noun which may take the genitive case particle 'no', noun
aseptic; sterile; abacterial
Medical term describing a condition, environment, or procedure free from living microorganisms. Often used attributively with の.
手術は無菌性の環境で行われた。
The surgery was performed in an aseptic environment.
無菌性髄膜炎は細菌が原因ではない。
Aseptic meningitis is not caused by bacteria.
滅菌 refers to the process of sterilization, whereas 無菌性 describes the resulting sterile state.
Compound of 無 (mu, 'without') + 菌 (kin, 'bacteria/germ') + 性 (sei, 'nature/characteristic'). The exact historical derivation is uncertain, but the components clearly indicate 'the quality of being germ-free'.