Will it one day be possible to predict the risk of pancreatic cancer using a simple oral swab? This may certainly be the case, according to a new study published in JAMA Oncology ¹. The study suggests that an imbalance in certain fungi and bacteria in our mouths may well be responsible for this cancer.

To demonstrate this, the authors used the medical records and oral microbiota samples of 122,000 individuals monitored over nine years, 445 of whom developed pancreatic cancer. 

Certain bacteria associated with increased risk

First, they discovered that the presence in the mouth of three bacteria involved in gingivitis and periodontitis (Porphyromonas gingivalis, Eubacterium nodatum, and Parvimonas micra) was associated with a higher risk of pancreatic cancer.

Whole-genome sequencing of oral microbes allowed the team to identify a total of 13 bacterial species linked to an increased risk, while 8 appeared to have a protective effect.

Key role of Candida fungi

The study was not limited to bacteria: the long-overlooked fungal microbiota was also analyzed. The researchers found that a greater abundance of Candida, the most common fungus in the oral cavity, is significantly associated with an increased risk of pancreatic cancer.

The researchers also observed that Candida fungi are found in tumor tissues, supporting the hypothesis of a migration of this microorganism from the mouth to the pancreas.
 

Towards a predictive biomarker

By combining all the microbial species identified, the researchers developed a microbial risk score. They found that each increase of one standard deviation in this score is associated with a nearly 3.5-fold increase in the risk of pancreatic cancer.

Taken together, these results strongly suggest that the oral microbiota is indeed involved in the development of pancreatic cancer. 
Could better oral health therefore help prevent this form of the disease? Further research will be needed to find out.

In any case, the oral microbiota could one day serve as a simple, non-invasive biomarker for the early identification of people most at risk of this deadly cancer. 
 

Pancreatic cancer remains one of the most deadly cancers, with a five-year survival rate of around 13%. Established risk factors (smoking, obesity, pancreatitis, and genetics) account for only 30% of cases.

Several epidemiological studies have shown that poor oral health, particularly the presence of periodontal disease and oral candidiasis, is associated with this cancer. Despite this, our knowledge about the actual involvement of oral microorganisms remains limited.

A large-scale prospective study using cohorts from the American Cancer Society Cancer Prevention Study-II and the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, has recently revealed that the oral microbiota, particularly bacteria and fungi, may play a significant role in the subsequent development of pancreatic cancer.

Periodontal bacteria: a strong link

Of the 122,000 participants who provided an oral sample, 445 developed pancreatic cancer during nearly nine years of follow-up. The researchers matched them with 445 healthy individuals to compare their oral microbiota.

The results published in JAMA Oncology ¹ show that three major pathogenic bacteria known to be involved in periodontal disease (Porphyromonas gingivalis, Eubacterium nodatum, Parvimonas micra) significantly increase the risk.

A comprehensive analysis of bacterial genomes revealed that a total of 21 species influence the risk of pancreatic cancer, some protective, others harmful. These taxa are thought to be associated with metabolic pathways that may promote the neoplastic transformation of pancreatic cells during their migration from the mouth to the pancreas.

Candida at the forefront

An analysis of the oral fungal microbiota—a parameter rarely explored in this context—also revealed that the genus Candida is associated with an increased risk of pancreatic cancer.

Candida tropicalis and Candida spp are associated with an increased risk, while C. albicans shows an inverse relationship. Within the Malassezia genus, only M. globosa was associated with cancer, and its effect was protective.

The researchers also report having confirmed the presence of Candida in biological samples of cancerous pancreatic tissue in cancer patients. This again supports the hypothesis of a migration of this fungus to the tumor and a direct role in carcinogenesis.

Towards early diagnosis and a better understanding of risk factors

In order to assess the impact of these microorganisms as a whole, the researchers calculated a Microbial Risk Score (MRS) for each participant, incorporating 27 bacterial and fungal species associated with cancer. They found that each increase of one standard deviation in the MRS more than triples the risk of pancreatic cancer (odds ratio [OR] 3.44).

