Abstract
Purpose:
Contact lens cases become contaminated with bacteria during use and this can lead to corneal infiltration or infection. Many bacterial species remain non-culturable with standard laboratory techniques. We performed culturing and next-generation DNA sequencing to identify both culturable and non-culturable organisms that reside on contact lens cases of patients during corneal infiltrative events.
Methods:
Contact lens cases were collected from patients with corneal infiltrative events and both wells were individually swabbed. Swabs from the right wells were cultured to isolate and identify viable microbes using standard culture techniques. Microbial DNA was extracted from the swabs of the left wells, and 16S rRNA amplicon sequencing performed using PCR primers 515/806 targeting the V4 variable region of 16S rRNA gene.
Results:
Six lens cases were collected from five subjects with corneal infiltrative events: microbial Keratitis (n=1), contact lens peripheral ulcer (n=1) and infiltrative keratitis (n=3). All six lens cases were culture positive for Gram-negative bacteria; no Gram-positive bacteria, fungi or Acanthamoeba were grown. Several bacterial strains were cultured from 5/6 of the lens case wells; S. marcescens (n=5), A. xylosoxidans (n=2), S. maltophilia (n=1), A. faecalis (n=1) and P. fluorescens (n=1). 16S rRNA sequencing of DNA from lens cases identified multiple microbial species (median = 30, max = 79, min = 21) including members of Proteobacteria (95.9%), Bacteroidetes (2.2%), Actinobacteria (1.8%), Firmicutes (0.1%), Cyanobacteria (0.01%), Candidate division OP11 and Deinococcus thermos (combined 0.01%).
Conclusions:
The results of this study confirm that a large number of microbes remain non-culturable and DNA analysis of lens cases can provide valuable information that may help understand the pathogenesis of contact lens related microbial keratitis and corneal infiltrative events.