Onset of meningitis is often rapid and severe, particularly when a bacterial infection is the cause. Several types of bacteria cause meningitis and each is sensitive to different antibiotics.
The faster the type of bacteria can be identified by DNA analysis, the faster patients can receive the most effective antibiotic for their condition. This also reduces the need for broadband antibiotics, overuse of which is increasing bacterial resistance.
Karen Faulds’ group at the University of Strathclyde, Glasgow, used SERS, a spectroscopic imaging technique, to identify which of Haemophilus influenzae, Streptococcus pneumoniae and Neisseria meningitidisis were present in a single sample, with a view to analysing cerebral spinal fluid from patients suspected to have meningitis. A series of DNA probes containing dyes detectable by SERS make it possible to single out the different pathogens.
‘The great advantage of SERS is this multiplexing capability,’ says Faulds. ‘This technique gives sharp, recognisable signals, like finger printing, so we can more easily discriminate what analytes are present in a mixture.’
Combining the SERS technique with chemometrics means the amount of bacteria in a sample can be measured whilst simultaneously identifying the bacteria. This would be particularly useful where co-infection of multiple species is common. Identifying the dominant pathogen present would allow targeted treatment.
‘Each individual pathogen in a mixture can be consistently identified and quantified much faster than conventional culture based methods,’ says Yiping Cui, director of the Advanced Photonic Center at Southeast University in Nanjing, China. ‘This facilitates the determination of a more effective course of treatment.’
Marc Porter, whose group at the University of Utah in the US uses SERS to examine biomarkers, says the ability to identify and concurrently quantify three common meningitis bacterial pathogens is impressive. ‘The work takes an important step in moving SERS and nanoparticle-based signalling much closer to meeting a critical need in pathogen detection,’ he adds.