Development and validation of a quantitative PCR assay using multiplexed hydrolysis probes for detection and quantification of Theileria orientalis isolates and differentiation of clinically relevant subtypes.

Theileria orientalis is an emerging pathogen of cattle in Asia, Australia, and New Zealand. This organism is a vector-borne hemoprotozoan that causes clinical disease characterized by anemia, abortion, and death, as well as persistent subclinical infections. Molecular methods of diagnosis are preferred due to their sensitivity and utility in differentiating between pathogenic and apathogenic genotypes. Conventional PCR (cPCR) assays for T. orientalis detection and typing are laborious and do not provide an estimate of parasite load. Current real-time PCR assays cannot differentiate between clinically relevant and benign genotypes or are only semiquantitative without a defined clinical threshold. Here, we developed and validated a hydrolysis probe quantitative PCR (qPCR) assay which universally detects and quantifies T. orientalis and identifies the clinically associated Ikeda and Chitose genotypes (UIC assay). Comparison of the UIC assay results with previously validated universal and genotype-specific cPCR results demonstrated that qPCR detects and differentiates T. orientalis with high sensitivity and specificiy. Comparison of quantitative results based on percent parasitemia, determined via blood film analysis and packed cell volume (PCV) revealed significant positive and negative correlations, respectively. One-way analysis of variance (ANOVA) indicated that blood samples from animals with clinical signs of disease contained statistically higher concentrations of T. orientalis DNA than animals with subclinical infections. We propose clinical thresholds to assist in classifying high-, moderate-, and low-level infections and describe how parasite load and the presence of the Ikeda and Chitose genotypes relate to disease.

Whole-genome analysis of extraintestinal Escherichia coli sequence type 73 from a single hospital over a 2 year period identified different circulating clonal groups.

Sequence type (ST)73 has emerged as one of the most frequently isolated extraintestinal pathogenic Escherichia coli. To examine the localized diversity of ST73 clonal groups, including their mobile genetic element profile, we sequenced the genomes of 16 multiple-drug resistant ST73 isolates from patients with urinary tract infection from a single hospital in Sydney, Australia, between 2009 and 2011. Genome sequences were used to generate a SNP-based phylogenetic tree to determine the relationship of these isolates in a global context with ST73 sequences (n=210) from public databases. There was no evidence of a dominant outbreak strain of ST73 in patients from this hospital, rather we identified at least eight separate groups, several of which reoccurred, over a 2 year period. The inferred phylogeny of all ST73 strains (n=226) including the ST73 clone D i2 reference genome shows high bootstrap support and clusters into four major groups that correlate with serotype. The Sydney ST73 strains carry a wide variety of virulence-associated genes, but the presence of iss, pic and several iron-acquisition operons was notable.

Prevalence of Theileria orientalis types in beef cattle herds on the North Coast of New South Wales.

OBJECTIVE: To estimate the prevalence of Theileria orientalis infection for Chitose, Ikeda and Buffeli major piroplasm surface protein (MPSP) types at a herd- and animal-level in beef cattle in the North Coast Livestock Health and Pest Authority (NCLHPA) region of New South Wales (NSW). METHODS: A total of 24 beef herds in the NCLHPA region containing more than 100 cattle were randomly selected. Blood samples were collected from five animals per herd and tested using Theileria PCR for Chitose, Buffeli and Ikeda. Samples were only taken from female cattle older than 2 years, born in the NCLHPA region and apparently healthy at the time of testing. RESULTS: The herd-level prevalence for all MPSP types (Chitose, Ikeda and Buffeli) was 100%, with a 95% confidence interval of 86.3-99.9%. The mean prevalence at an animal level was 83.3%, 92.5% and 95.0% for Theileria Chitose, Buffeli and Ikeda, respectively. Quantitative PCR testing showed that 81.9% of animals had a low-level infection, while 17.0% had a moderate level of infection, and only 1.0% had a high level of infection. The majority of animals had a mixed infection of two or three MPSP types and few animals showed single infection. CONCLUSION: The results indicate endemicity of T. orientalis, especially the Ikeda type, in the NCLHPA region of Australia.

Temporal dynamics and subpopulation analysis of Theileria orientalis genotypes in cattle.

In Australia, outbreaks of clinical theileriosis caused by Theileria orientalis have been largely associated with the Ikeda genotype which can occur as a sole infection, or more commonly, as a mixture of genotypes. The most prevalent genotype, Chitose, frequently co-occurs with type Ikeda, however the role of this genotype in clinical disease has not been clearly established. Furthermore, the dynamics of individual genotypes in field infection of cattle have not been examined. In this study we developed quantitative PCR (qPCR) and genotyping methods to examine the role of the Chitose genotype in clinical disease and to investigate the temporal dynamics of T. orientalis Ikeda, Chitose and Buffeli genotypes in naïve animals introduced to a T. orientalis-endemic area. Analysis of the major piroplasm surface protein (MPSP) genes of Chitose isolates revealed the presence of two distinct phylogenetic clusters, Chitose A and Chitose B. A genotyping assay aimed at determining Chitose A/B allele frequency revealed that the Chitose A phylogenetic cluster is strongly associated with clinical disease but nearly always co-occurs with the Ikeda genotype. qPCR revealed that the Chitose genotype (particularly Chitose A), undergoes temporal switching in conjunction with the Ikeda genotype and contributes substantially to the overall parasite burden. The benign Buffeli genotype can also undergo temporal switching but levels of this genotype appear to remain low relative to the Ikeda and Chitose types. Interplay between vector and host immunological factors is presumed to be critical to the population dynamics observed in this study. Genotypic switching likely contributes to the persistence of T. orientalis in the host.

Development and validation of an inexpensive and efficient method for the extraction of Theileria orientalis DNA from blood.

Theileria orientalis is an emerging bovine pathogen in Australasia. PCR-based detection methods for this parasite are sensitive but relatively expensive, partly due to costs associated with DNA extraction. An inexpensive and efficient technique was developed for the extraction of T. orientalis DNA from blood based on hypotonic erythrocyte lysis and detergent-proteinase K treatment (DPK method). The DPK method compares favourably to a commercial extraction kit when paired with a T. orientalis multiplex qPCR.