This study reports the programmatic introduction of targeted next-generation sequencing (tNGS) in Eswatini and shows that tNGS detected large amounts of rifampicin and bedaquiline resistance missed by routine diagnostics. Among 234 patient samples, tNGS reclassified many infections, revealed frequent co-occurrence of rpoB I491F and Rv0678 mutations, and guided treatment changes with high treatment success in a clinical subset.
0:00Welcome to Base by Base, the paper cast that brings genomics to you, wherever you are. Thanks for listening, and don't forget to follow and rate us in your podcast app. So, uh, imagine for a 2nd that you are relying on a massive high-tech security scanner to protect a building.
0:16State of the art, right. It beeps when it finds a threat and, you know, everyone feels safe. Right, like a metal detector at an airport. Exactly. But what happens if that exact scanner specifically fails to detect the most dangerous, most common type of threat walking through the door?
0:31Well, I mean, that would be a complete disaster. Right. So how does a health system fight an invisible enemy, when the very tools designed to find it are just, well, completely blind? It is, it's a terrifying scenario.
0:44And it perfectly captures the reality of the medical puzzle we are analyzing in our deep dive today. Yeah. We are looking at a pathogen that is literally outsmarting our routine diagnostic tests. In the world of infectious disease we call this a diagnostic escape.
1:00Diagnostic escape. Wow. Yeah, and has profound implications for, you know, how we treat patients every single day. It really does. Today we celebrate the work of the Eswatini National Tuberculosis Control Program.
1:13Eswatini Health Laboratory Services, the Baylor College of Medicine Children's Foundation, and the Research Center Borstol, who have advanced our understanding of drug resistant tuberculosis and genomic diagnostics.
1:25Yes, their work is just incredibly vital right now, because to truly grasp the sheer scale and gravity of this problem. We need to look closely at Eswatini. It is a country facing a massive overlapping burden of both tuberculosis and HIV.
1:43Just to give you a sense of the numbers. They have a TB incidence rate of 319 per 100,000 people. Wait, 319. That is an incredibly high baseline of infection. It is, but the primary issue threatening their health system right now isn't just, you know, standard TB.
1:58It is an epidemic of a specific multi-drug resistant strain of mycobacterium tuberculosis. Right. And the villain in this story is a very specific, stealthy, genetic mutation carried by this strain. It's known as the RPPB I 491F mutation.
2:13Yeah exactly. And I know that string of letters and numbers might just sound like a random typper to anyone listening, but it is actually the core driver of an entire public health crisis. It really is.
2:23What's fascinating here. Well, fascinating and alarming is how a single microscopic mutation can dismantle a national treatment strategy. Yeah. The Rco-B I 491 F mutation causes the bacteria to become resistant to Refampisson.
2:41And Refempson is, I mean, it's an absolute cornerstone of TV treatment, right? Absolutely. It is one of the most critical 1st line drugs we have to cure the disease. But the real danger isn't just the resistance itself.
2:53the blindness. Exactly. It's that diagnostic escape we mentioned earlier. This specific mutation is completely missed by the World Health Organization's routine diagnostic test. Okay, let's unpack this.
3:03If the standard rapid tests are missing the majority of the resistant cases, we aren't just failing to cure patients, we are actively giving them the wrong medication. And like allowing the resistance strain to spread unchecked.
3:16That is precisely the mechanical feel you're happening on the ground. Let's break down why these tests fail so we can understand the blind spot. Okay. Yeah. Globally, health systems rely on few standard tools.
3:27There is the Genex Spurt, MKBIIF Ultra, which is a rapid molecular test. There are line probe, assays, or LPAs, which use chemical strips to detect resistance. And there are standard, culture-based MGIT phenotypic tests.
3:45Wait, the culture ones? That's where you literally try to grow the bacteria in a tube with the drug. to see if it survives, right? Yes, exactly. You grow it and see what happens. So if you're listening to this and wondering why multiple different tests could all fail at the same time, you really have to understand how sneaky this specific mutation is.
4:02It's incredibly sneaky. Right, because the rapid tests are basically like doing a stround plus F search in a 500 page document. document for 3 specific spelling errors. That's a great way to think about it.
