Paper Out: Using the wax moth larva Galleria mellonella infection model to detect emerging bacterial pathogens

A good start of the year by having a paper published. I blogged about the bioarxiv* version a while back so will keep it short this time: we injected environmental (water and sediment) samples in the Galleria caterpillar and, where mortality was found to be high, isolated the bacterial pathogens responsible. Four isolates were whole-genome sequenced and two proved to be species never found before in the UK. No other methods would have detected such ‘known unknowns’; perhaps expensive and time-consuming metagenomics would have provided glimpses of the DNA of these species (provided they were at high relative abundance, which they might not have been), but this method would not have given much information on pathogenicity, which was our phenotype of interest. Although conceptually very simple, I am quite excited by the potential of this method. Please have a look, it is Open Access:

Hernandez RJ, Hesse E, Dowling AJ, Coyle NM, Feil EJ, Gaze WH, Vos M. 2019. Using the wax moth larva Galleria mellonella infection model to detect emerging bacterial pathogens. PeerJ 6:e6150 https://doi.org/10.7717/peerj.6150

P.S.

Getting this paper published was a right pain btw: a total of seven rejections over a half-year time period: a personal record! I played with the idea of writing up a detailed dissection of this process but decided against it as it might have come across as a boring moan. Suffice to say it reinforced my belief that there are many things wrong with publishing, including journals that do not accept papers published as preprints (but without explaining why, I am looking at you Emerging Infectious Diseases), journals that demand additional experiments sacrifing animals for no good reason (I am looking at you PLoS Pathogens) or journals rejecting a manuscript even when reviewer comments equate to a (very minor) revision (I am looking at you Emerging Microbes and Infections). OK OK I had a little moan after all.

* The good thing about using Bioarxiv was that during this arduous publication process the manuscript abstract was checked almost 2000 times and it was downloaded as a pdf 360 times.

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Apply to the NERC GW4 PhD studentship “Context-dependent acquisition of antibiotic resistance mechanisms”

Together with collaborators Prof. Will Gaze (College of Medicine and Health, Exeter), Prof. Angus Buckling (Biosciences, Exeter) and Prof. Ed Feil (Milner Centre for Evolution, Bath) I have an advert up for a 3.5 year PhD position here in Penryn. Funding is contingent on having an excellent (and eligible) candidate to apply. For all the technical details see HERE. A short summary is pasted below (with some more details on project aims, methods and training via the link above):

The dramatic increase in antimicrobial resistance (AMR) forms a global challenge to public health. It is increasingly understood that the natural environment plays a key role in AMR evolution. Pharmaceutical residues and other pollutants in the environment such as metals can select for AMR. Moreover, largescale mixing of human-associated- and environmental bacteria can promote the exchange of resistance genes between strains, providing the genetic substrate for selection. Recent work suggests that such horizontal gene transfer might occur at the same rate as mutation but the relative importance of these two fundamentally distinct genetic mechanisms in generating AMR is not known. In this PhD project, we will design experiments to quantify and compare the prevalence of point mutations versus horizontal gene transfer events in generating resistance. Using flow cytometry and genome sequencing, we will measure the type and rate of genetic change under different realistic pollution scenarios. These data will provide fundamental data on bacterial genome evolution but also provide a scientific basis for pollution management.

We have a great community of scientists on the Penryn Campus with many excellent collaborators in Exeter and in Bath as well. Plus Cornwall is a great place to live, as evidenced by this somewhat gratuituous photo.

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Eden Project: Invisible Worlds Exhibition

This is a bit overdue as the opening took place in May, but I still wanted to highlight the current Eden Project exhibition Invisible Worlds. This is a major new permanent exhibition that reveals the world beyond our senses: too big, too small, too fast, too slow, too far away in space and time. It includes plenty of interesting exhibits involving bacteria set up in collaboration with University of Exeter microbiologists based in Penryn, including collaborator Ben Raymond as well as Sean Meaden, the latter who is involved in practical workshops explaining fermentation organised by FOAM. The centrepiece of the exhibition is the sculpture “Infinity Blue” which depicts a cyanobacterium. The artists of Studio Swine who made it actually visited our lab to do some filming (although I am not sure if much ended up in the accompanying (beautifully shot) film).  The Invisible You exhibiton on the human microbiome that Will Gaze and I contributed to is also still available to see. I thoroughly recommend visiting, especially now the “rainy season” will start!

