UA-184069179-1 94: Of Microbes and Mud - Febrile
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Episode 94

94: Of Microbes and Mud

Drs. Genevieve Martin, Catherine Marshall, and Bart Currie from the Royal Darwin Hospital share their approach to Burkholderia pseudomallei aka melioidosis!

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Febrile is produced with support from the Infectious Diseases Society of America (IDSA). Audio editing/mixing provided by Bentley Brown.

Transcript
Sara Dong:

Hi, everyone.

Sara Dong:

Welcome to Febrile, a cultured podcast about all things infectious disease.

Sara Dong:

We use consult questions to dive into ID clinical reasoning, diagnostics,

Sara Dong:

and antimicrobial management.

Sara Dong:

I'm Sara Dong, your host and a MedPeds ID doc.

Sara Dong:

I am super pumped to bring you another international episode today.

Sara Dong:

We are joined by a team from Australia.

Sara Dong:

First up, I'll introduce our host, Dr.

Sara Dong:

Genevieve Martin.

Sara Dong:

She is undertaking her training in ID at the Royal Darwin Hospital in

Sara Dong:

the Northern Territory, Australia.

Sara Dong:

She completed her PhD in the immunology of early HIV infection

Sara Dong:

and HIV cure approaches at the University of Oxford in 2018.

Genevieve Martin:

Hi, my name is Genevieve Martin.

Genevieve Martin:

I'm an infectious diseases registrar at the Royal Darwin hospital, and

Genevieve Martin:

I'm really glad to be here today.

Sara Dong:

We have two additional consultants today.

Sara Dong:

Dr.

Sara Dong:

Catherine Marshall is the co director of the Department of

Sara Dong:

Infectious Diseases and is an ID physician at Royal Darwin Hospital.

Catherine Marshall:

I'm Dr.

Catherine Marshall:

Catherine Marshall, the co director of Infectious Diseases at Royal Darwin

Catherine Marshall:

Hospital, and I'm thrilled to be here.

Catherine Marshall:

Thanks.

Sara Dong:

And we are also joined by Professor Bart Currie, who is an ID

Sara Dong:

physician at Royal Darwin and also works in the Menzies School of Health Research.

Bart Currie:

Good morning or good evening, I'm Bart Currie, an infectious

Bart Currie:

disease physician here at Royal Darwin Hospital and also working at the

Bart Currie:

Menzies School of Health Research.

Bart Currie:

Thank you.

Sara Dong:

Great.

Sara Dong:

I'm so excited you guys are here.

Sara Dong:

Before we jump in, we always ask one quick question.

Sara Dong:

As everyone's favorite cultured podcast, I'd love to hear you share a little

Sara Dong:

piece of culture, you know, something that brings you joy outside of work.

Genevieve Martin:

It's early days to call it something good, but I've just

Genevieve Martin:

started reading The Bee Sting by Paul Murray, and I think it's going to be good.

Catherine Marshall:

So one of my favourite things to do in Darwin each year is to

Catherine Marshall:

visit the National Aboriginal and Torres Strait Islander Art Awards that are shown

Catherine Marshall:

at the Museum and Art Gallery of the Northern Territory, and there's a fabulous

Catherine Marshall:

array of art from all over the country.

Genevieve Martin:

Oh, it's great.

Genevieve Martin:

I went a couple of weeks ago.

Bart Currie:

My naturalist colleagues here up in the tropical north of

Bart Currie:

Australia have told me that the snakes have been very unusual in their behavior

Bart Currie:

over the last three or four months.

Bart Currie:

They've been on the move and they've also been, the newborns have been

Bart Currie:

hatching or the eggs have been hatching and the liveborns have been coming,

Bart Currie:

coming out earlier than normal.

Bart Currie:

We've had a substantial number of bites from snakes in the last few months,

Bart Currie:

more than I think we've ever seen.

Genevieve Martin:

In addition to being an infectious disease

Genevieve Martin:

physician, Bart Currie is also our snake bite management expert up here.

