Table 2.
Summary of work relating to Raman-based systems for bacterial detection. SERS: surface-enhanced Raman spectroscopy.
| Raman Modality | Spectral Information Used for Bacteria Classification | Sample | Limitation |
|---|---|---|---|
| Conventional RS | Bacteria species/strain differentiation [71,82,83,84] Amino/nucleic acids: 700–1100 cm−1 Amide I, II, III: 1640–80, 1552, and 1220–1310 cm−1 |
Cultured clinical oral Streptococci ssp. Cultured Escherichiacoli (E. coli) strains, Haemophilus influenzae/Moraxella catarrhalis/Streptococcus. Pneumoniae (S. pneumoniae), Group B Streptococcus/E. coli, and Staphylococcus aureus (S. aureus) | Requires low Raman background microscope slides such as calcium fluoride or quartz; Limited information via direct visual analysis; needs machine learning methods to provide discrimination |
| Culture-free patient samples [85,86] DNA: 788, 1093, and 1578 cm−1 Proteins: 1004, 1250, and 1658 cm−1 CH-vibrations: 1341 and 1452 cm−1 |
Urine (lab-on-a-chip device) | ||
| Antibiotic resistance [87] Amino acids/DNA: 765–935 cm−1 CH2/CH3 bending:1431–1464 cm−1: Carotenoids: 1159 and 1523 cm−1 |
Cultured S. aureus mutant strains | ||
| UV Resonance (~244 nm) | Bacteria classification [88,89] Nucleic acids: 1475–1600 cm−1 |
Cultured urine isolates, Bacillus strains | Photo-degradation effect causing cell damage; Limited information via direct visual analysis; needs machine learning methods to provide discrimination |
| Antibiotic resistance [90] Nucleic acid/protein ratio: 1480/1607 cm−1 |
Cultured Bacillus pumilus | ||
| Surface-enhanced Raman spectroscopy (culture-free) |
Nanoparticle growth external or inside cells [91,92,93,94] External (cell wall features) Amino acids, proteins, carboxylate, flavin adenine dinucleotide (FAD), lipids, and DNA Internal: Cytosolic protein (1250 cm−1) and nucleic acids |
E. coli, Pseudomonas aeruginosa, Methicillin-resistant Staphylococcus aureus and Listeria spp., Geobacter sulfurreducens, and Bacillus megaterium(B. megaterium) | Nanoparticles need to be in close proximity (<3 nm) with cell surface; Material, shape and size dramatically affect signal strength and spectral profile |
| Mixture of nanoparticles with bacteria Live vs. dead bacteria [95] Gram-positive vs. Gram-negative [96] |
E. coli O157, Salmonella typhimurium(S. typhimurium), S. aureus, and B. megaterium | ||
| Label-free SERS substrate Urinary tract infection [97] Bacterial meningitis [98] Human blood [99,100] Surface charge: poly-electrolyte coated magnetic nanoparticles [101] |
Lactobacillus plantarum, E. coli, S. aureus, Pseudomonas aeruginosa, Klebsiella oxytoca, S. pneumoniae, Haemophilus influenzae | ||
| SERS biomarker assays | SERS biomarker assays (indirect detection) Antibody assays [102,103,104] Aptamer assays [105,106] |
S. aureus, E. coli, Multi-drug resistant S. typhimurium, S. aureus, and E. coli |