According to the authors, the MRS score was reproducible between the two cohorts, suggesting the oral microbiota could one day be used as a biomarker in primary prevention to screen high-risk patients.

More generally, the data from this study reinforce the hypothesis that oral health is an important factor in the prevention of pancreatic cancer. Now we must try to better understand how oral fungal and bacterial communities promote cancerization processes.

To be continued...

We often conceptualize antimicrobial resistance (AMR) as a direct consequence of antibiotic overuse. However, a compelling new study published in npj Antimicrobials & Resistance shifts this paradigm, revealing that common "non-antibiotic" medications, drugs your patients likely take daily, may be silent drivers of this global health crisis, particularly in aged care settings ¹.

The hidden drivers in the medicine cabinet

We know that the gut microbiome is a complex ecosystem. Researchers examined how Escherichia coli, a common gut inhabitant and pathogen, responds to nine widely used non-antibiotic medications (NAMs) commonly prescribed in Residential Aged Care Facilities (RACFs), including ibuprofen, acetaminophen (paracetamol), and atorvastatin. The scientists from the University of South Australia didn't just dump drugs on a petri dish; they modeled specific "gut-relevant concentrations" to mimic the actual physiological environment of a patient taking these medications orally.

It appears that these drugs are not biologically inert regarding bacterial evolution. While they don't kill the bacteria like antibiotics do, they exert a stress that fundamentally changes bacterial behavior. Specifically, the study focused on whether these common drugs could enhance mutagenesis (sidenote: Mutagenesis The biological process by which the genetic information of an organism is changed, resulting in a mutation. ) when the bacteria were also exposed to ciprofloxacin, a fluoroquinolone antibiotic frequently used for UTIs in the elderly.

When painkillers mimic antibiotics

The most potent drivers of resistance weren't the obscure drugs, but the everyday painkillers. The data showed that ibuprofen and acetaminophen significantly increased the mutation frequency in E. coli. When exposed to these analgesics alongside ciprofloxacin, the bacteria developed high-level resistance much faster than with the antibiotic alone.

The mechanism uncovered is both sophisticated and alarming. Researchers utilized whole genome sequencing (sidenote: Whole genome sequencing A comprehensive laboratory method used to determine the complete DNA sequence of an organism's genome. Researchers utilized this technique to pinpoint specific mutations in resistance genes like GyrA, MarR and AcrR. ) to pinpoint key mutations: not only in the antibiotic's target, the GyrA gene (sidenote: GyrA gene A gene that encodes a specific subunit of the DNA gyrase enzyme, which acts as the primary biological target for fluoroquinolone antibiotics like ciprofloxacin. Mutations in this gene can prevent the antibiotic from binding effectively, leading to resistance. ) , but significantly, in MarR and AcrR, the regulatory genes controlling efflux pumps (sidenote: Efflux pumps Cellular transport proteins (specifically AcrAB-TolC in this context) that bacteria use to actively expel toxic substances from within the cell. The text describes them as acting like an internal "bilge pump" to flush out both the medication and the antibiotic. ) . Critically, the presence of common analgesics like ibuprofen or acetaminophen was found to induce the bacteria to overexpress the AcrAB-TolC efflux pump. This action is akin to the bacteria activating an internal "bilge pump" to expel the medication, which simultaneously flushes out the antibiotic and, disturbingly, solidifies genetic resistance.

The polypharmacy multiplier

The study went a step further to simulate "polypharmacy (sidenote: Polypharmacy The simultaneous use of multiple medications by a single patient. This practice is common in aged care settings and was shown to significantly increase the level of antibiotic resistance in bacteria exposed to drug combinations. ) ", or the use of multiple drugs, which is standard for many elderly patients. When E. coli was exposed to two NAMs simultaneously (like ibuprofen plus diclofenac), the results were striking. While the frequency of mutations didn't necessarily explode, the level of resistance did. Some mutants exhibited a staggering 64-fold increase in ciprofloxacin resistance compared to the wild type. This suggests that the "cocktail" of medications standard in aged care may be creating a perfect storm for evolving "superbugs". The takeaway for us isn't to stop prescribing pain relief, but to view these medications with new respect. They are active participants in the microbial environment, capable of accelerating resistance mechanisms that threaten public health.
 