Michiel

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Paper out: Staphylococcus cornubiensis sp. nov., a new member of the Staphylococcus intermedius Group (SIG)

My colleagues Aimee Murray, Lihong Zhang and Will Gaze and I have an ongoing collaboration with colleagues from the Royal Cornwall Hospital John Lee and Richard Bendall on the detection of ‘Staphylococcus intermedius Group’ (SIG) in human infections. These bugs are associated with wildlife and pets but are also able to infect humans (they are ‘zoonotic’). I wrote a short blog post about this collaboration a while back, and see that I failed to mention the resulting publication in the Journal of Clinical Microbiology: “Improved detection of Staphylococcus intermedius Group in a routine diagnostic laboratory“. In it, we described a simple scheme to differentiate these Staphylococci from the very similar-looking and ubiquitous species Staphylococcus aureus. We isolated a number of Staphylococcus pseudintermedius clones in the 2015 study, but also had a weird outlier in the phylogenetic tree: isolate ‘NW1’. In the new paper, we sequenced the genome of this isolate and found it to be sufficiently distinct from the three known SIG species to deserve its own name. As the isolate came from a patient travelling from the North of England, Staphylococcus starkensis was floated, but the nomenclature editors at IJSEM found that a bit too flamboyant. Luckily we had a great alternative inspired by the Romans: Staphylococcus cornubiensis. Our isolate is phenotypically very similar to the other SIG species but it is genomically quite distinct, with an Average Nucleotide Identity of 90.2% with closest relative S. intermedius. Although pathogenic, NW1 carries no known virulence genes or mobilizable antibiotic resistance genes. We hope to obtain funding to conduct further studies to assess the prevalence of this species in humans as well as its potential presence in companion animals.

Aimee K. Murray, John Lee, Richard Bendall, Lihong Zhang, Marianne Sunde, Jannice Schau Slettemeås, William Gaze, Andrew J. Page, Michiel Vos (2018): Staphylococcus cornubiensis sp. nov., a new member of the Staphylococcus intermedius Group (SIG). International Journal of Systematic and Evolutionary Microbiology, doi: 10.1099/ijsem.0.002992

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Workshop “Resolving Microbial Communities at Strain-level Resolution” a success.

At least, that was my distinct impression! As announced on the blog a while back, Nicolas Tromas, Pawel Sierocinski, Daniela Farina and myself hosted a workshop featuring talks and tutorials on cutting-edge metagenomic software aiming to progress from gene-based to genome-based metagenomics. In addition, we discussed what metagenome-assembled genomes (‘MAGs) represent in terms of units of diversity relevant to evolution, i.e. species. We had speakers Jesse Shapiro from the University of Montreal, Daniel Falush from the University of Bath and Elizabeth McDaniel from the University of Wisconsin talking about species concepts, genome evolution and MAGs. Chris Quince from the University of Warwick started with a metagenomics ‘bootcamp’ and also hosted a session on the DESMAN software. Murat Eren (‘meren‘) at the University of Chicago and Tom Delmont (was University of Chicago, now at GenoScope in Paris) talked about the Anvio software, whose exquisite visualisation capabilities of environmental genomes are illustrated below:

Over 60 participants diligently worked through hands-on tutorials and socialised during the breaks. It was great to see so many people travelling to Cornwall for this workshop: apart from the UK, people travelled from Ireland, Denmark, Switzerland, the Czech Republic, France, Belgium, The Netherlands, Spain, Canada and the US (including Hawaii) and probably a few more countries. We ended the four days with an afternoon of microbiology talks by local talent, including Aimee Murray, Anne Leonard (both Medical School), Elze Hesse and Pawel Sierocinski (Biosciences). Our workshop was supported by CLIMB Cloud Infrastructure for Bioinformatics, Exeter’s College of Life and Environmental Sciences as well as Agilent, Illumina, Eppendorf and Eurofins with the largest contribution made by the Innovation, Impact and Business Future Focus initiative (with lots of practical help by Hollie Kirk). Michiel

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on bioRxiv: Using the Wax moth larva Galleria mellonella infection model to detect emerging bacterial pathogens

In the past few years I have worked on and off (i.e. doing pilot experiments, having a grant proposal rejected) on a very simple, but I believe quite powerful, assay to detect pathogenic bacteria in environmental samples. As it stands, microbial water and food safety is based on the quantication of faecal indicator bacteria: more poo-related bacteria in your sample=bad. The problem is that some poo-related bacteria are not as harmful as others, and more importantly, there are some very harmful bacteria that are not associated with poo and thus are completely missed by this approach. Alternative ways to detect pathogens have their own limitations: for instance, molecular markers  are restricted to a (small) set of ‘known knowns’ and are usually costly.

