Bacteriostatic means "stops bacteria from growing". A bacteriostatic agent prevents bacteria from multiplying but does not necessarily kill the cells already present. Remove the agent and growth can resume.
Bacteriostatic vs. bactericidal
A bactericidal agent kills bacteria outright. Many antimicrobial compounds are bacteriostatic at low concentration and bactericidal at high concentration; the label describes the effect at the concentration used. Benzyl alcohol at the 0.9% used in bacteriostatic water is bacteriostatic: it holds a small accidental introduction of organisms in check between withdrawals from a multi-use vial.
Bacteriostatic vs. sterile
Sterile means no viable microorganisms are present at all. It is a state, achieved by sterilization and confirmed by testing, and it describes the sealed vial. Bacteriostatic describes what the preservative does after the seal is broken. A vial of bacteriostatic water is sterile and bacteriostatic; the two words are doing different jobs. See sterile vs. nonpyrogenic.
What it does not mean
A bacteriostatic preservative does not sterilize a contaminated solution, does not protect against careless handling, and does not extend an opened vial's life indefinitely. The laboratory convention is to discard a vial 28 days after first puncture. See what is bacteriostatic water and benzyl alcohol as a preservative.
All BAC Water Supply products are supplied for laboratory research use only and are not for human or veterinary use.