CBSE Class 9 Answered

Antibiotics are drugs used to treat infections caused by bacteria. Some antibiotics, such as the penicillins, are 'bactericidal'. They work by killing bacteria. They do this by interfering with the formation of the cell walls or cell contents of the bacteria. As a result bacteria die.  Other antibiotics are 'bacteriostatic'. They work by stopping the bacteria to multiply. Excess use of antibiotics can lead to bacteria becoming resistant to antibiotics so it is important to take them only when necessary.