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Simon Cheung, Simon Kilvington, Marina Nikolic, Nancy Brady; Biocidal Efficacy Of Multipurpose Contact Lens Care Solutions Against Stenotrophomonas And Delftia: Resistance And Regrowth. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5847.
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Stenotrophomonas and Delftia have been isolated frequently from the contact lens storage cases of asymptomatic wearers and reports of keratitis due to these bacteria have been described. Here, the biocidal efficacy of three multipurpose solutions (MPS) and a 1-step hydrogen peroxide against strains of these bacteria was investigated.
Three strains of S. maltophilia and D. acidovorans were tested. Commercial MPS studied contained the active biocidal agents of: polyquaternium-1 (PQ1) and polyhexamethylene biguanide (PHMB), PHMB alone, PQ1 and alexidine (ALX), PQ1 and myristamidopropyl dimethylamine (MAPD) with and nonanoyl ethylenediaminetriacetic acid (C9ED3A), and 3% hydrogen peroxide with a platinum disc neutralising system (PEROX). Biocidal testing was done in accordance with ISO14729 and viability assessed at 6 hr, 24 hr and 7-21 d. In addition, the ability of these bacteria to support growth and replication of Acanthamoeba castellanii (ATCC 50370) was studied.
After a 4 hour exposure time, formulations based on PQ1-ALX, PQ1-PHMB, PHMB or PEROX gave total kill (≥4.0 log) with all Stenotrophomonas and Delftia strains and no regrowth was observed up to 21 days. In contrast, PQ1-MAPD-C9ED3A showed ≤1.0 log kill of Stenotrophomonas after 6 hr and 0.6-3.2 log at 24 hr. By 7 days, a 3 log regrowth occurred with two strains and 0.4 log for the third (0.6 log kill at 24 hr). For Delftia, PQ1-MAPD-C9ED3A showed ≤1 log kill by 24 hr and regrowth by 1 log occurred after 7-14 d. All strains supported the excystment and trophozoite replication of A. castellanii at a rate comparable to Escherichia coli as a food source.
S. maltophilia and D. acidovorans are inherently resistant to the MPS composed of PQ1-MAPD-C9ED3A but not those based on PQ-Alex, PQ1-PHMB, PHMB or PEROX. The ability of such bacteria to survive and replicate in MPS may result in biofilm production inside the storage case, reduced disinfection efficacy and provide a food source and favorable habitat for the growth of Acanthamoeba.
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