rov - I am a little confused by your question.
Your initial comment suggests 2 things - Firstly,that antibiotic therapy kills off all bacteria within a human body, and secondly, at least on my reading, that human DNA is responsible for the bacterial repopulation. Have I understood you correctly?
The bacteria within our body consist of a balance between competing communities of bacteria, living in equilibrium and mostly residing withing the gut, separated from our other various functional organs by a membrane.Antibiotic therapy does not kill off all of the bacterial populations in their entirety. The level of effect is obviously very dependent upon individuals response to the dose they receive ( prescribed doseage and individuals resistance) and type of antibiotic ( broad spectrum etc).
It is probably more accurate to say that most antibiotic therapy achieves the effect of altering the relative balance of the bacterial communities that live within humans. The body, and principally the gut, is then recolonised by the remaining bacteria. It is this area of recolonisation that can lead to opportunistic infections by yeasts, for example, which are normally held in check by the normal bacterial population balance.
So bacteria are not formed from human DNA.
Secondly, your comment about "viruses in the throat", and then asking about the purpose. Again, maybe I am misunderstanding your point, but you seem to be inferring that the viruses are somehow manufactured by human DNA.Is this what you meant?
In any event, your disease example, meningitis, is not the best example of this.Meningitis is simply inflammation of the meninges, and the cause can be either bacterial ( meningococco or pneumococci )or viral ( H,Influenzae B, mumps). The purpose of the infection is the survival of the relevant viral or bacterial agent, and is an example of diffuse colonies - no guiding purpose, just a general survival ur