Resistant Bacteria, Biofilms, and the Test Most Sinus Patients Never Get

Short answer: When chronic sinus patients fail multiple antibiotics, allergy treatments, and standard testing, the next step is not another round of empiric antibiotics. It is the right diagnostic test. Standard culture grows only a fraction of the bacteria actually present, and limited PCR panels test for fewer than fifty pre-selected pathogens. Comprehensive genetic sequencing reads the DNA of every organism in the sample — using 16S rRNA gene sequencing for bacteria and ITS sequencing for fungi — and compares it against a database of thousands of species, including antibiotic resistance genes. For patients who have already been treated repeatedly, this is the test that finally explains why nothing has worked — and points to the targeted medical therapy that will! Personalized and targeted medical therapy!

Franklyn R. Gergits, MBA, DO, FAOCO
Board-Certified Otolaryngologist · Fellowship-Trained Otolaryngic Allergist · 30+ Years of Experience
Clinical Focus in Rhinology and Airway Disorders
Founder, Sinus & Allergy Wellness Center of North Scottsdale

Before I see a new chronic sinus patient face to face, I review the medical history carefully. Number of antibiotics. Reasons each one was prescribed. Dates. Lengths of courses. I have to go back years sometimes — because the history of antimicrobial exposure is the history of antimicrobial resistance. Many of these patients have been hit with multiple seven-to-ten day rounds of antibiotics. Some have been on six-week courses. And each antibiotic — when prescribed inappropriately or when it was not the right antibiotic for what was actually growing — can do real damage. Not just to the gut microflora. To the sinus, nasal, and airway microflora too.

We have protective bacteria in these regions that help keep harmful organisms in check. A single inappropriate antibiotic prescription a year ago can wipe those protective bacteria out. And every time a patient is treated again with another antibiotic that is not the personalized, correct antibiotic for their specific infection, the resistant bacteria flourish. Eventually they begin to form biofilms — protective communities that make the bacteria even harder to reach with oral medications.

So when a patient walks in frustrated, having failed three or four or more rounds of antibiotics, my first clinical question is not “what antibiotic should we try next.” It is “what test will actually tell us what is happening here?” Because if the wrong test is ordered, the result comes back as “no growth.” Does that mean there is no harmful bacteria present? Absolutely not. It usually means we chose the wrong diagnostic test.

What “no growth” really means

A patient hears “your culture was negative” or “you tested positive for nothing significant” and they walk out of the office still sick, with no plan, and the assumption that whatever is wrong must be something other than infection. In a chronic sinus patient who has been on multiple antibiotics over years, that interpretation is often wrong. A negative result on the wrong test is not the same as a negative result on the right test.

The three categories of testing — and what each one actually does

There are three fundamentally different ways to identify what is growing in a sinus specimen. Each one has a place. The question is which one fits the patient sitting in front of you.

1. Standard bacterial culture. A swab is placed in the nose or against the operated sinus mucosa, and the swab — with mucus on it — is sent to the lab. There, the specimen is placed onto a special plate containing a growth medium that encourages bacteria to grow. The plate goes into an incubator and is checked periodically for visible growth. This is the oldest method and still has a role. But it takes the longest to generate a result because the bacteria have to actually grow before they can be reported. It also misses anaerobes — bacteria that don’t grow well in standard culture conditions — fastidious organisms that require unusual growth requirements, and any organism that has been suppressed by recent antibiotic exposure. In published polymicrobial respiratory specimens, standard culture has been shown to identify only about twenty-one percent of the cultivatable organisms actually present. There is one additional point worth emphasizing here: major infectious disease society guidelines state that examination of nasal drainage material is of no diagnostic value in identifying the cause of sinusitis. The specimen has to come from the sinus itself — ideally an endoscopically obtained middle meatus swab or antral aspirate — not from the nostril.

2. Limited PCR panels. PCR — polymerase chain reaction — is a molecular biology technique that heats and cools a specimen to amplify the DNA of organisms present, then matches that DNA against a pre-selected panel of about twenty to thirty bacteria, viruses, and fungi that are typically found in that part of the body. Different panels exist for different anatomical regions: a urine PCR panel is different from a respiratory PCR panel which is different from an oral PCR panel. These tests are commercially available from labs such as Sozo Dx, and platforms such as the BioFire FilmArray Respiratory Pathogen Panel and the GenMark ePlex Respiratory Pathogen Panel are widely used in hospitals and urgent care settings. The advantage of PCR is speed. Results can come back in hours rather than days, which makes PCR invaluable in acute settings — emergency rooms evaluating for meningitis or sepsis, urgent care assessing community-acquired pneumonia. The limitation is the fixed menu. PCR only finds what it is designed to look for. If your infection is caused by something not on the panel, the result comes back negative even when bacteria are clearly present.