We usually think of antibiotic resistance as a war fought only with antibiotics. The logic is familiar: if you overuse them, the surviving bacteria adapt into "superbugs". But a groundbreaking new study reveals that this view is incomplete.

Research published in npj Antimicrobials & Resistance ¹ shows that the everyday medications in your cabinet, specifically non-antibiotic drugs like ibuprofen and acetaminophen, are active participants in your gut’s ecosystem. Surprisingly, they may be training bacteria to resist antibiotics, even when you aren't taking any antibiotics at all.

The surprise in your medicine cabinet

Researchers at the University of South Australia examined how Escherichia coli, a common gut bacterium, responds to standard non-antibiotic medications. They didn't just pour drugs on a dish; they carefully modeled "gut-relevant concentrations" to mimic exactly what happens in your body after swallowing a pill.

The findings were striking. While these drugs don't kill bacteria, they stress them. The study found that common painkillers, ibuprofen and acetaminophen (paracetamol), significantly increased the rate at which E. coli mutates. When these bacteria were later exposed to ciprofloxacin (a standard antibiotic), they evolved resistance much faster than bacteria that hadn't encountered the painkillers.

The "bilge pump" mechanism

How does a painkiller block an antibiotic? The mechanism is elegant and scientifically fascinating. The researchers found that these drugs flip specific genetic switches inside the bacteria.

These switches turn on what is called an efflux pump (sidenote: Efflux pumps Cellular transport proteins (specifically AcrAB-TolC in this context) that bacteria use to actively expel toxic substances from within the cell. The text describes them as acting like an internal "bilge pump" to flush out both the medication and the antibiotic. ) . Think of this like a bilge pump on a leaking ship. The bacteria sense the chemical stress of the painkiller and start pumping furiously to flush it out. The problem? This pump is non-specific. Once activated, it doesn't just eject the painkiller; it mechanically flushes out antibiotics too. 

The "cocktail effect"

The study also simulated taking multiple medications at once, which is common for older adults. When bacteria were exposed to two non-antibiotic drugs simultaneously (like ibuprofen plus diclofenac), the danger shifted.

While the number of mutants didn't necessarily explode, the strength of their resistance did. Some mutants from these drug cocktails developed a staggering 64-fold increase in resistance compared to normal bacteria. This means the bacteria weren't just resistant; they were practically immune to standard antibiotic treatments.

This isn't a reason to panic or stop taking necessary medication. However, it changes how we view our bodies. Your gut is an adaptive environment, and common drugs act as biological inputs that can inadvertently toughen up bacteria. Understanding this helps us use these tools more wisely.

During unprotected sex, thousands of microorganisms are also shared via semen and vaginal secretions. Yet for years, researchers have scrutinized the vaginal microbiota (which has been extensively studied) on the one hand, and the semen microbiota (which has been studied much less) on the other, as if they lived on two different planets. The idea that they might interact in a sexually active couple? Barely touched upon by 14 small studies.

Two very different worlds, but open to exchange

The seminal microbiota of men is completely different from the vaginal microbiota of women: it is generally more diverse, has a lower bacterial concentration, and a slightly alkaline pH of 7.5... whereas the vaginal microbiota is less diverse, dominated by lactobacilli, and has an acidic pH (a direct consequence of the abundance of lactobacilli, which secrete acids) .

However, unprotected sex means the exchange of fluids and bacteria. Female couples often share a similar vaginal microbiota. Male homosexual couples (men who have sex with men) are distinguished by a unique rectal microbiota, rich in Prevotella and less diverse than that of heterosexual men.

In heterosexual couples, these exchanges could have consequences for fertility. This is true for both women and men. For example, an increased abundance of Lactobacillus in the seminal microbiota would go hand in hand with more mobile and concentrated sperm, but also—on the flip side—an adherence of lactobacilli to sperm that would reduce fertility.

