Characterization Of Bacteria From Contact Lens Storage Cases Of Corneal Infiltrative Event Patients

Abstract

Purpose: : Adverse reactions such as corneal infiltrative events (CIEs) are being reported with increasing frequency in lens wearers and may be related to specific multipurpose disinfecting solution (MPDS) or contact lens type usage. Here, the efficacy of MPDS’s against bacteria from storage cases of patients with CIEs was investigated.

Methods: : Eighteen contact lens storage cases from patients with CIEs were cultured. All reported using the same MPDS (MPDS-1) based on PQ1 + Aldox + nonanoyl-EDTA. Bacteria were identified and tested for sensitivity to MPDS-1, MPSD-2 (PQ1 + alexidine) and MPDS-3 (PQ1 + PHMB), according to ISO 14723.

Results: : Here, 16/18 cases (89%) contained total viable bacterial counts (TVBC) of ≥10⁴-10⁸ /mL. All were Gram negative rods (GNR) of which 10/18 cases (56%) contained 13 strains of Achromobacter spp., 4/18 Stenotrophomonas maltophilia (22%), 3/18 Serratia marcescens (17%), 2/18 Delftia spp. (11%), and 6/18 (33%) Elizabethkingia spp. (3), Chryseobacterium sp. (2) and Sphingobacterium spiritivorum. (1). With MPDS-1 and 6 hr exposure, all 11 Achromobacter spp. tested showed 0-0.3 log kill and no significant regrowth in the solution over 21 days; S. maltophilia showed 0.7-2.0 log kill and regrowth by 1-2 log with 2 strains; Delftia spp. gave 0.6-2.0 log kill and 1-2 log regrowth. For S. marcescens,<1 log kill occurred; Elizabethkingia spp. showed <0.6 log kill; Chryseobacterium sp. 0.6-2.3 log kill band S. spiritivorum 1.5 log kill, all without regrowth. For MPDS-2, 10/11 Achromobacter spp. showed 4-5 log kill and 1/11 2 log; all S. maltophilia, Delftia spp., S. marcescens and S. spiritivorum gave >4 log kill; Chryseobacterium sp. gave 1.6-3.6 log kill and Elizabethkingia spp. 0.4-1.4. Regrowth after 21 days was not observed. With MPDS-3, 8/11 Achromobacter spp. showed 3-5 log kill and 3/11 0.6-2.5 log; all other bacteria gave 3-5 log kill and no regrowth.

Conclusions: : Bacteria isolated from the contact lens storage cases were found to be resistant to the MPDS formulation used by the patients with CIEs. The role of such high bacterial numbers and species present in the etiology of this condition is unclear. However, the significant bioburden may initiate an immunological response resulting in CIEs, either directly or through the presence of endotoxins (e.g. lipopolysaccharides) from the bacterial outer cell membrane.

Keywords: contact lens • bacterial disease