Gram negative

Role in disease

The outer membrane protects the bacteria from several antibiotics, dyes, and detergents that would normally damage either the inner membrane or the cell wall (made of peptidoglycan). The outer membrane provides these bacteria with resistance to lysozyme and penicillin. The periplasmic space (space between the two cell membranes) also contains enzymes which break down or modify antibiotics. Drugs commonly used to treat Gram negative infections include amino, carboxy and ureido penicillins (ampicillin, amoxicillin, pipercillin, ticarcillin). These drugs may be combined with beta-lactamase inhibitors to combat the presence of enzymes that can digest these drugs (known as beta-lactamases) in the peri-plasmic space. Other classes of drugs that have Gram negative spectrum include cephalosporins, monobactams (aztreonam), aminoglycosides, quinolones, macrolides, chloramphenicol, folate antagonists, and carbapenems.