Darwin Lab

Santiago, Chile

Darwin Lab

Santiago, Chile
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Van Den Hurk A.F.,Communicable Diseases Unit | Hall-Mendelin S.,Communicable Diseases Unit | Townsend M.,James Cook University | Edwards J.,Central Queensland Public Health Unit | And 7 more authors.
Vector-Borne and Zoonotic Diseases | Year: 2014

Effective arbovirus surveillance is essential to ensure the implementation of control strategies, such as mosquito suppression, vaccination, or dissemination of public warnings. Traditional strategies employed for arbovirus surveillance, such as detection of virus or virus-specific antibodies in sentinel animals, or detection of virus in hematophagous arthropods, have limitations as an early-warning system. A system was recently developed that involves collecting mosquitoes in CO2-baited traps, where the insects expectorate virus on sugar-baited nucleic acid preservation cards. The cards are then submitted for virus detection using molecular assays. We report the application of this system for detecting flaviviruses and alphaviruses in wild mosquito populations in northern Australia. This study was the first to employ nonpowered passive box traps (PBTs) that were designed to house cards baited with honey as the sugar source. Overall, 20/144 (13.9%) of PBTs from different weeks contained at least one virus-positive card. West Nile virus Kunjin subtype (WNVKUN), Ross River virus (RRV), and Barmah Forest virus (BFV) were detected, being identified in 13/20, 5/20, and 2/20 of positive PBTs, respectively. Importantly, sentinel chickens deployed to detect flavivirus activity did not seroconvert at two Northern Territory sites where four PBTs yielded WNVKUN. Sufficient WNVKUN and RRV RNA was expectorated onto some of the honey-soaked cards to provide a template for gene sequencing, enhancing the utility of the sugar-bait surveillance system for investigating the ecology, emergence, and movement of arboviruses. © 2014, Mary Ann Liebert, Inc.

PubMed | University of New South Wales, Darwin Lab, University of Queensland, Public Health Microbiology and 2 more.
Type: Journal Article | Journal: The Journal of antimicrobial chemotherapy | Year: 2016

The objective of this study was to develop a real-time PCR method for specific detection of the gonococcal GyrA amino acid 91 locus directly in clinical samples so as to predict Neisseria gonorrhoeae ciprofloxacin susceptibility.The real-time PCR assay, GyrA91-PCR, was designed using two probes, one for detection of the WT S91 sequence and the other for detection of the S91F alteration. The performance of the assay was initially assessed using characterized N. gonorrhoeae isolates (n = 70), a panel of commensal Neisseria and Moraxella species (n = 55 isolates) and clinical samples providing negative results by a commercial N. gonorrhoeae nucleic acid amplification test (NAAT) method (n = 171). The GyrA91-PCR was then applied directly to N. gonorrhoeae NAAT-positive clinical samples (n = 210) from the year 2014 for which corresponding N. gonorrhoeae isolates with susceptibility results were also available.The GyrA91-PCR accurately characterized the GyrA 91 locus of all 70 N. gonorrhoeae isolates (sensitivity = 100%, 95% CI = 94.9%-100%), whereas all non-gonococcal isolates and N. gonorrhoeae NAAT-negative clinical samples gave negative results by the GyrA91-PCR (specificity = 100%, 95% CI = 98.4%-100%). When applied to the 210 N. gonorrhoeae NAAT-positive clinical samples, the GyrA91-PCR successfully characterized 195 samples (92.9%, 95% CI = 88.5%-95.9%). When compared with the corresponding bacterial culture results, positivity by the GyrA91-PCR WT probe correctly predicted N. gonorrhoeae susceptibility to ciprofloxacin in 161 of 162 (99.4%, 95% CI = 96.6%-99.9%) samples.The use of a PCR assay for detection of mutation in gyrA applied directly to clinical samples can predict ciprofloxacin susceptibility in N. gonorrhoeae.

Goire N.,Royal Childrens Hospital and Health Service District | Goire N.,University of Queensland | Freeman K.,Darwin Lab | Tapsall J.W.,Prince of Wales Hospital | And 10 more authors.
Journal of Clinical Microbiology | Year: 2011

