Effect of Titanium Dioxide Nanoparticles on the Expression of Efflux Pump and Quorum-Sensing Genes in MDR Pseudomonas aeruginosa Isolates

Mechanistic Insights into Toxicity of Titanium Dioxide Nanoparticles at the Micro- and Macro-levels

Titanium oxide nanoparticles (TiO2 NPs) have been regarded as a legacy nanomaterial due to their widespread usage across multiple fields. The TiO2 NPs have been and are still extensively used as a food and cosmetic additive and in wastewater and sewage treatment, paints, and industrial catalysis as ultrafine TiO2. Recent developments in nanotechnology have catapulted it into a potent antibacterial and anticancer agent due to its excellent photocatalytic potential that generates substantial amounts of highly reactive oxygen radicals. The method of production, surface modifications, and especially size impact its toxicity in biological systems. The anatase form of TiO2 (<30 nm) has been found to exert better and more potent cytotoxicity in bacteria as well as cancer cells than other forms. However, owing to the very small size, anatase particles are able to penetrate deep tissue easily; hence, they have also been implicated in inflammatory reactions and even as a potent oncogenic substance. Additionally, TiO2 NPs have been investigated to assess their toxicity to large-scale ecosystems owing to their excellent reactive oxygen species (ROS)-generating potential compounded with widespread usage over decades. This review discusses in detail the mechanisms by which TiO2 NPs induce toxic effects on microorganisms, including bacteria and fungi, as well as in cancer cells. It also attempts to shed light on how and why it is so prevalent in our lives and by what mechanisms it could potentially affect the environment on a larger scale.

The enhanced antibacterial and antibiofilm properties of titanium dioxide nanoparticles biosynthesized by multidrug-resistant Pseudomonas aeruginosa

The emergence of Multidrug-resistant (MDR) bacteria are becoming a major worldwide health concern, encouraging the development effective alternatives to conventional antibiotics. The study identified P. aeruginosa and assessed its antimicrobial sensitivity using the Vitek-2 system. Carbapenem-resistant genes were detected through Polymerase chain reaction (PCR). MDR- P. aeruginosa isolates were used to biosynthesize titanium dioxide nanoparticles (TiO2NPs) and characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM). A study involving 78 P. aeruginosa isolates revealed that 85.8% were MDR, with meropenem and amikacin showing effectiveness against 70% of the isolates. The most prevalent carbapenemase gene was blaOXA-48, present in 83% of the isolates. Majority of the isolates formed biofilms, and biosynthesized TiO2NPs were able to reduce biofilm formation by 94%. TiO2NPs exhibited potent antibacterial action against MDR-Gram-negative bacilli pathogens and showed synergistic activity with antibiotics, particularly piperacillin, with a significant fold increase in areas (283%). A new local strain of P. aeruginosa, identified as ON678251 in the World GenBank, was found capable of producing TiO2NPs. Our findings demonstrate the potential of biosynthesized TiO2NPs to manage antibiotic resistance and regulate the formation of biofilms. This presents a promising direction for the creation of novel antimicrobial agents or substitutes for use in clinical settings, particularly in the management of isolates capable of resisting multiple drugs.

Review of Antimicrobial Properties of Titanium Dioxide Nanoparticles

There is a growing interest in the utilization of metal oxide nanoparticles as antimicrobial agents. This review will focus on titanium dioxide nanoparticles (TiO2 NPs), which have been demonstrated to exhibit high antimicrobial activity against bacteria and fungi, chemical stability, low toxicity to eukaryotic cells, and therefore high biocompatibility. Despite the extensive research conducted in this field, there is currently no consensus on how to enhance the antimicrobial efficacy of TiO2 NPs. The aim of this review is to evaluate the influence of various factors, including particle size, shape, composition, and synthesis parameters, as well as microbial type, on the antibacterial activity of TiO2 NPs against bacteria and fungi. Furthermore, the review offers a comprehensive overview of the methodologies employed in the synthesis and characterization of TiO2 NPs. The antimicrobial activity of TiO2 exhibits a weak dependence on the microorganism species. A tendency towards increased antibacterial activity is observed with decreasing TiO2 NP size. The dependence on the shape and composition is more pronounced. The most pronounced antimicrobial potential is exhibited by amorphous NPs and NPs doped with inorganic compounds. This review may be of interest to specialists in biology, medicine, chemistry, and other related fields.

