PCR amplification of triosephosphate isomerase gene of Giardia lamblia in formalin-fixed feces.

Giardia lamblia (syn G. intestinalis, G. duodenalis) is the intestinal protozoan producing non-bacterial diarrhea most prevalent in the world. PCR genotype classification of Giardia in feces depends on the quality and quantity of purified DNA and the removal of a great number of inhibitors. The aim of this study was to adapt a PCR protocol to the amplification of the triosephosphate isomerase (tpi) gene of Giardia lamblia in formalin-fixed feces. The tpi gene of G. lamblia was amplified in 28 of the 34 analyzed samples (82.35%) and the B genotype was obtained in all cases. Two major modifications were implemented to improve the performance of PCR from formolated fecal matter. One of these improvements was the use of polyvinylpyrrolidone (PVP) and the other was the addition of bovine serum albumin (BSA). The PCR protocol used in this study showed an amplification percentage exceeding the values reported by other authors with high sensibility and specificity.