Bacterial biofilm forms through a formation of extracellular polymeric substance matrix (primarily polysaccharide material) with irreversible attachment to a surface. Biofilms can form on surfaces such as living tissues, indwelling medical devices (e.g., catheters, endotracheal tubes, feeding tubes, amongst others), food processing or aquatic systems.

Studying disinfectant efficacy against bacterial biofilm is significant in the medical area, where it is highly common for bactericidal biofilm to form in wounds and certain invasive medical devices, and industrial areas for pharmaceuticals and food. Bacteria that have formed into biofilms differ widely from suspended planktonic bacterial cells in a variety of phenotypic aspects which leads to increased resistance towards many antimicrobial agents – not only do the protective coating of layers and layers of polymeric biofilm matrix limit the transportation and diffusion of antimicrobial agents, biofilm formation also detoxifies antibacterial compounds by enzymatic mechanism causing reduced antimicrobial efficacy, amongst other mechanisms. Within the biofilm structure, tolerant cells (known as persister cells) are highly concentrated which are dispersed which leads to further induction and relapse of chronic infections.

Figure above shows stages of bacterial biofilm formation consisting of polysaccharides, extracellular DNA
and matrix protein within the biofilm matrix.

The “bactericidal activity” blanket term of antimicrobial agent that is often taken to include efficacy against all bacteria may lead to unexpected ineffective disinfection within the healthcare facilities considering the increased resistance of biofilms, causing hospital-associated infections (HAIs). Therefore, it is important to ensure disinfectants used are additionally effective against biofilm when intended to be used in the related fields, especially so in the medical area.

ASTM E2871 is a standard method that employs the single tube method to evaluate the efficacy of disinfectants using in-vitro techniques while utilizing biofilm that is grown in the CDC Biofilm Reactor. The biofilm reactor allows specific controlled and reproducible growth and operating conditions that is favourable for the formation of the most relevant biofilms, allowing these structures to be used in antimicrobial evaluations in our laboratory. We delve more into the procedure and test parameters below.