Bart Currie:

I guess it is mixing work with pleasure.

Sara Dong:

Well, thank you guys so much for sharing.

Sara Dong:

Genevieve, well, I'm looking forward to hearing about your consult.

Genevieve Martin:

Okay, perfect.

Genevieve Martin:

This scenario is, you receive a call in late January, the wet season,

Genevieve Martin:

from the emergency department that a 42 year old male has arrived,

Genevieve Martin:

having been flown in from a remote community in the Northern Territory.

Genevieve Martin:

The patient's being brought into his local clinic by family members.

Genevieve Martin:

History reveals two to three days of cough and subjective fevers.

Genevieve Martin:

The observations taken in the remote clinic showed a fever of 38.

Genevieve Martin:

9 degrees Celsius, tachycardia at 108 beats per minute, a blood

Genevieve Martin:

pressure of 109/62, and a respiratory rate of 28, meeting SIRS criteria.

Genevieve Martin:

One set of blood cultures was taken and the patient was given a stat dose

Genevieve Martin:

of ceftriaxone and gentamicin, along with crystalloid fluid resuscitation.

Genevieve Martin:

Having now arrived in the ED, he remains tachypneic and tachycardic

Genevieve Martin:

with a GCS of 14, scored for confusion.

Genevieve Martin:

He is now requiring 2 litres of oxygen to maintain oxygen

Genevieve Martin:

saturations greater than 94%.

Genevieve Martin:

Initial blood work is taken and is pending.

Genevieve Martin:

At this point, what further information would you like, and what

Genevieve Martin:

investigations would you suggest that the emergency department request?

Catherine Marshall:

Thanks Genevieve.

Catherine Marshall:

So I guess I would be concerned that this patient has bacterial sepsis due

Catherine Marshall:

to a lower respiratory tract infection and I would want to know what their

Catherine Marshall:

comorbidities were and whether they were a smoker or a heavy drinker of alcohol.

Catherine Marshall:

We know that excessive alcohol consumption is a risk factor for

Catherine Marshall:

both melioidosis and community acquired Acinetobacter infection.

Catherine Marshall:

I'd also want to know whether they've had any water or animal exposures that

Catherine Marshall:

would put them at risk of infections such as leptospirosis or Q fever,

Catherine Marshall:

and I'd want to know whether they've had any recent skin infections or

Catherine Marshall:

abscesses that may indicate a risk for disseminated Staph aureus infection.

Catherine Marshall:

I'd recommend that the emergency department undertook further blood

Catherine Marshall:

cultures, sputum and urine cultures, and a chest x ray in the first instance.

Catherine Marshall:

In our emergency department, they'd also do a gene expert

Catherine Marshall:

PCR for COVID/Influenza/RSV.

Catherine Marshall:

I'd also suggest sending serology for melioidosis, and we also do a,

Catherine Marshall:

or recommend a throat and rectal swab that is then incubated in a

Catherine Marshall:

selective media called Ashdown's Media, looking specifically for melioidosis.

Catherine Marshall:

Given the confusion in this patient, I think that they're going to likely need

Catherine Marshall:

imaging of the brain with at least a CT scan and probably a lumbar puncture

Catherine Marshall:

to exclude a meningoencephalitis after they're stable from an initial

Catherine Marshall:

resuscitation perspective, and I guess although less likely, I may also

Catherine Marshall:

suggest sending a blood and urine for say, leptospirosis PCR, and serology.

Genevieve Martin:

Well, we have some of that information.

Genevieve Martin:

So in terms of past medical history, the emergency department staff have been

Genevieve Martin:

unable to identify any relevant past medical history, and they've confirmed

Genevieve Martin:

that the, the patient, uh, does not, has very little contact with his local clinic.

Genevieve Martin:

With regards to alcohol use, they've spoken with family who've reported

Genevieve Martin:

that he does not drink any alcohol and is not a smoker, but that he

Genevieve Martin:

does spend a lot of time fishing in the rivers around the community.

