Bacterial Biofilm in Orthopaedic Implant Infections: Advances in Detection, Phenotypic Characterization, and Diagnostic Utility of Congo Red Agar and Tube Methods

Abstract

Introduction: Orthopaedic implant–associated infections (OIAIs) represent one of the most challenging complications in trauma and reconstructive surgery due to capacity of microbes to develop structured biofilms that cohere strongly to biomaterial surfaces. Biofilm-embedded bacteria exhibit high-level tolerance to antibiotics and immune clearance, making infections chronic, recurrent, and difficult to eradicate. Early detection and characterization of biofilm-forming pathogens are pivotal to guiding appropriate clinical management.

 Aim and Objective: This review synthesizes findings from 36 key studies and provides a consolidated analysis of phenotypic techniques such as Congo Red Agar (CRA) and the Tube Adherence Method (TAM) for detecting biofilm formation in clinical isolates. It also analyzes advanced diagnostic modalities including microtiter plate assays, electron microscopy, confocal microscopy, and molecular assays targeting icaA, icaD, agg, and polysaccharide intercellular adhesin (PIA) genes.

Material and Methods: A methodological overview is provided for literature selection, followed by a synthesis of results across studies. The discussion expands on the microbiological, clinical, and therapeutic implications of biofilm formation and summarizes current challenges in diagnosis and management. This review integrates findings from 36 published studies and concludes with clinical recommendations and limitations of current detection methods, overwhelmingly emphasizing the significance of combining phenotypic and genotypic techniques for enhancing diagnostic accuracy in orthopaedic implant infections.

Results: Bacterial biofilm on orthopaedic implants is a major cause of chronic, difficult‑to‑treat infections because the structured biofilm community protects pathogens from host immunity and markedly reduces antibiotic effectiveness. Phenotypic methods including tube method and Congo Red Agar (CRA) are simple, inexpensive tools that can screen clinical isolates for biofilm production, making them especially valuable in resource‑limited laboratories. Although they are less standardized than quantitative plate‑based assays, both CRA and tube methods demonstrate reasonable sensitivity and specificity and can be integrated into routine workflows to identify strong biofilm producers that may require more aggressive treatment strategies

Conclusion: Early and reliable detection of these biofilms, together with accurate phenotypic characterization, is therefore critical for guiding appropriate surgical management and antimicrobial therapy and for preventing implant failure.