Latest Bacterial Infection Biomarker: HNL Empowers Precision Guidance for Rational Antibiotic Use

In the long-standing battle between humans and pathogenic microorganisms, antibiotics have undoubtedly been a powerful weapon. However, the crisis of antibiotic resistance caused by misuse now looms over global healthcare systems. The World Health Organization has repeatedly warned that antimicrobial resistance is one of the greatest threats to human health.

In this fight against resistance, accurately identifying bacterial infections and managing antibiotic use scientifically has become a key breakthrough. Bacterial infection biomarkers have emerged in this context as indispensable clinical tools for standardizing rational antibiotic use. They guide decisions across the entire treatment process—from initiation and effectiveness monitoring to safe discontinuation.

The Diagnostic Dilemma

When patients present with fever and elevated inflammatory markers, clinicians face a critical challenge: Is it a bacterial infection? Viral? Or non-infectious inflammation? Traditional indicators such as symptoms, white blood cell count (WBC), and C-reactive protein (CRP) provide some value, but they lack specificity, often leading to overuse of antibiotics. For instance, CRP can rise significantly in non-bacterial conditions such as trauma or surgery.

This is where more specific bacterial biomarkers become crucial. When these markers are significantly elevated, they offer strong evidence of bacterial infection that requires antimicrobial intervention. This allows clinicians to make more objective and evidence-based prescribing decisions, effectively reducing unnecessary antibiotic exposure and curbing overuse at its source. Conversely, if the marker levels remain low, physicians can confidently opt for observation or delay treatment.

Monitoring Effectiveness

Antibiotics are not “one-and-done” solutions. After initiating treatment, evaluating therapeutic effectiveness in a timely manner is critical. Traditional methods rely on subjective symptom improvement, temperature normalization, and WBC recovery—all of which are often delayed indicators and may not reflect the real-time response of pathogens.

Serum biomarkers can offer quicker and more objective feedback. When antibiotics effectively control the source of infection and clear pathogens, related biomarker levels typically drop sharply—often within 24 to 48 hours. This trend is strong evidence of treatment success.

On the other hand, persistently elevated or rising biomarker levels strongly suggest ineffective treatment, uncontrolled infection sources, complications (e.g., abscess), or antibiotic resistance. These signals can alert clinicians to promptly adjust the treatment plan—such as switching antibiotics or re-evaluating the infection site—thus avoiding disease progression.

When to Stop Antibiotics?

Deciding when to discontinue antibiotics is another complex issue in infection management. Ending treatment too early can lead to relapse or treatment failure; prolonged therapy increases the risk of side effects, economic burden, and, most critically, promotes resistance.

Traditionally, clinicians rely on fixed treatment durations or wait for all symptoms to fully resolve—approaches that lack individualization.

Here, biomarkers offer a scientific basis for safe discontinuation. Studies show that when biomarkers (e.g., PCT) return to near-normal levels under effective treatment, antibiotics can be safely stopped earlier than fixed-duration protocols, without increasing risk. This biomarker-guided, personalized discontinuation strategy is a core method to optimize antibiotic use, reduce exposure, and mitigate resistance pressure.

Clinical Value of Bacterial Biomarkers in Antibiotic Stewardship

The integration of biomarkers throughout the initiation–monitoring–discontinuation cycle drives the standardization, precision, and personalization of antibiotic therapy:

1. Improved Diagnostic AccuracyReduces empirical misuse; avoids unnecessary antibiotic initiation.

2. Optimized Treatment DecisionsProvides real-time efficacy monitoring; allows timely adjustment of ineffective regimens.

3. Shortened Treatment DurationEnables evidence-based discontinuation; minimizes exposure and over-treatment.

4. Reduced Resistance DevelopmentCuts selective pressure by avoiding overuse and prolonged courses.

5. Enhanced Patient Outcomes & SafetyLowers adverse effects, eases financial burdens, and improves healthcare efficiency.

The Triad of Core Biomarkers

Among infection biomarkers, Procalcitonin (PCT) is internationally recognized for its high specificity to systemic bacterial infections/sepsis and favorable kinetics (rapid rise and fast decline with effective treatment). It is widely endorsed in clinical guidelines, especially for respiratory tract infections and sepsis.

Meanwhile, new candidates are gaining attention:

• Heparin-Binding Protein (HBP):A potent inflammatory mediator released early upon neutrophil activation. It offers unique value in early detection, severity assessment, and prognosis evaluation for bacterial infections.

• Human Neutrophil Lipocalin (HNL):A marker of neutrophil functional activation. HNL testing is fast and simple, and it shows excellent potential for distinguishing bacterial from viral infections, particularly in localized conditions (e.g., urinary tract infections), offering clinicians a powerful new tool.

The Power of Synergy

Together, PCT, HBP, and HNL form a complementary triad, covering systemic and localized infections, early detection, and treatment monitoring—making them the frontline indicators in precise antibiotic management.

Choosing scientific, accurate infection biomarkers is the wise choice of every clinician committed to combating resistance and promoting rational antibiotic use. It is also the necessary path to improving patient safety and healthcare quality.

Let the light of precision diagnostics illuminate the future of responsible antibiotic use!