Search

The antimicrobial efficacy of preservatives in ophthalmic solutions was tested. Five strains were used as challenge organisms. They represented bacteria, yeasts and molds. Sixty per cent of the ophthalmic solutions showed a good preservation against S. aureus ATCC 6538, according to the standards and in 40% of cases, the bacteria disappeared on the second week. Against E. coli ATCC 8739, 90% of the samples were well preserved and in 10% the bacteria disappeared by the second week. Against Ps. aeruginosa ATCC 9027, C. Albicans ATCC 10231 and Asp. niger ATCC 16404, the ophthalmic solutions showed a 100% preservation. The majority of the products showed a satisfactory preservation. They contained declared preservatives and sometimes combinations of two antimicrobial agents.

Twenty disinfectants were tested against a strain of K. pneumoniae. A suspension test with incremental addition of microorganisms was used. The influence of interfering substances (proteins and hard water) on the activity of disinfectants was also determined. Iodine compounds were influenced by proteins in distilled and hard water. The presence of mineral ions inactivated the polyvinylpyrrolidone-iodine 10% and chloroxylenol preparations against K. pneumoniae. The activity of some iodine products disappeared at the second and third incremental addition of microorganisms; the chloroxylenol and the phenolic compounds were inactivated by proteins at the third incremental addition. The sensibility of K. pneumoniae to the other disinfectants was not influenced by proteins, ions and incremental bacterial additions.

The bactericidal activity of twenty disinfectants against S. aureus was evaluated by a suspension and capacity test. The effect of interfering substances (organic matter and hard water) on the activity of these disinfectants was investigated by a number of experimental trials. The sensibility of S. aureus to sodium laurylsulfate and zinc pyrithione was affected by proteins. The interference of proteins was not evident for the other disinfectants. The polyvinylpyrrolidone-iodine 7% and the cresol saponatum tolerated the presence of proteins in distilled water, but they were influenced by them in hard water; on the contrary, the zinc pyrithione was more active in hard water than in distilled water. Generally, the second and third incremental addition of microorganisms did not practically alter the bactericidal effect of the majority of disinfectants.