The In Vitro Anti-Microbial Activity of Multipurpose Contact Lens Solutions against Standard Strains of Common Ocular Pathogens: The Effect of Duration from First Use

Abstract

Objective: This study aims to determine the in vitro anti-microbial efficacy of opened multi-purpose contact lens solutions on common contact lens-related ocular pathogens. Specifically, this study intend to compare the log reduction in microbial concentration when exposed to newly opened, 5 months-opened, and 10 months-opened multi-purpose contact lens solutions.Methods: This is a single-blind controlled experiment that evaluated five locally available multi-purpose contact lens solutions (MPS) in terms of their antimicrobial efficacy towards common contact lens-related ocular pathogens using the stand alone criteria. Newly opened, 5-month old, and 10 -month old multipurpose contact lens solutions were compared based on their effect in reducing microbial concentration at 6 hours of exposure.Results: Multi-purpose contact lens solutions (MPS) containing polyquaternium-1 and myristamidopropyl dimethylamine (MAPD) as well as polyhexamide reduced the bacterial concentrations by 3 log and fungal concentrations by 1 log, enabling them to fulfill the stand alone criteria for disinfecting solutions. This antimicrobial efficacy was most evident with newly-opened contact lens solutions, followed by those opened for five months. Those which were opened for 10 months showed limited anti-microbial activity for both bacteria and fungi. Conclusion:Multipurpose contact lens solutions demonstrated variability in their antimicrobial activity, which are significantly affected by the kind of MPS used and the duration from the date of first use. Multi-purpose contact lens solutions (MPS) containing polyquaternum and MAPD are preferred due to its broad spectrum efficacy and effectivity. They must be utilized before their expiration date since results have shown a decrease in anti-microbial activity with an increase in duration from first use. This is to prevent contact-lens related ocular infections brought about by exposure to humid climate.

The antibacterial activity of contact lens solutions against microbial keratitis

“…Contact lens solutions were tested by nonprobability sampling method. [1] The bacterial suspension obtained was determined as 1. 0×10 6 colony-forming units per mililiter using 0.5 McFarland standard, which contained NaCl 0.9% based on the ISO criteria for contact lens solutions (ISO/CD 14729).…”

“…These test solutions were categorized based on their identified disinfecting ingredient. [1] The contact lens solutions tested in this experiment are listed in (Table 1). …”

“…A bacterial colony was selected from an agar plate culture, incubated at a temperature of 35-37°C for 24 h, and suspended in a tube containing NaCl 0.9% to achieve turbidity comparable to a 0.5 McFarland standard [1,9] 1 mL of the microbial solution was added to 1 mL of each contact lens solution to achieve a 1:1 concentration. The solutions were termed "biotest solutions.…”

“…Although the incidence rates of contact lens-related microbial keratitis are low, this complication can cause poor visual outcome and blindness. [1,2] Contact lens-related microbial keratitis is commonly caused by Staphylococcus aureus and P. aeruginosa. [3] P. aeruginosa is a Gram-negative bacterium that is commonly found in many environments, including water.…”

“…Hence, it is necessary to determine the contact time of a contact lens solution. [1] Besides, most people do not clean the contact lens according to the procedure.…”