomal Gene 18S rRNA in the Classification of the Main House Dust Mites Involved in Hypersensitivity

Between 1% and 2% of the world's population is sensitised to mites. Aetiological diagnosis is key to the management of allergic patients. However, methods based solely on morphological criteria are ambiguous in many cases. Polymerase chain reaction of ribosomal genes represents a valuable complementary approach. The 5 most representative species (<i>Dermatophagoides pteronyssinus</i>, <i>Dermatophagoides farinae</i>, <i>Tyrophagus putrescentiae</i>, <i>Blomia tropicalis</i> and <i>Lepidoglyphus destructor</i>) were selected as sources of allergens. They were first identified morphologically and the 18S rRNA gene sequences were obtained from the GenBank database. Alignment of the nucleotide sequences of the 18S rRNA ribosomal gene enabled the identification of the conserved and divergent regions in all of them. The alignment allowed the design of a pair of oligonucleotides in conserved regions of the gene, to amplify the sequence of interest in each of the species. We performed genomic DNA extraction, quantification and purity. PCR, using oligonucleotides designed to amplify the 18S sequence fragment of interest, showed the exact size for each species. Amplification, efficiency curves and melting points resulting from the amplification of the 18S amplicon of the five species were obtained. The oligonucleotides designed for real-time PCR studies, allow species identification by amplifying the specific fragment of each species using real-time PCR.