How New Consensus Guidance Supports More Personalized Antibiotic Therapy

Written by: Xiana Fontno

Caring for critically ill patients poses significant challenges if proper analysis and treatment decisions are not considered. For patients presenting with severe bacterial infections, selecting and dosing the correct antibiotics is critical for recovery. Decision-making in a course of treatment must be educated and calculated in order to target a patient’s specific needs, yet a current practice often falls short.

For years, clinicians have often relied on standardized dosing frameworks based primarily on static markers like body weight and estimated renal clearance. While these formulas adjust for baseline traits, they still represent a “one-size-fits-all" population model, assuming every patient within a given category processes drugs identically. Consequently, fixed dosing fails to account for the rapid, dynamic physiological changes in a critically ill patient, increasing the risk of therapeutic failure or adverse effects.

The newly published 2026 American College of Clinical Pharmacy (ACCP) document, Consensus Guidance for Beta-Lactam Antibiotic Dose Individualization in Acutely Ill Patients, directly addresses these limitations. The guidance outlines evidence-based strategies for tailoring beta-lactam dosing to the complex, shifting biology of individual patients, contrasting sharply with fixed-dose regimens. By incorporating therapeutic drug monitoring (TDM) and pharmacokinetic principles, individualized dosing aims to optimize clinical outcomes while minimizing the development of antimicrobial resistance (AMR).

Published in Pharmacotherapy, the consensus guidance has been endorsed by high-standing organizations such as the American College of Clinical Pharmacy and authored by leading experts in the pharmaceutical industry, including two CLSI Subject Matter Experts Audrey Schuetz, MD, a professor of Laboratory Medicine and Pathology at Mayo Clinic College of Medicine and Science and Marc Scheetz, Pharm.D., M.SC, and the Associate Dean for the College of Pharmacy-Downers Grove at Midwestern University. Both are involved in the CLSI subcommittee on Antimicrobial Susceptibility Testing (AST).

Dr. Audrey Schuetz highlighted the laboratory and clinical collaboration needed to support individualized beta-lactam therapy, noting:

“Beta-lactams are widely used, and critically ill patients experience unpredictable exposure to these agents due to pharmacokinetic variability. Close collaboration between clinical microbiologists, infectious diseases pharmacy teams, and chemistry laboratorians who offer beta-lactam therapeutic drug monitoring ensures a robust healthcare infrastructure which supports proper interpretation and use of beta-lactams for targeted utilization of this important class of drugs.”

Dr. Marc Scheetz emphasized the guidance’s practical value for care teams, noting:

“Because substantial variability in beta-lactam exposure is well documented among critically ill patients, the guidance’s most important practical contribution is establishing a consistent process for identifying those most likely to benefit from therapeutic drug monitoring and for obtaining and interpreting drug concentrations. It provides a shared roadmap for close collaboration between clinical and laboratory teams to implement precision dosing, while clearly defining the evidence gaps that future studies must address.”

Reflecting on the significance of this published guidance, CLSI CEO Dr. Barb Jones noted:

“While personalized medicine has long been recognized as the future of patient care, prescription drug dosing has often been one of the last treatment modalities to evolve. Given the variable effectiveness of beta-lactam antibiotics, this is an area where progress cannot wait. CLSI applauds the efforts of these esteemed colleagues for addressing this important challenge head-on.”

The Flaw in Standardized Dosing (One-Size-Fits-All)

When preparing to start a critically ill patient on a course of antibiotics, understanding how the drug moves through and acts upon the body (its pharmacokinetics and pharmacodynamics, or PK/PD) is just as vital as selecting the drug itself. Historically, standardized dosing regimens have relied on population-level PK/PD models derived from healthy subjects or broad clinical trial cohorts. Because standard dosing fails to account for rapid, real-time physiological shifts, clinicians are often left relying on static calculations, increasing the likelihood for therapeutic failure or drug toxicity.

Without monitoring how an individual patient clears and metabolizes medications, clinicians risk either severe underexposure or overexposure. Overexposure is a critical concern for older patients and those with impaired renal function who cannot clear a drug efficiently, leading to accumulation and potential organ damage. Underexposure frequently occurs in patients experiencing hypermetabolism or augmented renal clearance, common in early sepsis. The body flushes standard drug doses too quickly, dropping the therapeutic threshold. When antibiotic levels fall too low, the infection survives, giving bacteria the opportunity to mutate and create “superbugs.”

Underdosing has been identified as a contributing factor driving the emergence of resistant bacteria, which has sparked a growing global health concern and a need to act by organizations like the World Health Organization (WHO) and the National Institutes of Health (NIH). Addressing the threat of antimicrobial resistance (AMR) requires dosing strategies that achieve therapeutic efficacy while minimizing selective pressure on bacteria. That is precisely where the individualized framework of the beta-lactam dosing approach plays a pivotal role, moving away from rigid population models toward precise, patient-centered care.