Genevieve Martin:

Initial blood work is now back, which shows a raised white cell count at 23.

Genevieve Martin:

2 with a predominant neutrophilia and a C reactive protein at 391 mg per litre.

Genevieve Martin:

His creatinine is elevated at 156 giving a GFR of 46 with a lactate of 3.

Genevieve Martin:

2, ketones 2.

Genevieve Martin:

4 and sodium 129.

Genevieve Martin:

He has a normal bilirubin of 7 with liver enzyme derangement

Genevieve Martin:

that's predominantly cholestatic.

Genevieve Martin:

The patient's noted to have a macrocytic anemia with a hemoglobin

Genevieve Martin:

of 110 and an MCV of 105.

Genevieve Martin:

Chest X ray shows bilateral consolidation and neuroimaging is still pending.

Genevieve Martin:

Despite a further 2 litres of fluid resuscitation, he remains hypotensive

Genevieve Martin:

and is being transferred to the intensive care unit for vasopressor support.

Genevieve Martin:

At this stage, what empiric antimicrobials would you suggest and why?

Catherine Marshall:

So I would initially recommend treatment for severe community

Catherine Marshall:

acquired pneumonia, which according to our local guidelines in the wet season

Catherine Marshall:

would include a combination of meropenem that covers the usual well known organisms

Catherine Marshall:

that cause community acquired pneumonia such as streptococcal pneumoniae.

Catherine Marshall:

But we'll also cover Burkholderia pseudomallei, the agent causing

Catherine Marshall:

melioidosis, and community acquired Acinetobacter baumannii, which also

Catherine Marshall:

can be a cause of community acquired pneumonia in our tropical region.

Catherine Marshall:

And that would also provide cover for leptospirosis.

Catherine Marshall:

I'd also recommend vancomycin to cover for MRSA, and azithromycin

Catherine Marshall:

to provide some atypical cover, particularly thinking of Legionella.

Genevieve Martin:

Okay, thank you for that.

Genevieve Martin:

So the patient's been admitted to the intensive care unit, and on your

Genevieve Martin:

advice has been commenced on meropenem, vancomycin, and azithromycin, but has

Genevieve Martin:

an ongoing noradrenaline requirement.

Genevieve Martin:

He's requiring oxygen via nasal prongs, but no additional respiratory

Genevieve Martin:

supports, and has been commenced on an insulin infusion to assist in

Genevieve Martin:

management of hyperglycemia and ketosis.

Genevieve Martin:

An HbA1c has just returned at 10.

Genevieve Martin:

2%, consistent with undiagnosed diabetes mellitus.

Genevieve Martin:

The intensive care team have received a phone call to say that a blood culture

Genevieve Martin:

taken in community is growing in atypical motile gram negative bacillus, which

Genevieve Martin:

they suspect may be a contaminant.

Genevieve Martin:

The two further sets taken in the emergency department

Genevieve Martin:

remain negative at this stage.

Genevieve Martin:

Based on this information, Burkholderia pseudomallei is strongly suspected

Genevieve Martin:

to be the causative organism.

Genevieve Martin:

I'm wondering, Bart, if you could tell us a little bit more about the

Genevieve Martin:

additional diagnostic tests that might be available at this stage

Genevieve Martin:

to help us confirm the diagnosis.

Bart Currie:

Yes, thanks Genevieve.

Bart Currie:

So, melioidosis is always diagnosed still by having a culture.

Bart Currie:

That's the only thing that will fulfill the definition of confirmed

Bart Currie:

melioidosis is a laboratory culture for Burkholderia pseudomallei.

Bart Currie:

The organism was thought by the laboratory initially, not our hospital

Bart Currie:

laboratory, but the external laboratory, to maybe be a contaminant, which is

Bart Currie:

not unusual for places where they may not see this organism so commonly.

Bart Currie:

So, the thing about the organism is that it's a motile gram negative rod,

Bart Currie:

it's oxidase positive, non lactose fermenting, and it has bipolar staining.