Deciphering the impact of Acinetobacter baumannii on human health, and exploration of natural compounds as efflux pump inhibitors to treat multidrug resistance

Acinetobacter baumannii is an ESKAPE pathogen and threatens human health by generating infections with high fatality rates. A. baumannii leads to a spectrum of infections such as skin and wound infections, endocarditis, meningitis pneumonia, septicaemia and urinary tract infections. Recently, strains of A. baumannii have emerged as multidrug-resistant (MDR), meaning they are resistant to at least three different classes of antibiotics. MDR development is primarily intensified by widespread antibiotic misuse and inadequate stewardship. The World Health Organization (WHO) declared A. baumannii a precarious MDR species. A. baumannii maintains the MDR phenotype via a diverse array of antimicrobial metabolite-hydrolysing enzymes, efflux of antibiotics, impermeability and antibiotic target modification, thereby complicating treatment. Hence, a deeper understanding of the resistance mechanisms employed by MDR A. baumannii can give possible approaches to treat antimicrobial resistance. Resistance-nodulation-cell division (RND) efflux pumps have been identified as the key contributors to MDR determinants, owing to their capacity to force a broad spectrum of chemical substances out of the bacterial cell. Though synthetic inhibitors have been reported previously, their efficacy and safety are of debate. As resistance-modifying agents, phytochemicals are ideal choices. These natural compounds could eliminate the bacteria or interact with pathogenicity events and reduce the bacteria's ability to evolve resistance. This review aims to highlight the mechanism behind the multidrug resistance in A. baumannii and elucidate the utility of natural compounds as efflux pump inhibitors to deal with the infections caused by A. baumannii.

Targeting bacterial biofilm-related genes with nanoparticle-based strategies

Persistent infection caused by biofilm is an urgent in medicine that should be tackled by new alternative strategies. Low efficiency of classical treatments and antibiotic resistance are the main concerns of the persistent infection due to biofilm formation which increases the risk of morbidity and mortality. The gene expression patterns in biofilm cells differed from those in planktonic cells. One of the promising approaches against biofilms is nanoparticle (NP)-based therapy in which NPs with multiple mechanisms hinder the resistance of bacterial cells in planktonic or biofilm forms. For instance, NPs such as silver (Ag), zinc oxide (ZnO), titanium dioxide (TiO2), copper oxide (Cu), and iron oxide (Fe3O4) through the different strategies interfere with gene expression of bacteria associated with biofilm. The NPs can penetrate into the biofilm structure and affect the expression of efflux pump, quorum-sensing, and adhesion-related genes, which lead to inhibit the biofilm formation or development. Therefore, understanding and targeting of the genes and molecular basis of bacterial biofilm by NPs point to therapeutic targets that make possible control of biofilm infections. In parallel, the possible impact of NPs on the environment and their cytotoxicity should be avoided through controlled exposure and safety assessments. This study focuses on the biofilm-related genes that are potential targets for the inhibition of bacterial biofilms with highly effective NPs, especially metal or metal oxide NPs.