STIs and dysbiosis also on the menu

Unprotected sex contributes to the transmission of sexually transmitted infections (STIs) but also disrupts the balance of intimate microbiota (dysbiosis (sidenote: Dysbiosis An imbalance in the microbial community, characterized by reduced beneficial bacteria and increased harmful species, potentially leading to adverse health outcomes. ) ).

Take, for example, the dreaded bacterial vaginosis, linked to a decrease in Lactobacillus and an increase in bacteria such as Gardnerella vaginalis. In heterosexual women, the increase in vaginal pH induced by semen could be a triggering factor for imbalance. It is also important to note that circumcision alters the microbiota of the penis skin, reducing its diversity and the presence of bacteria associated with bacterial vaginosis. Whether this protects women is still a matter of scientific debate.

Assisted reproduction

The microbiota in semen and the vagina may also play a role in the outcome of IVF (sidenote: In vitro fertilization (IVF) A medical assistance technique for procreation where fertilization takes place in the laboratory, in a test tube (“in vitro”), and not in the woman’s uterus: eggs retrieved from the woman after hormonal stimulation are placed in a nutrient solution with sperm collected from the man. The embryos thus conceived in the laboratory will then be transferred to the future mother’s uterus via the vagina. If an embryo implants, the pregnancy begins. https://www.service-public.fr/particuliers/vosdroits/F31462
https://medclinics.com/fr/fiv/
https://www.fiv.fr/fecondation-fiv/ ) , with certain seminal (Acinetobacter) or vaginal (L. crispatus) bacteria being associated with a higher chance of success. Conversely, Prevotella and Porphyromonas bacteria in parents reduce the chances of success.

A couple's reproductive health therefore appears to be linked to the so-called semivaginal (sidenote: Microbiote séminovaginal L’ensemble des micro-organismes provenant des écosystèmes séminal et vaginal qui sont transférés et partagés entre les partenaires lors de rapports sexuels non protégés, s’influençant mutuellement et impactant la santé et les fonctions reproductives. ) microbiota, which is still largely unknown. It is high time to gain a better understanding of how these microbiotas interact, coexist, and sometimes clash. Because yes, in a couple, intimate microbiotas also share a life together.

Serotonin is essential to the digestive system: it regulates essential gastrointestinal functions (peristalsis, vasodilation, visceral sensitivity) and promotes the development and maintenance of the enteric nervous system. Although serotonin production is mainly endogenous (in two stages: tryptophan -> 5-HTP -> serotonin), certain human enteric bacteria are suspected of contributing to it. Scientists have recently identified these bacteria and evaluated the physiological activity of this microbial serotonin on colonic innervation and intestinal motility.

Serotonin-producing lactobacilli

The results confirm that the gut microbiota synthesizes serotonin and contributes to intestinal levels of this substance: in vitro (anaerobic cultures), the human fecal microbiota of healthy volunteers produces serotonin; in vivo, serotonin is found in the stools of mice that are genetically incapable of synthesizing it once they are given microbiota. Which bacteria are responsible? Researchers have identified a pair of serotonin-producing lactobacilli (named Ls), consisting of Ligilactobacillus ruminis and Limosilactobacillus mucosae. Ls does not produce 5-HTP or serotonin from tryptophan (step 1 of synthesis), but produces serotonin in the presence of 5-HTP (step 2). This step 2 of decarboxylation of 5-HTP to serotonin requires the simultaneous presence of both bacteria in the consortium.

Effects of intestinal colonization by the bacterial duo

In axenic mice unable to produce endogenous serotonin, colonization by Ls strains alone increases entero-serotonin levels, promotes colonic innervation, and increases the number of serotonin-immunoreactive neurons. However, serum serotonin levels in mice are unchanged, suggesting that bacterial serotonin primarily regulates local intestinal functions.

