Double Trouble: When Co-Infections and Antimicrobial Resistance Collide, Challenges Ensue 

This is part of a series about topics presented during APHL ID Lab Con 2025, a forum to discuss the latest developments on the detection and characterization of infectious diseases of public health concern.  

Have you ever had a bad cold? The whole shebang—sore throat, fever, headache. Miserable, right? Now, imagine that same cold while nursing an injury. Or after a sleepless night. Or worse, while dealing with food poisoning. Suddenly, that bad cold feels 10 times worse. 

In the world of infectious diseases, we often think of illness as a one-and-done situation—one infection, one problem.  

But microbes don’t follow those rules. Sometimes, a person can be infected by more than one pathogen at the same time. Maybe it’s COVID-19 and a urinary tract infection. Or norovirus and RSV. This is known as co-infection, and while not all co-infections are cause for alarm, some can create serious public health challenges—especially when antimicrobial resistance (AR) enters the equation. 

Why Co-Infections and AR Are a Big Deal 

Treatment becomes more complicated when a person becomes infected with multiple pathogens, whether they’re viruses, bacteria or parasites. But when one or more of those pathogens is resistant to the drugs typically used to treat infections—otherwise known as antimicrobial resistance—the situation becomes far more dangerous. 

Antimicrobial resistance is a global public health threat. There’s a long list of pathogens classified as serious to mission-critical, and public health officials have dedicated funding and other resources to combatting this threat.  

In short, AR is a big deal. 

A typical AR infection is already challenging to manage. Limited treatment options increase the risk of prolonged illness, secondary complications and even treatment failure. Fortunately, we’ve made significant progress in understanding AR pathogens, their resistance mechanisms and even the genes that drive this resistance. But co-infections throw a wrench in the system. 

Lessons From ID Lab Con: Real-World Challenges 

I attended APHL ID Lab Con 2025 and was present at the session “Novel Approaches in Antimicrobial Resistance Detection: Innovations in Laboratory Testing.” One speaker highlighted a sexually transmitted infection (STI) pathogen with a relatively high prevalence of AR that frequently appears in co-infections with other STIs. What does that mean for patients with these infections? Without proper management, co-infections of this type can lead to infertility, pelvic inflammatory disease and more. 

Thankfully, there’s good news in this case.  

Because of a strong commitment to AR research, industry and public health partners have developed FDA-cleared assays that test for multiple pathogens at once. Some large laboratories have even developed their own tests to detect resistance, and there’s a growing recommendation for resistance-guided therapy, which has demonstrated cure rates of over 90% for this particular pathogen. Resistance-guided therapy can detect whether a pathogen is vulnerable to a more common drug treatment, meaning that last-line treatments can be saved for those who truly need them. This is a great example of collaboration between industry, labs and public health officials leading to workable solutions. 

When Co-Infections Get Even More Complex: Multiple AR Pathogens 

But what happens when a patient is infected with multiple AR pathogens?  

Another speaker at the AR session shared a striking example from recent journal articles in Europe. Due to the medical treatment of Ukrainian victims of the Russia-Ukraine conflict, hospitals across Europe are encountering patients infected with multiple carbapenem-producing organisms (CPOs). 

CPOs are one of the most serious public health threats. They are organisms that antibiotics don’t work well against; they spread easily in healthcare settings and between patients. In one case, a Ukrainian soldier treated in the European Union was infected with not one, not two, but nine CPOs. While treatment options may be similar for these pathogens, the ease with which CPOs spread in hospitals raises serious concerns. Infections don’t care about borders, and with people traveling for healthcare, the risk of transmission to a wider population is very real. 

AR Testing and Innovation: A Critical Piece of the Puzzle 

In cases like these, testing and tracking have become even more critical—but it’s not as simple as saying, “All labs should test for this.” AR tests are expensive and can take days. However, there’s hope. During her presentation, an APHL AR fellow at the New York State Department of Health Wadsworth Center shared how they implemented a new workflow that detects CPOs in less than 24 hours—and in a cost-effective manner. 

Is their process easy to replicate in every lab? No. But it’s progress. Wadsworth Center’s work is being shared with a national audience, contributing to a growing network of experts committed to improving AR testing and management. This is applied research at its finest—innovative, practical and making a real-world impact. 

Why Commitment to AR Testing Matters 

Co-infections with AR pathogens add a layer of complexity to patient care that cannot be ignored. It’s not enough to develop treatment guidelines—we need continued investment in testing, research and tracking to stay ahead of evolving threats. As these examples illustrate, commitment to AR testing saves lives. 

When public health experts, laboratories and industry come together, we don’t just manage infections—we prevent devastating outcomes. But to stay ahead, we must keep investing in the tools and systems that make this work possible. The fight against antimicrobial resistance is far from over, and the stakes are too high to slow down now.