Nanomaterials Regulate Bacterial Quorum Sensing: Applications, Mechanisms, and Optimization Strategies

Anti-virulence therapy that interferes with bacterial communication, known as "quorum sensing (QS)", is a promising strategy for circumventing bacterial resistance. Using nanomaterials to regulate bacterial QS in anti-virulence therapy has attracted much attention, which is mainly attributed to unique physicochemical properties and excellent designability of nanomaterials. However, bacterial QS is a dynamic and multistep process, and there are significant differences in the specific regulatory mechanisms and related influencing factors of nanomaterials in different steps of the QS process. An in-depth understanding of the specific regulatory mechanisms and related influencing factors of nanomaterials in each step can significantly optimize QS regulatory activity and enhance the development of novel nanomaterials with better comprehensive performance. Therefore, this review focuses on the mechanisms by which nanomaterials regulate bacterial QS in the signal supply (including signal synthesis, secretion, and accumulation) and signal transduction cascade (including signal perception and response) processes. Moreover, based on the two key influencing factors (i.e., the nanomaterial itself and the environment), optimization strategies to enhance the QS regulatory activity are comprehensively summarized. Collectively, applying nanomaterials to regulate bacterial QS is a promising strategy for anti-virulence therapy. This review provides reference and inspiration for further research on the anti-virulence application of nanomaterials.

Biogenic synthesized copper oxide nanoparticles by Bacillus subtilis: Investigating antibacterial activity on the mexAB-oprM efflux pump genes and cytotoxic effect on MCF-7 cells

One of the main characteristics of Pseudomonas aeruginosa is remarkable intrinsic antibiotic resistance which is associated with production of β-lactamases and the expression of inducible efflux pumps. Nanoparticles (NPs) are a novel option for coping with this resistant bacteria. Hence, the aim of present study was production of CuO NPs via Bacillus subtilis and applied them to deal with resistant bacteria. For this purpose, first NPs were synthesized and were analyzed with different standard techniques containing scanning electron microscope, Fourier-transform infrared spectroscopy, and X-ray powder diffraction. Microdilution Broth Method and real-time polymerase chain reaction were used to antibacterial properties of the CuO NPs and expression of mexAB-oprM in clinical samples of P. aeruginosa, respectively. The cytotoxic effect of CuO NPs was also evaluated on MCF7 as a breast cancer cell line. Finally, the data were analyzed by one-way analysis of variance and Tukey's tests. The size of CuO NPs was in the range of 17-26 nm and showed antibacterial effect at <1000 μg/mL concentrations. Our evidence noted that the antibacterial effects of the CuO NPs occurred through the downregulation of mexAB-oprM and upregulation of mexR. The interesting point was that CuO NPs had an inhibitory effect on MCF7 cell lines with the optimal inhibition concentration at IC50 = 25.73 µg/mL. Therefore, CuO NPs can be considered as a promising medical candidate in the pharmaceutical industry.

Efflux systems as a target for anti-biofilm nanoparticles: perspectives on emerging applications

INTRODUCTION

Understanding the role of efflux pumps in biofilm resistance provides valuable insights for developing effective therapeutic strategies. Drugs designed for targeting efflux pumps in drug design holds promise for combating biofilm-related infections. Nanoparticles offer unparalleled advantages in designing drugs targeting efflux pumps.

AREAS COVERED

This review rigorously examines the existing body of knowledge on the prospective targeting of efflux pumps using metal-based nanoparticles. It includes and analyses the pertinent research findings sourced from the PubMed and SciFinder databases. It covers the experimental studies on efflux inhibition by nanoparticles and provides detailed analyses of their mechanisms of action, elucidating their interactions with the efflux system and their influence on biofilm formation and persistence.

EXPERT OPINION

The potential of nanoparticles to act as potent antibacterial agents through efflux pump inhibition remains tantalizing, although hindered by limited mechanistic understanding. From the burgeoning research landscape nanoparticles emerge as a novel direction for shaping antimicrobial drug design. Notably, beyond their contribution to drug resistance, efflux pumps play a pivotal role in biofilm development. The deliberate disruption of these pumps can effectively reduce biofilm adhesion and maturation. More details however are needed to exploit this potential.