It would be much more useful to directly screen for bacteria able to cause disease, whatever their identity. Visiting student Rafael Hernandez took water and sediment samples and directly injected these in the the wax moth larva Galleria mellonella, a model for the innate immune system. There are many studies that inject particular pathogen strains in Galleria to quantify the rate of  killing, and this has been shown to correlate well with death in infected mice. What is novel about our approach is that we inoculated Galleria not with specific strains but with samples containing entire microbial communities to detect where pathogens might be present.

Most samples from local beaches (water and sediment) we assayed did not result in Galleria death after injection, but for some samples, mortality after overnight incubation at 37C was very high. Rafael could isolate clones from infected Galleria, which then were used to infect Galleria again to confirm that they were the cause of death, and were subsequently whole-genome sequenced. The results were exciting. We found usual suspect E. coli, as well as another well known (but not gastro-intestinal-associated) human pathogen Pseudomonas aeruginosa, both harbouring many virulence and antibiotic resistance genes. However, the most virulent clone was a Proteus mirabilis strain harbouring a Salmonella Genomic Island that has been reported in recent years from human and animal infections but (to my knowledge) not from the natural environment or from the UK. We also found Vibrio injenensis, a species only very recently described from human patients in Korea and not reported from anywhere else. The figure above shows on the left panel Galleria cumulative death (inoculation with 100, 10.000 and 1.000.000 cells) and on the right genome characteristics (virulence genes in blue, antibiotic resistance genes in red) for the four characterised clones.

The combination of climate change, changing farming practices, increased exposure through water-based recreation and rising levels of antibiotic resistance is expected to lead to an increase in hard-to-treat opportunistic infections. The approach described here looks promising to uncover the prevalence and identity of pathogenic bacteria in the environment, including potential emerging pathogens, which is key to assessing environmental transmission risks.

This study is out but not ‘out out’; I have used bioarxiv for the first time to make results accessible before peer-reviewed publication. Read it here:

Using the Wax moth larva Galleria mellonella infection model to detect emerging bacterial pathogens.

Rafael Hernandez, Elze Hesse, Andrea Dowling, Nicola Coyle, Edward Feil, Will Gaze & Michiel Vos

 

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Symposium Penryn 28-31 August 2018: Resolving Microbial Communities at Strain-level Resolution

I have the pleasure to announce a symposium/workshop to be held here at the University of Exeter’s Penryn Campus 28-31 August focusing on strain-level resolution metagenomics.

Metagenomics involves the high-throughput sequencing of random DNA fragments isolated from microbial communities, followed by assembly into longer fragments and assignment of gene functions and taxonomic identities. Novel computational developments are allowing us to increasingly resolve strain- and species level differences from metagenomic data. Rather than viewing communities as ‘bags of genes’, this approach enables us to gain deeper insights into the composition and functioning of microbial communities.The main focus of the workshop will be metagenome-assembled genomes(MAGs) which are operationally defined as metagenomic assemblies binned according to nucleotide composition and depth of coverage across multiple samples.

Training will be delivered by experts Chris Quince (at the University of Warwick and a research fellow at CLIMB, who are co-sponsoring the event) and Murat Eren and Tom Delmont at the University of Chicago. We will also have some presentations, including by Rachel Whitaker from the University of Urbana-Champaign and Jesse Shapiro who is at the University of Montreal. For more information, please have a look at the symposium website.

We strive to to stimulate participation by early-career researchers and to have an equal gender ratio. Please follow this link to register an expression of interestand to send an email expressing how this workshop could benefit your work and what your current position (e.g. PhD student, lecturer) is. At the start of June, you will be notified of the success of your application, and sent a link with payment details and accommodation options. For any specific questions please shoot me an email.

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