Survival of micro-organisms in eye ointments

The literature relating to the contamination of ophthalmic ointments has been reviewed. The survival of microorganisms deliberately incorporated into various eye ointments has been studied, both qualitatively and quantitatively, for organisms in pure and mixed culture. The use of isopropyl myristate (IPM) as a dilutent for nonaqueous products during the isolation (membrane filtration) of contaminating organisms has been examined. Both sterile filtered and autoclaved IPM were used. Plastic and aluminium containers (tubes) were compared on an in-use, swept volume basis as part of contamination control, IPM did not interfere with organism recovery and results suggest that bacteria may survive for several days in such ointments. Observations are discussed with respect to the need for the inclusion of an added preservative in ophthalmic ointments.