4:13And if the bacteria invents a brand new, highly effective typo, which is what this I 491 F mutation is, your search just comes back with 0 results. That is a perfect analogy. The probes in those rapid tests are simply not designed to bind to that specific region of the gene where this mutation occurs.
4:31And even the physical culture tests, the MGITs, can miss it. Because this specific mutation sometimes causes low-level resistance that standard drug concentrations in the testing tubes just don't catch.
4:44So the tests all look at this dangerous strain and report it back to the doctor as susceptible. Exactly. They essentially say, go ahead, use the standard drugs, they will work perfectly. But the bacteria is actively resistant.
4:56It is like trying to put out a grease fire with water because your sensors told you it was just burning paper. Oh, wow. You are actually making the problem worse by giving the bacteria the perfect environment to thrive.
5:07Exactly. And this isn't a sudden overnight phenomenon either. It is a rapidly escalating, compounding failure. Right. The numbers in the paper are wild. They are. When health officials conducted a national survey back in 2009.
5:19This undetected strain accounted for 30% of all multi-drug resistant or refempisin resistant cases in Eswatini. 30% is already huge. Right. But by 2018, that number had ballooned to 58%. The standard tools were just missing a massive growing piece of the puzzle.
5:38And the resistance strain was quietly taking over. Okay, but rolling out next generation sequencing in the middle of a global pandemic sounds nearly impossible. How did they actually manage to get doctors on the ground to understand and trust these massive data readouts instead of their usual rapid tests?
5:55It required a monumental, highly coordinated effort. It went far beyond just you know, buying new equipment. can imagine. In 2019, Eswatini initiated an intervention using targeted next generation sequencing or TNGS.
6:09They managed to open their specialized sequencing lab at the National Tuberculosis Reference Laboratory in April 2021. Right. In the teeth of severe COVID-19 pandemic delays. Exactly. And the technology they implemented was the Deplex Mike TV assay, run on alumina, I seek 100 sequencers.
6:25So going back to our earlier analogy. If the rapid tests are just doing a quick seatroll plus F for a few loan typos, this next generation sequencing is like hiring an expert editor to sit down and read the entire book word for word, like cover to cover to find absolutely every single mistake.
6:43Precisely. Instead of looking for one or 2 specific mutations, The deeplex assay scans 18 different drug resistance associated genes simultaneously. Wow, 18 genes. Yes. It provides a comprehensive, high resolution genetic profile of the bacteria.
7:00But you correctly identified the logistical hurdle, earlier raw genomic data is incredibly dense. Oh, absolutely. A busy clinician treating dozens of patients a day cannot just sit down and decode a complex genetic sequencing report.
7:14Right, you can't just hand a doctor a spreadsheet of base pairs and expect them to know what pill to prescribe. Exactly. So the intervention was integrated directly into the clinical workflow. They formed a clinical advisory committee or CAC.
7:25Okay, so a dedicated team. Right. If a patient showed any sign of resistance on the routine tests, or if they were simply failing to get better on their current treatment, their sample was automatically routed for next generation sequencing.
7:38And then the committee takes over. Yes. The cockies, this team of experts, then took those complex genetic readouts and translated them into actionable, individualized treatment recommendations for the doctors.
7:50So they have the lab running, they have the committee formed. When the 1st wave of patient samples goes through this new system. What did this deeper genetic blueprint actually reveal about why the old tests were failing?
8:02Well, the diagnostic gap revealed by the sequencing was massive, and honestly, quite alarming. I bet. The researchers analyze 234 patient samples. Out of those, the targeted sequencing detected refampus and resistance in an incredible 68% of the samples.
8:19Wow. That is 159 resistance drains. Let's make sure you, the listener, catch the weight of those numbers. Sequencing found resistance in 68% of the samples. What did the standard routine tests find in that exact same group of patients?
8:32The standard expert ultra test only found resistance in roughly 32% of those samples. South and half. Yeah. And the line probe assays and the MGIT culture tests hovered around a mere 20%. The routine tests were completely blind to more than half of the danger.
8:48Exactly. And when the researchers looked closer at the genetics of those 159 resistant strains found by the sequencers, 96 of them carried that exact elusive RPB I 491 F mutation. Here's where it gets really interesting, because the sequencing didn't just find hidden refampesin resistance.
