How do some of non-resistant bacteria become antibiotic-resistant

When an antibiotic is given for a non- resistant bacteria it inactivates or kills the bacteria however some microbes do not die and survive and multiply and pass the infection to other people making the bacteria antibiotic resistant.

Explanation:

The antibiotic resistant bacteria are those that are able to resist the effect of antibiotic and renders them ineffective that was once able to kill or inactivate bacteria.

While antibiotic non-resistant bacteria are those that are not able to resist the effect of antibody.

The reason some non-resistant bacteria becomes resistant is that a mutation in the nonresistant bacteria may occur or continuous exposure of the antibiotic would make it resistant to it.

Every time an antibiotic is taken for some bacterial infection it kills the bacteria but some that survive become resistant and grow in numbers and get transfer to other people causing them to be antibiotic resistance. The infection transfer to other people would not be treated by once used antibiotic as the microbe has become resistant.

During the cell replication due to some mutation caused they get resistant to antibiotic by a process called selective  pressure.