Identification and susceptibility to multipurpose disinfectant solutions of bacteria isolated from contact lens storage cases of patients with corneal infiltrative events

Corneal infiltrative events (CIEs) are being reported with increasing frequency in lens wearers and may be related to specific multipurpose disinfecting solution (MPDS), contact lens type or bacterial bio-burden. Here, the efficacy of MPDS's against bacteria from contact lens storage cases (CLSC) of patients with CIEs was investigated. Eighteen CLSC from patients with CIEs were cultured. All reported using the same MPDS based on PQ-1 + Aldox + nonanoyl-EDTA prior to experiencing CIEs. Bacteria were identified and tested for sensitivity to MPDS-1 and three other MPSDs. 16/18 CLSC (89%) contained bacterial counts of ≥104–108/mL. Achromobacter spp. was most frequently identified and was found in 11/18 cases (61%). This was followed by 4/18 (22%) Stenotrophomonas maltophilia, 3/18 (17%) Serratia marcescens, 3/18 (17%) Delftia spp., 2/18 (11%) Elizabethkingia spp., 2/18 (11%) Chryseobacterium indologenes and 1/18 Sphingobacterium spiritivorum. Acanthamoeba was not isolated. All of the Achromobacter strains were resistant to MPDS-1 with <1 log10 kill up to 14 days exposure and the solution also showed reduced efficacy against the other isolates at the manufacturer's recommended disinfection time of 6 h. Two strains of S. maltophilia and Delftia spp. grew in the solution over 14 days. Factors responsible for causing adverse events such as CIEs in contact lens wearers remain unclear. However, the presence of significant bio-burden in the contact lens storage case and lens may initiate an immunological response resulting in CIEs either directly or through the release of endotoxins (e.g. lipopolysaccharides) from the bacterial outer cell membrane.