Bacteria living in biofilms in fluids: can we improve our cultural examination ofsynovial and other organic liquids ?
Background: Biofilms represent the primary physiological state of microorganisms, characterized by surface-associated communities sequestered within an extracellular polymeric matrix. In clinical orthopedics and broader medical practice, these structures are implicated in 65% to 80% of human infections, including periprosthetic joint infections. While traditionally classified as planktonic cells, bacteria in synovial fluid, blood, and cerebrospinal fluid frequently exist as suspended aggregates. These aggregates exhibit heightened tolerance to antimicrobial therapy and host immune responses compared to isolated cells, contributing to the persistence of chronic infections and the failure of conventional treatments.
Objective: This review examines the presence of microbial biofilms within human biological fluids, focusing on their pathological roles and the resulting limitations of standard diagnostic culture techniques in identifying biofilm-associated infections.
Key Points: Biofilm aggregates in synovial fluid significantly reduce the sensitivity of microbiological investigations, with reported rates ranging from 41.6% to 90%. These structures alter bacterial phenotypes and virulence factors, hindering antibiotic penetration. Similar phenomena are observed in catheter-associated urinary tract infections, bloodstream infections, and cerebrospinal fluid shunt malfunctions. Conventional colony-forming unit counts often underestimate bacterial presence due to cellular aggregation. Chemical pre-treatment with dithiothreitol (DTT) facilitates the disruption of the biofilm matrix by reducing disulfide bonds. This process releases microorganisms into a planktonic state without compromising viability, thereby enhancing the sensitivity of subsequent cultures and molecular assays for both solid tissue and liquid biological samples.
Conclusion: The presence of biofilm aggregates in biological fluids complicates the diagnosis and management of chronic infections. Implementing DTT-based chemical disaggregation as a routine pre-treatment for liquid samples may improve pathogen detection and guide more effective therapeutic interventions in biofilm-associated infections.