Zinc-Based Nanoparticles Reduce Bacterial Biofilm Formation

Biofilm formation is important for microbial survival in hostile environments and a phenotype that provides microorganisms with antimicrobial resistance. Zinc oxide (ZnO) and Zinc sulfide (ZnS) nanoparticles (NPs) present potential antimicrobial properties for biomedical and food industry applications. Here, we aimed to analyze, for the first time, the bactericidal and antibiofilm activity of ZnS NPs against Staphylococcus aureus, Klebsiella oxytoca, and Pseudomonas aeruginosa, all medically important bacteria in developed countries. We compared ZnS NPs antimicrobial activity to ZnO NPs, which have been extensively studied. Using the colorimetric XTT reduction assay to observe the metabolic activity of bacterial cells and the crystal violet assay to measure biofilm mass, we demonstrated that ZnS and ZnO had similar efficacy in killing planktonic bacterial cells and reducing biofilm formation, with S. aureus being more susceptible to both therapeutics than K. oxytoca and P. aeruginosa. Crystal violet staining and confocal microscopy validated that Zn NPs inhibit biofilm formation and cause architectural damage. Our findings provide proof of principle that ZnS NPs have antibiofilm activity, and can be potentially used in medical and food industry applications, such as treatment of wound infections or package coating for food preservation. IMPORTANCE Zinc (Zn)-based nanoparticles (NPs) can be potentially used in medical and food preservation applications. As proof of principle, we investigated the bactericidal and antibiofilm activity of zinc oxide (ZnO) and zinc sulfide (ZnS) NPs against medically important bacteria. Zn-based NPs were similarly effective in killing planktonic and biofilm-associated Staphylococcus aureus, Klebsiella oxytoca, and Pseudomonas aeruginosa cells. However, S. aureus was more susceptible to these investigational therapeutics. Although further studies are warranted, our findings suggest the possibility of future use of Zn-based NPs in the treatment of skin infections or preservation of food.

Common viral and bacterial avian respiratory infections: an updated review

Many pathogens that cause chronic diseases in birds use the respiratory tract as a primary route of infection, and respiratory disorders are the main leading source of financial losses in the poultry business. Respiratory infections are a serious problem facing the poultry sector, causing severe economic losses. Avian influenza virus, Newcastle disease virus, infectious bronchitis virus, and avian pneumovirus are particularly serious viral respiratory pathogens. Mycoplasma gallisepticum, Staphylococcus, Bordetella avium, Pasteurella multocida, Riemerella anatipestifer, Chlamydophila psittaci, and Escherichia coli have been identified as the most serious bacterial respiratory pathogens in poultry. This review gives an updated summary, incorporating the latest data, about the evidence for the circulation of widespread, economically important poultry respiratory pathogens, with special reference to possible methods for the control and prevention of these pathogens.

Mechanisms of Metallic Nanomaterials to Induce an Antibacterial Effect

Pathogenic microorganisms, including bacteria, are becoming resistant to most existing drugs, which increases the failure of pharmacologic treatment. Therefore, new nanomaterials were studied to spearhead improvement against the same resistant pathogenic bacteria. This has increased the mortality in the world population, principally in under-developed countries. Moreover, recently there has been research to find new drug formulations to kill the most dangerous microorganisms, such as bacteria cells which should avoid the spread of disease. Therefore, lately, investigations have been focusing on nanomaterials because they can exhibit the capacity to show an antibacterial effect. These studies have been trying oriented in their ability to produce an improvement to get antibacterial damage against the same pathogenic bacteria resistance. However, there are many problems with the use of nanoparticles. One of them is understanding how they act against bacteria, "their mechanism(s) action" to induce reduction or even kill the bacterial strains. Therefore, it is essential to understand the specific mechanism(s) of each nanomaterial used to observe the interaction between bacteria cells and nanoparticles. In addition, since nanoparticles can be functionalized with different antibacterial drugs, it is necessary to consider and distinguish the antibacterial activity of the nanoparticles from the antibacterial activity of the drugs to avoid confusion about how the nanoparticles work. Knowledge of these differences can help better understand the applications of the primary nanoparticles (i.e., Ag, Au, CuO, ZnO, and TiO², among others) described in detail in this review which are toxic against various bacterial strains.

