There is confusion about over-use of antibiotics. The expert opinion is that doctors prescribe them too often and so there are too many opportunities for them to allow resistant organisms to form (primarily bacteria and fungi (although fungal treatments are usually termed anti-fungals)). The fact that some people do not finish the course of antibiotics encourages resistant strains to emerge as the shorter treatment course just kills off the weaker organisms. This is a sort of under-use by the patient but the actual problem is over -use. The development of resistance to antibiotics is simply a form of natural selection from survival of the fittest. The use of antibiotics as growth supplements in cattle and other livestock and the improper dumping of antibiotics by pharmaceutical companies makes the situation even worse. New antibiotics are not being discovered fast enough to replace the ones which now have limited use due to resistance to them. There is discussions about powerful computers/AI being able to create new ones synthetically, as most originated from natural sources ( as with penicillin from a fungus). Also, viruses are being thought about as they can kill bacteria (these type of viruses are called bacteriophages) as effectively as they can kill humans!