Reasons for bacterial resistance: Indiscriminate exposure to antibiotics, incomplete course of antibiotics, taking antibiotics for viral diseases, malnutrition, chronically ill patients, etc.
How do bacteria acquire resistance?
1. Drug resistance developed by one bacterium can be transferred to another one through conjugation. The drug-resistant gene is transferred to the normal bacterium and this in turn multiplies to give rise to a large number of bacteria. Plasmids are fragments of bacteria which can give drug-resistance to other bacteria.
2. Viruses which infect bacteria may sometimes incorporate the drug-resistant genes of the bacteria. When this virus attacks another bacteria, this gene may get transferred to the new bacteria and produce a drug-resistant strain.