Nanoparticle Impact on the Bacterial Adaptation: Focus on Nano-Titania

Titanium dioxide nanoparticles (nano-titania/TiO₂ NPs) are used in different fields and applications. However, the release of TiO₂ NPs into the environment has raised concerns about their biosafety and biosecurity. In light of the evidence that TiO₂ NPs could be used to counteract antibiotic resistance, they have been investigated for their antibacterial activity. Studies reported so far indicate a good performance of TiO₂ NPs against bacteria, alone or in combination with antibiotics. However, bacteria are able to invoke multiple response mechanisms in an attempt to adapt to TiO₂ NPs. Bacterial adaption arises from global changes in metabolic pathways via the modulation of regulatory networks and can be related to single-cell or multicellular communities. This review describes how the impact of TiO₂ NPs on bacteria leads to several changes in microorganisms, mainly during long-term exposure, that can evolve towards adaptation and/or increased virulence. Strategies employed by bacteria to cope with TiO₂ NPs suggest that their use as an antibacterial agent has still to be extensively investigated from the point of view of the risk of adaptation, to prevent the development of resistance. At the same time, possible effects on increased virulence following bacterial target modifications by TiO₂ NPs on cells or tissues have to be considered.

AgNPs Targeting the Drug Resistance Problem of Staphylococcus aureus: Susceptibility to Antibiotics and Efflux Effect

The present work presents translational research with application of AgNPs targeting the global drug resistance problem. In vivo fieldwork was carried out with 400 breeding farm cows sick with a serous mastitis. Ex vivo results revealed that after cow treatment with LactobayTM (a mixture of antibiotic drugs) the susceptibility to 31 antibiotics of S. aureus isolates from cow breast secretion decreased by 25%, while after treatment with Argovit–CTM silver nanoparticles S. aureus susceptibility increased by 11%. The portion of isolates with an efflux effect leading to elimination of antibiotics from S. aureus after Lactobay-treatment resulted in a 15% increase, while Argovit-C-treatment led to a 17.5% decrease. The obtained results showed that mastitis treatments with Argovit-CTM AgNPs can partially restore the activity of antibiotics towards S. aureus and shorten the duration of mastitis treatment by 33%.

Eltarahony M, E. Moustafa M. The impact of titanium oxide nanoparticles and low direct electric current on biofilm dispersal of $Bacillus~cereus$ and $Pseudomonas~aeruginosa$: A comparative study

Bacteria growing in biofilms cause a wide range of environmental, industrial and public health risks. Because biofilm bacteria are very resistant to antibiotics, there is an urgent need in medicine and industry to develop new approaches to eliminating bacterial biofilms. One strategy for controlling these biofilms is to generate an antibiofilm substance locally at the attachment surface. Direct electric current (DC) and nanoparticles (NPs) of metal oxides have outstanding antimicrobial properties. In this study we evaluated the effect of titanium oxide nanoparticle (TiO$_2$-NP) concentrations from 5 to 160 $\mu$g/mL on Bacillus cereus and Pseudomonas aeruginosa biofilms, and compared this with the effect of a 9 V, 6 mA DC electric field for 5, 10 and 15 min. TiO$_2$-NPs were characterized using transmission and scanning electron microscopes, X-ray diffraction and FTIR. They exhibited an average size of 22-34 nm. The TiO$_2$-NP concentrations that attained LD50 were $104 \pm 4$ $\mu$g/mL and $63 \pm 3$ $\mu$g/mL for B. cereus and P. aeruginosa, respectively. The eradication percentages obtained by DC at 5, 10, and 15 min exposure were 21%, 29%, and 33% respectively for B. cereus and 30%, 39%, and 44% respectively for P. aeruginosa. Biofilm disintegration was verified by exopolysaccharide, protein content and cell surface hydrophobicity assessment, as well as scanning electron microscopy. These data were correlated with the reactive oxygen species produced. The results indicated that both DC and TiO$_2$-NPs have a lethal effect on these bacterial biofilms, and that the DC conditions used affect the biofilms in a similar way to TiO$_2$-NPs at concentrations of 20-40 $\mu$g/mL.