2-Hydroxy-4-methoxybenzaldehyde from Hemidesmus indicus is antagonistic to Staphylococcus epidermidis biofilm formation

Acinetobacter baumannii biofilm was inhibited by tryptanthrin through disrupting its different stages and genes expression

Biofilm formation plays a significant role in antibiotic resistance, necessitating the search for alternative therapies against biofilm-associated infections. This study demonstrates that 20 μg/mL tryptanthrin can hinder biofilm formation above 50% in various A. baumannii strains. Tryptanthrin impacts various stages of biofilm formation, including the inhibition of surface motility and eDNA release in A. baumannii, as well as an increase in its sensitivity to H202. RT-qPCR analysis reveals that tryptanthrin significantly decreases the expression of the following genes: abaI (19.07%), abaR (33.47%), bfmR (43.41%), csuA/B (64.16%), csuE (50.20%), ompA (67.93%), and katE (72.53%), which are related to biofilm formation and quorum sensing. Furthermore, tryptanthrin is relatively safe and can reduce the virulence of A. baumannii in a Galleria mellonella infection model. Overall, our study demonstrates the potential of tryptanthrin in controlling biofilm formation and virulence of A. baumannii by disrupting different stages of biofilm formation and intercellular signaling communication.

Bacterial biofilm inhibitors: An overview

Bacteria that cause infectious diseases adopt biofilms as one of their most prevalent lifestyles. Biofilms enable bacteria to tolerate environmental stress and evade antibacterial agents. This bacterial defense mechanism has rendered the use of antibiotics ineffective for the treatment of infectious diseases. However, many highly drug-resistant microbes have rapidly emerged owing to such treatments. Different signaling mechanisms regulate bacterial biofilm formation, including cyclic dinucleotide (c-di-GMP), small non-coding RNAs, and quorum sensing (QS). A cell density-dependent phenomenon, QS is associated with c-di-GMP (a global messenger), which regulates gene expression related to adhesion, extracellular matrix production, the transition from the planktonic to biofilm stage, stability, pathogenicity, virulence, and acquisition of nutrients. The article aims to provide information on inhibiting biofilm formation and disintegrating mature/preformed biofilms. This treatment enables antimicrobials to target the free-living/exposed bacterial cells at lower concentrations than those needed to treat bacteria within the biofilm. Therefore, a complementary action of antibiofilm and antimicrobial agents can be a robust strategic approach to dealing with infectious diseases. Taken together, these molecules have broad implications for human health.

Antibacterial activity of 2-hydroxy-4-methoxybenzaldehyde and its possible mechanism against Staphylococcus aureus

AIM

Staphylococcus aureus causes several complicated infections. Despite decades of research on developing new antimicrobials, methicillin-resistant S. aureus (MRSA) remains a global health problem. Hence, there is a dire need to identify potent natural antibacterial compounds as an alternative to antimicrobials. In this light, the present work divulges the antibacterial efficacy and the action mechanism of 2-hydroxy-4-methoxybenzaldehyde (HMB) isolated from Hemidesmus indicus against S. aureus.

METHODS AND RESULTS

Antimicrobial activity of HMB was assessed. HMB exhibited 1024 µg ml-1 as the minimum inhibitory concentration (MIC) and 2 × MIC as the minimum bactericidal concentration against S. aureus. The results were validated by spot assay, time kill, and growth curve analysis. In addition, HMB treatment increased the release of intracellular proteins and nucleic acid contents from MRSA. Additional experiments assessing the structural morphology of bacterial cells using SEM analysis, β-galactosidase enzyme activity, and the fluorescence intensities of propidium iodide and rhodamine123 dye divulged that the cell membrane as one of the targets of HMB to hinder S. aureus growth. Moreover, the mature biofilm eradication assay revealed that HMB dislodged nearly 80% of the preformed biofilms of MRSA at the tested concentrations. Further, HMB treatment was found to sensitize MRSA cells upon combining tetracycline treatment.

CONCLUSIONS

The present study suggests that HMB is a promising compound with antibacterial and antibiofilm activities and could act as a lead structure for developing new antibacterial drugs against MRSA.

Resistance, Tolerance, Virulence and Bacterial Pathogen Fitness-Current State and Envisioned Solutions for the Near Future

The current antibiotic crisis and the global phenomena of bacterial resistance, inherited and non-inherited, and tolerance-associated with biofilm formation-are prompting dire predictions of a post-antibiotic era in the near future. These predictions refer to increases in morbidity and mortality rates as a consequence of infections with multidrug-resistant or pandrug-resistant microbial strains. In this context, we aimed to highlight the current status of the antibiotic resistance phenomenon and the significance of bacterial virulence properties/fitness for human health and to review the main strategies alternative or complementary to antibiotic therapy, some of them being already clinically applied or in clinical trials, others only foreseen and in the research phase.

Regulation of Staphylococcus aureus Virulence and Application of Nanotherapeutics to Eradicate S. aureus Infection

Staphylococcus aureus is a versatile pathogen known to cause hospital- and community-acquired, foodborne, and zoonotic infections. The clinical infections by S. aureus cause an increase in morbidity and mortality rates and treatment costs, aggravated by the emergence of drug-resistant strains. As a multi-faceted pathogen, it is imperative to consolidate the knowledge on its pathogenesis, including the mechanisms of virulence regulation, development of antimicrobial resistance, and biofilm formation, to make it amenable to different treatment strategies. Nanomaterials provide a suitable platform to address this challenge, with the potential to control intracellular parasitism and multidrug resistance where conventional therapies show limited efficacy. In a nutshell, the first part of this review focuses on the impact of S. aureus on human health and the role of virulence factors and biofilms during pathogenesis. The second part discusses the large diversity of nanoparticles and their applications in controlling S. aureus infections, including combination with antibiotics and phytochemicals and the incorporation of antimicrobial coatings for biomaterials. Finally, the limitations and prospects using nanomaterials are highlighted, aiming to foster the development of novel nanotechnology-driven therapies against multidrug-resistant S. aureus.