3. Comprehensive genetic sequencing. This is a different category of test entirely. Comprehensive next-generation sequencing reads the DNA of every organism in the specimen — using 16S rRNA gene sequencing for bacteria and ITS gene sequencing for fungi — rather than amplifying against a fixed panel. The reads are then compared against a database of thousands of species rather than a pre-selected panel of twenty to thirty. Bacteria, fungi, and in some platforms additional organisms are all detected from the same specimen. Antibiotic resistance genes are detected simultaneously — mecA for methicillin-resistant Staphylococcus, ESBL genes, tetracycline resistance genes — which means we know what the bacteria can and cannot be treated with before we ever pick up the prescription pad. Labs offering this level of comprehensive sequencing include commercial reference laboratories such as MicroGenDX, and academic medical center laboratories such as the University of Washington Molecular Microbiology Laboratory and Johns Hopkins clinical microbiology. The turnaround at MicroGenDX is approximately twenty-four hours from when the specimen reaches the Texas-based lab, with total turnaround including shipping typically running three to five days. The current out-of-pocket cost is approximately two hundred forty-nine dollars.

Why this matters clinically

Three clinical decision branches determine which test fits which patient.

Speed first: In an acute emergency — suspected meningitis, sepsis, pneumonia in an unstable patient — a rapid PCR can be life-saving. A diagnosis in two hours versus three days is the difference between targeted therapy and empiric guessing. PCR earns its place here.

Recent antibiotic exposure: If a patient has been on antibiotics recently, standard culture loses sensitivity dramatically. The bacteria may still be present and causing inflammation, but they may not grow well enough to be cultured. Genetic testing — either PCR or comprehensive sequencing — detects the DNA of organisms whether they are alive or recently killed. This is a decisive advantage in chronic sinus patients who have nearly always had multiple courses of antibiotics before they reach a specialist.

Complex, chronic, multiply-treated patients: When a patient has been through many providers, many antibiotics, and many “no growth” results — comprehensive sequencing is the test that finally yields actionable information. We have repeatedly seen patients where a PCR panel returned negative and a comprehensive sequencing test from the same anatomical region returned multiple organisms, several of them resistant. When the out-of-pocket cost is around two hundred forty-nine dollars and the patient has cycled through repeated antibiotic courses, repeat office visits, repeat imaging, and lost work — the return on investment of one comprehensive sequencing test is enormous.

A patient who illustrates this

A patient came to us after years of chronic sinus problems treated by many different providers. She had been on antibiotic after antibiotic. She had undergone a complex sinus surgery that required a prolonged recovery and a temporary disability to keep her from losing her job. She eventually quit that job and moved to a warmer climate where she felt better when she had previously visited family in that area. She found similar work in the new city — and within months, her symptoms returned. She found our practice online and came in for an evaluation.

We asked her whether she had ever had a culture-type test where mucus from her sinuses was sent to a lab to identify exactly what was causing her infections. She could not recall. She thought maybe one had been done during her surgery, but she was not sure. So we performed an endoscopic procedure to obtain a specimen from the middle meatus and at the back of her nasal cavity — where the thick, discolored mucus was collecting — and sent it for comprehensive sequencing.

What came back was clinically significant. Multiple resistant bacteria were identified, almost certainly living in biofilms — which explained why oral antibiotics had failed her again and again. Her maxillary sinuses were bright red with inflammation but showed no overt signs of acute pus or active discharge — exactly the picture of biofilm-driven chronic inflammation rather than the simple bacterial infection oral antibiotics are designed to treat. If these findings were seen via nasal endoscopy, they will still be invisible to the investigative eye, unless careful thought is occurring.

With the comprehensive sequencing results in hand, we ordered a topical antibiotic from a compounding pharmacy — chosen specifically based on what her bacteria were and were not resistant to — and added it to her daily sinus rinse. Approximately two weeks into therapy, we added a steroid to the rinse to address the inflammation that the infection had driven. After several more weeks, when she returned for follow-up reporting improvement, we transitioned her to plain sinus rinses followed by a separate steroid nasal spray as maintenance.

She is not cured. She is better. The duration of topical antibiotic therapy, when steroids are added to the rinse, and when a patient transitions to maintenance — all of this is personalized and targeted based on bacterial load measured by the sequencing test, the resistance genes present, the number of pathogens identified, and the patient’s clinical symptom course. Some patients need three weeks. Some need three months. The point is that the plan was finally specific to her — not empiric, not guessed.

Why topical delivery works when oral antibiotics keep failing

Oral antibiotics travel through the gut, into the bloodstream, and then have to reach the sinus mucosa via systemic circulation. By the time they arrive, the concentration at the actual site of biofilm bacteria can be far below what is needed to kill them. Biofilms add another barrier — the bacteria living inside the biofilm matrix are physically harder to reach with any orally delivered drug, even when the right drug is selected.

