Inhibition of Biofilm and Virulence Properties of Pathogenic Bacteria by Silver and Gold Nanoparticles Synthesized from Lactiplantibacillus sp. Strain C1.

The emergence of antibiotic resistance in microbial pathogens necessitates the development of alternative ways to combat the infections that arise. The current study used nanotechnology as an alternate technique to control virulence characteristics and biofilm development in Pseudomonas aeruginosa and Staphylococcus aureus. Furthermore, based on the acceptance and biocompatibility of the probiotic bacteria, we chose a lactic acid bacteria (LAB) for synthesizing two types of metallic nanoparticles (NPs) in this study. Using molecular techniques, the LAB strain C1 was isolated from Kimchi food samples and identified as Lactiplantibacillus sp. strain C1. The prepared supernatant from strain C1 was used to produce gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs). C1-AuNPs and C1-AgNPs were characterized physiochemically using a variety of instruments. C1-AuNPs and C1-AgNPs had spherical shapes and sizes of 100.54 ± 14.07 nm (AuNPs) and 129.51 ± 12.31 nm (AgNPs), respectively. C1-AuNPs and C1-AgNPs were discovered to have high zeta potentials of -23.29 ± 1.17 and -30.57 ± 0.29 mV, respectively. These nanoparticles have antibacterial properties against several bacterial pathogens. C1-AuNPs and C1-AgNPs significantly inhibited the initial stage biofilm formation and effectively eradicated established mature biofilms of P. aeruginosa and S. aureus. Furthermore, when P. aeruginosa was treated with sub-MIC levels of C1-AuNPs and C1-AgNPs, their different virulence features were significantly reduced. Both NPs greatly inhibited the hemolytic activity of S. aureus. The inhibition of P. aeruginosa and S. aureus biofilms and virulence features by C1-AuNPs and C1-AgNPs can be regarded as viable therapeutic strategies for preventing infections caused by these bacteria.

Inhibition of Polymicrobial Biofilms of Candida albicans-Staphylococcus aureus/Streptococcus mutans by Fucoidan-Gold Nanoparticles.

The polymicrobial proliferation and development of complex biofilm morphologies by bacterial and fungal pathogens in the host are some of the key factors contributing to the failure of antimicrobial treatments. The polymicrobial interaction of Candida albicans and some bacterial species has been extensively studied in both in vitro and in vivo model systems. Alternative strategies for disrupting polymicrobial interaction and biofilm formation are constantly needed. Among several alternative strategies, the use of nanoparticles synthesized using a natural product in the treatment of microbial infection has been considered a promising approach. The current study aimed to synthesize gold nanoparticles (AuNPs) using a natural product, fucoidan, and to test their efficacy against mono and duo combinations of fungal (Candida albicans) and bacterial (Staphylococcus aureus/Streptococcus mutans) biofilms. Several methods were used to characterize and study Fu-AuNPs, including UV-vis absorption spectroscopy, FTIR, FE-TEM, EDS, DLS, zeta potential, and XRD. The concentration-dependent inhibition of early-stage biofilms and the eradication of mature biofilms of single species of C. albicans, S. aureus, and S. mutans have been observed. Early biofilms of a dual-species combination of C. albicans and S. aureus/S. mutans were also suppressed at an increasing concentration of Fu-AuNPs. Furthermore, Fu-AuNPs significantly eradicated the established mature biofilm of mixed species. The treatment method proposed in this study, which involves the use of marine-bioinspired nanoparticles, is a promising and biocompatible agent for preventing the growth of polymicrobial biofilms of bacterial and fungal pathogens.

Antibiofilm and Antivirulence Activities of Gold and Zinc Oxide Nanoparticles Synthesized from Kimchi-Isolated Leuconostoc sp. Strain C2.

