By transferring resistance genes, bacteria have mechanisms that counteract antimicrobials. Antimicrobials trigger cellular dysfunction in bacteria by binding to specific target-‐receptors. Successful antibiotic function depends heavily on the affinity between the antimicrobial and the target-‐receptor on bacteria (Michigan State University, 2011). Bacteria can achieve resistance by obscuring the target-‐ receptor by changing its location or enclosing themselves in capsules or S-‐layers. In Staphylococci against methicillin, altering the position of the target-‐receptor makes it difficult for the antimicrobial to bind with (Saravolatz, Stein & Johnson, 2011). Alterations to the structure of receptor-‐binding sites can occur where the conformational change inhibits the antimicrobial to have an affinity with the receptor, making it ineffective (much like the specific nature of enzymes). Exemplifying this mechanism is Enterococcus’ resistance towards Cephalosporin, a class of beta-‐lactam antibiotics, through modification of its target-‐receptor site (Lambert, 2005).
The effectiveness of antibiotic function is proportional to the concentration of antimicrobial agents within bacteria. Intracellular concentrations of antibiotics are decreased through transmembrane proteins acting as “efflux pumps”, which actively uses energy pushing antimicrobial compounds out the cell membrane (Borges-‐
McKeegan & Walmsley, 2003). The pump gives Escherichia coli resistance against a range of antibiotics due to its flexible recognition of molecules (Bambeke, Baltis & Tulkens, 2000), a significant advantage. A final mechanism, exhibited by Pseudomonas aeruginosa against imipenem (Michigan State University, 2010) is