Bart Currie:

In laboratories which do not have a lot of resources, there's a 3 disk

Bart Currie:

diffusion test that can be used, which is using gentamicin, to which

Bart Currie:

Burkholderia pseudomallei is resistant, and also colistin disc, and also an

Bart Currie:

amoxicillin cladolanic acid disc.

Bart Currie:

And Burkholderia pseudomallei is sensitive to amoxi-clav, but resistant

Bart Currie:

to gentamicin and colistin, so that three disc test has been very useful

Bart Currie:

to make people think that this is B.

Bart Currie:

pseudomallei.

Bart Currie:

Then to confirm that the organism is B.

Bart Currie:

pseudomallei, there have traditionally been various biochemical profiles,

Bart Currie:

but there are also automated tests such as Vitek and MaldiTOF.

Bart Currie:

The problem with Vitek and MaldiTOF, and there have been a number of publications

Bart Currie:

over the years, is that historically, they would sometimes misidentify B.

Bart Currie:

pseudomallei as another Burkholderia species or indeed some other organisms,

Bart Currie:

but more recently, with improved database profiles, such as an increased number

Bart Currie:

of mass spectra profiles in the MALDI TOF, the specificity of these automated

Bart Currie:

detection systems have been much improved, so that the final confirmation

Bart Currie:

can be made on those systems usually.

Bart Currie:

However, in addition to that, there is also the ability to do a PCR on a culture

Bart Currie:

and also there is a non commercial lateral flow assay that can be used.

Genevieve Martin:

Okay.

Genevieve Martin:

Fantastic.

Genevieve Martin:

That's really helpful.

Genevieve Martin:

So to return briefly to the case, based on some advice provided by our team, some

Genevieve Martin:

further investigations are performed.

Genevieve Martin:

A CT of the chest and abdomen and pelvis is performed revealing a dense right

Genevieve Martin:

sided consolidation and left middle zone changes without any cavitation

Genevieve Martin:

or associated pleural effusion.

Genevieve Martin:

There is evidence of multiple splenic hypodensities reported to

Genevieve Martin:

favour infection or infarction.

Genevieve Martin:

This CT has also identified a very large 24 by 18 millimetre prosthetic abscess.

Genevieve Martin:

Urology have been referred to consider drainage of this.

Genevieve Martin:

And the urine sent on admission has greater than 100 leukocytes on

Genevieve Martin:

microscopy and is now growing a motile gram negative organism with bipolar

Genevieve Martin:

staining, which the lab has confirmed is morphologically consistent with

Genevieve Martin:

Burkholderia pseudomallei, and a PCR of a throat rectal swab cultured in Ashdown's

Genevieve Martin:

media is also positive for this organism.

Genevieve Martin:

Together, these investigations confirm a diagnosis of melioidosis.

Genevieve Martin:

What is your approach to the initial management of this infection?

Catherine Marshall:

Thanks Genevieve.

Catherine Marshall:

So I think we'd be comfortable now that this patient, as you mentioned,

Catherine Marshall:

has disseminated melioidosis with involvement with pneumonia, likely

Catherine Marshall:

splenic abscesses and a prostatic abscess.

Catherine Marshall:

So, our initial management would include appropriate antimicrobial therapy,

Catherine Marshall:

which would be intravenous in the first instance with either meropenem

Catherine Marshall:

or ceftazidime, and we usually prefer meropenem in the intensive care setting.

Catherine Marshall:

Given that there's deep abscesses, particularly in the prostate, we

Catherine Marshall:

would also add a second agent, so cotrimoxazole, as, you know, additional

Catherine Marshall:

agent to improve penetration, particularly within the prostate.

Catherine Marshall:

The other critical component of initial management is source control, so in

Catherine Marshall:

this case we would recommend drainage of the prostatic abscess, which might

Catherine Marshall:

be done either by the urologist or is sometimes done by our radiology colleagues

Catherine Marshall:

transrectally using ultrasound guidance.

