Antimicrobial Tolerance in Biofilms

Abstract

Tolerance to antimicrobial agents is a common feature of microbial biofilm formation ( 1 – 7 ). Table 1 presents a few examples of biofilm tolerance to biocides and antiseptics, and Table 2 summarizes some examples of antibiotic tolerance in biofilms. Neither of these listings is comprehensive, but these two data sets can be analyzed to gain insight into the factors that influence biofilm tolerance. The examples have been selected to illustrate the wide variety of microbial species, growth environments, and antimicrobial chemistries for which biofilm reduced susceptibility has been reported. The short list in Table 1 encompasses studies designed to mimic biofilms in dental plaque, hot tubs, paper mills, drinking water, household drains, urinary catheters, food processing plants, cooling water systems, and hospitals. These examples employ a range of individual and mixed species biofilms and diverse biocidal chemistries including halogens, phenolics, quaternary ammonium compounds, aldehydes, a plant essential oil, and peroxides. The studies captured in Table 2 cover 19 antibiotics and 9 organisms that include aerobic bacteria, strict anaerobes, and a fungus.