What Is MicroGenDX — And Why Does It Change How We Treat Sinus Infections?

If you have had a sinus culture done — a swab sent to the lab — and been told the results were negative or inconclusive, but you are still not getting better, there is a reason for that. Standard culture-based laboratory testing was designed decades ago and has not fundamentally changed since. It is slow, it misses organisms that cannot survive the transport and growth process, and it gives your physician an incomplete picture of what is actually driving your infection.

MicroGenDX is a different kind of diagnostic tool entirely. And at the Sinus and Allergy Wellness Center of North Scottsdale (SAWC), it has changed how we approach the patients who have failed everything else.

What MicroGenDX Actually Is

MicroGenDX is a molecular diagnostics laboratory that uses Next-Generation Sequencing (NGS) — DNA-based technology — to identify every bacterium and fungus present in a clinical sample. Instead of trying to grow organisms in a laboratory dish and waiting to see what survives, NGS extracts the DNA directly from the sample, sequences it, and compares it against a database of over 50,000 bacterial and fungal organisms.

The result is a comprehensive molecular fingerprint of everything living in your sinuses — not just the organisms robust enough to survive a standard culture process.

The technology also uses quantitative Polymerase Chain Reaction (qPCR) — the same platform used in COVID-19 testing — to measure the relative abundance of each organism detected. This tells your physician not just what is present, but how much of it is present and which organism is the dominant driver of the infection. It also identifies Antimicrobial Resistance (AMR) genes — genetic markers that indicate an organism has developed resistance to specific antibiotic classes, allowing your physician to avoid prescribing an antibiotic that will not work before a single dose is taken.

How MicroGenDX Differs From Standard Sinus Culture

Standard sinus culture — the traditional swab or aspirate sent to a hospital microbiology laboratory — works by attempting to grow organisms from your sample on laboratory growth media. This process takes 48 to 72 hours at minimum, requires the organism to survive the collection and transport process, and can only identify organisms that are willing to grow under laboratory conditions.

The clinical limitations of this approach are documented and significant.

In a prospective study of 50 chronic sinusitis patients, DNA sequence analysis detected 31.9% more microorganisms compared to standard hospital culture. Standard culture failed to identify the dominant species in the microbiome 53% of the time. Twenty percent of patients had anaerobic bacteria detected by DNA analysis that were completely missed by standard culture. Most critically — antimicrobial therapy based on standard culture results would have been adequate for only 44% of patients, compared to 74% based on DNA results.

That means if your physician is prescribing antibiotics based on a standard culture result, there is better than a 50% chance the prescription is based on incomplete or inaccurate information.

The specific organisms standard culture misses most consistently include anaerobes — bacteria that cannot survive in oxygen and die during the standard transport process — biofilm-forming organisms that are present in their protective community structure rather than as free-floating planktonic bacteria, and fungi, which require specialized growth conditions that standard sinusitis cultures do not routinely use.

Based on approximately 80,000 sinus and ear samples processed by MicroGenDX, more than 86% of specimens are polymicrobial, more than 50% contain anaerobes, and more than 20% contain fungi — all of which are costly and time-consuming for standard culture to detect.

Those numbers tell the story of why so many sinus patients cycle through repeated antibiotic courses without resolution. They were never being treated for what was actually driving their infection.

Where MicroGenDX Specifically Benefits the ENT Physician

For the otolaryngologist treating chronic rhinosinusitis (CRS), recurrent acute rhinosinusitis (RARS), and treatment-refractory sinus disease, MicroGenDX provides clinical intelligence that standard testing simply cannot deliver.

Polymicrobial infections: When multiple organisms are present — which happens in over 86% of sinus samples — standard culture typically identifies one and misses the rest. A patient being treated for Staphylococcus aureus may also have Extended-Spectrum Beta-Lactamase (ESBL)-producing gram-negative organisms that require an entirely different antibiotic class. MicroGenDX identifies all of them simultaneously, along with their relative contributions to the total bacterial load.

Odontogenic sinusitis: One of the most consistently missed diagnoses in rhinology. When a maxillary sinus infection is driven by a dental source — a periapical abscess, periodontal disease, or a failed root canal — the organisms responsible are oral anaerobes that standard culture almost never identifies. In a study of 142 patients, DNA sequencing identified odontogenic sinusitis with sensitivity and specificity values above 80%. Identifying oral anaerobes in a sinus culture is the signal that directs the patient to dental evaluation before sinus surgery — without it, the source of the infection is never addressed.

