Distribution of giardia duodenalis assemblages A and B among children living in a remote Indigenous Community of the Northern Territory, Australia

Giardiasis is a communicable gastrointestinal disease caused by Giardia duodenalis and two genetic assemblages, A and B, cause human infection. In remote Indigenous communities of Australia, giardiasis is highly prevalent among children but disease transmission is poorly understood. This study investigated the prevalence of Giardia and genetic subtypes contributing to human disease in a remote Indigenous community, in the Northern Territory of Australia. Eighty-seven faecal samples were collected from 74 children (<15 years) over an 18 month period, and the distribution of positive cases relative to participant age and gender were examined. Screening by microscopy and 18S rRNA PCR amplification showed 66.7% (58/87) of faecal samples were positive for Giardia. Both males and females were equally affected and high detection rates were obtained for participants aged 0–<5 years and 5–<10 years (66.0 and 60.0% respectively). For 58.6% of the positive samples, Giardia was only detected by 18S rRNA PCR. Approximately 75% of cases were assemblage B, and subassemblage analyses using terminal restriction fragment length polymorphism of the glutamate dehydrogenase gene demonstrated that a variety of genetic variants were present. The high proportion of positive cases that were not detectable by microscopy, and dominance of assemblage B cases highlights the need for further research in this community, to assess the contribution of Giardia to chronic gastrointestinal disease among children, and to understand conditions conductive to assemblage B transmission

An Aspartic Protease of the Scabies Mite Sarcoptes scabiei Is Involved in the Digestion of Host Skin and Blood Macromolecules

BackgroundScabies is a disease of worldwide significance, causing considerable morbidity in both humans and other animals. The scabies mite Sarcoptes scabiei burrows into the skin of its host, obtaining nutrition from host skin and blood. Aspartic proteases mediate a range of diverse and essential physiological functions such as tissue invasion and migration, digestion, moulting and reproduction in a number of parasitic organisms. We investigated whether aspartic proteases may play role in scabies mite digestive processes.Methodology/Principle FindingsWe demonstrated the presence of aspartic protease activity in whole scabies mite extract. We then identified a scabies mite aspartic protease gene sequence and produced recombinant active enzyme. The recombinant scabies mite aspartic protease was capable of digesting human haemoglobin, serum albumin, fibrinogen and fibronectin, but not collagen III or laminin. This is consistent with the location of the scabies mites in the upper epidermis of human skin.Conclusions/SignificanceThe development of novel therapeutics for scabies is of increasing importance given the evidence of emerging resistance to current treatments. We have shown that a scabies mite aspartic protease plays a role in the digestion of host skin and serum molecules, raising the possibility that interference with the function of the enzyme may impact on mite survival

Quantitative PCR-based genome size estimation of the astigmatid mites Sarcoptes scabiei, Psoroptes ovis and Dermatophagoides pteronyssinus

Background: The lack of genomic data available for mites limits our understanding of their biology. Evolving high-throughput sequencing technologies promise to deliver rapid advances in this area, however, estimates of genome size are initially required to ensure sufficient coverage. Methods. Quantitative real-time PCR was used to estimate the genome sizes of the burrowing ectoparasitic mite Sarcoptes scabiei, the non-burrowing ectoparasitic mite Psoroptes ovis, and the free-living house dust mite Dermatophagoides pteronyssinus. Additionally, the chromosome number of S. scabiei was determined by chromosomal spreads of embryonic cells derived from single eggs. Results: S. scabiei cells were shown to contain 17 or 18 small (< 2 M) chromosomes, suggesting an XO sex-determination mechanism. The average estimated genome sizes of S. scabiei and P. ovis were 96 ( 7) Mb and 86 ( 2) Mb respectively, among the smallest arthropod genomes reported to date. The D. pteronyssinus genome was estimated to be larger than its parasitic counterparts, at 151 Mb in female mites and 218 Mb in male mites. Conclusions: This data provides a starting point for understanding the genetic organisation and evolution of these astigmatid mites, informing future sequencing projects. A comparitive genomic approach including these three closely related mites is likely to reveal key insights on mite biology, parasitic adaptations and immune evasion

