Antibiotics are given prophylactically for several indications (e.g. prior to dental surgery).

Why are the treatment periods for prophylactic antibiotics much shorter than when treating an infection?

  • Example: Prophylactic antibiotics may be the day before surgery, but in the case of infection, they are often given for 10-14 days.

Is there something different about pre-infection bacteria (or the body) compared with after the infection has set in?

Looking for general concepts here, as I recognize there are many different types of bacteria and antibiotics.

  • 3
    $\begingroup$ Generally when you have an infection, pathogenic bacteria have colonized a tissue, and you need to keep antibiotics circulating in that tissue long enough to kill all/the great majority of them. To prevent infection, you only need to kill the few that might be able to settle in and multiply (which would lead to infection down the line.) If the antibiotic level is already acceptably high in the target tissue before a procedure, the bacteria will die, not colonize and infect. Is this an adequate explanation? $\endgroup$ – anongoodnurse May 19 '16 at 3:04
  • $\begingroup$ @anongoodnurse I think your comment answers the question nicely. Why not post it as an answer? $\endgroup$ – Thawn May 19 '16 at 9:14
  • $\begingroup$ @anongoodnurse In the case of a septic surgery, most infections are localised sepsis, hence I do not think that the main concern is to just prevent bacterial seeding, as they might not need to undergo a hematogenous spread before infection ensues. Not sure though. $\endgroup$ – stochastic13 May 19 '16 at 9:43
  • $\begingroup$ @SatwikPasani - It doesn't matter where the bacteria might end up (though some places are more likely than others.) Oral antibiotics generally cover the entire body with obvious limitations. Dental procedures are covered in susceptible patients to prevent hematogenous seeding of a heart valve. Does that answer your question or have I misunderstood your comment? $\endgroup$ – anongoodnurse May 19 '16 at 14:25
  • $\begingroup$ @anongoodnurse That is a good explanation thanks! $\endgroup$ – Minnow May 19 '16 at 18:21

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