The rapid emergence of antimicrobial resistance (AMR) among bacterial pathogens results in antimicrobial treatment failure and the high mortality rate associated with AMR. The application of nanoparticles synthesized from probiotics will be widely accepted due to their efficacy and biocompatibility in treating microbial infections in humans. The current work sought to isolate and identify lactic acid bacteria (LAB) from Kimchi. Based on 16S rRNA gene sequencing, the LAB isolate C2 was identified as a member of the genus Leuconostoc. The obtained supernatant from Leuconostoc sp. strain C2 was employed for the green synthesis of metal (AuNPs) and metal oxide (ZnONPs) nanoparticles. UV-vis absorption spectra, FTIR analysis, XRD, DLS, FE-TEM, and EDS mapping were used to fully characterize these C2-AuNPs and C2-ZnONPs. The C2-AuNPs were found to be spherical in shape, with a size of 47.77 ± 5.7 nm and zeta potential of -19.35 ± 0.67 mV. The C2-ZnONPs were observed to be rod-shaped and 173.77 ± 14.53 nm in size. The C2-ZnONPs zeta potential was determined to be 26.62 ± 0.35 mV. The C2-AuNPs and C2-ZnONPs were shown to have antimicrobial activity against different pathogens. Furthermore, these nanoparticles inhibited the growth of Candida albicans. The antibiofilm and antivirulence properties of these NPs against Pseudomonas aeruginosa and Staphylococcus aureus were thoroughly investigated. C2-AuNPs were reported to be antibiofilm and antivirulence against P. aeruginosa, whereas C2-ZnONPs were antibiofilm and antivirulence against both P. aeruginosa and S. aureus. Furthermore, these nanoparticles disrupted the preformed mature biofilm of P. aeruginosa and S. aureus. The inhibitory impact was discovered to be concentration-dependent. The current research demonstrated that C2-AuNPs and C2-ZnONPs exhibited potential inhibitory effects on the biofilm and virulence features of bacterial pathogens. Further studies are needed to unravel the molecular mechanism behind biofilm inhibition and virulence attenuation.

Simultaneous isolation and enumeration of virulent Vibrio cholerae and Vibrio vulnificus using an advanced MPN-PCR method.

Vibrio cholerae and Vibrio vulnificus are critical foodborne pathogens that need to be intensively controlled for their infection due to the intake and distribution of seafood, especially raw oysters. For this reason, various methods have already been developed for the detection and enumeration of these bacteria. The most probable number (MPN)-PCR (polymerase chain reaction) method is commonly used with the selective-differential medium for the efficiency and convenience of cell enumeration. One of the most frequently used for detecting Vibrio spp. is thiosulfate-citrate-bile salts-sucrose (TCBS) agar. But this selective-differential medium can fail to distinguish between V. cholerae, V. vulnificus, and Vibrio alginolyticus. For this reason, the conventional MPN-PCR method with TCBS medium for the detection of Vibrio spp. has a problem with processing PCR two times. This study suggests a simple and minimized detection method using one-time PCR and non-NaCl Luria-Bertani (LB-0) medium culture. This detection method is based on the difference in salt requirement between V. cholerae and V. vulnificus. Employing the developed methodology, the simultaneous cell enumeration of V. cholerae and V. vulnificus can be possible at a low cost. Furthermore, this study proposes a new specific primer to detect virulence-related genes from V. cholerae and V. vulnificus. This advanced MPN-PCR method was verified using bioaccumulated pacific oysters (Crassostrea gigas) by V. cholerae and V. vulnificus.

Phloroglucinol-Gold and -Zinc Oxide Nanoparticles: Antibiofilm and Antivirulence Activities towards Pseudomonasaeruginosa PAO1.

With the advancement of nanotechnology, several nanoparticles have been synthesized as antimicrobial agents by utilizing biologically derived materials. In most cases, the materials used for the synthesis of nanoparticles from natural sources are extracts. Natural extracts contain a wide range of bioactive components, making it difficult to pinpoint the exact component responsible for nanoparticle synthesis. Furthermore, the bioactive component present in the extract changes according to numerous environmental factors. As a result, the current work intended to synthesize gold (AuNPs) and zinc oxide (ZnONPs) nanoparticles using pure phloroglucinol (PG). The synthesized PG-AuNPs and PG-ZnONPs were characterized using a UV-Vis absorption spectrophotometer, FTIR, DLS, FE-TEM, zeta potential, EDS, and energy-dispersive X-ray diffraction. The characterized PG-AuNPs and PG-ZnONPs have been employed to combat the pathogenesis of Pseudomonas aeruginosa. P. aeruginosa is recognized as one of the most prevalent pathogens responsible for the common cause of nosocomial infection in humans. Antimicrobial resistance in P. aeruginosa has been linked to the development of recalcitrant phenotypic characteristics, such as biofilm, which has been identified as one of the major obstacles to antimicrobial therapy. Furthermore, P. aeruginosa generates various virulence factors that are a major cause of chronic infection. These PG-AuNPs and PG-ZnONPs significantly inhibit early stage biofilm and eradicate mature biofilm. Furthermore, these NPs reduce P. aeruginosa virulence factors such as pyoverdine, pyocyanin, protease, rhamnolipid, and hemolytic capabilities. In addition, these NPs significantly reduce P. aeruginosa swarming, swimming, and twitching motility. PG-AuNPs and PG-ZnONPs can be used as control agents for infections caused by the biofilm-forming human pathogenic bacterium P. aeruginosa.