Catherine Marshall:

There would also need to be assessment of the splenic abscess about whether

Catherine Marshall:

that would need further drainage, but often we can manage those

Catherine Marshall:

conservatively with antibiotics alone.

Genevieve Martin:

On day four of ICU admission, the patient's being

Genevieve Martin:

weaned off inotropic support with improving inflammatory markers.

Genevieve Martin:

Atraumatic swelling of the left knee is noted and a diagnostic aspirate

Genevieve Martin:

performed at the bedside reveals a synovial white cell count of 38, 000

Genevieve Martin:

cells with no organisms or crystals seen.

Genevieve Martin:

Burkholderia pseudomallei PCR and a lateral flow assay for the

Genevieve Martin:

Burkholderia pseudomallei antigen on synovial fluid is positive.

Genevieve Martin:

How frequently is musculoskeletal involvement encountered and does

Genevieve Martin:

this change your management?

Bart Currie:

Thanks Genevieve.

Bart Currie:

So just taking a step back, this, this patient represents the severe

Bart Currie:

end of the spectrum of melioidiosis.

Bart Currie:

So it's a person who has severe sepsis, they're bacteremic, and the organism is

Bart Currie:

primarily probably caused a pneumonia initially and then seeded to prostate,

Bart Currie:

spleen, and now, as evident, to a joint.

Bart Currie:

Overall, over half of the patients who present with melioidiosis are bacteremic,

Bart Currie:

and the primary presentation in around half of the patients is a pneumonia,

Bart Currie:

with subsequent seeding in some of them.

Bart Currie:

Overall, 21 percent of the patients do present like this with septic shock

Bart Currie:

requiring intensive care management.

Bart Currie:

Then the lesser end of the spectrum of presentation, which is not this patient,

Bart Currie:

are people who may have a primary skin lesion without systemic sepsis

Bart Currie:

or people presenting primarily with a genitourinary infection where the prostate

Bart Currie:

abscess may be the initial presentation rather than having seeded there, with

Bart Currie:

pneumonia being the primary presentation.

Bart Currie:

So overall, in answer to the question, septic arthritis is very

Bart Currie:

rare as a primary presentation, around about 3 percent of our cases.

Bart Currie:

And osteomyelitis, even less common, 1 percent of our primary cases, but

Bart Currie:

within the three weeks following initial presentation, seeding to bone

Bart Currie:

and joint is certainly well recognized.

Bart Currie:

So an additional 3 percent of patients will seed to joints,

Bart Currie:

such as in this patient, 3 percent seed to joint with osteomyelitis.

Bart Currie:

And we also have seeding to muscles, so muscle abscesses in sometimes

Bart Currie:

multiple different muscles will present in 3 percent of patients, subsequent

Bart Currie:

to their initial presentation.

Bart Currie:

So that's the spectrum of melioidiosis.

Bart Currie:

And if the way it changes management is, is that, as Katherine mentioned,

Bart Currie:

abscesses often need to be drained and certainly joints need to be, initially

Bart Currie:

after the aspiration, usually washed out.

Bart Currie:

And it's not uncommon for joints to need to have a second washout.

Bart Currie:

And so what we do is that we reset the clock for the intravenous

Bart Currie:

antibiotics every time we do an aspirate, or a washout, or a drainage

Bart Currie:

of an abscess, provided that it is culture positive, which it usually is.

Bart Currie:

So that then resets our clock for the antibiotic duration for

Bart Currie:

the intravenous antibiotics.

Genevieve Martin:

And I guess that leads into the next question.

Genevieve Martin:

Once appropriate source control has been achieved, and we're happy that that's

Genevieve Martin:

the case, the duration of antimicrobials used for melioidiosis is much longer

Genevieve Martin:

than other gram negative infections.

Genevieve Martin:

How long do you need to treat for, and what's the approach to this?

Catherine Marshall:

As alluded by Bart, the treatment of melioidiosis

Catherine Marshall:

involves an intensive intravenous phase, which is followed then by an oral

Catherine Marshall:

eradication phase, and the duration of the intensive phase varies depending on

Catherine Marshall:

the source and extent of the infection.

