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Aqueous black carpenter ant extract (ABCAE) was used to synthesize silver nanoparticles (AgNPs). The ABCAE was rich in water-soluble compounds such as hydrophilic polypeptides that behaved as both reducing and stabilizing agents for generating AgNPs from Ag+ ion precursors. The diameter of the observed AgNPs was mostly in the range of 20–60 nm. The AgNPs were tested as an antibacterial agent for the growth inhibition of two pathogenic bacteria (Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 27661) and one common bacteria (Escherichia coli K12 ATCC 10798). Disk diffusion test showed that the AgNPs selectively inhibited the growth of P. aeruginosa but not for the other two species, suggesting the potential application of the green-chemically synthesized AgNPs as a selective antibacterial agent without harming other beneficial bacteria. [ABSTRACT FROM AUTHOR]

Bacterial infections continue to threaten public health due to limitations in rapid and accurate diagnostic techniques. While broad-spectrum antibiotics offer empirical treatment, their overuse has fuelled the emergence of antimicrobial resistance (AMR) pathogens, posing a critical global public health challenge. In this critical scenario, nanomaterial-based antibacterial agents emerge as a promising solution to combat bacteria and inhibit their proliferation. However, selective elimination of pathogenic bacteria is paramount. This review highlights recent advancements in developing nanomaterials for selective antibacterial activity. We categorize these agents based on their mode of action, exploring how they selectively interact with bacteria and their potential antibacterial mechanisms. This review offers crucial insights for researchers exploring the potential of nanotechnology to address the growing threat of AMR., (© 2024 Wiley-VCH GmbH.)

In recent years, the selective antibacterial properties of certain fatty acids (FA) against Staphylococcus aureus have received significant attention. In this study, the antibacterial properties of palmitoleic acid (16:1 FA) in oil (triolein), surfactant (Tween® 60), and water ternary systems were evaluated to demonstrate the effects of the mixed states on the biological activity. The 16:1 FA exhibited selective antibacterial activity against Staphylococcus aureus, with a minimum inhibitory concentration (MIC) of 18.8 μg mL−1. In contrast, palmitoleic acid did not display any activity in water‐in‐oil (W/O) emulsions and liquid crystal systems. In some micelle and surfactant‐free oil‐in‐water (O/W) emulsions, the FA showed significant selective antibacterial properties against Staphylococcus aureus. These results suggested that the mixed state of the ternary mixtures affects the antibacterial behavior of FA molecules. The findings of the present study provide a valuable platform for the design of formulations of cosmetics, topical skin products, and skin cleansers. [ABSTRACT FROM AUTHOR]

Fatty acids and their derivatives are interesting cosmetic ingredients because they show the selective antibacterial activity against Staphylococcus aureus (S. aureus). However, the antibacterial activity in mixed systems containing several active ingredients is unclear because previous studies focused antibacterial systems containing one kind of fatty acid. In the present study, the minimal inhibitory concentration (MIC) and the fractional inhibitory concentration (FIC) were evaluated for myristic acid/lauric acid, myristic acid/palmitoleic acid, and myristic acid/lactic acid mixed systems to show the effect of the coexisting components on the selective antibacterial activity of myristic acid. In the myristic acid/palmitoleic acid mixed system, the antibacterial activity against S. aureus was enhanced by additive effect, whereas the antibacterial activity was not observed against S. epidermidis. On the other hand, the myristic acid/lauric acid mixed system showed antibacterial activity against S. epidermidis: Lauric acid impaired the selectivity of antibacterial activity of myristic acid. These results suggest that the selective activity of myristic acid varies with the additives. The present findings are useful for designing formulations of cosmetics and body cleansers containing myristic acid. [ABSTRACT FROM AUTHOR]

Despite long‐term efforts for exploring antibacterial agents or drugs, potentiating antibacterial activity and meanwhile minimizing toxicity to the environment remains a challenge. Here, it is experimentally shown that the functionality of reduced graphene oxide (rGO) through copper ions displays selective antibacterial activity that is significantly stronger than that of rGO itself and no toxicity to mammalian cells. Remarkably, this antibacterial activity is two‐orders‐of‐magnitude greater than the activity of its surrounding copper ions. It is demonstrated that rGO is functionalized through the cation–π interaction to massively adsorb copper ions to form a rGO–copper composite and result in an extremely low concentration level of surrounding copper ions (less than ≈0.5 µm). These copper ions on rGO are positively charged and strongly interact with negatively charged bacterial cells to selectively achieve antibacterial activity, while rGO exhibits the functionality to not only actuate rapid delivery of copper ions and massive assembly onto bacterial cells but also result in the valence shift in the copper ions from Cu2+ into Cu+, which greatly enhances the antibacterial activity. Notably, this rGO functionality through cation–π interaction with copper ions can similarly achieve algaecidal activity but does not exert cytotoxicity against neutrally charged mammalian cells. [ABSTRACT FROM AUTHOR]

