I read your post and recognized P. aeruginosa from microbiology lab. I got my old micro text out and found the following information . . . Basically it is a very common organism, found in soil, fridges, hospitals, etc. Its a very hardy bug, as it can live in pretty much anything with a carbon source, this even includes some antiseptics. Resistance is a major problem. My text states, The fluoroquinolones and the newer, antipseudomonal beta-lactam antibiotics are the usual drugs of choice. Silver sulfadiazine is very useful in the treatment of burn infections . . . Keep in mind this is in relation to humans.
Additionally, the text states, except for superficial skin infections and otitis externa, infection by P. aeruginosa is rare in healthy people. However, it does cause a lot of secondary infections in people with compromised immune systems (approx. 32% of nosocomial infections).
Here is a link for some additional info. on antibiotics, etc. in relation to dogs. http://www.gbvma.com/managing_otitis_externa_and_medi.htm
Havent ever had this with my dogs, but I hope this helps and that your girl gets feeling better soon.