HOW DO THEY WORK
Antibiotics halt bacterial growth and cure infection through two main mechanisms. Antibiotics are either bactericidal or bacteriostatic. Bactericidal antibiotics kill the bacteria causing the infection through direct action, usually by causing the cells to split open, or lyse. Bacteriostatic antibiotics act on the internal workings of the bacterial cell to stop it dividing and so slow down the advance of the infection. A bacterial population that divides more slowly, or that cannot divide at all is much more easily dealt with by the body’s immune system.
As the antibiotic is taken into the cell, it stops the biochemical machinery of the cell producing or attaching one the major components of cell wall structure.
The cell wall produced is thinner than usual. As the cell divides, the two daughter cells then also have weaker cell walls and they cannot strengthen them because they are also prevented from making all of the necessary components. As they try to divide subsequently, the cell walls of these daughter bacteria fail. Lysis of the cell follows and the bacterium dies. Penicillin antibiotics work in this way, as do the cephalosporins.
Other antibiotics in the aminoglycoside class are also bactericidal in some infections (they are bacteriostatic in others). They bind to part of an intracellular structure - the ribosome. This usually assembles amino acids together to form complete proteins. When the antibiotic is bound to the ribosome, it cannot make proteins efficiently, and fewer proteins, or proteins that contain mistakes, are made. Vital proteins that are required by the bacterium are therefore in short supply and the cell dies.
[pic][pic][pic][pic][pic]The quinolones disable bacterial enzymes that normally replicate bacterial DNA – making it impossible for the bacterium to divide. This happens quickly, and the affected bacteria die within a few hours. Quinolone antibiotics enter human cells very easily, so are...