I agree with trying to find out which germ it is. I like the idea of the swab test...might be worthwhile in the long run rather than trying different medications to no avail.
In the meantime, there are a couple of links I like to pass out to folks in case they need them:
http://edis.ifas.ufl.edu/ps044
diagnosis charts at bottom
http://shagbarkbantams.com/contents.htm
click on "my chicken has a cold, part I, II, and III"
he lists the incubation periods which might be helpful to your case especially
In the meantime, there are a couple of links I like to pass out to folks in case they need them:
http://edis.ifas.ufl.edu/ps044
diagnosis charts at bottom
http://shagbarkbantams.com/contents.htm
click on "my chicken has a cold, part I, II, and III"
he lists the incubation periods which might be helpful to your case especially