The isolated Ls community produces serotonin in vitro. However, this effect is not reproduced in culture conditions with pure strains (L. mucosae or L. ruminis) or with their reconstituted co-culture, whereas this co-culture increases fecal serotonin in vivo. This suggests that microbial serotonin production may depend on specific intestinal conditions (substrates, pH, oxygen, cofactors, microbial interactions).

Restoring patients' intestinal motility?

Finally, Ls normalizes intestinal transit time in axenic mice. However, in patients with irritable bowel syndrome, the fecal abundance of L. mucosae (but not L. ruminis) is significantly lower than in healthy controls. And the less this bacterium is present, the harder the stools are. Could a mechanism linked to the microbiota affect local serotonin biosynthesis and intestinal motility in these patients? According to the authors, future research could determine whether these serotonin-producing bacteria are capable of restoring physiological serotonin levels in patients with intestinal motility disorders.
 

Obesity, type 2 diabetes, cardiovascular disease, cancer: soda consumption is implicated in numerous health problems, with effects that are sometimes underestimated. This list could grow longer and now include depression (sidenote: Depression Depressive disorder (also known as depression) is a common mental disorder. It involves a depressed mood or loss of pleasure or interest in activities for long periods of time. A depressive episode is different from regular mood fluctuations. They last most of the day, nearly every day, for at least two weeks. A depressive episode can be categorized as mild, moderate, or severe depending on the number and severity of symptoms, as well as the impact on the individual’s functioning.

Source : https://www.who.int/news-room/fact-sheets/detail/depression ) , according to the intriguing results of a new German study ¹. 

When science takes an interest in your soda can

To get to the bottom of this, a team of researchers analyzed data from more than 900 Germans aged 18 to 65, recruited in two large cities (Marburg and Münster).
Among them were 405 people (two-thirds of whom were women) suffering from major depressive disorder and 527 healthy controls of comparable age and gender.
Their goal was to understand whether the amount of soda consumed could predict a diagnosis of depression or the severity of symptoms.

The unexpected role of gut microbiota

The researchers continued to dig deeper, going beyond the simple link between soda and depression. They looked at what was happening in the gut microbiota, the vast microbial ecosystem that influences digestion, immunity, and even mood... and whose composition and balance vary with our diet, including soda.

In particular, they focused on two gut bacteria suspected by previous studies of being involved in major depressive disorders:

• Eggerthella
• and Hungatella.

The result: in the women in this study, soda consumption was indeed associated with an increase in Eggerthella in the microbiota; Hungatella, on the other hand, appeared to be unrelated.
Eggerthella alone could explain 3.8% of the link between soft drinks and depression and 5% of the link between soft drinks and symptom severity. . 

Thus, soft drink consumption appears to be linked to major depressive disorder (MDD), and the gut bacterium Eggerthella may be involved by affecting the balance of the microbiota.

This finding is particularly worrying given that consumption of these drinks is increasing worldwide, especially among children and adolescents. These results also provide further evidence in favor of the gut-brain axis and the link between gut microbiota and mental illness.
But there is some good news. Certain dietary approaches can also support a more balanced microbiota and help regulate mood. 

Find out how certain foods could play a protective role by reading our article: 

Antibiotic resistance is a major challenge, in which the vaginal microbiota could play the role of a reservoir for resistance genes. This is the conclusion of a study that investigated the presence of 14 genes conferring resistance to macrolides, tetracyclines, beta-lactams, or quinolones in the vaginal microbiota of 105 Italian female students aged 19 to 30.

Resistance influenced by lifestyle

The vaginal microbiota of the students mainly belonged to CST (sidenote: Five community state types (CST) - CST I dominated by Lactobacillus crispatus, 
- CST II dominated by L. gasseri,
- CST III dominated by L. iners 
- CST V dominated by L. jensenii
- and the more diverse CST IV, which is not dominated by Lactobacillus but by a group of anaerobic bacteria, including Gardnerella, Atopobium, Prevotella, and Finegoldia. 
  ) I, dominated by L. crispatus (41.9%), and CST III, dominated by L. iners (30.5%). In terms of antibiotic resistance genes, the most frequently detected were linked to tetracyclines and macrolides: tet(M) (present in 74.3% of women), erm(F) (72.2%), erm (B) (68.6%), erm(A) (66.7%) and tet(W) (65.7%). 

