Infectious diseases: explain question

A 45-year-old patient with a wound infection was treated with penicillin. The infection initially cleared but returned two weeks later, and the causative bacterium was found to be resistant to penicillin.

Explain: (a) how penicillin acts on bacteria; (b) why antibiotics such as penicillin do not affect viruses; (c) the consequences of antibiotic resistance for treatment of bacterial infections; (d) steps that can be taken by hospitals and patients to reduce the impact of antibiotic resistance.