The term that is used is called ANTIBIOTIC RESISTANCE.
Antibiotic resistance refers to the ability of a pathogen to resist the effects of a drug that has been used to destroy it previously. This often occur when micro organisms change in such a way that they are able to grow and multiply in the presence of a drug, without been negatively affected.
Antibiotic resistance can occur naturally but misuse of antibiotic drugs is the major reason behind the resistance. Antibiotic resistance is a very big threat to global health and is rapidly increasing medical costs and death of patients.