Prospective Study in a Porcine Model of Sarcoptes scabiei Indicates the Association of Th2 and Th17 Pathways with the Clinical Severity of Scabies

BackgroundUnderstanding of scabies immunopathology has been hampered by the inability to undertake longitudinal studies in humans. Pigs are a useful animal model for scabies, and show clinical and immunologic changes similar to those in humans. Crusted scabies can be readily established in pigs by treatment with the glucocorticoid dexamethasone (Dex).Methodology/ Principal FindingsProspective study of 24 pigs in four groups: a) Scabies+/Dex+, b) Scabies+/Dex-, c) Scabies-/Dex+ and d) Scabies-/Dex-. Clinical symptoms were monitored. Histological profiling and transcriptional analysis of skin biopsies was undertaken to compare changes in cell infiltrates and representative cytokines. A range of clinical responses to Sarcoptes scabiei were observed in Dex treated and non-immunosuppressed pigs. An association was confirmed between disease severity and transcription of the Th2 cytokines IL-4 and IL-13, and up-regulation of the Th17 cytokines IL-17 and IL-23 in pigs with crusted scabies. Immunohistochemistry revealed marked infiltration of lymphocytes and mast cells, and strong staining for IL-17.Conclusions/ SignificanceWhile an allergic Th2 type response to scabies has been previously described, these results suggest that IL-17 related pathways may also contribute to immunopathology of crusted scabies. This may lead to new strategies to protect vulnerable subjects from contracting recurrent crusted scabies

Heterogeneous ketonic decarboxylation of dodecanoic acid: studying reaction parameters

Ketonic decarboxylation has gained significant attention in recent years as a pathway to reduce the oxygen content within biomass-derived oils, and to produce sustainable ketones. The reaction is base catalysed, with MgO an economic, accessible and highly basic heterogeneous catalyst. Here we use MgO to catalyse the ketonic decarboxylation of dodecanoic acid to form 12-tricosanone at moderate temperatures (250 °C, 280 °C and 300 °C) with low catalyst loads of 1% (w/w), 3% (w/w) and 5% (w/w) with respect to the dodecanoic acid, with a reaction time of 1 hour under batch conditions. Three different particle sizes for the MgO were tested (50 nm, 100 nm and 44 μm). Ketone yield was found to increase with increasing reaction temperature, reaching approximately 75% yield for all the samples tested. Temperature was found to be the main control on reaction yield, rather than surface area or particle size

Chlamydia trachomatis genotypes in a cross-sectional study of urogenital samples from remote Northern and Central Australia

his is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/Abstract OBJECTIVES: The objective was to determine the frequency of trachoma genotypes of Chlamydia trachomatis-positive urogenital tract (UGT) specimens from remote areas of the Australian Northern Territory (NT). SETTING: The setting was analysis of remnants of C. trachomatis positive primarily UGT specimens obtained in the course of clinical practice. The specimens were obtained from two pathology service providers. PARTICIPANTS: From 3356 C. trachomatis specimens collected during May 2012-April 2013, 439 were selected for genotyping, with a focus on specimens from postpubescent patients, in remote Aboriginal communities where ocular trachoma is potentially present. PRIMARY AND SECONDARY OUTCOME MEASURES: The primary outcome measure was the proportion of successfully genotyped UGT specimens that were trachoma genotypes. The secondary outcome measures were the distribution of genotypes, and the frequencies of different classes of specimens able to be genotyped. RESULTS: Zero of 217 successfully genotyped UGT specimens yielded trachoma genotypes (95% CI for frequency=0-0.017). For UGT specimens, the genotypes were E (41%), F (22%), D (21%) and K (7%), with J, H and G and mixed genotypes each at 1-4%. Four of the five genotyped eye swabs yielded trachoma genotype Ba, and the other genotype J. Two hundred twenty-two specimens (50.6%) were successfully genotyped. Urine specimens were less likely to be typable than vaginal swabs (p<0.0001). CONCLUSIONS: Unlike in some other studies, in the remote NT, trachoma genotypes of C. trachomatis were not found circulating in UGT specimens from 2012 to 2013. Therefore, C. trachomatis genotypes in UGT specimens from young children can be informative as to whether the organism has been acquired through sexual contact. We suggest inclusion of C. trachomatis genotyping in guidelines examining the source of sexually transmitted infections in young children in areas where trachoma genotypes may continue to circulate, and continued surveillance of UGT C. trachomatis genotypes

