How do I introduce new mother cat (and litter) to my resident cats?

[Sera]

I have 4 cats living with me from 5 months to 15 years old. Few days ago I rescued a mother cat and her 4 babies from a box placed near the dumpster. I suspect the previous owner decided to abandon them there upon learning the cat was pregnant or had given birth. The mother cat seems tame, affectionate. I have bathed all of them with a gentle lemon dishwashing soap, and given the mother flea treatment. I am keeping them in a separate room in the house.

I just don't know when they will be ready to be integrated with my cats, or how do I do it. First of all, how do I know for sure that the mom and babies are completely free of fleas. I've only found 1 so far on one of the babies and that's when I did flea treatment on the mom and bathed the babies. Second, do I introduce the mother first to my cats without her babies, or do I bring them all in and place them in a temporary cage in my bedroom? I'd like to have them close to me so I can monitor them. I intend to get them healthy, litter trained, neutered, dewormed and vaccinated next week.

 

[Alex]

you need to let the babies get older before trying to introduce them to the other cats. they will smell the other cats under the door, and your cats will get used to the idea that there is another cat and her babies, in their territory.
your cats will feel that their territory has been invaded, so they may be violent towards the new cats. if the babies are small, they could be hurt.
i would get something called Feliway. it is a spray or plug-in that gives off a synthetic pheromone which mimics the pheromone that cats use to mark their territory. the pheromone makes the cats feel safe. when cats feel safe, they are far more likely to get along with newer additions to the family. the Feliway will take about two weeks to work, and needs to be used for at least a month.
when you do decide to let the mom out, after about two weeks in her room, just let her out for ten minutes. she most likely will hiss at your cats, but that is ok. after ten minutes, put her back in the room. extend the time she is out a bit each day. if there are fights, you will need to break them up, but hissing is ok. they are just telling each other that they are not thrilled with the situation.
i would allow the other cats to meet the babies, one cat at a time. bring the cat in, and let them see the babies, and maybe sniff at them, then take the cat out. once the mother has been accepted, you will have to let the kittens out for very short periods every day, and keep an eye on them. they may try to play with the adults, and that might freak the adults out.
the whole process needs to take a month or two, as cats are pretty slow reacters. they need time to get used to new ideas.
you might want to call the vet and ak them about fleas and kittens. they will have some ideas, and will not charge you for the call.
you are an angel for taking these little ones in