It is imperative for the microbial monitor after opening the bottle of eyedrops in order to ensure the safety during use of ophthalmic solutions with multi-dose packaging.

This study was to research the microbiological properties and sterile duration of methylcellulose (MC) eye drops in three common environmental conditions, including room temperature condition of community, refrigeration condition of community and room temperature condition of hospital.

MC eye drops were assigned to the community room temperature group, community refrigeration group and hospital room temperature group, and 200 bottles of MC eye drops with or without ethylparaben were collected in each group, including sealed or unsealed drugs at average. The containers of all the eye drops were opened and the opening times were record. The drugs was admistered 1 drop for 3 times per day, with the opening period for 5-10 seconds. Then the drugs were preserved in different environments based on grouping. Microbial isolation and purification were performed by the same lab technician at 8: 00 from 1 through 10 days after opening of drugs with automatic microbial analyzer.

In the unsealed MC eye drops without ethylparaben, the bacterial positive rates were about 30% in the community room temperature group, community refrigeration group and hospital room temperature group, but no microbial colony was seen in the sealed eye drops. Ten days after opening of containers, the bacterial cultured rates were 30%, 32% and 36% in the eye drops without ethylparaben in the community room temperature group, community refrigeration group and hospital room temperature group, and those in the eye drops with ethylparaben were 15%, 19% and 23%, respectively, showing significant differences between the eye drops with and without ethylparaben (χ²=6. 452, 4. 448, 4. 063, all at P<0. 05). The 95% confidence interval (CI) of difference values of intergroup bacterial rates were -0. 166-0. 126, -0. 110-0. 190 and -0. 088-0. 208 between the community room temperature group and the community refrigeration group, between the hospital room temperature group and the community refrigeration group, between the hospital room temperature group and the community room temperature group respectively in the unsealed eye drops without ethylparaben, and those in the unsealed eye drops with ethylparaben were -0. 159-0. 079, -0. 089-0. 169 and -0. 043-0. 203 respectively, indicating insignificant differences among the groups. Cultured bacteria were identified as Micrococcus luteus, Acinetobacter lwoffii, Bacillus subtilis, Acinetobacter radioresistens, Myroides and Staptococcus xylosus.

Ethylparaben can reduce the contamination rate of microorganisms after opening of MC eye drops. Three environmental conditions do not play an influence on microbial contamination of MC eye drops after opening. The bacteria of contaminated eye drops appear to be common microorganisms in atmosphere and soil, rather than eye common pathogens.

Ophthalmic solutions; Drug contamination; Preservatives, pharmaceutical; Bacteria/isolation & purification; Methylcellulose eye drops; Antibacterial preservative; Ethylparaben