Bidirectional Interactions between Antigen-bearing Respiratory Tract Dendritic Cells (DCs) and T Cells Precede the Late Phase Reaction in Experimental Asthma: DC Activation Occurs in the Airway Mucosa but Not in the Lung Parenchyma

The airway mucosal response to allergen in asthma involves influx of activated T helper type 2 cells and eosinophils, transient airflow obstruction, and airways hyperresponsiveness (AHR). The mechanism(s) underlying transient T cell activation during this inflammatory response is unclear. We present evidence that this response is regulated via bidirectional interactions between airway mucosal dendritic cells (AMDC) and T memory cells. After aerosol challenge, resident AMDC acquire antigen and rapidly mature into potent antigen-presenting cells (APCs) after cognate interactions with T memory cells. This process is restricted to dendritic cells (DCs) in the mucosae of the conducting airways, and is not seen in peripheral lung. Within 24 h, antigen-bearing mature DCs disappear from the airway wall, leaving in their wake activated interleukin 2R+ T cells and AHR. Antigen-bearing activated DCs appear in regional lymph nodes at 24 h, suggesting onward migration from the airway. Transient up-regulation of CD86 on AMDC accompanies this process, which can be reproduced by coculture of resting AMDC with T memory cells plus antigen. The APC activity of AMDC can be partially inhibited by anti-CD86, suggesting that CD86 may play an active role in this process and/or is a surrogate for other relevant costimulators. These findings provide a plausible model for local T cell activation at the lesional site in asthma, and for the transient nature of this inflammatory response

High burden of complicated skin and soft tissue infections in the Indigenous population of Central Australia due to dominant Panton Valentine leucocidin clones ST93-MRSA and CC121-MSSA

BACKGROUND: Superficial skin and soft tissue infections (SSTIs) are common among the Indigenous population of the desert regions of Central Australia. However, the overall burden of disease and molecular epidemiology of Staphylococcus aureus complicated SSTIs has yet to be described in this unique population. METHODS: Alice Springs Hospital (ASH) admission data was interrogated to establish the population incidence of SSTIs. A prospective observational study was conducted on a subset of S. aureus complicated SSTIs (carbuncles and furuncles requiring surgical intervention) presenting during a one month period to further characterize the clinical and molecular epidemiology. High resolution melting analysis was used for clonal complex discrimination. Real-time polymerase chain reaction identifying the lukF component of the Panton Valentine leucocidin (pvl) gene determined pvl status. Clinical and outcome data was obtained from the ASH medical and Northern Territory shared electronic health records. RESULTS: SSTIs represented 2.1% of ASH admissions during 2014. 82.6% occurred in Indigenous patients (n&nbsp;=&nbsp;382) with an estimated incidence of 18.9 per 1, 000 people years compared to the non-Indigenous population of 2.9 per 1000, with an incident rate ratio of 6.6 (95% confidence interval 5.1-8.5). Clinical and molecular analysis was performed on 50 isolates from 47 patients. Community-associated methicillin-resistant S. aureus (CA-MRSA) predominated (57% of isolates). The high burden of SSTIs is partly explained by the prevalence of pvl positive strains of S. aureus (90% isolates) for both CA-MRSA and methicillin-susceptible S. aureus (MSSA). ST93-MRSA and CC121-MSSA were the most prevalent clones. SSTIs due to ST93-MRSA were more likely to require further debridement (p&nbsp;=&nbsp;0.039), however they also more frequently received inactive antimicrobial therapy (p&nbsp;&lt;&nbsp;0.001). CONCLUSIONS: ST93-MRSA and CC121-MSSA are the dominant causes of carbuncles and furuncles in Central Australia. Both of these virulent clones harbor pvl but the impact on clinical outcomes remains uncertain. The high prevalence of CA-MRSA supports empiric vancomycin use in this population when antimicrobial therapy is indicated. Prompt surgical intervention remains the cornerstone of treatment