Abstract
SERS spectra excited at 785 nm of the bacteria Chlamydia trahomatis (elementary bodies, EB) and Neisseria gonorrheoae, the causative pathogens for the two most common sexually transmitted diseases (STD), chlamydia and gonorrhea, respectively, are reported. Although both are Gram-negative bacteria, the SERS signatures of C. trachomatis and N. gonorrheoae are completely different. N. gonorrheoae SERS spectra are due to the starvation induced nucleotide metabolites adenine and guanine, and the surface associated co-enzyme nicotinamide adenine dinucleotide and are very similar on Au and Ag although the spectrum appears more rapidly on Ag. The C. trachomatis SERS spectrum is dominated by the vibrational features of cell surface proteins. While features attributable to specific residues and the amide backbone characterize the C. trachomatis spectrum on Ag, the corresponding SERS spectrum on Au substrates displays vibrational characteristics of aggregated proteins. The prospects for the development of a SERS based platform for rapid (<one hour), low-cost bacterial STD diagnostics are promising based on these initial studies. Furthermore, this biomedical application demonstrates the potential for SERS to be a sensitive real time probe of the dynamics of biochemical activity in the cell wall and extracellular regions of microorganisms.
Highlights
Transmitted diseases (STDs) continue to be a significant cause of morbidity in the US with ~$15.9 billion spent annually on healthcare costs related to their diagnosis and treatment[1]
The SERS spectra of N. gonorrhoeae appear fairly similar on both Au and Ag substrates (Fig. 2a,b), the SERS spectra of C. trachomatis cells on Au and Ag are dramatically different
In other words, isolated C. trachomatis cells are unable to produce the purine metabolites via nucleotide degradation pathways and in contrast to N. gonorrhoeae and all the other bacteria we have studied via SERS, no purine metabolites contribute to its SERS spectra
Summary
Transmitted diseases (STDs) continue to be a significant cause of morbidity in the US with ~$15.9 billion spent annually on healthcare costs related to their diagnosis and treatment[1]. The most common bacterial sexually transmitted disease (STD) in the US, is caused by infection from the Gram-negative bacterium Chlamydia trachomatis[2]. The second most commonly reported bacterial STD in the US, results from infection by the Gram-negative bacterium Neisseria gonorrhoeae. Nucleic acid amplification tests (NAAT) are the current best technology for chlamydia and gonorrhea diagnostics[13] It is a growth-free diagnostic offering sensitivity and specificity comparable to culturing methods but with a faster turnaround time (~hours)[16]. The development of alternative, low-cost, easy-to-use, point-of-care approaches for the detection and simultaneously differentiation of C. trachomatis and N. gonorrhoeae infections in clinical settings in a useful timeframe (≤one hour) for narrow spectrum antibiotic drug prescription remains a critical strategy for improving reproductive and sexual health worldwide
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