Abstract Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardant. Most studies regarding TBBPA have concentrated on its occurrence, distribution, toxicity and degradation in the environment. However, little is known about its ecological effects on soil microbial communities. In this study, we investigated the effect of TBBPA on soil microbial community. Overall, the data suggested that the growth and composition of soil microorganisms were correlated to the TBBPA concentration and exposure time. Phospholipid-derived fatty acid analysis (PLFAs) showed that significant microbial growth inhibitions were 46.1% and 46.9% in 40 mg/kg TBBPA-treated soils after 45-day incubation under aerobic and anaerobic conditions, respectively. Results of PLFAs and llumina sequencing indicated that TBBPA mainly inhibited Gram-positive bacteria, but not Gram-negative bacteria. The selective antibacterial activity of TBBPA toward Gram-positive bacteria was further confirmed in pure bacteria cultures. These data suggested that, in addition to their effect on microbial growth and composition, TBBPA may affect the microbial ecology. Additional research should be carried out to identify the ecological risk of TBBPA in soil. Highlights • Higher TBBPA concentration entails more severe impact on microbial biomass. • The soil microbial community was significantly influenced by TBBPA application. • TBBPA mainly inhibited Gram-positive bacteria, but not Gram-negative bacteria. [ABSTRACT FROM AUTHOR]

Escherichia coli K99 (E. coli K99) is one of the important pathogenic bacteria in calf production causing massive loss every year, and Lactobacillus acidophilus (L. acidophilus) is an important probiotic in the gut. Essential oils in Citrus have selective antibacterial activity and the capacity to be an alternative to antibiotics. In this study, we analyzed the chemical component of Citrus Medica Limonum essential oil (LEO) and d -limonene, β-pinene, and γ-terpinene by GC-MS, then compared their selective antibacterial activities against E. coli K99 and L. acidophilus and investigated the antibacterial mechanism of LEO. The principal component of LEO, d -limonene, β-pinene, and γ-terpinene were d -limonene (47.19%), d -limonene (77.94%), β-pinene (93.52%) and γ-terpinene (89.27%) respectively. The MIC and MBC of LEO against E. coli K99 were 5 mg/mL and 10 mg/mL, while against L. acidophilus were 80 mg/mL and 160 mg/mL, which showed its best selective antibacterial activity among four EOs. LEO damaged the cell membrane structure, leading to the leakage of intracellular proteins and nucleic acids of both bacteria. Moreover, LEO improved the cell-surface hydrophobicity of both bacteria and decreased the soluble protein content of E. coli K99. In conclusion, LEO has selective antibacterial activity and the potential to be applied in calf feed. • The inhibitory effect of LEO on E. coli K99 is stronger than that of L. acidophilus. • LEO can inhibit E. coli K99 and L. acidophilus by disrupting cell membrane. • The effects of LEO on the cell membrane of both bacteria are different. [ABSTRACT FROM AUTHOR]

In this research, we report a straightforward route for the synthesis of a cationic supramolecular structure via covalently anchoring an ionic liquid-containing pyridinium moiety onto c-methylcalix[4]resorcinarene. Antibacterial activity of the new functionalized c-methylcalix[4]resorcinarene was evaluated against Gram-positive and Gram-negative bacteria. Surprisingly, this compound exhibited a selective antibacterial effect on Gram-positive bacteria, which is very important from the industrial and medicinal point of view. These preliminary results are attractive for the development of a new antibacterial agent. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Aims: C16 monounsaturated fatty acid (C16:1) show antibacterial activity against Staphylococcus aureus , a pathogen associated with various diseases such as atopic dermatitis and bacteremia, while the compound does not exhibit antibacterial activity against Staphylococcus epidermidis , an epidermal commensal that inhibits the growth of S. aureus . In this study, we aimed to find bifidobacterial strains with the ability to produce C16:1 and to find a practical manner to utilize C16:1-producing strains in industry. Methods: Various Bifidobacterium strains were screened for their content of C16:1. The chemical identity of C16:1 produced by a selected strain was analyzed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). Medium components that affect the C16:1 content of the selected strain were investigated. Antibacterial activity against staphylococci was compared between the authentic C16:1 isomers and total fatty acids (TFA) extracted from the selected strain. Results: B. adolescentis 12451, B. adolescentis 12-111, B. boum JCM 1211, and Bifidobacterium sp. JCM 7042 showed high C16:1 content among the tested strains. TFA extracted from Bifidobacterium sp. JCM 7042 contained C16:1 at 2.3% as the fatty acid constituent (2.4 mg/L of broth). Through GC-MS and LC-MS analyses, the C16:1 synthesized by Bifidobacterium sp. JCM 7042 was identified as 7- cis -hexadecenoic acid (7- cis -C16:1 showed strong and selective antibacterial activity against cis -C16:1 showed strong and selective antibacterial activity against S. aureus , similar to 6- cis -C16:1, with a minimum inhibitory concentration (MIC) of < 10 µg/mL. Components that increase C16:1 productivity were not found in the MRS and TOS media; however, Tween 80 was shown to considerably reduce the C16:1 ratio in TFA. Antibacterial activity against S. aureus was observed when the TFA extracted from Bifidobacterium sp. JCM 7042 contained high level of 7- cis -C16:1 (6.1% in TFA) but not when it contained low level of 7- cis -C16:1 (0.1% in TFA). Conclusion: The fatty acid, 7- cis -C16:1, which can selectively inhibit the S. aureus growth, is accumulated in TFA of several bifidobacteria. The TFA extracted from cultured cells of Bifidobacterium sp. JCM 7042 demonstrated antibacterial activity. From a practical viewpoint, our findings are important for developing an efficient method to produce novel skin care cosmetics, functional dairy foods, and other commodities., Competing Interests: All authors declared that there are no conflicts of interest., (© The Author(s) 2023.)

