Increasing frequency of sheen isolates detected among Pseudomonas aeruginosa keratitis isolates over the past 20 years

Abstract

Purpose : Pseudomonas aeruginosa causes vision-threatening keratitis. Approximately 20% of keratitis P. aeruginosa isolates from the SCUT study demonstrated a colony sheen appearance, and these sheen positive isolates correlated with a worse clinical outcome. These sheen isolates were found in India between 2006 and 2010. The basis of the sheen phenotype is a build up of 4-hydroxy-2-heptylquinoline predominantly due to mutation of the lasR gene. It is not known whether North American P. aeruginosa keratitis isolates have this sheen phenotype. In this study, we examined P. aeruginosa keratitis isolates from the Charles T. Campbell Ophthalmic Microbiology Laboratory dating from 1998-2017 for the sheen phenotype.

Methods : 281 P. aeruginosa keratitis isolates from a 20-year period were streaked out on blood agar plates and analyzed for colony sheen phenotypes. Sequencing of the lasR gene for a subset of isolates was performed.

Results : Overall sheen positive isolates were found in 18% of isolates in the Campbell Laboratory collection of P. aeruginosa keratitis isolates. There is an increasing trend in the frequency of sheen positive isolates, with 11% from isolates from 1998-2002 (n=63), 15% from 2003-2007, 16% from 2008-2012, and 26% from isolates between 2013-2017 (n=101). The majority of tested sheen positive isolates had mutations in the lasR gene.

Conclusions : We demonstrate that P. aeruginosa sheen producing strains isolated from North American keratitis patients have a similar sheen positive frequency to those observed in India. There is a trend for increasing sheen isolates that is concerning given the likely increased pathogenesis of these strains.

This is a 2020 ARVO Annual Meeting abstract.