Fungal involvement: More than 20% of sinus samples contain fungal elements. Standard sinusitis culture protocols do not routinely include fungal culture unless specifically requested. A patient with unidentified fungal sinusitis will cycle through bacterial antibiotic courses indefinitely without improvement because antibiotics have no activity against fungi.

Antimicrobial resistance profiling: MicroGenDX identifies resistance genes directly from the DNA — detecting MRSA (Methicillin-Resistant Staphylococcus aureus), ESBL-producing organisms, and other resistance patterns before the physician selects a treatment. This is antibiotic stewardship practiced at its most precise level — prescribing the right antibiotic the first time rather than the empiric antibiotic that might work.

How I Use MicroGenDX at SAWC — At the Time of Balloon Sinuplasty

The most powerful application of MicroGenDX in my clinical practice is not as a standalone diagnostic test ordered from a swab in the office. It is as an intraoperative tool used at the time of balloon sinuplasty.

Here is the clinical sequence: when I perform balloon sinuplasty in the office under local anesthesia, I open the blocked sinus drainage pathways using the balloon catheter. Once the sinus is open, I can suction directly into the sinus cavity — removing accumulated mucus, debris, and inflammatory material that has been trapped behind the obstruction. That suctioned material is the cleanest, most representative sample of what is actually living in the diseased sinus. It has not been contaminated by nasal flora during collection. It comes directly from the site of the infection.

That sample goes to MicroGenDX for Next-Generation Sequencing (NGS) analysis.

What comes back is a complete molecular profile of every organism present — bacterial species with their relative abundance, fungal elements if present, and antimicrobial resistance genes. Armed with that information, I can prescribe culture-directed topical antibiotic therapy delivered directly into the now-open sinus cavities — targeting the specific organisms identified at the specific concentrations needed to overcome their resistance profile.

Another unique option we perform at Sinus and Allergy Wellness Center of North Scottsdale is one where if we are able to identify a mucopurulent sinus discharge or if we examine the posterior nasal cavity and observe thickened discolored mucus streaming to the nasopharynx, we may be able to obtain a specimen for MicroGenDX evaluation at that initial patient presentation. We then prescribe MicroGenDX directed topical medical rinse therapy and ask our patient to bring a dose to our clinic on the day of their in-office balloon sinuplasty. After balloon dilation, we are able to use a special device called a “Cyclone Sinus-Irrigation Kit” to suction/irrigate the affected sinus/sinuses first with sterile saline then when after the sinus rinses clean, we are able to introduce the patient’s tailored sinus rinse based on MicroGenDX’s findings directly into the infected sinus/sinuses. This direct inoculation of the antibiotic/anti-fungal solution into the sinus/sinuses begins the treatment and recovery. The patient then continues this therapy for the rest of their prescription.

This is precision rhinology. The anatomy has been corrected. The infection has been sampled at its source. The treatment is directed at what is actually there.

For patients who have had repeated empiric antibiotic courses without resolution — the patients cycling through amoxicillin, then augmentin, then a Z-pack, then levofloxacin, without ever identifying what is actually driving their disease — this approach frequently produces resolution in a single directed treatment course after years of treatment failure.

What This Means for Your Care

If you are a patient with chronic or recurrent sinusitis who has not responded to standard antibiotic treatment, the most important question to ask your physician is not “what antibiotic should I take next?” It is “do we actually know what organism is driving this infection?”

Standard culture may not give you that answer. Molecular diagnostics can.

At SAWC, MicroGenDX is part of our precision rhinology protocol for patients with treatment-refractory sinus disease — used alongside comprehensive allergy evaluation, immune function testing, and upstream inflammatory driver assessment to build a complete picture of why a patient is not getting better and exactly what needs to be treated.

Want to Understand More?

This post is part of the Why Sinus Treatments Fail — And What Starts Before Them series on the Airway & Sinus Wellness Review.

→ Why Won’t My Doctor Give Me Antibiotics for My Sinus Infection?

→ Why Do I Keep Getting Sinus Infections Even After Surgery?

→ Chapter 6: The Precision Era — Office-Based Rhinology and Molecular Diagnostics

Franklyn R. Gergits, DO, MBA, FAOCO
Otolaryngologist & Rhinologist | 30+ Years Clinical Experience
Founder, Sinus & Allergy Wellness Center of North Scottsdale
SinusAndAllergyWellnessCenter.com · 480-525-8999
ORCID: 0009-0000-4893-6332
Preprint: https://doi.org/10.20944/preprints202603.0858.v1

This content is for educational purposes only and does not constitute medical advice. If you are experiencing severe symptoms, orbital swelling, high fever, or neurological changes, seek immediate medical care.