Hello, and thank you for listening to the Microbinfeed podcast. Here, we will be
discussing topics in microbial bioinformatics. We hope that we can give you some
insights, tips, and tricks along the way. There's so much information we all
know from working in the field, but nobody writes it down. There is no manual,
and it's assumed you'll pick it up. We hope to fill in a few of these gaps. My
co-hosts are Dr. Nabil Ali Khan and Dr. Andrew Page. I am Dr. Lee Katz. Both
Andrew and Nabil work in the Quadram Institute in Norwich, UK, where they work
on microbes in food and the impact on human health. I work at Centers for
Disease Control and Prevention and am an adjunct member at the University of
Georgia in the U.S. Hi, and welcome to the Microbinfeed podcast. I'm Nabil, and
I'm your host for today. Today we're going to be talking about our study into
invasive non-typhoidal salmonella in rural Gambia. Joining me today is two
special guests. We have Grant McKenzie, who is a clinical epidemiologist working
at the MRC unit, the Gambia, at the London School of Hygiene and Tropical
Medicine, and also Abdoulaye Kante, who is a higher scientific officer in the
Genomics Core Facility, also working at the MRC unit, the Gambia, at the London
School of Hygiene and Tropical Medicine. Since it's both of your first times,
who are you and what do you both typically do? Let's start with Grant. Thank
you, Nabil and Andrew, for inviting us to join you. I'm working for the last 13
years, actually, in West Africa in Gambia with the MRC unit. I'm a clinical
epidemiologist and pediatrician by background, and I'm usually involved in
invasive bacterial disease surveillance in the rural area of the Gambia. We have
lots of doctors and nurses and microbiology laboratory and x-ray service, data
centre, about 500 kilometres from the coast in the middle of nowhere, where
we've got a population of three or four hundred thousand people under
demographic surveillance. All of this system works in with the government health
system to detect cases of pneumonia or sepsis or meningitis or malaria coming to
the health facilities in the area. We investigate the sick children and we can
use that surveillance data to look at the effects of certain interventions over
time. We're also doing other sort of interventional studies as well, but that's
the main thing that I'm involved in. OK, and what about you, Abdele, who are you
and what do you typically do? Thank you very much, Nabil. I work at the Genomics
Core Facility at the MRC unit in Gambia at London School of Hygiene and Tropical
Medicine. I joined the unit in 2007 as a laboratory technician, and over the
years I've worked in different projects and laboratories, including
microbiology, molecular biology, as well as genomics. I'm currently working in
the genomics platform. So my background is microbiology. I have an MSc in
bioinformatics from the University of London. So at the genomics lab, my typical
day would involve either sitting on my desk doing bioinformatics analysis on
genomics samples, or maybe in the lab preparing library for sequencing. So I do
both. Just to say, our genomics platform is a well-equipped, state-of-the-art,
state-of-the-art equipment for next-generation sequencing. So we have both the
Illumina and the Nanopore technologies in our lab. So I'm happy to say we are
the first to be certified by Nanopore as a service provider in Africa. Okay.
And, I mean, this is a very naive question. Last time when we were talking about
Norwich and Norfolk, we had to explain where that actually is. So just indulge
me, Abdele, could you tell us where the Gambia actually is and who are the
people who live there? So the Gambia is named after its navigable river, which
runs from the western part of the country to the eastern part. It's found in the
western part of Africa, and sometimes it is called the Smiling Coast of Africa.
It is a small country with a population of about 2 million people. The country
is made of six regions. MRCG operates in almost all these regions. One of the
regions where we did our study is called the URR, Upper River Region, and is
found in the eastern part of the country, where the Pneumococcal Surveillance
Project has been going on since 2007, led by Dr. Grant, looking at the impact of
pneumococcal conjugate vaccine introduced in the Gambia. And Grant, I mean, you
did touch in your introduction some of the different work that you're doing, but
specifically, what is some of the more critical projects you're handling through
the MRC unit? I'll just mention some of the historical work at the MRC unit in
the Gambia. So actually, malaria transmission was defined in the Gambia, defined
as a mosquito-borne disease. Then there's been further fairly groundbreaking
research over 40 or 50 years. So the use of insecticide-treated bed nets to
prevent malaria was first demonstrated in large, randomized trials in the
Gambia. Hepatitis B vaccine was first trialed in the Gambia and shown with a
30-year follow-up to prevent hepatocellular carcinoma. Haemophilus influenzae
type B vaccines were trialed in the Gambia. Pneumococcal vaccines have been
trialed in the Gambia. Both of those vaccine trials directly led to global
vaccine policy change. Malaria vaccines and malaria treatments have been
investigated a lot. There's a lot of TB research as well. We're now sort of
starting to explore other areas in those strict infectious diseases. Personally,
myself, I'm more involved in child health. So as we look into pneumococcal
vaccine effectiveness in the country, we also study the effect of malnutrition
on susceptibility to sepsis or meningitis or pneumonia. We also study how to
best diagnose these conditions, what gives risk factors for these conditions.