The influence of lifestyle, health, and antibiotic consumption was largely confirmed, with the presence of resistance going hand in hand with:

• higher microbial diversity in the vaginal microbiota,
• smoking, which doubles the total number of resistance genes,
• a higher BMI (sidenote: Body Mass Index (BMI) Body Mass Index (BMI) assesses the corpulence of an individual by estimating the body fat mass calculated by a ratio between weight ((kg) and height squared (m2). https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm https://www.euro.who.int/en/health-topics/disease-prevention/nutrition/a-healthy-lifestyle/body-mass-index-bmi ) ,
• low use of oral contraceptives,
• poor diet quality,
• the presence of Candida spp.,
• antibiotic use in the previous year, while better past adherence to antibiotic treatment and greater awareness of resistance were associated with fewer resistance genes.

Links between bacterial taxa and antibiotic resistance

The Lactobacillus genus appeared to be protective: the more L. crispatus/jenesenii/gasseri were present, the fewer resistance genes were observed, particularly tet(M) and tet(Q). However, there were a few exceptions to this rule, with positive associations between L. gasseri and erm(A), or between L. iners and tet(Q).

Conversely, the more Gardnerella-Prevotella bacteria were present, the more macrolide and tetracycline resistance genes were observed. Similarly, several taxa associated with bacterial vaginosis (Prevotella, Dialister, Finegoldia, Porphyromonas, Anaerococcus) were linked to a higher number of resistance genes.

A reservoir of resistance

The vaginal microbiota therefore appears to represent a dynamic reservoir of antibiotic resistance genes, which are transferred to vaginal bacteria via mobile genetic elements such as plasmids (sidenote: Plasmide Petites molécules d’ADN mobiles qui peuvent passer d’une bactérie à une autre (au sein de la même espèce mais aussi entre espèces différentes). Source : https://www.pasteur.fr/fr/accueil/journal-recherche/actualites/mecanisme-defense-bacterie-escherichia-coli-fixe-resistance-antibiotique ) and transposons (sidenote: Transposons Séquence d'ADN qui présente la particularité de pouvoir se déplacer du chromosome bactérien vers un plasmide et d'un plasmide à un autre. Porteurs de gènes de résistance, les transposons jouent un rôle majeur dans la dissémination de gènes de résistances entre bactéries d'espèces éloignées. Source : https://www.vetofish.com/definition/transposon ) , making the vagina a critical site for the spread of antibiotic resistance. Since some vaginal bacteria are typical of the gut microbiota, bacterial translocation from the gastrointestinal tract to the vagina is considered a possibility. 

Basil extracts have powerful antimicrobial effects that could be used to restore imbalances in the vaginal flora responsible for bacterial vaginosis and vulvovaginal candidiasis (vaginal yeast infection). These were the findings of a study recently carried out in Korea. ¹

Fragile but precious vaginal lactobacilli

The vagina is home to a microbiota composed of several hundred bacterial species and a small number of fungi, including yeasts of the genus Candida. All of them contribute to maintaining a healthy environment. For example, lactobacilli secrete lactic acid, which acidifies the vaginal environment (maintaining a pH between 3.8 and 4.5), thereby helping to keep many pathogenic microorganisms at bay.

When the natural acidity of the vagina is disrupted or lactobacilli become depleted, an imbalance (dysbiosis) can develop, promoting proliferation of microorganisms associated with bacterial vaginosis (BV) and vulvovaginal candidiasis (VVC), i.e. vaginal yeast infections (see box).

Search for alternative treatments

These infections are often still treated with antimicrobials, such as antibiotics or antifungals. However, the overuse of these treatments promotes the emergence of resistant bacteria and fungi and can affect populations of vaginal lactic acid bacteria, thereby weakening the vaginal microbiota.