Catherine Marshall:

For a simple limited bacteremia or limited mild pneumonia, that may be you

Catherine Marshall:

know, two weeks of intravenous therapy.

Catherine Marshall:

But if there is disseminated disease, say, for example, with central

Catherine Marshall:

nervous system involvement, this may be as long as eight weeks.

Catherine Marshall:

And as Bart mentioned before, time is taken from either the date of the

Catherine Marshall:

last positive culture or the time that source control has been achieved with

Catherine Marshall:

either, you know, drainage of an abscess.

Catherine Marshall:

In this case, where there are deep collections and septic arthritis, the

Catherine Marshall:

patient would require a minimum of four weeks of intravenous therapy from

Catherine Marshall:

the time of source control, but if it subsequently discovered that they had

Catherine Marshall:

osteomyelitis associated with their septic arthritis, then that would

Catherine Marshall:

need to be extended to six weeks.

Catherine Marshall:

Following the intravenous phase, there is ongoing eradication therapy, which

Catherine Marshall:

usually involves oral cotrimoxazole for a minimum of three months.

Catherine Marshall:

That would be extended out to six months if there were CNS

Catherine Marshall:

involvement or osteomyelitis.

Catherine Marshall:

If cotrimoxazole is not tolerated, then doxycycline is

Catherine Marshall:

used as a second line therapy.

Genevieve Martin:

This patient is improving and nearing discharge from

Genevieve Martin:

our hospital in the home service, having completed six weeks of

Genevieve Martin:

intravenous therapy with ceftazamine.

Genevieve Martin:

They've been established on trimethoprim-sulfamethoxazole at a

Genevieve Martin:

high dose of 320 / 1600 milligrams orally twice a day with additional

Genevieve Martin:

folic acid supplementation.

Genevieve Martin:

They're tolerating this regimen well with no significant adverse reactions.

Genevieve Martin:

They ask you why they became sick with this infection in the first place.

Genevieve Martin:

How do you counsel them about risk factors and prevention of infection?

Bart Currie:

I think that taking a step back in, in relation to prevention

Bart Currie:

of melioidiosis, which would also be the information passed on to this

Bart Currie:

patient because people can get a second infection with melioidiosis.

Bart Currie:

What we have recognized over time with our studies here in Darwin is that

Bart Currie:

melioidiosis is very much considered as an opportunistic infection, so healthy people

Bart Currie:

rarely get very sick from melioidiosis.

Bart Currie:

And indeed, only 16 percent of our cases are people who have

Bart Currie:

identified clinical risk factors.

Bart Currie:

So that our emphasis for public health is on the people who have the risk

Bart Currie:

factors and for them to avoid exposure to the organism during the wet season

Bart Currie:

when 85 percent of our cases happen.

Bart Currie:

Our wet season here is from basically November through to the end of April.

Bart Currie:

And it's during that time that the majority of our cases happen when

Bart Currie:

people have an exposure to wet season, soil, mud, or surface water.

Bart Currie:

What are those risk factors?

Bart Currie:

Well, up to 50 percent of our cases are people living with diabetes.

Bart Currie:

Sometimes, diabetes has not been diagnosed until the episode of meliodosis.

Bart Currie:

Hazardous alcohol use is unfortunately common in our part of the world here

Bart Currie:

as a risk factor for meliodosis.

Bart Currie:

And then people with chronic lung disease, chronic kidney disease, and then

Bart Currie:

increasingly we're seeing our patients who have malignancies and particularly

Bart Currie:

after they go on immunosuppression and most notably corticosteroid therapy, they

Bart Currie:

are people who are really magnets for melioidiosis during the wet season and so

Bart Currie:

for those people in the high risk groups.

