Molecular Identification of Biofilm-producing Staphylococcus aureus in Contact Lens Storage Solutions

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Abstract
Purpose: This study aimed to evaluate the presence of biofilm-producing Staphylococcus aureus in contact lens storage solutions (CLSS) used for both cosmetic and vision-correcting purposes. Microbiological assays and molecular methods were used to detect biofilm-associated genes, specifically icaA and icaD. The findings could provide molecular evidence of contamination in CLSS and identify behavioral risk factors associated with biofilm-forming strains. Methods: A total of 162 CLSS samples were collected from asymptomatic students living in dormitories and hospital staff. Bacterial isolation and identification were performed using standard culture methods and biochemical tests. Biofilm formation was evaluated phenotypically, and molecular confirmation of S. aureus and biofilm-associated genes (icaA and icaD) was performed using polymerase chain reaction (PCR). Associations between contamination and lens type, and also user behaviors, including lens-washing practices, showering, and swimming while wearing lenses, were analyzed. Results: This study evaluated 162 CLSS samples from 162 asymptomatic participants (mean age: 24.8 ± 4.2 years). Of these, 148 subjects (91.35%) were females. Staphylococcus aureus contamination was detected in 7 of 162 samples (4.32%), and 4 of the 7 isolates (57.14%) carried biofilm-associated icaA and icaD genes. Staphylococcus aureus contamination was found in 5 of 108 CLSS used for vision-correcting purposes (4.62%; P = 0.53). Contamination was significantly associated with lack of lens washing before wearing, which occurred in 4 of 141 participants (2.83%; P = 0.005), and lack of hand washing before handling contact lenses, which was observed in 7 of 159 participants (4.40%; P = 0.043). Conclusion: This study provides molecular evidence that CLSS can act as reservoirs for biofilm-producing S. aureus. The detection of icaA- and icaD-positive strains highlights the risk of persistent contamination and the potential development of contact lens-related infectious keratitis. Modifiable behaviors, especially proper lens washing, may significantly reduce the risk of contamination with biofilm-producing S. aureus.

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