Before the large-scale medical treatment of antibiotics, the effect of drug resistance was almost meaningless to bacteria, and the harmful effect of mutation itself was more important  The normal use of antibiotics could kill almost all target bacteria, and individual fish that escaped the net would usually be wiped out by the human immune system
Although some bacterial individuals had sprouts of drug resistance, these sprouts were not enough to resist the normal dose of antibiotics, and will disappear with the individual's death
After the pathogenic bacteria become resistant, antibiotics will not be able to attack the bacteria.