Are there any effective and microbiota-friendly therapeutic alternatives to treat and prevent vaginal infections? A team of Korean researchers sought to answer this question by studying basil.

Basil, a traditional remedy for infections

Basil (Ocimum basilicum L.) is a medicinal plant traditionally used as a folk remedy in many cultures to treat respiratory infections, and has been shown to have powerful antibacterial effects due to its high content of bioactive compounds.

To assess its impact on vaginal microorganisms, the scientists tested the effect of various fractions of basil essential oil on in vitro cultures of the microorganisms involved in vaginitis: Gardnerella vaginalis, Fannyhessea vaginae, Chryseobacterium gleum, and Candida albicans.

Their results show that basil essential oil, even at low concentrations, has powerful antimicrobial effects against the four pathogens tested, without showing any toxicity to beneficial lactobacilli (Lactobacillus crispatus) or skin cells (dermal fibroblasts). 
 

Synergistic effect

A particular compound, called methyl trans-cinnamate, appears to explain some of these effects, but the researchers suspect a synergy exists between different molecules present in basil essential oil.

While these findings are encouraging, they relate solely to laboratory tests. Effectiveness as a treatment—and above all safety—still needs to be confirmed by clinical studies in women. In the meantime, avoid self-medication and seek advice from your doctor or pharmacist. While plants continue to be an interesting avenue of research, they are not a substitute for recommended treatments.

Immunotherapy is rewriting oncology, but in most solid tumours, PD-1 inhibitors (sidenote: PD-1 inhibitors Drugs that release the “brakes” on T cells by blocking the PD-1 receptor, allowing the immune system to attack tumours more effectively. ) still fail the majority of patients. Our story starts in a place every clinician knows matters but few can yet “dose”: the gut microbiome. Oncologists have seen that some patients ride a wave of durable response to treatment, while others, seemingly similar on paper, barely respond at all. A new study published in Nature ¹ asks a simple but profound question: a single gut microbe that can reprogram dendritic cells, send them on a “road trip” from the intestine to the tumour, and make checkpoint inhibitors work better? And the answer appears to be yes.

A hidden player in PD-1 response

Researchers from National Cancer Center Research Institute, Tokyo followed patients with lung and gastric cancer receiving PD-1 blockade and looked at their stool microbiome just before treatment. Responders consistently had richer bacterial diversity and, more specifically, more members of the Ruminococcaceae (sidenote: Ruminococcaceae A family of gut bacteria often linked to a healthier, more diverse microbiome and better immune activation.
  ) family. From this group they isolated an unassuming anaerobe, a strain of Hominenteromicrobium mulieris they call YB328.

Patients with higher levels of YB328 had longer progression-free survival across several cohorts and cancer types. In contrast, those enriched with a common Bacteroidaceae member, Parabacteroides vulgatus, tended to do worse. When these microbes were moved into mice, the story held: YB328 turned PD-1 therapy into a much more potent anti-tumour tool, while P. vulgatus left tumours largely unbothered.

Microbial competition and therapeutic imitation

Equally striking is what happens when ecology works against us. In mice colonized with a “non-responder” microbiome, adding YB328 can rescue PD-1 efficacy, but only if competing strains like P. vulgatus don’t block its engraftment (sidenote: Engraftment The successful establishment and persistence of a microbial strain in the gut after it is introduced.
  ) . One microbe can cancel out another’s benefit, a sobering reminder for any future live biotherapeutic strategy.

Finally, the authors show that a defined cocktail of TLR agonists (sidenote: TLR agonists Molecules that activate Toll-like receptors, stimulating innate immune pathways and boosting immune cell activation. ) can mimic much of YB328’s effect on cDC1 programming and PD-1 synergy. This work reframes the gut not just as a biomarker source, but as a tunable upstream regulator of dendritic cell biology and checkpoint response, opening the door to microbiome-guided or TLR-based adjuvants that might turn more of our “non-responders” into durable responders.