Bactericidal effect of ultraviolet C light-emitting diodes: Optimization of efficacy toward foodborne pathogens in water.

The elimination of bacterial pathogens from water using ultraviolet C light-emitting diodes (UVC-LEDs) is a critical technology in terms of hygiene and sanitation. This technology has several advantages, such as low energy consumption, no heating requirements, and high effectiveness. Although several studies have reported the bactericidal effect of UVC-LEDs, little information is available on their bactericidal effect on water reservoirs contaminated with microorganisms. Therefore, the aim of this study was to optimize the bactericidal effects of UVC-LED irradiation, particularly at a wavelength of 278 nm, against major foodborne gram-positive and gram-negative pathogenic bacteria, such as Escherichia coli, Staphylococcus aureus, Bacillus cereus, Salmonella Typhimurium, and Listeria monocytogenes. The efficiency of the bactericidal effect of UVC-LED irradiation was determined based on three variables: exposure time (A, 0-60 min), stirring speed (B, 0-100 rpm), and volume of water (C, 400-1200 mL). To optimize the conditions, the operation of the designed model and results analysis were carried out using Box-Behnken design (BBD) and response surface method (RSM). The final conditions optimized for an effective bactericidal activity included a 60 min exposure time, a 100 rpm stirring speed, and 400 mL of liquid volume. Furthermore, the validation of the optimized model using the predicted values was calculated by the program, which was conducted by matching the actual values within standard deviations. The present study revealed that the optimization of a UVC-LED irradiation model is a promising approach for effectively controlling the contamination of water reservoirs by bacterial pathogens.

Effectiveness of depuration of Pacific Oyster (Crassostrea gigas): removal of bioaccumulated Vibrio vulnificus by UV-treatment.

The present study aimed to evaluate the efficacy of a depuration system equipped with UV-irradiation to control Vibrio vulnificus infection such as septicemia (or sepsis) using alive oysters. After 6 h of bioaccumulation of V. vulnificus, Pacific oyster Crassostrea gigas were found to be contaminated by > 8.0 log MPN/g of V. vulnificus cells. After 60 h of depuration, the V. vulnificus cell number significantly decreased to < 4.0 log MPN/g. The present depuration process meets the standard effectiveness in reducing V. vulnificus cells by > 3.52 log and < 30 MPN/g as recommended by the National Shellfish Sanitization Procedure Molluscan Shellfish Control guidelines. Furthermore, no significant changes in pH value and glycogen content indicate that the depuration process did not affect the freshness and quality of the oyster samples. The present study could help control any potential infection associated with the consumption of raw oysters without losing their quality.

Polyvinyl alcohol covalently grafted CNT for free-standing, flexible, and high-performance thermoelectric generator film.

We introduce a strategic approach to synthesize covalntly cross-linked carbon nanotube (CNT)-polymer nanocomposites, which can be applied as a free-standing and flexible organic thermoelectric generator film. Esterification of polyvinyl alcohol (PVA) to render PVA-COOH followed by an amide reaction with single-walled CNTs (SWCNTs) functionalized with amino groups (SWCNT-NH2) yielded a covalently grafted PVA/SWCNT composite film with an excellent dispersion of SWCNTs within the polymer matrix as confirmed using Fourier-transform infrared spectroscopy and scanning electron microscopy. This amide reaction could be further optimized with the addition of a small amount of Triton™ X-100, which resulted in a better dispersion of SWCNT prior to the amide condensation reaction. Consequently, a covalently cross-linked PVA/SWCNT composite film showed better Seebeck coefficients than those of previously reported non-covalently, physically wrapped polymer/CNT composite films, resulting in a high power factor up to 275 µW m-1 K-2. Furthermore, a covalent amide-linking between PVA and SWCNT yielded a free-standing film (30 × 30 mm) with excellent flexibility and notable shelf stability as confirmed by negligible changes in thermoelectric parameters after bending test for 10 000 times with a bending radius of 2 mm and also shelf stability test in ambient condition without any passivation layer for 30 d.