Investigating Antibacterial Effects of Garlic (Allium sativum) Concentrate and Garlic-Derived Organosulfur Compounds on Campylobacter jejuni by Using Fourier Transform Infrared Spectroscopy, Raman Spectroscopy, and Electron Microscopy

Abstract

Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy were used to study the cell injury and inactivation of Campylobacter jejuni from exposure to antioxidants from garlic. C. jejuni was treated with various concentrations of garlic concentrate and garlic-derived organosulfur compounds in growth media and saline at 4, 22, and 35°C. The antimicrobial activities of the diallyl sulfides increased with the number of sulfur atoms (diallyl sulfide < diallyl disulfide < diallyl trisulfide). FT-IR spectroscopy confirmed that organosulfur compounds are responsible for the substantial antimicrobial activity of garlic, much greater than those of garlic phenolic compounds, as indicated by changes in the spectral features of proteins, lipids, and polysaccharides in the bacterial cell membranes. Confocal Raman microscopy (532-nm-gold-particle substrate) and Raman mapping of a single bacterium confirmed the intracellular uptake of sulfur and phenolic components. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to verify cell damage. Principal-component analysis (PCA), discriminant function analysis (DFA), and soft independent modeling of class analogs (SIMCA) were performed, and results were cross validated to differentiate bacteria based upon the degree of cell injury. Partial least-squares regression (PLSR) was employed to quantify and predict actual numbers of healthy and injured bacterial cells remaining following treatment. PLSR-based loading plots were investigated to further verify the changes in the cell membrane of C. jejuni treated with organosulfur compounds. We demonstrated that bacterial injury and inactivation could be accurately investigated by complementary infrared and Raman spectroscopies using a chemical-based, "whole-organism fingerprint" with the aid of chemometrics and electron microscopy.

Protective effects of garlic (Allium sativum) and ginger (Zingiber officinale) on physicochemical and microbial attributes of liquid smoked silver carp (Hypophthalmichthys molitrix) wrapped in aluminium foil during chilled storage

“…The increase of TVC in fish flesh during storage has been demonstrated by Bahmani et al (2011). The high levels of microorganisms shown on control samples from day 6 of storage, resulted into significant differences (P<0.05) in TVC when compared with counterpart samples due to the strong antimicrobial activity of the organ sulfur compounds and other active components contained in garlic and ginger (Lu et al, 2011). TVC is the most common microbiological method aimed to detect and enumerate Means with different superscript letters in the same column indicate significant differences (p<0.05).…”

Cellular injury evidenced by impedance technology and infrared microspectroscopy

“…The applications of the technique include structure elucidation of compounds [1] and peptides [2,3], identification of different bacterial strains [4,5] and antimicrobial compounds affecting bacterial viability [6], the discrimination of diseased and healthy tissues or cells [7][8][9], cell cycle analysis [10], the effects of known toxins on cells [11] and the identification of molecular targets of natural and synthetic anticancer drugs [12][13][14][15].…”

Comprehensive Detection and Discrimination of Campylobacter Species by Use of Confocal Micro-Raman Spectroscopy and Multilocus Sequence Typing

“…Both infrared and Raman spectroscopy methods are forms of vibrational spectroscopy, and their spectral patterns for biological samples have shown good reproducibility and high discriminatory power (41)(42)(43)(44). In addition, these bioanalytical techniques are fast, reagentless, and easy to conduct.…”

“…Among the spectroscopy-based pattern recognition methods, unsupervised principal-component (PC) analysis (PCA), hierarchical cluster analysis (HCA), and supervised discriminant function analysis (DFA) are three major types, providing either cluster plots or dendrogram structures for segregation and discrimination (31,32). Recently, soft independent modeling of class analog (SIMCA) has been extensively employed to study bacterial identification to the species level (42). In addition, Bayesian probability of vibrational spectral feature significance has been employed to validate PCs selected by PCA for classification model construction (23) and the stability of the derived supervised and/or unsupervised chemometric models could be determined by using Monte Carlo estimations (14,68).…”

“…Recently, complementary infrared and Raman spectral features of C. jejuni planktonic cells, sessile cells in biofilm, and biofilm extracellular polymeric substance were characterized by our lab (42,44). The biochemical compositions (i.e., carbohydrates, lipids, proteins, and nucleic acids) of Campylobacter cells were determined by using confocal micro-Raman spectroscopy on the basis of whole-organism fingerprinting (42).…”