Just at the moment, we've started a large cluster randomized trial looking at
two different schedules of pneumococcal vaccination to see whether instead of
the usual three-dose schedule, you can safely use a two-dose schedule. This is
relevant because the vaccine is relatively expensive and a good number of
countries have not even introduced the vaccine because of its expense. So we'll
be determining whether you can safely use two doses rather than three. That's
keeping me busy at the moment. Is that the PCV13? That's right. Yes. It's
actually following on the heels of the UK. The UK is the first country in the
world to transition from a three-dose to a two-dose pneumococcal vaccine
schedule. But trying to see whether that type of approach is safe in a high
transmission, high burden area in Africa. And are you backing that up with
genome sequencing? We are not actually, no. Sorry. Disappointing. Steve Bentley
was doing a lot of work on pre and post vaccination for pneumococcal disease. I
think we need to do something. Okay. Well, let's dive into a specific topic then
of invasive non-typhoidal salmonella. And I think really, if we're going to dive
deep into it, we've got to lay a bit of background down and help people along
who aren't too up to speed on the biology. So let's start off with just defining
like, what's the difference between invasive versus non-invasive salmonella?
Abdoulaye, what would you say to that? Yeah, I mean, to make it very simple for
our listeners, invasive salmonella, that could mean infection of salmonella
outside the gut, because we know salmonella is normally found in the gut
microbiome. So this is sometimes called extra-intestinal disease, where
salmonella infects invasive sites as blood, causing sepsis, bacteremia, or other
phenotypes. Non-invasive salmonella is the infection of salmonella in the gut.
This is normally self-limiting, gastroenteritis, and it normally comes in the
form of diarrhea. Okay. And then I guess the other axis we've got to explain is
the difference between typhoidal and non-typhoidal salmonella. Yeah. So here
we're talking about salmonella enterica. So we know taxonomically, salmonella
can be divided into two, salmonella bongori and then salmonella enterica. So,
but the latter is also subdivided into six subspecies. The subspecies one is the
one that is well studied because it's the one that infects humans and animals.
So we have more than 2,500 cerebus. So some cerebus within these species are
implicated in life-threatening infection, and they exclusively infect humans.
This includes salmonella enterica typhi.  So this collectively, they call them
typhoid or paratyphoid disease. They normally cause typhoid and paratyphoid
disease respectively. This group of cerebral are called typhoid or salmonella.
And we have other cerebral that are not within this group, and they are called
non-typhoid or salmonella. So the two major ones we know that causes disease in
the world and in Africa is the typhimidium and the enterodontitis. They are
known to cause more than 75 million cases a week, 25,000 deaths or more. But in
sub-Saharan Africa, they are also implicated in causing life-threatening
infections such as septicemia, pneumonia and meningitis. So that is a big
difference. So that is why clinically it's difficult to distinguish between the
typhoid and non-typhoid in sub-Saharan Africa because both these cerebrals are
known to cause invasive disease in our setting. I was just going to ask, is the
typhoid vaccine being used in The Gambia? I'm not very sure about that. And
second question, is there much burden of typhoid? In our surveillance over 10
years, we were taking blood cultures from all ages in our population of about
300,000. And I think we isolated about 20 cases, 25 cases of typhoid disease or
typhoid isolates. So it's not highly prevalent. It's quite different in other
countries in Africa. In Ghana, there's a lot of typhoid disease and in East
Africa and Southern Africa, I think there's more. Why is this an issue in The
Gambia specifically then? What drives that major change that we see? We don't
see typhoid, we see other cerebrals instead. That's a very good question. I
don't think we really know the answer. I mean, we know that typhoid is often
associated with poor hygiene and food handling. In West Africa, I guess the
density of living, urban living is not so great as some of the more dense areas
of East and Southern Africa. But really, I don't think we know the answer to
that question. So it's all speculation, really. Typhoid is very much a problem
in Asia, Southeast Asia and Asia. I guess the next question is, this is an area
of more research. And then how can whole genome sequencing help us combat
Salmonella in The Gambia generally? Yeah, so we know that sequencing of
bacterial pathogens is getting cheaper. And we know that in The Gambia, MRC in
The Gambia has the genomic facility, which makes it very important for pathogen
genomics studies. We understand that the ability to dig into the Salmonella
genome could set light on the different virulent factors, as well as
antimicrobial resistant genes and plasmids that have been harbored by these