9:06Oh, did? The new technology read the rest of the book and dropped an absolute bombshell regarding an entirely different, incredibly important drug called the daquiline. Yes. The sequencing picked up mutations in the RV 0678 gene, specifically the M146 T and N98 D mutations.
9:23And this raises an important question. Why does a mutation in this specific gene matter so much? Right. Well, the RV 0678 gene acts as a regulatory switch for the bacteria's FLX pumps. Think of an e-flux pump like a tiny biological sump pump inside the bacteria.
9:38Oh, I like that visual. So when a drug like bedaquiline enters the bacterial cell to kill it, These mutated pumps just actively spit the drug right back out before it can work. So it never even gets a chance to attack the bacteria.
9:51Exactly. These mutations confer resistance to both bedak wine and another drug called clefosamine. And bedagoline is not just a standard run-of-the-mill antibiotic. If a patient has severe multi-drug resistant TB, bedacoline is the vital 2nd line anchor of their treatment.
10:09the heavy artillery. Exactly. And the sequencing revealed that this heavy artillery was already compromised. The targeted sequencing found this badacquilian resistance in 87 of the strains. Wait, 87? Yes.
10:23That means 55% of all the rafampisin resistant strains they found were also resistant to bedackling. That is terrifying. Gets worse. If you look exclusively at the strains carrying that stealth RPB I 491 F mutation, a staggering 85% of them were carrying this pedaculane resistance as well.
10:40Wait, out of the patients with prior TB history who had these bedackling resistant strains, only one had actually been treated with bedackling before. Does that mean this superbug is just spreading directly from person to person?
10:52You've hit on one of the most chilling biological realities in the entire paper? Yeah. Yes. Wow. In the vast majority of these cases, we are not looking at acquired resistance. Because acquired resistance is when a single patient takes their medication inconsistently, right?
11:08Right, which allows the bacteria to mutate within their own body. But what the data shows here is active transmission of a highly resistant, dominant strain. So people are just walking down the street and catching a version of TV from their neighbor that is already genetically hardwired to resist both the 1st line defense and the crucial 2nd line defense.
11:28Yes. And until they flip the switch on these sequencers, the entire health system was blind to it. That is the grim reality. But, you know, there is a very bright silver lining here. Okay, good. We need one.
11:40Once the health system could actually see the genetic blueprint of the enemy, they could fight back effectively. The researchers had complete clinical data for 59 patients in this cohort. When the clinical advisory committee review their sequencing data, It led to immediate treatment changes for 53% of those patients.
11:59So over half, got a totally different plan. Exactly. They completely rerouted their care based entirely on the genetics. And the result of moving from blind guessing to genomic precision. An impressive 88% treatment success rate.
12:14They literally saved lives by ditching the one size fits all approach and prescribing exactly what the individual bacteria's blueprint demanded. It is a remarkable testament to the power of precision medicine.
12:26However, these localized successes in Eswatini create a massive ripple effect that challenges the entire global framework for how we categorize and manage tuberculosis. Oh, totally. The findings literally break the current world health organization classifications.
12:42Let's dive into that because if you are sitting at the WHO in Geneva, this data should be setting off alarm bells. Everything in global public health relies on standardized definitions. How a country procures drugs, how they secure international funding.
12:56It all depends on fitting into a predefined clinical box. Exactly. Under the current W Joe rules. For a TB case to be classified as pre-extensively drug resistant or pre-XDR, it requires the bacteria to be resistant to refampissin, and to a class of drugs called fluoroquinolones.
13:14Okay, so fluoquinolones are the key there. Yes. And to step up to extensively drug resistant, or XDR, it requires bedacoline, or line solid resistance, plus that fluoroquinolone resistance. Right. The entire classification system hinges on the presence of fluoquinoline resistance.
13:31But the sequencing data from SWATini. throws a massive wrench into that system. Half of the multi-drug resistance strains they sequenced have robust podacaline resistance without any fluoroquinalone resistance.