Bart Currie:

We actually recommend that when the wind and rains come, that they stay

Bart Currie:

indoors during periods of heavy wind and rain because while the majority

Bart Currie:

of infections are thought to be percutaneous exposure through either

Bart Currie:

cuts or trauma, there's clearly a shift to inhalational melioidiosis when there

Bart Currie:

is actually windy and rainy events and so we recommend people with those risk

Bart Currie:

factors stay indoors and if they have to go outside they even wear a mask.

Bart Currie:

One of the things we've found most recently, in the last few years,

Bart Currie:

is that people using high pressure hoses to clean off pavements or to

Bart Currie:

clean their cars have been getting infected through aerosolization.

Bart Currie:

So these are all the things that can put people at risk of melioidiosis.

Bart Currie:

And the final point is that children are not at risk

Bart Currie:

usually of getting melioidiosis.

Bart Currie:

We of course will have the occasional case with a single skin sore or an

Bart Currie:

immunosuppressed child unfortunately may well get melioidiosis and become sick.

Bart Currie:

But overall, less than 4 percent of our patients are children aged under 15 years.

Genevieve Martin:

I guess we've talked a little bit about melioid

Genevieve Martin:

up here in the top end, Burkholderia pseudomallei is found in the soil

Genevieve Martin:

in tropical and subtropical regions, including the top end of Australia

Genevieve Martin:

where we work in endemic areas.

Genevieve Martin:

The incidence of melioidiosis, as you've mentioned, has a

Genevieve Martin:

strong link with weather events.

Genevieve Martin:

What do we know about the environmental niche of Burkholderia

Genevieve Martin:

pseudomallei, and is this linked to changing regions of endemicity?

Bart Currie:

That's a fascinating area, and there's a lot of our colleagues

Bart Currie:

around the world and including in the Americas, working on this.

Bart Currie:

Issue of what is or what are the environmental niches for

Bart Currie:

Burkholderia pseudomallei.

Bart Currie:

We know that it's been endemic for a long period of time in much of the

Bart Currie:

tropics and subtropics and it's only been when people have brought laboratory

Bart Currie:

resources to regions such as in parts of Africa and indeed in South America and

Bart Currie:

the Caribbean that people have started to diagnose cases of melioidiosis.

Bart Currie:

The organism is natural to many of these tropical environments, and

Bart Currie:

it has a selective advantage over other environmental organisms, in

Bart Currie:

particularly soils which are nutrient deplete, so poor soils with lower

Bart Currie:

pH, where the organism is able to survive and outcompete other organisms.

Bart Currie:

There's a natural role in the environment.

Bart Currie:

Its hypothesized to be in symbiosis with the rhizosphere of various

Bart Currie:

plants, or the root systems, where this organism, Burkholderia pseudomallei,

Bart Currie:

is able, through its vast array of virulence factors, to provide a

Bart Currie:

biodefense for those plants against invading bacteria, fungi, and protozoa.

Bart Currie:

The issue for the Americas is fascinating because, while melioidiosis has

Bart Currie:

been endemic for a long time in many parts of the world, in the United

Bart Currie:

States, it is now being found for the first time to be actually endemic

Bart Currie:

in the Gulf State of Mississippi.

Bart Currie:

And this was published in the New England Journal of Medicine just last

Bart Currie:

year, following three cases in the years between 2020 and 2023 from a particular

Bart Currie:

county on the Gulf Coast of Mississippi.

Bart Currie:

So this is an emerging issue.

Bart Currie:

And our colleagues at CDC in the U.

Bart Currie:

S.

Bart Currie:

are working hard with the state health authorities in Mississippi

Bart Currie:

to find out how it got there and how widespread it might be.

Bart Currie:

Is it in other Gulf states in the United States?

Bart Currie:

What the genotyping has shown of those bacteria is that they

Bart Currie:

are a Western Hemisphere strain.

Bart Currie:

So it has potentially moved from the Americas through the Caribbean and then

Bart Currie:

from Southern America and Caribbean into the Southern United States.

Bart Currie:

Our colleagues at the CDC are experts at advising people on that and they have

Bart Currie:

resources available for both diagnosis and advice on therapy as well if there

Bart Currie:

should be an emerging case somewhere.