pathogens. So we've also seen that using whole genome sequencing, we can
actually tell the dominant genotypes that are circulating in our setting with
possible explanation of why are they dominant. So, for example, in Malawi, we've
seen that they've used whole genome sequencing, but have highlighted a distinct
genotype of Salmonella-type medium ST313. So with a possible clonal replacement,
it was driven by acquisition of chloramphenicol resistance. So this was actually
done using whole genome sequencing. Similarly, in our study that we're going to
talk about today, we've seen that some of these NTS non-typhoidal Salmonellas
that harbor a cytolithic distending toxin gene, a particular gene that has been
known to be harbored by Salmonella typhi in most of our serovas. So we probably,
we think this is the reason why we have an expulsion of these serovas, because
invasive disease is more than the known predominant serovas, typhimidium and
enterovirus. Yeah, before we get into the study, before you actually started
this work, what were you hoping to find? So over the years, during the PSP
study, Dr. Grant actually observed that some of these non-typhoidal Salmonella
serovas which were not reported to be predominant are actually coming up. And
when we had a discussion, the first thing I thought about was, my first guess
was actually that they might be acquiring some viral factors that are not in the
other serovas. Or maybe there is an environmental factor that is giving them
this selective advantage. But yes, that was actually my guess when we had this
discussion. Grant, anything you'd like to add? In most of Africa actually,
enteritidis and typhimidium have been the dominant causes of invasive non-
typhoidal Salmonella disease throughout all of Africa. And a lot of vaccine
development is based on those serovar antigens. Even in the year 2000-2005, we
were seeing that typhimidium was causing 60-80% of our invasive cases. But then
we started to see quite a dramatic change where typhimidium and enteritidis were
becoming less common and other serovars were becoming more common. And this was
a concern because it could have implications for vaccine development. Antibiotic
resistance is relatively common. But the real question is, could this be a
change that might spread throughout other regions in Africa or have important
implications for vaccine strategies? Because it's a relatively active field to
try and develop a vaccine against non-typhoidal Salmonella. So, as Abdoulaye
mentioned, we thought we would try and look at genomic aspects that might
explain this. Why does invasive non-typhoidal Salmonella generally only happen
in Africa? Not so much in developed countries. It's probably just because of a
poor gut lining with malnutrition and tropical enteropathy. And the bacteria,
you know, translocate from the gut into the blood a lot easier when you've got a
very poor gut lining. So, I don't think that this problem is going to go away.
And we just wanted to understand more about why the serovars were changing in
prevalence. Let's get down into the actual study itself. And just before we talk
results, I mean, which samples are you investigating and how were they
collected? So, we had the population-based surveillance for nine years. So, the
strength of that design is that you theoretically try and detect every case in
the community. You avoid bias due to healthcare seeking, due to potential
hospitalized cases being different to the general cases in the community. So,
whenever a sick child came to a health facility, to nine of our health
facilities, we would do a blood culture. And so, we had about three or four
thousand blood cultures every year for nine years. And we looked at blood
culture to provide advice for doctors to provide treatment for children. And,
you know, we obviously found quite a bit of Salmonella disease. Maybe 10% of it
was typhoid, but a lot of it is non-typhoid. At the beginning, we were finding
maybe 20%, 25% of the cases were not typhimurium and not enteritidis. But then
by the last five years, it was more like 60% of the cases were not typhi and not
typhimurium. So, that's a pretty dramatic change and we really wanted to
understand why that might happen. Yeah, you're seeing this replacement to
Salmonella that aren't the usual suspects. And from that large sample set that
you have over several years, some were selected for sequencing. And maybe
Abdoulaye wants to comment, how were they done? How were they sequenced? Yeah,
so the sequencing was not done in the Gambia. At that time, we don't have the
sequencing facility. So, all the samples that grew Salmonella were isolated and
extraction was done here in Fajara, where I am. And then they were sent to
Sanga, where the sequencing was done. So, they were sequenced using the Illumina
Hi6 2500, producing 125 base pairs, sequencing FASCQ-5. So, this was generally
done in Sanga. I suppose that's where I come in. Because I got involved in this
project by being in a Sanger. And by complete chance, one day, a guy called
Gordon Dugan walks in with a guy called Nooradeen, who works with Grant. And he
had some data and we did some analysis. And out of that, I got talking to him.