Fatty acids and their derivatives are interesting cosmetic ingredients because they show the selective antibacterial activity against Staphylococcus aureus (S. aureus). However, the antibacterial activity in mixed systems containing several active ingredients is unclear because previous studies focused antibacterial systems containing one kind of fatty acid. In the present study, the minimal inhibitory concentration (MIC) and the fractional inhibitory concentration (FIC) were evaluated for myristic acid/lauric acid, myristic acid/palmitoleic acid, and myristic acid/lactic acid mixed systems to show the effect of the coexisting components on the selective antibacterial activity of myristic acid. In the myristic acid/palmitoleic acid mixed system, the antibacterial activity against S. aureus was enhanced by additive effect, whereas the antibacterial activity was not observed against S. epidermidis. On the other hand, the myristic acid/lauric acid mixed system showed antibacterial activity against S. epidermidis: Lauric acid impaired the selectivity of antibacterial activity of myristic acid. These results suggest that the selective activity of myristic acid varies with the additives. The present findings are useful for designing formulations of cosmetics and body cleansers containing myristic acid.

Targeted bactericide nanosystems hold significant promise to improve the efficacy of existing antimicrobials for treatment of severe bacterial infections, minimizing the side effects and lowering the risk of the development of antibiotic resistance. In this work, we developed antibody-functionalized nanocapsules (NCs) containing antibacterial essential oil (EO) for selective and effective eradication of Staphylococcus aureus . Antibacterial EO NCs were produced via self-assembly nanoencapsulation in the plant-derived protein zein. The obtained EO NCs were decorated with aminocellulose to provide more reactive surface groups for carboxyl-to-amine immobilization of a antibody that is specific against S. aureus . The antibody-enabled EO NCs (Ab@EO NCs) demonstrated 2-fold higher bactericidal efficacy against the targeted bacterium compared to the pristine EO NCs at the same concentrations. The improved antibacterial effect of the Ab@EO NCs toward S. aureus was also confirmed in a real-time assay by monitoring bacterial cells elimination using a quartz crystal microbalance. Furthermore, the Ab@EO NCs selectively decreased the load and changed the cell morphology of the targeted S. aureus in a mixed inoculum with nontargeted Pseudomonas aeruginosa . Applying the nanoformulated antibacterial actives to an in vitro coculture model of the bacteria and skin fibroblasts resulted in suppression of S. aureus growth while preserving the human cells viability. The novel antibody-enabled antibacterial NCs showed potential for improving the treatment efficacy of staphylococcal infections, minimally affecting the beneficial microbial and human cells.

Essential oils (EOs), as substitutes for antibiotics in animal diets, should have selective antibacterial activity between pathogenic and beneficial bacteria from the animal gut. Thus, this study evaluated the selective antibacterial activity of Eucalyptus globulus (EG) and Pimenta pseudocaryophyllus (PP) EOs on Enterococcus faecalis as a surrogate model of pathogenic bacterium and on Lactobacillus rhamnosus as a beneficial bacterium model. The EOs antibacterial activity was evaluated by determination of minimal inhibitory concentrations (MICs), minimal bactericidal concentration (MBCs), and fractional inhibitory concentration (FIC) indices. The time-kill and sequential exposure assays were also performed, but using only the EG oil, which was the best selective EO, since it had a MIC lower on E. faecalis (7.4 mg/mL) than on L. rhamnosus (14.8 mg/mL). FIC index values showed that the combination of the two EOs had an indifferent effect (1.25 and 2.03) on E. faecalis and an additive effect (1.00) on L. rhamnosus. The time-kill assay showed that EG oil was able to kill E. faecalis within 15 min of treatment (∼5 log reduction) and caused a reduction ∼3 log of L. rhamnosus viability. The sequential exposure assay showed that EG oil (at MIC/2) produced higher reduction on E. faecalis viability (∼3 log) than on L. rhamnosus (∼2 log) as well. Therefore, L. rhamnosus presented higher tolerance to the antibacterial activity of EG oil than E. faecalis did.

In this work, a cationic polymer was synthesized to bear quaternized N-methyl-imidazole groups in the side chains. Positively charged PPV-M could selectively bind to Gram-negative and Gram-positive bacteria over fungi and exhibit enhanced antibacterial activity with the aid of white light because PPV-M could sensitize oxygen to generate reactive oxygen species (ROS) that would damage bacteria. In addition, green fluorescent and positively charged PPV-M has the ability to enter mammalian cells and be specifically accumulated in lysosome. Moreover, PPV-M could stay in live cells for a relatively long time, which implies that PPV-M has the potential to be a long-term imaging agent.