This article: Imagining the Post-Antibiotics Future points out that over the years, it has taken fewer and fewer years for antibiotic resistant strains of bacteria to emerge after every new antibiotic is discovered. Is it likely that in the near future bacteria will evolve quickly enough, and the corresponding diseases spread fast enough that there will be lots of infectious diseases that are not treatable by antibiotics?
No. Although the usefulness of antibiotics has become attenuated by the spread of resistant strains, they will never become useless. There is generally a fitness cost associated with antibiotic resistance: either in maintaining additional genes and proteins that confer resistance, or in the decreased performance of genes mutated to confer resistance. Thus in the absence of selective pressure - that is, in the absence of antibiotic use - the frequency of antibiotic resistant strains decreases. Not right away, and certainly not to zero, but it does decrease. We are seeing this effect in the case of methicillin-resistant S. aureus (MRSA), where the frequency of MRSA among all S. aureus in US hospitals has dropped from 50-60% to 40-50% in the last decade. Although the cause of this decrease is not known with certainty, it is likely that increased efforts to promote prudent use of antibiotics has played a role.
Nearly all strains of pathogenic bacteria are susceptible to at least one antibiotic. The trick is to determine which one within a clinically meaningful time frame. This determination results in more effective treatment for the patient and less selective advantage for resistant strains. Unfortunately, there are few rapid tests available for susceptibility determinations, and hospitals have been slow to adopt the ones that are available. Apparently 23,000 deaths per year and a 40-50% misprescription rate are not a sufficient incentive to make the investment in labs and testing that are required.
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