grant and I went to the Gambia twice and I never met Grant in the Gambia but I
did meet Ablai and we have worked on it over the past few years worked on this
data and Ablai has come over to visit Quadram as well for a month to work with
myself and Nabil so it's been a great informal collaboration no grants are
written about this it's just we've come together and we've worked on the project
together to get a little paper out so it's very important to network so that's
just a little aside yeah it's worked very well it's been very good yeah so as
Andrew mentioned so when I went to Quadram it was really a great pleasure to
meet you there and Andrew himself so some of the skills that I learned during my
bioinformatics course in Kilimeri and in Quadram I was able to come up with a
pipeline and the pipeline includes basically to do a phylogenetic analysis to
look at the relationship of these serovas and the phylogenetic relationship of
these serovas so I first had to do a QC so I had to QC all the sequencing all
the reads using FastQC and then assemble the genomes using spades because most
of the time the assemblies are not really up to par you have to do some QCs on
them so I was able to do all QCs and then we found out that three of the samples
had very large genomes compared to the normal salmonella so we had to remove
those because then probably the potential contaminants we screen for viral genes
antimicrobial resistant genes as well as plasmid genes and from all the samples
so we also construct a phylogenetic tree using Slippy so we're able to use the
core genome alignment then I've constructed using IQ3 and then annotate using
ITO so we used Aurora to do to look at the plant genome and the core genome
analysis of all our samples so basically that was kind of the pipeline that I've
used to look at the genomes from the salmonella samples. Okay good sounds like a
tried and tested a reliable workflow and so based off that what were some of the
key findings out of all of this work? Overall when we look at it so we found out
that there were a lot of non-typhoid salmonella that is not typhimidium that
kind of overtook the whole show so we had about 60 or more percent of those
synovas not typhimidium and entered this so we are really that was a bit
surprising because we know previously a study was done in the same setting by
Nurudin that most of the synovas that were causing invasive disease were
entreated and followed by typhimidium so and then the other synovas that were
not typhimidium entreated contributed only a little but what we found here was
the river so we found more of the synovas they're not typhimidium entreated and
typhoid and also what we found that was really interesting is that there was
high fatality rate or mortality rate that we are associated with these synovas
if you compare the different synovas that we have what we saw was that most of
the mortality of people that died due to infection of salmonella were actually
from these synovas that we call in our people atp cover and one of the things
when we look at the genome what we found was that there was this particular gene
that was really common in our in those synovas that we're talking about and it's
called the cytolytal and distended toxin gene so actually the gene was known to
be only harbored by typhi which is a human specific synova and it's also known
to be to contribute to its pathogenicity what we saw was that majority of our
samples more than 60 percent which are not typhimidium entities or typhi we
actually need harboring this gene so in that sense we kind of speculate that
this particular gene could be contributing to what we are seeing i think i'll
throw in a reviewer three kind of question here i mean is any of these trends
due to perhaps differences in the sample collection over different years was the
number of samples total number of samples per year more or less consistent can
these results be explained by some sort of sample bias or something like that
and abdelay or grant if you want to comment yeah i can just comment on the rate
of blood cultures from year to year you know that does change because you don't
have a selected number that you do every year you have to attend to each child
that comes into the surveillance system and it's generally related to the
rainfall and malaria prevalence if you have a heavy rainfall year you get more
malaria you get more respiratory virus activity in the wet season and you get
more children coming in and you do more blood cultures so like for example the
the year where we had the smallest number of blood cultures done in in children
i was 2009 that was like 1900 blood cultures but then we had a flood and then we
had 3500 blood cultures in 2015 so if you do more tests you will find more cases
so in terms of the you know the incidence of disease or the number of cases that
will change with the number of tests that you do i haven't seen any evidence
though that in other settings malaria prevalence predisposes to particular
serovars of non-typhoidal salmonella and usually well it's actually quite well
known that the susceptibility is mainly due to neutrophil dysfunction following
