Bacterial Detection and Differentiation via Direct Volatile Organic Compound Sensing with Surface Enhanced Raman Spectroscopy

Abstract

Current methods for detecting bacterial infections, such as culture and morphological analysis of bacterial colonies, are time and labor intensive. Through the direct detection of bacterial volatile organic compounds (VOCs), via surface enhanced Raman spectroscopy (SERS), we report here a reconfigurable assay for the identification and monitoring of bacteria. We demonstrate differentiation between highly clinically relevant organisms: Escherichia coli, Enterobacter cloacae, and Serratia marcescens. This is the first differentiation of bacteria via SERS of bacterial VOC signatures. The assay also detected as few as 10 CFU/ml of E. coli in under 12 hrs, and detected E. coli from whole human blood and human urine in 16 hrs at clinically relevant concentrations of 103 CFU/ml and 104 CFU/ml, respectively. In addition, the recent emergence of portable Raman spectrometers uniquely allows SERS to bring VOC detection to point‐of‐care settings for diagnosing bacterial infections.

A Filter Supported Surface-Enhanced Raman Scattering “Nose” for Point-of-Care Monitoring of Gaseous Metabolites of Bacteria

“…After 10 h of growth under 37 °C, these samples showed a series of SERS peaks at 678 cm –1 ( v (CS) of methyl sulfide), 758 cm –1 (γ­(CH) of aromatic ring), 1001 cm –1 ( v (CC) of aromatic ring), 1063 and 1123 cm –1 ( v (CO) of aldehyde or ketone), 1486 cm –1 ( v (CC) of aromatic ring), 1673 and 1684 cm –1 ( v (CO) of ketone and aldehyde), 2856, 2870, and 2912 cm –1 ( v (CH) of alkane), which indicated the presence of methyl sulfide, alkane, ketone, aldehyde, and aromatic compounds in their metabolites (Figure c,d). These results were consistent with those from mass spectrometry ,− and SERS measurements. , Furthermore, the intensities of the same SERS peaks were different among these samples. For instance, E.…”

“…These results were consistent with those from mass spectrometry 15,39−41 and SERS measurements. 16,42 Furthermore, the intensities of the same SERS peaks were different among these samples. For instance, E. coli showed stronger signals of a characteristic aromatic ring at 785, 1001, and 1486 cm −1 , which resulted from the relatively extensive secretion of indole.…”

Are plasmonic optical biosensors ready for use in point-of-need applications?

“…In addition, the reproducibility of detection with SERS is still relatively low, yielding to poor reliability for these applications. Better substrates are required in this case, and new developments in various labs indicate improved spot-to-spot reproducibility for certain substrates such as nanobowl arrays 82 gold nanofingers, 63 or nanoposts, 175 among others.…”

Sniffing Out Urinary Tract Infection—Diagnosis Based on Volatile Organic Compounds and Smell Profile

“…Recently, GCxGC-TOF-MS methods were used to discover 28 new P. aeruginosa VOCs as well as confirming 28 former VOCs [86]. This area of research seemed to gain further interest between 2017-2019, since a number of works relating to this topic were published [87][88][89][90][91][92][93]. Most research groups used a metabolite detection approach: GC-MS [87,88], GCxGC-TOF-MS [93], and TD-GC-MS (GC-MS coupled with a thermal desorption, TD, system) [91].…”

“…Most research groups used a metabolite detection approach: GC-MS [87,88], GCxGC-TOF-MS [93], and TD-GC-MS (GC-MS coupled with a thermal desorption, TD, system) [91]. DeJong et al identified E. coli in human urine (simulated infection samples) using surface enhanced Raman spectroscopy [92].…”