Why Individualized Beta-Lactam Therapy Matters

Beta-lactam therapeutic drug monitoring has several key features that help keep a patient’s treatment personal, safe, and effective. In consideration of a patient’s dynamic and unpredictable biological function, TDM can help clinicians monitor the concentration of a beta-lactam antibiotic in the patient’s blood and keep exposure above the minimum inhibitory concentration (MIC). This concentration level helps position the dose above the required threshold to effectively treat the infection without over or under exposing the patient to the medication. TDM is completely data-driven and specific to a patient’s blood concentrations, illness, and observed changes over time during the course of treatment. Using real-time biomarkers also allows doctors to determine the appropriate way to administer antibiotics, including injections or infusions.

TDM with beta-lactam antibiotics can serve as a vital safeguard during a patient’s treatment. When beta-lactams are used against serious infections such as meningitis, pneumonia, and sepsis, TDM helps support precise, well-considered care for some of the most vulnerable patients. Its attention to biomarkers and individualized treatment also makes it an important tool in the fight against AMR, aligning with standards-based work reflected in CLSI guidance such as CLSI M100 | Performance Standards for Antimicrobial Susceptibility Testing.

What the Consensus Guidance Recommends

Within Consensus Guidance for Beta-Lactam Antibiotic Dose Individualization in Acutely Ill Patients, the panel outlines recommendations and statements for best practice when using beta-lactam dose individualization.

While the panel acknowledges the value of this treatment method, it does not suggest that every patient needs the same level of beta-lactam dose individualization. Instead, it identifies situations where patient variability and infection severity make optimized dosing especially important:

Critically ill patients

Patients with sepsis or septic shock

Patients with altered kidney function

Patients receiving extracorporeal support

Patients with difficult-to-treat infections or high-risk pathogens

Individualized dosing relies on access to TDM, PK/PD expertise, timely laboratory data, antimicrobial stewardship, and coordination among numerous laboratory and clinical stakeholders. For laboratories, there is a lot to consider, but that work intersects with standards-based support that CLSI provides: individualized therapy depends on reliable susceptibility testing results, consistent interpretive criteria, and communication between the laboratory and care team.

How Does the Guidance Connect to CLSI Standards?

When a clinician opts for beta-lactam antibiotic dose individualization, the results that drive that treatment depend on reliable laboratory results. Doctors need confidence in the AST results to make the best-informed decision for their treatment. CLSI standards provide the essential foundation for that work and for care patients and doctors can trust.

CLSI’s most vital AST document, CLSI M100, is referred to as the gold standard for AST. This guidance provides evidence-based breakpoints and quality control parameters that produce consistent and reproducible standardized results, which is vitally important for seriously ill patients. CLSI M23 | Development of In Vitro Susceptibility Test Methods, Breakpoints, and Quality Control Parameters, supports the process behind breakpoint development, including the data and methods used to evaluate AST breakpoints and quality control parameters.

While CLSI standards help laboratories produce reliable, standardized AST results, the consensus of guidance extends that data into clinical practice, factoring in patient-specific variables like illness severity, renal function, and drug exposure. Together, these efforts reinforce the same goal of helping laboratory and clinical teams use antimicrobial data more effectively to support timely, appropriate, and individualized patient care.

Why This Matters for AST Stewardship and Patient Care

AST stewardship is fundamentally about ensuring a patient receives the right antibiotic at the right dose and right time. By bridging high-quality laboratory data with clinical practice, health care teams can use antibiotics responsibly while delivering tailored care that improves patient outcomes.

It’s equally important for multidisciplinary care teams to work together to uphold these standards and guidance. Various stakeholders within diagnostic laboratory medicine can work together to emphasize that AST data becomes more powerful when paired with patient-specific dosing decisions.

Turning Guidance into More Individualized Care

The consensus guidance reflects an important step advocating for more individualized beta-lactam therapy. By centering care around a patient’s biological changes, those with critical illnesses can receive treatment that is better suited for their bodies, leading to better recovery outcomes. And with these individualized dosing strategies, care teams can better support effective therapy while advancing proper AST and AMR stewardship.

CLSI standards and consensus guidance support the data collection that helps make beta-lactam TDM effective and keeps a patient’s care centered on their individual needs. As individualized antimicrobial therapy continues to take shape, collaboration between laboratory and clinical care teams will be essential to turning high-quality AST data into more targeted, effective, and responsible care.

Sign Up for our Newsletter

You'll receive the latest updates on new standards, guidelines, and educational resources, as well as expert insights to help enhance your laboratory's performance and compliance.