13:43That is the SOTini Pteradox. These incredibly dangerous, highly resistant strains literally do not fit into the WHOs classification boxes. If a strain is resistant to your best 1st line drug and your best 2nd line drug, but remains susceptible to fluoquinolones, it officially doesn't exist within the global tracking framework as an extensively drug resistant threat.
14:05That is wild. It proves that the global definitions we are using to track and fund the fight against this disease need urgent fundamental updating. The bacteria has evolved completely outside the bureaucratic boxes we built for it.
14:18And if you don't update the definitions, you can't build the right treatment policies. Wait, if B poem is the new gold standard globally, are you telling me that WHO is actively recommending a treatment that is effectively useless for the majority of patients in this region?
14:32That is exactly the critical danger. That's Watini, like many countries, recently adopted the new B Paul M standard regimen. Okay, remind us what BPOM stands for. Right. Right. B. Paul M stands for bedaquiline, predomanid, linosolid, and moxophlaxin.
14:47It is a highly celebrated, shorter, more tolerable regimen for drug resistant TV. But if 85% of your dominant hidden strain is already resistant to bedaquilin. The B and B polm rolling out this miracle regimen is a recipe for clinical disaster.
15:03That one size fits all regiment might fail right out of the gate for the majority of the patients receiving it. You're basically putting them on a failing drug combination and hoping for the best. When you blindly apply new regimens without mapping the underlying genomic landscape of the local epidemic, you risk widespread treatment failure.
15:22Yeah. Worse, you risk further amplifying drug resistance to the remaining drugs in that DPOLM cocktail. Which is the last thing we need. Exactly. However, as robust as this data is, it is important to note the study's limitations.
15:36We mentioned that routine MGIT testing at a single concentration underestimates pedaquiline resistance. Right. But the targeted sequencing might also be underestimating the total threat. The current deplex assay used in the study only scans the RV 0678 gene for bedaquiline resistance.
15:53Ah, so it's missing other parts of the puzzle. Yes. It misses other known genetic targets, like the FBE gene. So, the true but aquiline resistance rates might actually be even higher than what is reported in this paper.
16:06So what does this all mean? When you zoom out and look at the sheer scale of the diagnostic failure with the rapid tests, combined with the hidden person-to-person transmission of a highly resistant superbug, it paints a very clear picture.
16:20It really does. Global health policy is currently flying blind. And bringing advanced genomic sequencing out of the research lab and integrating it into routine programmatic care is the only way to turn the lights back on.
16:34If we connect this to the bigger picture, the mandates are clear. First, the rapid molecular tests use globally, like the gen expert machines, must be urgently updated and expanded to catch this I 491 F mutation.
16:47We cannot rely on foundational tools that are structurally blind to dominant threat. Right, that just doesn't make sense. Exactly. Second, targeted next generation sequencing is no longer just a fancy experimental luxury for high incomnations.
16:59Yeah, this proves it's a necessity. It needs to be rolled out programmatically in high burdened regions immediately. We have to identify the exact genetic profile of the pathogen to prescribe the right drugs from day one.
17:11It is the ultimate shift from guessing to knowing. We've reached the point in this deep dive where we need to distill everything down to a single core takeaway. Standard diagnostic tests are dangerously blind to a dominant, highly transmissible strain of multi-drug resistant tuberculosis.
17:29However, implementing targeted next generation sequencing on a programmatic level allows doctors to bypass these diagnostic escapes, tailoring lifesaving treatments to the exact genetic profile of the bacteria, and achieving remarkably high curates.
17:44It proves that with the right technology, the right molecular understanding and the right clinical support systems, we can intercept and outsmart the pathogens that are constantly evolving to outsmart us.
17:55It certainly does. But it leaves us with a lingering question for you to ponder. What does this mean for the future of global public health if our pathogens are evolving faster than our standard diagnostic classifications can keep up with?
18:06That is the $1000000 question. This episode was based on an open access article under the CCBY 4.0 license. You can find a direct link to the paper and the license in our episode description. If you enjoyed this, follow or subscribe in your podcast app and leave a 5 star rating.
18:23If you'd like to support our work, use the donation link in the description. Now stay with us for an original track, created especially for this episode, and inspired by the article you've just heard about.
18:32Thanks for listening and join us next time as we explore more science based by base.
