A comparison of regimen methods for the removal and inactivation of bacteria, fungi and Acanthamoeba from two types of silicone hydrogel lenses.
OBJECTIVE
To compare the antimicrobial efficacy of commercial contact lens solutions when used according to the manufacturers' recommended regimens with two types of silicone hydrogel lenses.


METHODS
Four multipurpose contact lens care solutions were examined, representing manufacturer recommended regimens of "rub & rinse", "no rub, rinse" or "no rub, no rinse". Test organisms were Pseudomonas aeruginosa, Serratia marcescens, Staphylococcus aureus, Fusarium solani, Candida albicans and Acanthamoeba castellanii (trophozoites and cysts). Organisms, in the presence of organic soil, were inoculated on to Acuvue Oasys or Air Optix lenses and subjected to the solution manufacturer's recommended regimen. The number of surviving organisms on the lenses and in the soak solution was enumerated in accordance with ISO 14729.


RESULTS
ISO 14729 dictates that for a given organism the combined average number of surviving microbes from the lenses and disinfectant soaking solution must be <or=10 colony forming units (cfu)/ml. By this criterion, only Complete Easy Rub ("rub & rinse" regimen) gave satisfactory results for all bacteria, fungi and Acanthamoeba with both lens types. Solutions employing "no rub, rinse" were less satisfactory but significantly better than "no rub, no rinse". Significant differences were found in organism survival on the lenses with greater numbers remaining on the Air Optix compared to Oasys (p<0.01-0.0001).


CONCLUSIONS
The findings of this study demonstrate that the use of a manual rubbing step is more effective than rinsing or soaking alone in removing pathogenic microbes from silicone hydrogel lenses. Accordingly, it would seem prudent to recommend that contact lens care systems include a rub step as part of the hygiene regimen.
Kilvington
Simon
S
Department of Infection, Immunity & Inflammation, University of Leicester, Leicester, United Kingdom. simon.kilvington@amo-inc.com
Lonnen
James
J
D000048:Acanthamoeba / Q000187:drug effects*; D000818:Animals; D001419:Bacteria / Q000187:drug effects*; D018639:Contact Lens Solutions / Q000494:pharmacology*; D003263:Contact Lenses, Hydrophilic / Q000145:classification / Q000382:microbiology* / Q000469:parasitology*; D004203:Disinfection / Q000379:methods*; D004348:Drug Labeling; D005658:Fungi / Q000187:drug effects*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D008826:Microbial Sensitivity Tests; D021261:Parasitic Sensitivity Tests; D012828:Silicones
D018639:Contact Lens Solutions; D012828:Silicones; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate