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Table 5: Mechanisms of bacterial resistance to biocides at the cell level

Mechanisms References
Change in cell permeability Decrease in concentration (that reaches the target sites) Spores (layers: cortex, spore envelope)

Gram-negative (outer membrane)
- Lipopolysaccharides
- Proteins (porins)
- Fatty acid
- Phospholipids

Mycobacteria mycoylarabinagalactan
Russell 1990; Russell et al. 1997; Denyer and Maillard 2002; Lambert 2002; Cloete 2003, Hawkey 2004; Champlin et al. 2005;

Munton and Russell 1970; Ayres et al. 1998; McDonnell and Russell 1999; Tattawasart et al. 2000a, b; Denyer and Maillard 2002; Fraud et al. 2003; Stickler 2004; Braoudaki and Hilton 2005 Gandhi et al. 1993; Brözel and Cloete 1994; Winder et al. 2000 Jones et al. 1989; Méchin et al. 1999; Guérin-Méchin et al. 1999, 2000 Boeris et al. 2007
McNeil and Brennan 1991; Broadley et al. 1995; Russell, 1996; Russell et al. 1997; Manzoor et al. 1999; Walsh et al. 2001; Lambert, 2002
Change in surface properties Decrease binding and interaction between biocide and cell surfaces Surface charge Bruinsma et al. 2006
Efflux mechanisms Decrease intracellular concentration of a biocide
- Small multidrug resistance (SMR) family (now part of the drug/metabolite transporter (DMT) superfamily)
- Major facilitator superfamily (MFS)
- ATP-binding cassette (ABC) family
- Resistance-nodulation-division (RND) family
- Multidrug and toxic compound extrusion (MATE) family
Nikaido, 1996; Paulsen et al. 1996; Schweizer 1998, 2001; Brown et al. 1999; Putman et al. 2000; Borges- Walmsley and Walmsley, 2001; Poole, 2001, 2002a, b; Levy 2002; Chuanchuen et al. 2003; McKeegan et al. 2003; Piddock 2006
Enzymatic modification Decrease intracellular and exocellular concentration of a biocide Demple 1996; Kummerle et al.1996; Valkova et al. 2001; Cloete 2003;
Target mutation FabI mutation in Mycobacterium smegmatis McMurry et al. 1999;
By-pass metabolic blockage Increase in pyruvate synthesis and fatty acid production via an altered metabolic pathway (expression of ‘triclosan resistance network’) Webber et al. 2008b

Source: SCCS,  Opinion on triclosan (antimicrobial resistance) (2010) , p.23