Fifty-one chemical substances, not heretofore employed as preservatives in ophthalmic solutions, were examined for their effectiveness as antibacterial agents against 13 different strains of Pserrdomonas aeruginosa. In uitro and in uiuo methods were employed. Eleven of these agents showed a satisfactory sterilizing time against these strains. Further study of the following is indicated to determine their practical use as effective preservatives in ophthalmic preparations: Intexsan LB, Intexsan MB, Dichloran, DMBC, Cetol, Arquad 16, Virac, Betadine, Biopal VRO, chlorhexidine. and colistin.
COMMONLY FOUND and hazardous contami-
A nant in ophthalmic solutions is Ps. aerzrginosa. The latter causes a serious type of corneal ulcer encountered in ophthamology, often resulting in the loss of the infected eye.
The chemicals which are commonly employed as antibacterial agents in multidose ophthalmic solutions were investigated for their effectiveness against 13 strains of Ps. aeruginosa, utilizing in each instance inactivating media of determined neutralizing activity for subculturing (1). Only benzalkonium chloride had a sterilizing time of less than 1 hour against the 13 strains of bacteria (1). An antibacterial substance which has a sterilizing time greater than 1 hour may be arbitrarily considered to be too slow-acting for use as a preservative i n multidose ophthalmic solutions. Accordingly, this investigation was undertaken to determine the length of time required for sterilization b y various antibacterial agents not heretofore employed as preservatives in ophthalmic solutions against Ps. aeruginosa.
The main purpose was to ascertain whether any of these chemicals were capable of sterilizing in less than 1 hour.
EXPERIMENTAL'
Antibacterial Agents.-The chemicals studied for their effectiveness as antibacterial agents for ophthalmic solutions against Ps. aeruginosa were