From an Uncle John's bathroom reader:
"Bacteria are tiny little things, and they can get into places they're not supposed to be with surprising rapidity, where they are happy to procreate until they kill you. This isn't very smart on the part of the bacteria (killing one's host tends to cause the food supply to tap out), but it's not like bacteria have brains, and anyway, they live for about 20 minutes. What do they care?
In order for bacteria to survive, they have to build a cell wall as they reproduce; antibiotics mess with the assembly process and keep the bacteria from building these walls. The bacteria die, exposed to the elements.
Human beings, convinced as we are that anything worth doing is worth overdoing, have spent the better part of the last 60 years wantonly misusing antibiotics in lots of dumb ways. We use antibiotics for viral infections, which is pointless. We feed antibiotics to animals who aren't sick to make 'em bigger and fatter. We take antibiotics only until we feel better instead of following the directed medication course (If you feel better, you are better, right?)
The result is that we've bred some amazingly drug-resistant strains of bacteria. We've got some TB bacteria running around these days that is, in fact, resistant to ever single antibiotic we can throw at it, even the incredibly toxic antibiotics that hurt you as much as they hurt the bug.
And it's not just TB of course: Streptococcus, Staphylococcus, and Pneumococcus, heck, all of the really popular coccuses have virulently drug-resistant strains out there. Enterococcus faecalis and Pseudomonas aeruginosa are just waiting to poison your blood. And here's a thought for you: streptomycin-resistant e.coli has been found in the diapers of today's infants. Thing is, streptomycin hasn't been used to treat much of anything for decades.
It's evolution, baby. Anyone who doesn't believe in the process is going to be mighty surprised when an ear infection sends them to the morgue. But what can I do about it, you ask? Well, for one, stop using that stupid antibacterial soap. You're just making things worse, you know."