Abstract
Purpose :
Staphylococcus aureus (S. aureus), Streptococcus pneumoniae (S. pneumoniae) and Pseudomonas aeruginosa (P. aeruginosa) are ocular pathogens that commonly cause bacterial conjunctivitis and keratitis. Bacterial conjunctivitis can typically be resolved without severe complication. However, bacterial keratitis can lead to blindness due to corneal scarring. P. aeruginosa is of particular concern since it contains virulence factors that can degrade the cornea, leading to enucleation within 2 to 3 days. Raman Spectroscopy is a non-contact, non-destructive, optical technique that provides a unique molecular fingerprint of a pathogen making it a promising platform for microbial keratitis detection.
Methods :
S. aureus, S. pneumoniae and P. aeruginosa are investigated to identify Raman spectral biomarkers that indicate P. aeruginosa infection as well as discriminate between cytotoxic and non-cytotoxic strains. Raman Spectra are analyzed using Discriminant Function Analysis to build a predictive model for group membership.
Results :
The three groups of ocular pathogens classified 100% correctly using one biomarker located at a spectral frequency of 1640 cm-1 which corresponds to β-sheet vibrations of the Amide I band. Discrimination of P. aeruginosa strains based on cytotoxicity resulted in 93.7% correct classification using biomarkers at 980, 1340, and 1450 cm-1 which correlate to a) C-C stretching of proteins, =CH bending of lipids, phosphate, b) nucleic acid mode vibrations, C-H deformation (proteins, carbohydrates), and c) C-H deformation (lipids, proteins, carbohydrates).
Conclusions :
A Raman Spectroscopy based platform has high potential to be an important modality in the evaluation of microbial keratitis. The ability to detect and characterize P. aeruginosa at an early stage of infection, as well as monitor antibiotic effectiveness, can lead to better patient outcome and reduce hospital related costs.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.