Who This Post Is For
This is not a post for the 300 million people with well-controlled asthma.
This is for the subset — the patients who have done everything right, taken every medication, tried every biologic — and still cannot breathe freely. The ones whose disease keeps advancing despite maximal therapy. The ones whose doctors keep adjusting the same tools while the underlying cause goes uninvestigated.
We call this group the bacterial dysbiosis subpopulation of severe asthma. And here is the most troubling thing we know about them:
We don’t know how many there are.
The Numbers We Do Know
The global severe asthma population is estimated at 30 million people — roughly 10% of the 300 million living with asthma worldwide.
Of those, the data is sobering:
- 15–17% of severe asthma patients are complete non-responders to biologic therapy — no meaningful clinical benefit despite the most advanced treatments available
- 43–69% are only partial responders — some improvement, but disease remains poorly controlled
- Biologic super-responders — those who achieve true remission — represent only 14–24% of patients on these expensive therapies
That means the majority of severe asthma patients are not achieving the outcomes biologics promise. And for a significant subset, the reason may not be that the treatment is wrong. It may be that the diagnosis is wrong.
The Subpopulation Nobody Is Counting
Peer-reviewed research has established clearly that severe asthma is not one disease. It is a collection of endotypes — distinct pathological subtypes with different drivers and different treatment needs.
One endotype is driven by Type 2 inflammation — eosinophilic, allergic, TSLP-mediated. Biologics were designed for this group. They work reasonably well here.
Another endotype is driven by something fundamentally different: bacterial dysbiosis — a disrupted lung microbiome dominated by opportunistic pathogens that standard diagnostics routinely miss.
The published science is clear on this:
- Patients with severe eosinophilic asthma show significantly greater abundances of Haemophilus and Streptococcus in bronchial specimens compared to healthy controls — correlating with eosinophil counts and disease severity
- Steroid use and antibiotic exposure — the two most common interventions in severe asthma management — are now known to severely impair both gut and lung microbiota, creating the conditions for dysbiosis to worsen over time
- Microbial dysbiosis may contribute to corticosteroid resistance — meaning the treatment itself is compounding the problem
- The lung was once considered a sterile organ. It is not. It is a living ecosystem, and when that ecosystem fails, standard inhalers and biologics cannot restore it
How large is this bacterial subpopulation? We don’t know. The diagnostic tools to identify them — molecular sequencing, metagenomics, DNA-level microbial profiling — are not part of standard severe asthma workup. We are counting the patients we can see with the tools we have. The rest remain invisible.
That is a diagnostic failure. And it needs to be said plainly.
The Smoking Gun From One Patient’s Data
I am the founder of the World Asthma Foundation. I am also a patient.
After 20 years of daily prednisone and multiple biologic trials — including Tezepelumab, which improved my lungs but left every systemic symptom completely unchanged — I pushed for a bronchoscopy with molecular diagnostic sequencing.
The result: 39% MDR Streptococcus pseudopneumoniae dominant in my lungs.
Not identified by any standard culture in 20 years. Not addressed by any of the treatments I received. Thriving — because the immunosuppressive environment created by two decades of corticosteroids gave it exactly what it needed.
The bifurcated Tezepelumab response was not a treatment failure. It was a diagnostic signal. The biologic controlled the TSLP-driven airway inflammation. The bacterial colonization — operating on a completely independent disease axis — was untouched.
Two axes. One patient. One missed for twenty years.
What the Steroid Trap Looks Like From the Inside
Here is what nobody tells patients when they start long-term prednisone:
Corticosteroids suppress the adaptive immune response that would normally hold bacterial colonization in check. Over years and decades, this creates a microbiome vacuum in the lung — and opportunistic pathogens like MDR S. pseudopneumoniae fill it.
Standard care then interprets the worsening symptoms as treatment failure — and adds more immunosuppression. The cycle deepens.
The 2025 peer-reviewed literature confirms this mechanism explicitly: steroid use is now a documented risk factor for gut and lung microbiota disruption. The treatment is compounding the disease in a subgroup nobody is measuring.
The Diagnostic Standard Is Not Keeping Up
Standard asthma diagnostics in 2026 still rely primarily on:
- Spirometry and lung function testing
- Blood eosinophil counts and IgE levels
- Sputum cytology
- Standard bacterial culture — which misidentifies or misses S. pseudopneumoniae entirely
These tools were designed to characterize the Type 2 inflammatory endotype. They are largely blind to the bacterial dysbiosis endotype.
Molecular diagnostic sequencing — metagenomic DNA analysis of bronchoscopic samples — exists right now. It is not experimental. It is not expensive relative to the cost of years of failed biologic therapy. It is simply not part of the diagnostic algorithm for severe asthma.
We need it to be.
Until molecular diagnostics become standard of care for severe asthma patients who fail conventional therapy, we will continue to treat the wrong thing in a subpopulation we cannot even count.
The Neurological Warning
There is one more dimension to this story that the severe asthma community needs to hear.
When bacterial dysbiosis goes undetected and untreated for years — when the systemic inflammatory cascade it drives is suppressed but not resolved — the consequences can extend far beyond the lungs.
In my case, 15 years of unaddressed bacterial-driven systemic inflammation has produced confirmed progressive Small Fiber Neuropathy — nerve damage advancing from feet to upper thighs, hips, and shoulders. And emerging peer-reviewed research now links chronic Borrelia infection — which frequently co-occurs in immunocompromised patients with chronic bacterial burden — directly to SFN that resolves with antibiotic treatment.
The lungs were the smoking gun. The nervous system is the consequence.
This is what untreated bacterial asthma looks like at 20 years. It doesn’t stay in the lungs.
What We Are Calling For
For patients who have failed standard therapy: Demand molecular diagnostic sequencing before accepting that your disease is simply “poorly controlled.” You may be in the bacterial dysbiosis subpopulation — and the only way to know is through DNA-level analysis that standard care is not providing.
For pulmonologists: The bifurcated biologic response — improvement in some domains, none in others — is a diagnostic signal, not a treatment failure. It points toward an independent disease axis that deserves independent investigation.
For diagnostic standards bodies: Molecular sequencing must be incorporated into the diagnostic pathway for severe asthma patients who fail conventional therapy. We cannot treat a subpopulation we refuse to measure.
For researchers: The bacterial dysbiosis endotype of severe asthma needs its own epidemiological study. We do not know how many patients fall into this category. That is an unacceptable gap in 2026.
For policymakers: Better diagnostics require reimbursement pathways. Molecular sequencing for severe asthma patients who fail biologics should be covered. The cost of one year of biologic therapy far exceeds the cost of a single diagnostic test that could redirect treatment entirely.
The Bottom Line
The severe asthma community has made extraordinary progress with biologics. But progress for the Type 2 inflammatory endotype is not progress for everyone.
There is a subpopulation — poorly defined, inadequately counted, diagnostically invisible under current standards — for whom the answer is not a better biologic. It is a better diagnostic.
We don’t know how big this subpopulation is. That is not an acceptable answer in 2026.
The World Asthma Foundation is calling for molecular diagnostic standards, endotype-specific research funding, and a formal definition of the bacterial dysbiosis subpopulation of severe asthma — so that we can finally begin counting the patients we have been missing.
Bill Cullifer is the founder of the World Asthma Foundation and a 69-year-old patient with confirmed Small Fiber Neuropathy, severe refractory asthma, and 35 years of documented disease. His personal case is the basis for this advocacy.
World Asthma Foundation | worldasthmafoundation.org | worldasthmaday.org
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