respiratory issue

I would like to know what to do to doctor up some outdoor cats and keep the the problem away. A few of them every once in awhile experience sneezing and a green glob of crud flies everywhere. The cats seem healthy and all just like they have a cold. My wife gives them ; I think 10 mg omixicillin for a couple days and it seems to go away and then awhile later- it comes back. Is there anyone that knows what this might be and what med to give them that is a bit stronger to totally get rid of this stuff. I can find out exactly what she gives them if it would help. Thanks for any info you all can provide

The green glob stuff definitely indicates that they are not healthy. The only way to completely cure the problem is to get them to the vet and have a culture and sensitivity test on the discharge. The fact that it comes back indicates that the amoxicillin isn't working and something else is needed. The culture and sensitivity test will tell the vet exactly what type of infection you're dealing with and the sensitivity test will tell the vet exactly which med(s) will treat the infection.