Figure 3. Biocide usage and antibiotic resistance.

Biocides such as triclosan and chlorhexidine exert their antimicrobial activity through non-specific interactions with cellular targets. An innate bacterial defence to toxic compounds, such as these, is up-regulation of multidrug efflux pumps, such as qacA in the Gram-positive organism S. aureus and mexAB-oprM in the Gram-negative organism P. aeruginosa. Once expressed, these efflux pathways will not only export biocides, but also antibiotics, antiseptics, heavy metals and dyes – hence resulting in the development of multidrug resistance.