You should sterilize your baby's bottles and nipples daily, if possible, to reduce the risk of infection.
For the first several months of your infant’s life, your baby is particularly vulnerable to viruses and bacteria that can live and grow on normal surfaces. It is a good idea to sterilize bottles and nipples at the end of each day in order to have a clean supply on hand when you need them. There are tons of commercially available sterilizers out there that can be used relatively quickly in the microwave. Just read their directions carefully to know how to use them.