title: Discrimination of gastrointestinal nematode eggs from crude fecal egg preparations by inhibitor-resistant conventional and real-time PCR.
abstract: Diagnosis of gastrointestinal nematodes relies predominantly on coproscopic methods such as flotation, Kato-Katz, McMaster or FLOTAC. Although FLOTAC allows accurate quantification, many nematode eggs can only be differentiated to genus or family level. Several molecular diagnostic tools discriminating closely related species suffer from high costs for DNA isolation from feces and limited sensitivity since most kits use only small amounts of feces (<1 g). A direct PCR from crude egg preparations was designed for full compatibility with FLOTAC to accurately quantify eggs per gram feces (epg) and determine species composition. Eggs were recovered from the flotation solution and concentrated by sieving. Lysis was achieved by repeated boiling and freezing cycles - only Trichuris eggs required additional mechanic disruption. Egg lysates were directly used as template for PCR with Phusion DNA polymerase which is particularly resistant to PCR inhibitors. Qualitative results were obtained with feces of goats, cattle, horses, swine, cats, dogs and mice. The finally established protocol was also compatible with quantitative real-time PCR in the presence of EvaGreen and no PCR inhibition was detectable when extracts were diluted at least fourfold. Sensitivity was comparable to DNA isolation protocols and spiked samples with five epg were reliably detected. For Toxocara cati a detection limit below one epg was demonstrated. It was possible to distinguish T. cati and Toxocara canis using high resolution melt (HRM) analysis, a rapid tool for species identification. In human samples, restriction fragment length polymorphism (RFLP) and HRM analysis were used to discriminate Necator americanus and Ancylostoma duodenale. The method is able to significantly improve molecular diagnosis of gastrointestinal nematodes by increasing speed and sensitivity while decreasing overall costs. For identification of species or resistance alleles, analysis of PCR products with many different post PCR methods can be used such as RFLP, reverse-line-blot, Sanger sequencing and HRM.
authors.affiliation: Institute for Parasitology and Tropical Veterinary Medicine, Freie Universität Berlin, Berlin, Germany.
authors.forename: Janina
authors.initials: J
authors.lastname: Demeler
authors.forename: Sabrina
authors.initials: S
authors.lastname: Ramünke
authors.forename: Sonja
authors.initials: S
authors.lastname: Wolken
authors.forename: Davide
authors.initials: D
authors.lastname: Ianiello
authors.forename: Laura
authors.initials: L
authors.lastname: Rinaldi
authors.forename: Jean Bosco
authors.initials: JB
authors.lastname: Gahutu
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Cringoli
authors.forename: Georg
authors.initials: G
authors.lastname: von Samson-Himmelstjerna
authors.forename: Jürgen
authors.initials: J
authors.lastname: Krücken
mesh_terms: D000818:Animals; D018509:DNA, Helminth / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D004795:Enzyme Stability; D005243:Feces / Q000469:parasitology*; D041981:Gastrointestinal Tract / Q000469:parasitology*; D006801:Humans; D009348:Nematoda / Q000302:isolation & purification*; D009691:Nucleic Acid Denaturation; D010063:Ovum / Q000166:cytology*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D013045:Species Specificity; D013696:Temperature; D013698:Templates, Genetic
chemical_list: D018509:DNA, Helminth; D004259:DNA-Directed DNA Polymerase