dont think ill of your vet ... `many normal residents of birds can be - turn pathogenic (think salmonella, E.Coli etc)
Re the Mirabellis I
finally (re)found info for you
http://www.vin.com/WebLink.plx?URL=http://www.vet.uga.edu/vpp/ivcvm/1998/index.php
(click on article Potential Pathogens of the Upper Respiratory Tract
excerpt :
"....All bacteria (Streptococcus sp., Staphylococcus xylosus, Escherichia coli, Klebsiella pneumoniae pneumoniae, Klebsiella oxytoca, and
Proteus mirabilis) isolated from birds with upper respiratory tract disease
are considered to be pathogenic and associated with upper respiratory system infections. 8,9 Two recognised fungal pathogens, Candida albicans and Aspergillus flavus, were recovered from psittacines with sinusitis. ...."
...in my estimation your vet is simply taking precautions and as chickens may (or not) have a problem with this I do not believe your vet is incompetant for being concerned....these miniscule differences as to what may be pathogenic can vary from species to species and as avian specialists do not deal with chickens daily (and your farm vets rarely treat at this level being more inclined to simply cull) a little leeway is indicated IMHO
After all we want to
encourage the avian specialists to become more interested in treating our pet poultry !!!! (If you think Avian vets are scarce try finding a
poultry specialist (avian vet specializing in poultry) to treat your bird!)