malaria infection which lasts for three or four months and usually neutrophil
dysfunction is not going to be predisposing to one serovar over another serovar
so yes we do see changes in incidence and number of cases over time but i don't
see it's obviously going to be related to a change in serovar proportions over
time yeah and presumably since it's driven by those factors i assume that even
on years where there was low sampling or recent years with low sampling in
recent years with high samplings you're still seeing a drop in enteritis and
typhimurium and an increase in these other serovars yeah that's right it's been
consistent for the last five years that the so-called atypical serovars are
causing 60 65 percent of invasive disease yeah and you mentioned this previous
study that that did not show that so when was that actually conducted relative
to this one yeah that was from 2000 to 2005 in the same geographic area and the
so-called atypical serovars caused about 15 percent 10 to 15 percent of the
invasive disease at that time this is a reasonably rapid change over quite a few
years but reasonably rapid so what has changed do you think to explain this
shift our study was not designed to answer this question so our data are not
ideal you know 70 or 80 percent of households have sheep or goats in them and
that hasn't changed over seven years poultry ownership is 80 or 90 percent in
different in the households in the study area that hasn't changed we don't see a
lot of pig production in our area i think the domestic animal data that we have
are really capturing the main domestic animal use in the area i think
malnutrition prevalence has not changed we have good data on that hiv is
definitely a risk factor for invasive nts that has not changed in terms of its
prevalence it's actually very low prevalence maybe one or two percent that
hasn't changed over time malaria incidents you know it goes up and down over
time but actually malaria in general is becoming less common but as i said it's
it's hard to hypothesize a biologic mechanism whereby malaria falling in
prevalence or incidents would actually give you a seer of our specific risk so
that's really why we went to the the bacteria to try and investigate the genomic
aspects that might be associated with this change yeah so that's very
interesting i also mentioned one of the things that we've observed in our data
is that in 2010 and 2011 we've seen a very high peak of salmonella entry to this
in our setting there was this flood that happened in 2010 and it lasted for more
than two months in passe potentially there could be contaminations of waters and
livestock so um and then when i look at the phylogenetic tree um realized that
all  the samples that were collected in 2010, 2011, actually clustered together
with a very short, I mean, some of them, the branches are, you can actually see
that these genomes are actually very, very related or closely related. So
digging into that is my next kind of step to look at actually what is happening
in 2010 and 2011. So especially on the entrances, but apparently I'm just
speculating that that could be a reason why we have that spike there. Can I ask
a question? Yeah, sure. You know, interested from the Salmonella experts,
whether the gene that Abdullahi mentioned being identified in these atypical
serovars and it possibly being related to clades, does it make sense to you that
you've got quite a number of different atypical serovars which have this gene or
these particular clades? And what sort of mechanisms might lead to multiple
atypical serovars becoming more common? I mean, I can't see that Enteritidis and
Typhimurium have some, well, I don't know, maybe we could investigate those to
see whether they have lost virulence elements. So I recall when looking at this
data with Abdullahi that this particular gene was very prevalent in Typhi, but
then not really in all the other published genomes is very, very rarely
observed, except in your atypical ones, it seemed to be everywhere. So that
would suggest multiple independent introductions. I don't know what the
mechanism is, but it seems to be quite an outlier, certainly in your data, and
it does seem interesting. But probably the only way you could uncover the full
story would be to go back into the lab and maybe do long read sequencing and
just double check everything and see does it actually have some kind of
influence or is it just a random thing that has happened and we're not looking
at the real thing, we're looking at something else? I can imagine that if you
have a genomic change that provides some advantage for transmission or adherence
or virulence, that because the niche of the gut is only a certain size, that
might then, if it does have advantages, it might displace the other cerevals.
And I think, is it, Abdoulaye, your investigation into the activity of this
gene, you found that it was associated with adherence and colonization as well
as virulence, wasn't it? Yeah, that's true. Yeah, I'm not exactly sure what is
mobilizing the CDT, the cytolethal distending toxin in these different cerevals.
