Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine: Brussels, Belgium. 15-18 March 2016

[This corrects the article DOI: 10.1186/s13054-016-1208-6.].

Specific and quantitative detection and identification of Cryptosporidium hominis and C. parvum in clinical and environmental samples

Cryptosporidium is an enteric protozoan parasite that is resistant to inactivation by commonly used drinking water disinfectants. Between 2004 and 2010, it was responsible for 60% of all waterborne protozoan parasitic outbreaks reported worldwide. Most sporadic infections in humans and almost all outbreaks are caused by Cryptosporidium parvum and Cryptosporidium hominis. We report the development and validation of a quantitative qPCR assay using minor groove binder (MGB)-probes targeting a unique Cryptosporidium specific protein-coding gene, that directly detects, quantitates and identifies C. hominis and C. parvum in environmental and faecal samples. An internal amplification control (IAC) was also developed and included in this assay. The qPCR assay was compared with an 18S nested PCR assay for sensitivity and specificity. The analytical sensitivity for the qPCR assay was 1 oocyst and 1-10 oocysts for the 18S assay. Evaluation of analytical specificity of the qPCR assay revealed no cross-reactions with other genera and detected all C. parvum and C. hominis isolates correctly. The diagnostic sensitivity and specificity of the qPCR was 100% compared to 96.9% and 98.4%, respectively for the 18S assay. The qPCR assay was also highly reproducible with RSD (relative standard deviation) values of 1.4-9.4%, when the assay was performed by four different technicians. When tested on water samples, the qPCR assay was more sensitive than the 18S assay, detecting positives in 37 of 138 water samples compared to 35 for the 18S locus. This qPCR assay should be a valuable tool for the detection and differentiation of C. hominis and C. parvum in both clinical and environmental samples.

Insecticide detoxification indicator strains as tools for enhancing chemical discovery screens

BACKGROUND

Insecticide discovery screens carried out on whole organisms screen for potency resulting from chemical activity at the target site. However, many potentially insecticidal compounds are naturally detoxified in vivo and do not make it to the target site. It is hypothesised that insect strains with their xenobiotic detoxification machinery compromised could be used to identify such compounds that normally fail to show up in screens; these compounds could then be more rationally designed to increase their bioavailability. This strategy was tested with transgenic Drosophila lines with altered expression of Cyp6g1 and Dhr96.

RESULTS

It was observed that Cyp6g1 knockdown transgenic lines have increased susceptibility to the test compound imidacloprid, while Dhr96 knockdown transgenic lines are resistant. Evidence was found for a systemic response to xenobiotic exposure, uncovered by piperonyl butoxide treatment and by gene expression profiling. Sex-specific gene expression regulated by DHR96 was also observed.

CONCLUSION

The results confirm that this approach to chemical discovery could identify compounds that escape traditional screens. The complexity of the system means that a panel of single and multiple gene knockdown transgenic lines may be required.

Meeting report: Application of genotyping methods to assess risks from cryptosporidium in watersheds

A workshop titled "Application of Genotyping Methods to Assess Pathogen Risks from Cryptosporidium in Drinking Water Catchments" was held at the International Water Association biennial conference, Marrakech, Morocco, 23 September 2004. The workshop presented and discussed the findings of an interlaboratory trial that compared methods for genotyping Cryptosporidium oocysts isolated from feces. The primary goal of the trial and workshop was to assess the utility of current Cryptosporidium genotyping methods for determining the public health significance of oocysts isolated from feces in potable-water-supply watersheds. An expert panel of 16 watershed managers, public health practitioners, and molecular parasitologists was assembled for the workshop. A subordinate goal of the workshop was to educate watershed management and public health practitioners. An open invitation was extended to all conference delegates to attend the workshop, which drew approximately 50 interested delegates. In this report we summarize the peer consensus emerging from the workshop. Recommendations on the use of current methods by watershed managers and public health practitioners were proposed. Importantly, all the methods that were reported in the trial were mutually supporting and found to be valuable and worthy of further utility and development. Where there were choices as to which method to apply, the small-subunit ribosomal RNA gene was considered to be the optimum genetic locus to target. The single-strand conformational polymorphism method was considered potentially the most valuable for discriminating to the subtype level and where a large number of samples were to be analyzed. A research agenda for protozoan geneticists was proposed to improve the utility of methods into the future. Standardization of methods and nomenclature was promoted.

