The dogs body never " gets used to antibiotics" using inappropriate Antibiotics, inadequate doses and or duration can cause bacteria which are resistant the antibiotic/s used to dominate in that infection.
Not using the right antibiotics at proper doses for long enough is what causes the problem, not using the right amount often.
Swelling in working dogs is normally caused by mechanical damage (bite pressure and punctures) the dogs inflammatory response, aggressive cleaning/washing and lastly by infection.
This is worth a read( a few times)
http://www.merckvetmanual.com/mvm/index