Population structure and zoonotic potential of Cryptosporidium parvum in Italy inferred using a multi-locus sequence typing scheme.

Abstract

<h4>Background</h4>The genetic variability of a large collection of European samples of the zoonotic pathogen Cryptosporidium parvum has been recently explored on the basis of a novel multi-locus sequence typing (MLST) scheme. In this work, we assessed the usefulness of this scheme to type C. parvum samples from Italy, a country where this pathogen is widespread and associated with human infections.<h4>Methods</h4>Polymerase chain reaction (PCR) and sequencing for the eight markers of the MLST scheme were performed on 31 human- and 21 animal-derived C. parvum samples. MLST data from 27 samples of animal origin previously sequenced at the genome level were also included. Sequence data for the glycoprotein 60 (gp60) gene were also generated. Phylogenetic and cluster analyses were conducted.<h4>Results</h4>Full genotyping data were obtained for 72 of 79 samples, and 39 different profiles were categorized, 28 of which were found in individual samples (singletons). A new allele was found at the marker on chromosome 2 in a human-derived sample. When compared with the 154 profiles previously described in Europe, 30 of the 39 profiles (76%) were found to be restricted to Italy, a result compatible with a model of isolation by distance, with geographically structured populations. Analysis of the gp60 sequences identified 19 different subtypes among the 55 samples belonging to family IIa, and 7 different subtypes among the 16 samples belonging to family IId. Phylogenetic and haplotype analyses did not identify clusters related to the host, the geographic origin (i.e., the Italian regions), or the time of collection of the samples but did identify two different populations, mirroring data obtained from whole genome comparative analyses.<h4>Conclusions</h4>The MLST scheme appears to be a promising method for genotyping C. parvum samples, as it provided higher discrimination compared with gp60 and enabled the recognition of the two major populations circulating in Europe and in Italy.