Direct comparison of selected methods for genetic categorisation of Cryptosporidium parvum and Cryptosporidium hominis species

A study was undertaken to compare the performance of five different molecular methods (available in four different laboratories) for the identification of Cryptosporidium parvum and Cryptosporidium hominis and the detection of genetic variation within each of these species. The same panel of oocyst DNA samples derived from faeces (n=54; coded blindly) was sent for analysis by: (i) DNA sequence analysis of a fragment of the HSP70 gene; (ii) DNA sequence analysis and the ssrRNA gene in laboratory 1; (iii) single-strand conformation polymorphism analysis of part of the ssrRNA; (iv) SSCP analysis of the second internal transcribed spacer (ITS-2) of nuclear ribosomal DNA region in laboratory 2; (v) 60 kDa glycoprotein (gp60) gene sequencing with prior species determination using PCR with restriction fragment length polymorphism analysis of the ssrRNA gene in laboratory 3; and (vi) multilocus genotyping at three microsatellite markers in laboratory 4. For detecting variation within C. parvum and C. hominis, SSCP analysis of ITS-2 was considered to have superior utility and determined 'subgenotypes' in samples containing DNA from both species. SSCP was also most cost effective in terms of time, cost and consumables. Sequence analysis of gp60 and microsatellite markers ML1, ML2 and 'gp15' provided good comparators for the SSCP of ITS-2. However, applicability of these methods to other Cryptosporidium species or genotypes and to environmental samples needs to be evaluated. This trial provided, for the first time, a direct comparison of multiple methods for the genetic characterisation of C. parvum and C. hominis samples. A protocol has been established for the international distribution of samples for the characterisation of Cryptosporidium. This can be applied in further evaluation of molecular methods by investigation of a larger number of unrelated samples to establish sensitivity, typability, reproducibility and discriminatory power based on internationally accepted methods for evaluation of microbial typing schemes.

Calcium receptor messenger ribonucleic acid levels in the parathyroid glands and kidney of vitamin D-deficient rats are not regulated by plasma calcium or 1,25-dihydroxyvitamin D3

The level of extracellular ionized calcium ([Ca2+]o) is the primary physiological regulator of PTH secretion. Complementary DNAs encoding the calcium receptor (CaR) protein that mediates this response have been cloned from bovine and human parathyroid glands. This protein is a seven-transmembrane, G-protein-coupled receptor linked to the mobilization of intracellular Ca2+ in response to increases in [Ca2+]o. More recently, a rat kidney CaR has been cloned and shown to be 92% identical at the amino acid level to the bovine parathyroid CaR. Homologous or heterologous regulation of the expression and/or function of a variety of G-protein-coupled receptors has been documented in numerous cell types. Therefore, we determined whether [Ca2+]o and 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], major regulators of PTH synthesis and secretion, affect CaR gene expression in parathyroid gland and kidney in rats. CaR messenger RNA (mRNA) levels were quantified in pairs of parathyroid glands and single kidneys from individual animals using a solution hybridization assay. The effects of Ca2+ and 1,25-(OH)2D3 on CaR gene expression were assessed independently in vitamin D-deficient (-D) rats. A wide range of plasma Ca2+ levels (0.7-1.9 mM) was produced by supplementing -D diets with varying amounts of calcium and by infusing CaCl2 i.v. for 7 days using osmotic minipumps. There was no correlation between plasma Ca2+ levels and steady state CaR mRNA levels in parathyroid gland (r = -0.18) or kidney (r = 0.25). In another group of -D rats, 1,25-(OH)2D3 was infused sc at 25 and 275 ng/kg.day for 10-12 days. Dietary calcium was adjusted to maintain normocalcemia in some of the groups. No effect of 1,25-(OH)2D3 administration on CaR mRNA levels occurred in parathyroid glands or kidney regardless of the resultant plasma Ca2+ or 1,25-(OH)2D3 levels. In conclusion, neither parathyroid gland nor kidney CaR mRNA levels are regulated by plasma Ca2+ and 1,25-(OH)2D3 levels in the experimental models examined here.