Antimicrobial Susceptibility Testing in Chlamydia trachomatis: The Current State of Evidence and a Call for More National Surveillance Studies

Chlamydia trachomatis (C. trachomatis) remains the most common bacterial sexually transmitted agent worldwide. Although current treatment regimens are highly effective, sporadic reports of reduced antimicrobial susceptibility and treatment failure raises concerns, especially in the context of increasing global antibiotic consumption and the well-documented rise of antimicrobial resistance (AMR) in other sexually transmitted pathogens. A key factor contributing to the continued efficacy of antimicrobials against C. trachomatis is the unique biology of this species, including its obligate intracellular life cycle, reduced genome, and capacity to enter a persistent state. However, this same biology poses significant challenges to antimicrobial susceptibility testing (AST). Different national surveillance studies have consistently demonstrated low rates of resistance, confirming that C. trachomatis remains largely susceptible to first-line therapies. Nonetheless, these efforts are scarce and have also revealed significant variability in testing protocols, limited geographic coverage, as well as a lack of continuous monitoring. Since antibiotic consumption patterns differ between regions, systematic surveillance will become indispensable to detect emerging resistance trends before they translate into widespread clinical failure. This narrative review synthesizes on a molecular basis the current evidence of C. trachomatis resistance and available AST methods, evaluates findings from different national surveillance studies, and underscores the need for standardized, well-funded surveillance strategies to preserve the long-term efficacy of treatment options for chlamydiosis.