Exhausted pet rat with labored breathing

Question
I have a female agouti hooded pet rat, Chandra, who is about a year and seven months old. About three days ago, she started becoming exhausted, having labored breathing consistently throughout the day with clicking noises every once in a while.
She has been in the same home for the past year. The thing that has changed, however, is I have recently begun fostering pet rats and I brought in two new pet rats about four days ago,one day before she started showing extreme signs of respiratory infection.
Before it reached this point, Chandra would make noises (much like those of a guinea pig) and my boyfriend and I just figured it was her way of communicating with us. Now, I fear, it was earlier symptoms of a respiratory infection.
She also seemed a bit overweight to me-weight that she put on after losing her last and only cagemate-and I worry that could have interfered with her health as well.
I am incredibly worried about her as she is always full of energy and has not been herself lately. I worry that in my attempt to help out and foster rats, I put her risk at health.
Please let me know what you think I should do as soon as you get the chance.
I appreciate your time and hope to hear back from you soon.

-Shannon Barry

Answer
Hi Shannon

Thanks for fostering rats. Thats the first thing I want to say. We need people like you to help our rats have a forever home.
As for them passing something to your rat, it can happen which is why I suggest quarantine, but if your rat got sick in a day or two after being exposed to the new rats, she was getting sick before she even met the foster rats. Incubation is much longer than a day or two. usually 7 to 10 days or more which is why quarantine is supposed to be for 2 to 3 weeks. It sounds like she has mycoplasmosis pulmonis, which is what causes respiratory infection in rats. She may now have chronic lung disease and needs treatment right away. She may have developed pneumonia.
Do you  have a good vet that is qualified to see rats?

please refer to my Critter city site and read up on mycoplasmosis to get a better understanding as to what it really is and how to treat it, although there is no cure. It can be contained if done properly.  

The url is
Sandyscrittercity.com