Resistance and Growth of Fusarium species in Contact Lens Disinfectant Solutions

Abstract

To compare the biocidal efficacy of contact lens care solutions against clinical isolates and the American Type Culture Collection (ATCC) 36031 reference strain of Fusarium species and to determine the ability of the organism to survive and grow in such systems. The ISO 14729 reference method to assess biocidal efficacy was applied to the purified conidial form of 10 strains of Fusarium species. Six multipurpose disinfectant solutions (MPDSs), a one-step hydrogen peroxide (Per-1) system, a hydrogen peroxide-sodium chlorite (Per-2) system, and a one-step povidone iodine (PI) system were compared. Challenge organism viability was determined at various intervals, including the manufacturers' recommended disinfection time for the products (4 to 6 hours) and thereafter to 21 days. All MPDSs achieved a 3- to 4-log10 reduction in viability of ATCC 36031 within the recommended disinfection time of 6 hours. For the clinical strains, MPDS-1 (PQ-1 + alexidine) and MPDS-2 (PQ-1 + PHMB) produced 3 to 5 log₁₀ kill after 6 hours. Multipurpose disinfectant solution 3 (PQ-1 + Aldox 0.0006%), MPDS-4 (PQ-1 + Aldox 0.0005% + C-9 ED3A), and MPDS-5 (PQ-1 + Aldox 0.0005%) showed reduced efficacy for the same two strains, with 0.6 to 1.7 log₁₀ kill. Multipurpose disinfectant solution 6 (PHMB) gave 1.6 log₁₀ for one strain and 3 to 4 log₁₀ for the remainder. Growth in all the MPDS was not detected up to 21 days incubation. Per-1 showed less than 1 log₁₀ kill at 6 hours for six of 10 strains, including ATCC 36031, and growth (1.2 to 2.7 log₁₀) occurred with three of 10 strains by 7 days. Per-2 gave less than or equal to 0.5 log₁₀ kill after 6- or 24-hour exposure without growth. The PI system showed 4 to 5 log₁₀ kill for all strains tested by the first time point of 4 hours. However, with the exception of ATCC 36031, growth (1.7 to 4.0 log₁₀) occurred with all strains by 7 days in PI. All MPDSs were effective against the ATCC 36031 reference strain of Fusarium solani. However, reduced efficacy was found for some MPDSs against the clinical isolates. Unlike MPDSs, peroxide- and povidone iodine-based systems have no continued antimicrobial presence once neutralized, and this can allow growth of surviving Fusarium in the solution. Accordingly, lenses should be subject to fresh disinfection if stored in such solutions for extended periods.