From Pathogen to Infectious Disease Diagnosis
[LISTEN TIME: 22 min, 20 seconds]
Listen to the full episode for more from Allan-Blitz on the future of resistance-guided diagnostics.
New gyrA testing guides ciprofloxacin use for gonorrhea, cutting ceftriaxone reliance while tackling resistance, access, and FDA hurdles.
From Pathogen to Infectious Disease Diagnosis is a Contagion podcast hosted by Rodney E. Rohde, PhD, SV/SM/MB(ASCP)CM, FACSc, a University Distinguished and Regents' Professor at Texas State University, that connects laboratory professionals and infectious disease clinicians to discuss how the latest generation of diagnostic testing can help identify pathogens and guide treatment. Each episode brings a guest expert into conversation with Rohde to explore how emerging diagnostics are reshaping the relationship between the lab and the clinic.
The most recent episode focuses on how a single-gene diagnostic could let clinicians safely reintroduce a once-abandoned antibiotic for gonorrhea. In this episode, Lao-Tzu Allan-Blitz, MD, MPH, assistant clinical professor of medicine in the Division of Infectious Diseases at the David Geffen School of Medicine at UCLA, joins Rohde to discuss resistance-guided therapy for gonorrhea. Allan-Blitz's research focuses on infectious diseases, global health equity, and the development of low-cost molecular diagnostics for sexually transmitted infections, with clinical collaborations spanning multiple countries. The conversation centers on a single gene mutation that can predict which gonorrhea infections remain treatable with ciprofloxacin, a drug largely abandoned 2 decades ago.
"I'd like to look at this resistance-guided therapy with ciprofloxacin as the beginning, not the end."
—Lao-Tzu Allan-Blitz, MD, MPH
Neisseria gonorrhoeae has developed
[LISTEN TIME: 22 min, 20 seconds]
Listen to the full episode for more from Allan-Blitz on the future of resistance-guided diagnostics.
Resistance-guided therapy, already standard of care for Helicobacter pylori and methicillin-resistant Staphylococcus aureus, offers a near-term path back to ciprofloxacin for gonorrhea.1 Investigators have identified a single mutation in codon 91 of the gyrA gene that is 98% sensitive and 98% specific for predicting ciprofloxacin resistance, and rapid molecular assays targeting this mutation are now commercially available in the United States and elsewhere.1 Roughly 60% of N gonorrhoeae strains circulating in the US remain susceptible to ciprofloxacin, meaning most patients could avoid ceftriaxone if their strain's genotype is known. Across 3 clinical studies, ciprofloxacin achieved cure rates of 100% or greater than 98% across all anatomic sites, including the pharynx, where cure is notoriously difficult even with ceftriaxone.
"We have identified a single mutation in codon 91 of the gyrA gene that is 98% sensitive and 98% specific for predicting ciprofloxacin resistance."
—Lao-Tzu Allan-Blitz, MD, MPH
Because more than half of gonorrhea infections are asymptomatic, clinicians often have time between sample collection and treatment to reflex a positive result to gyrA genotyping, delivering both results simultaneously.1 When the assay was introduced in 2017, genotype turnaround took about 24 hours;1 a more recent study found it added closer to 2.5 days, though most surveyed patients said they would still wait the extra time to avoid an injection. Beyond the ecologic benefit of preserving ceftriaxone, an oral option eliminates the need for a return clinic visit and can be dispensed through a pharmacy or delivered to a patient's sex partner directly.
Allan-Blitz was clear that resistance-guided therapy with ciprofloxacin is a beginning, not an endpoint, a point he has
FDA clearance and insurance reimbursement remain the primary barriers to routine use in the US. A large trial supporting 510(k) applications for 3 gyrA-testing devices is expected to conclude soon, with FDA-cleared devices anticipated in early 2027. On reimbursement, Allan-Blitz pointed to a recently approved CPT code for a Mycoplasma genitalium resistance assay as a precedent his group hopes to replicate for the gyrA codon 91 assay.