Topical compounded antibiotic added directly to a sinus rinse bypasses both problems. The drug reaches the mucosa at a much higher local concentration. The mechanical action of the irrigation helps disrupt mucus and exposes bacteria that biofilms would otherwise protect. And because the rinse drains out the nose into the sink rather than being swallowed, the gut microflora is spared additional damage. A patient who has already had years of antibiotic-driven dysbiosis does not need another oral course making it worse.

For biofilm-rich infections, we sometimes add xylitol to the rinse — or, in selected patients, xylitol with a small amount of Johnson’s baby shampoo — to help mechanically and chemically disrupt the biofilm matrix and expose the bacteria within. These adjuncts are added based on each patient’s specific situation, not as routine for everyone.

The cost conversation

When patients hear “two hundred forty-nine dollars out of pocket for a test,” many hesitate. I understand. Patients with chronic sinus disease have often already maxed out credit cards. They have missed vacation days they cannot get back. They have stress, depression, allergy injections, weekly drives to allergy offices, hours in waiting rooms, urgent care copays, exam room copays, recovery from procedures that did not fully fix the problem.

What I ask them to consider is the comparison. The same level of comprehensive sequencing from some other platforms — particularly hospital-based metagenomic testing that is sometimes only available to inpatients — can cost thousands of dollars. Some commercial sequencing tests are covered by insurance and the patient’s out-of-pocket exposure depends on deductible status at the time the test is ordered. When weighed against the cumulative cost of multiple empiric antibiotic courses that did not work, multiple office visits for treatment failure, repeat CT scans, missed work, and the personal cost of remaining sick — one comprehensive sequencing test that finally points to a working therapy is one of the highest-yield investments in chronic sinus care that exists.

What to ask your next doctor

If you have been told “your culture was negative” or “you tested positive for nothing significant” and you are still sick — do not accept that as a final answer. The most important thing you can do is to ask, by name, for a comprehensive genetic sequencing test — such as MicroGenDX — rather than another standard culture or another limited PCR panel. If you are sick enough that you find yourself in an urgent care or a primary care office, ask whether they can obtain the specimen and send it for comprehensive sequencing. The best yield, however, comes from an endoscopic specimen taken by an ENT physician who can place the swab directly where the thick, discolored mucus is actually collecting — typically the anterior common pathway that the anterior ethmoid, the nasofrontal and maxillary sinuses drain into the nasal cavity. Another area to focus attention, that is often missed, is the posterior nasal cavity, not just the front of the nose.

Two honest cautions. First, even a comprehensive sequencing test cannot guarantee a positive result every time. If the bacterial load is low, or if the bacteria are concentrated in a sinus cavity that the specimen could not access, the test can return as no growth. We use the endoscope to maximize yield, but no test is perfect. Second, when we do find the bacteria responsible, this is not a quick fix. The problem most often took years to reach this point. It will take time to resolve. Patients who understand that — and who commit to the process — almost always do better than patients who expect a one-week cure.

When patients commit to us and we commit to them, that is a partnership. The decision to order the right test, to deliver therapy in a way that actually reaches the bacteria, and to follow the patient through to maintenance — none of that works without both sides showing up. The right diagnostic test is the beginning of the right plan. Not the end of it.

Want to understand more

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

→ Why Do Antibiotics Keep Failing My Sinus Infections?

→ Are There Holistic Sinus Rinses That Actually Work?

→ Why Do I Keep Getting Sinus Infections After Treatment?

About the Author

Dr. Franklyn R. Gergits, MBA, DO, FAOCO is a Board-Certified Otolaryngologist and Fellowship-Trained Otolaryngic Allergist with a Clinical Focus in Rhinology and Airway Disorders and over 30 years of clinical experience. He is the founder of the Sinus & Allergy Wellness Center of North Scottsdale, where he performs in-office balloon sinuplasty, turbinate reduction, NEUROMARK® posterior nasal nerve ablation (Neurent Medical, FDA-cleared radiofrequency ablation system), and Eustachian tube dilation under local anesthesia. He performed the first balloon sinuplasty in Pennsylvania and holds dual Entellus Centers of Excellence certifications. Dr. Gergits is the originator of the Posterior Sinonasal Syndrome (PSS) hypothesis — a clinical framework identifying pepsin-mediated posterior nasal mucosal injury as an upstream driver of chronic rhinosinusitis. Preprint available at Preprints.org (DOI: 10.20944/preprints202603.0858.v1). ORCID: 0009-0000-4893-6332.

Dr. Gergits has no financial relationship with MicroGenDX, Sozo Dx, BioFire, GenMark, or any laboratory referenced in this article.

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This content is for educational purposes only and does not constitute medical advice. If you are experiencing recurrent or chronic sinus symptoms, please consult a qualified physician for evaluation and individualized treatment recommendations. Diagnostic testing decisions should be made between you and your treating physician based on your specific clinical situation.