With increasing concerns regarding diminishing treatment options for gonorrhea, maintaining the efficacy of currently used treatments and ensuring optimal Neisseria gonorrhoeae antimicrobial resistance surveillance are of the utmost importance. Penicillin is still used to treat gonorrhea in some parts of the world. In this study, we developed and validated a real-time PCR assay for the detection of penicillinase-producing N. gonorrhoeae (PPNG) in noncultured clinical samples with the aim of enhancing penicillin resistance surveillance. The assay (PPNG-PCR2) was designed to be an indirect marker of penicillinase activity, by targeting a region of sequence predicted to be conserved across all N. gonorrhoeae plasmid types harboring the beta-lactamase gene while not specifically targeting the actual beta-lactamase-encoding sequence. The assay was evaluated by using a total of 118 N. gonorrhoeae clinical isolates and 1,194 clinical specimens, including 239 N. gonorrhoeae-positive clinical samples from which N. gonorrhoeae cells were isolated and for which phenotypic penicillinase results are available. Overall, the PPNG-PCR2 assay provided 100% sensitivity and 98.7% specificity compared to bacterial culture results for the detection of PPNG in clinical specimens. PPNG-PCR2 false-positive results, presumably due to cross-reactions with unrelated bacterial species, were observed for up to 1.3% of clinical samples but could be distinguished on the basis of high cycle threshold values. In tandem with phenotypic surveillance, the PPNG-PCR2 assay has the potential to provide enhanced epidemiological surveillance of N. gonorrhoeae penicillin resistance and is of particular relevance to regions where penicillin is still used to treat gonorrhea. Copyright © 2011, American Society for Microbiology. All Rights Reserved.

PubMed | Melbourne Sexual Health Center, University of New South Wales, Darwin Lab, University of Queensland and 2 more.
Type: Journal Article | Journal: The Journal of antimicrobial chemotherapy | Year: 2016

The objective of this study was to develop a real-time PCR assay targeting the gonococcal porB gene (PorB-PCR) for predicting susceptibility of Neisseria gonorrhoeae to penicillin. This complements a previously described PCR assay for detecting penicillinase-producing N. gonorrhoeae (PPNG) developed by our laboratory (PPNG-PCR).The PorB-PCR assay was designed using six probes to characterize various combinations of amino acids at positions 101 and 102 of the PorB1b class protein, including the WT G101/A102 and mutant G101K/A102D, G101K/A102N and G101K/A102G sequences, as well as the PorB1a sequence. The ability of these sequences to predict penicillin susceptibility was initially assessed using 2307 N. gonorrhoeae isolates from throughout Australia for which phenotypic susceptibility data were available. The assay was then applied to N. gonorrhoeae-positive clinical specimens (n=70). Specificity was assessed by testing commensal Neisseria strains (n=75) and N. gonorrhoeae-negative clinical specimens (n=171).Testing of the 2307 N. gonorrhoeae isolates using PorB-PCR to detect G101/A102 and PorB1a sequences identified a total of 78.4% (61.2% and 17.2%, respectively) of penicillin-susceptible isolates with specificities of 97.4% and 99.3% and positive predictive values of 98.8% and 98.9%, where PPNG strains were simultaneously identified and excluded. Similar performance data were obtained when the PorB-PCR assay was applied to the N. gonorrhoeae-positive clinical specimens. No false-positive results were observed for the N. gonorrhoeae-negative samples and no cross-reactions were observed with the non-gonococcal species.When used in parallel with the previously described PPNG-PCR, the PorB-PCR approach has the potential to facilitate individualized treatment of gonorrhoea using penicillin.

PubMed | Melbourne Sexual Health Center, Sexual Health and Blood Borne Virus Unit, Health Diagnostic Laboratory, Darwin Lab and 8 more.
Type: Journal Article | Journal: Clinical infectious diseases : an official publication of the Infectious Diseases Society of America | Year: 2016

Antimicrobial resistance (AMR) by Neisseria gonorrhoeae is considered a serious global threat.In this nationwide study, we used MassARRAY iPLEX genotyping technology to examine the epidemiology of N. gonorrhoeae and associated AMR in the Australian population. All available N. gonorrhoeae isolates (n = 2452) received from Australian reference laboratories from January to June 2012 were included in the study. Genotypic data were combined with phenotypic AMR information to define strain types.A total of 270 distinct strain types were observed. The 40 most common strain types accounted for over 80% of isolates, and the 10 most common strain types accounted for almost half of all isolates. The high male to female ratios (>94% male) suggested that at least 22 of the top 40 strain types were primarily circulating within networks of men who have sex with men (MSM). Particular strain types were also concentrated among females: two strain types accounted for 37.5% of all isolates from females. Isolates harbouring the mosaic penicillin binding protein 2 (PBP2)-considered a key mechanism for cephalosporin resistance-comprised 8.9% of all N. gonorrhoeae isolates and were primarily observed in males (95%).This large scale epidemiological investigation demonstrated that N. gonorrhoeae infections are dominated by relatively few strain types. The commonest strain types were concentrated in MSM in urban areas and Indigenous heterosexuals in remote areas, and we were able to confirm a resurgent epidemic in heterosexual networks in urban areas. The prevalence of mosaic PBP2 harboring N. gonorrhoeae strains highlight the ability for new N. gonorrhoeae strains to spread and become established across populations.

