Addition of antibiotic to the culture medium - (Apr/05/2013 )

I gave some questions regarding cell culture
1. Is it benificial or harmful to add antibiotic with the known conc 1 % to my medium ? some people claim that it is better not to add antibiotic to ur medium if u have sterile experiment.
2. what are the disadvantages of this addition ?
3. I know that it is better not to add antibiotic to primary cells. why especially primary cell ?


Thanks

Well, a disadvantage is for instance that low level infections are suppressed by the antibiotic but could actually still effect your experiments.