I should point out for the listeners that the cerevals are very distinct as far
as the population structure of salmonella is concerned they are pretty much,
they're all salmonella enterica, but that's about it. The split would go back to
the central split of all salmonella. So these are, I think the major cerevals,
Dublin, then things like Bredny, Miami, Softenburg, Oranienburg, Verkhov, and
Dublin's a known operator to be concerned about. But most of these really aren't
the canonical ones that you go after. And the fact that, yeah, we find
consistently find the CDT in a lot of these probably suggests that there is some
element that's being passed around that these are all acquiring and causing
invasive disease. Are they passing it from each other? Probably not. It probably
is something spontaneous where they are picking these up because of some
selective pressure in the environment that's pushing them to pick these up. So I
don't know what mobilizes CDT in this case. It could be just a recombination. It
could be driven by some mobile genetic element or something like that. And I
think that is where Andrew's saying that coming back with long reads and really
breaking down the gene synteny and looking at how the genome structure changes
between these cerevals would give us an idea of how these are actually acquiring
this virulence. So there's definitely a lot more to do. I think the strong
evidence that entrants in typhimurium are being replaced by other cerevals, all
other things considered, is a very interesting result. It's something that I
have spotted in the literature over the last couple of years that people are
seeing other cerevals that are popping up. Again, it's dependent on, is it
simply because we're testing more and more or not, depends in each case. But
this does seem to be a trend. And then this does have an implication of if we
can't just have a single target for going after enteritidis or just going after
typhimurium, we have to start thinking about all Salmonella enterica or even
Salmonella genus wide being an issue and being something that we have to have,
something to work against at any given Salmonella. Yeah, I'd be quite concerned
whether this type of phenomenon is going to spread geographically in Africa. I
think there are vaccine platforms which are not CeroVar specific, like whole
cell or attenuated bacterial platforms as well as outer membrane vesicles. But
there's also a lot of effort being put into CeroVar specific. And I think Nabil,
if you have seen trends along this in other settings as well, it may be that
it's not so worthwhile pursuing those CeroVar specific strategies anymore. I
mean, it's going to be a whack-a-mole kind of problem where we're going to need
a multi-pronged approach to target this. Getting rid of enteritidis and getting
rid of typhimurium is good. That's going to help anybody with disease burden.
But yeah, I think it's just a thing of not being too narrow, not having too much
tunnel vision on just those two. And it comes back to how we think about
pathogens and what is a pathogen versus what is something that's quite benign.
And the logic is that if you have typhi, you have a problem. If you have
typhimurium and enteritidis, you have a problem. Everything else we're not
bothered about. That I think is an old-fashioned view and needs to change. I
think pathogenesis, given the right conditions, can come from anywhere. So just
to finish up, what are the next steps given your findings? My next step, I want
to look at the non-sterile sites. So NTS, we now have to see samples from the
global enteritic multicenter study, GEMS, which was done also in rural Gambia,
Basset. So the aim is to look at those serovas too, and then probably compare it
to what we have from the pneumococcal surveillance study. So those samples we
have not sequenced yet. So I think it will be important to look at those serovas
because these are coming from the gut. And then they have cases and controls. So
it will be important to have a look at those serovas. I'm also thinking of doing
a microbiome analysis to assess what's going on during salmonella infections. So
if we have that stool samples coming from the GEMS study, it would also be an
important thing to look at. And host genetic factors as well as environment. So
including the domestic animals. So we probably want to go and check what is
happening at the domestic level. The serovas that we're talking about, probably
they're coming from the food that we're eating or perhaps from the environment.
So it's something that I'm thinking about. And I think, Graeme, if you agree,
this is one of the things that I think might help us know where these things are
coming from. And also I hear you're looking for a PhD as well. So I'm sure if
anyone listening has any positions that would be suitable, they should get in
touch with Mir and Nabil or with you directly. Grant, anything you want to add
following that? No, I think it would be important to just understand more about
this gene. I think it would be worthwhile to look at the case fatality in the
NTS cases where this gene is present and not present just to see whether the
case fatality is truly associated with that gene in specific, specifically. And
I would just encourage other investigators in West Africa to be looking at their
serovar distributions in invasive NTS to be monitoring for this type of
phenomenon. Okay. And so I think at that point we'll wrap up. So that's all the
time we have.  for this episode. We've been talking about invasive non-typhoidal
salmonella in rural Gambia, and much of what we've been talking about will be
available in a preprint if you want to learn more. So I'd like to thank our
guests, Grant and Abdulleh, and I'll see you next time on the MicroPinfey
podcast. Thank you all so much for listening to us at home. If you like this
podcast, please subscribe and like us on iTunes, Spotify, SoundCloud, or the
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anything. This podcast was recorded by the Microbial Bioinformatics Group and
edited by Nick Waters. The opinions expressed here are our own and do not
necessarily reflect the views of CDC or the Quadrant Institute.