Bart Currie:

And remember that also that of those 12 cases, the majority have

Bart Currie:

been imported cases through various products brought into the U.

Bart Currie:

S.

Bart Currie:

or returned travellers.

Bart Currie:

There was a case in 2019 related to an aquarium that had fish which

Bart Currie:

were imported from Southeast Asia.

Bart Currie:

The, aquarium was positive for Burkholderia pseudomallei, the

Bart Currie:

water was, and that linked, uh, was identical on genotyping to

Bart Currie:

the isolate from the patient.

Bart Currie:

You might be aware that there was the tragedy of the four cases in the U.

Bart Currie:

S.

Bart Currie:

which was from imported aromatherapy spray from India.

Bart Currie:

Four cases, two fatal, and one of those fatalities was in a child

Bart Currie:

who was co infected with COVID.

Bart Currie:

That was in four different states, and it was an aromatherapy product

Bart Currie:

imported, which was contaminated with B.

Bart Currie:

pseudomallei.

Bart Currie:

And again, the genotyping, we've linked the isotopes from the

Bart Currie:

patients to that aromatherapy spray.

Bart Currie:

So these are the sort of scenarios, so imported cases certainly happen, return

Bart Currie:

travellers have melioid and now you have it endemic in the US, so watch this space.

Genevieve Martin:

Okay, fantastic.

Genevieve Martin:

I feel like I'm always learning so much listening to you talk about melioid.

Genevieve Martin:

Before we wrap up, are there any other pearls of wisdom you

Genevieve Martin:

have to share with the audience?

Bart Currie:

I guess there's a number of things of interest and importance.

Bart Currie:

One is our lack of understanding still of how quickly it is

Bart Currie:

spreading around the world.

Bart Currie:

And so in other words, the unmasking of long term endemicity versus, uh,

Bart Currie:

spread such as I mentioned into the Southern United States, and then what

Bart Currie:

will happen over the next few decades.

Bart Currie:

There is modeling suggesting that with global warming, the organism will continue

Bart Currie:

to proliferate potentially more rapidly and in a more diverse geographic range

Bart Currie:

because of the nature of the weather that we're facing and the climate

Bart Currie:

future that we're facing in the world.

Bart Currie:

The other thing is, is that as an opportunistic pathogen, which particularly

Bart Currie:

is an issue for people living with diabetes, the incredible increase in

Bart Currie:

diabetes worldwide, particularly in lower income countries and such as in Southeast

Bart Currie:

Asia, parts of Southeast Asia, and in the Americas as well, and also in Africa.

Bart Currie:

It means that there's going to be an enormous number of people

Bart Currie:

who are susceptible to getting unwell should they become infected.

Bart Currie:

And I guess the final point is that the positive side of things is that

Bart Currie:

there's actually a vaccine on the horizon, and there are three vaccines

Bart Currie:

that are currently in active study, and it's hoped that there will be, in

Bart Currie:

the next 12 to 18 months, the first ever in human trial of some of the

Bart Currie:

first of these vaccines for mellidosis.

Genevieve Martin:

Okay, fantastic.

Sara Dong:

Thank you so much to Genevieve, Catherine, and

Sara Dong:

Bart for joining Febrile today.

Sara Dong:

This was a really awesome episode.

Sara Dong:

Don't forget to check out the website, febrilepodcast.

Sara Dong:

com, where you'll find the Consult Notes, which are written complements

Sara Dong:

of the show with links to references, our library of ID infographics,

Sara Dong:

and a link to our merch store.

Sara Dong:

Febrile is produced with the support of the ID Society of America.

Sara Dong:

Audio editing and mixing is provided by Bentley Brown.

Sara Dong:

Please reach out if you have any questions, suggestions for future shows,

Sara Dong:

or want to be more involved with Febrile.

Sara Dong:

Thanks for listening, stay safe, and I'll see you next time.

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Febrile
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