Common mechanisms for resistance include the production of enzymes that attack the structure of antibiotics (for example, β-lactamases inactivating β-lactam antibiotics), modification of the target site that the antibiotic targets so that it can no longer bind properly, efflux pumps, and biofilm production.[1] Efflux pumps are a feature of the membrane of Gram-negative bacteria that allows them to constantly pump out foreign material, including antibiotics, so that the inside of the cell never contains a high enough concentration of the drug to have an effect.[4] Biofilms are a mixture of diverse microbial communities and polymers that protect the bacteria from antibiotic treatment by acting as a physical barrier.[4]