Oates A.C.,Max Planck Institute of Molecular Cell Biology and Genetics | Morelli L.G.,Max Planck Institute of Molecular Cell Biology and Genetics | Morelli L.G.,CONICET | Ares S.,Max Planck Institute for the Physics of Complex Systems | Ares S.,Darwin Lab
Development | Year: 2012

The segmentation clock is an oscillating genetic network thought to govern the rhythmic and sequential subdivision of the elongating body axis of the vertebrate embryo into somites: the precursors of the segmented vertebral column. Understanding how the rhythmic signal arises, how it achieves precision and how it patterns the embryo remain challenging issues. Recent work has provided evidence of how the period of the segmentation clock is regulated and how this affects the anatomy of the embryo. The ongoing development of realtime clock reporters and mathematical models promise novel insight into the dynamic behavior of the clock. © 2012. Published by The Company of Biologists Ltd.

Broderick D.,Molecular Fisheries Laboratory | Ovenden J.R.,Molecular Fisheries Laboratory | Buckworth R.C.,Darwin Lab | Buckworth R.C.,CSIRO | And 3 more authors.
Journal of Fish Biology | Year: 2011

This study used mtDNA sequence and microsatellite markers to elucidate the population structure of Scomberomorus semifasciatus collected from 12 widespread sampling locations in Australia. Samples (n = 544) were genotyped with nine microsatellite loci, and 353 were sequenced for the control (384 bp) and ATPase (800 bp) mtDNA gene regions. Combined interpretation of microsatellite and mtDNA data identified four genetic stocks of S. semifasciatus: Western Australia, north-west coast of the Northern Territory, Gulf of Carpentaria and the eastern coast of Queensland. Connectivity among stocks across northern Australia from the Northern Territory to the eastern coast of Queensland was high (mean F ST = 0·003 for the microsatellite data and Φ ST = 0·033 and 0·009 for control region and ATPase, respectively) leading to some uncertainty about stock boundaries. In contrast, there was a clear genetic break between the stock in Western Australia compared to the rest of northern Australia (mean F ST = 0·132 for the microsatellite data and Φ ST = 0·135 and 0·188 for control region and ATPase, respectively). This indicates a restriction to gene flow possibly associated with suboptimal habitat along the Kimberley coast (north Western Australia). The appropriate scale of management for this species corresponds to the jurisdictions of the three Australian states, except that authorities in Queensland and Northern Territory should co-ordinate the management of the Gulf of Carpentaria stock. © 2011 State of Queensland. Journal of Fish Biology © 2011 The Fisheries Society of the British Isles.

Lu P.,Darwin Lab | Lu P.,Energy Resources of Australia Ltd.
Acta Horticulturae | Year: 2013

Water status in trees is commonly studied by measuring leaf water potential with a pressure bomb, but due to mango's excessive latex exudation, leaf water potential measurements can not be reliably measured this way. We have measured xylem sap flow in the tree trunk, microvariation of branch diameter (microdendrometry), and leaf gas exchange to study mango water relations. The main Australian mango cultivar 'Kensington Pride' is very sensitive to air dryness, more so than most Florida cultivars. Both sap flow (tree water use) and twig/branch shrinkage have been shown to be good plant-based indicators of plant water status and been successfully used to control irrigation. However, at the present time, both techniques are far from being practical or economical enough to be used by growers for their irrigation scheduling. A low cost, farmer friendly tool for irrigators, 'FullStop' wetting front detectors, was developed by CSIRO in Australia. 'FullStop' is a simple device buried in the ground in the rooting zone, which will tell the irrigators when to switch off irrigation. This system has great potential as an aid to irrigation decision making. © ISHS 2013.

PubMed | Darwin Lab
Type: | Journal: RNA biology | Year: 2017

High-throughput RNA sequencing (RNA-Seq) has uncovered hundreds of small RNAs and complex modes of RNA regulation in every bacterium analyzed to date. This complexity agrees with the adaptability of most bacteria to varied environments including, in the case of pathogens, the new niches encountered in the host. Recent RNA-Seq studies have analyzed simultaneously gene expression in the intracellular pathogen Salmonella enterica and infected host cells at population and single-cell level. Distinct polarization states or interferon responses in the infected macrophage were linked to variable growth rates or activities of defined virulence regulators in intra-phagosomal bacteria. Intracellular Salmonella, however, exhibit disparate intracellular lifestyles depending the host cell, ranging from a hyper-replicative cytosolic state in epithelial cells to a non-replicative intra-phagosomal condition in varied host cell types. The basis of such diverse pathogen-host communications could be examined by RNA-Seq studies in single intracellular Salmonella cells, certainly a challenge for future investigations.

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