Targeted Anti-Biofilm Therapy: Dissecting Targets in the Biofilm Life Cycle

Biofilm is a crucial virulence factor for microorganisms that causes chronic infection. After biofilm formation, the bacteria present improve drug tolerance and multifactorial defense mechanisms, which impose significant challenges for the use of antimicrobials. This indicates the urgent need for new targeted technologies and emerging therapeutic strategies. In this review, we focus on the current biofilm-targeting strategies and those under development, including targeting persistent cells, quorum quenching, and phage therapy. We emphasize biofilm-targeting technologies that are supported by blocking the biofilm life cycle, providing a theoretical basis for design of targeting technology that disrupts the biofilm and promotes practical application of antibacterial materials.

Methanolic extract of Hemidesmus indicus root augments the antibacterial and antibiofilm activity of amoxicillin and clindamycin against methicillin-resistant Staphylococcus aureus of bovine origin

The present study evaluated the antibacterial and antibiofilm activity of MHIR in combination with amoxicillin and clindamycin against biofilm-forming MRSA isolated from milk samples of mastitic cows. Microdilution susceptibility testing and microtiter plate assays were used to evaluate the in-vitro efficacy of MHIR and antibiotic combinations against MRSA (n=12). Furthermore, in-vitro findings were validated in a murine model. Minimum inhibitory concentration and minimum biofilm inhibitory concentration of amoxicillin and clindamycin in combination with MHIR were significantly (P<0.05) lower than when used alone against MRSA. In terms of antibacterial activity, MHIR showed additive interaction (Fractional inhibitory concentration_index >0.5-4) with amoxicillin and clindamycin against all the MRSA isolates, whereas MHIR synergizes (Fractional biofilm inhibitory concentration_index ≤0.5) the antibiofilm activity of amoxicillin and clindamycin against 58.33% and 83.33% of the MRSA isolates, respectively. Amoxicillin/clindamycin in combination with MHIR significantly (P<0.05) reduced disease activity score, and,; bacterial load and Gram-positive spots in kidney and liver of MRSA infected mice. The combined efficacy of MHIR and amoxicillin/clindamycin was comparable to clindamycin alone but superior to amoxicillin alone. Hence, the combination of MHIR with amoxicillin/clindamycin is advocated in the treatment of MRSA-associated infections.

Functional and expression characteristics identification of Phormicins, novel AMPs from Musca domestica with anti-MRSA biofilm activity, in response to different stimuli

Antibiotic-resistant bacteria (including MRSA) in the clinic pose a growing threat to public health, and antimicrobial peptides (AMPs) have great potential as efficient treatment alternatives. Houseflies have evolved over long periods in complex, dirty environments, developing a special immune system to overcome challenges in harmful environments. AMPs are key innate immune molecules. Herein, two differentially expressed AMPs, Phormicins A and B, were identified by screening transcriptomic changes in response to microbial stimulation. Structural mimic assays indicated that these AMPs exhibited functional divergence due to their C-terminal features. Expression analysis showed that they had different expression patterns. Phormicin B had higher constitutive expression than Phormicin A. However, Phormicin B was sharply downregulated, whereas Phormicin A was highly upregulated, after microbial stimulation. The MIC, MBC and time-growth curves showed the antibacterial spectrum of these peptides. Crystal violet staining and SEM showed that Phormicin D inhibited MRSA biofilm formation. TEM suggested that Phormicin D disrupted the MRSA cell membrane. Furthermore, Phormicin D inhibited biofilm formation by downregulating the expression of biofilm-related genes, including altE and embp. Therefore, housefly Phormicins were functionally characterized as having differential expression patterns and antibacterial & antibiofilm activities. This study provides a new potential peptide for clinical MRSA therapy.

Bacterial Biofilm Inhibition: A Focused Review on Recent Therapeutic Strategies for Combating the Biofilm Mediated Infections

Biofilm formation is a major concern in various sectors and cause severe problems to public health, medicine, and industry. Bacterial biofilm formation is a major persistent threat, as it increases morbidity and mortality, thereby imposing heavy economic pressure on the healthcare sector. Bacterial biofilms also strengthen biofouling, affecting shipping functions, and the offshore industries in their natural environment. Besides, they accomplish harsh roles in the corrosion of pipelines in industries. At biofilm state, bacterial pathogens are significantly resistant to external attack like antibiotics, chemicals, disinfectants, etc. Within a cell, they are insensitive to drugs and host immune responses. The development of intact biofilms is very critical for the spreading and persistence of bacterial infections in the host. Further, bacteria form biofilms on every probable substratum, and their infections have been found in plants, livestock, and humans. The advent of novel strategies for treating and preventing biofilm formation has gained a great deal of attention. To prevent the development of resistant mutants, a feasible technique that may target adhesive properties without affecting the bacterial vitality is needed. This stimulated research is a rapidly growing field for applicable control measures to prevent biofilm formation. Therefore, this review discusses the current understanding of antibiotic resistance mechanisms in bacterial biofilm and intensely emphasized the novel therapeutic strategies for combating biofilm mediated infections. The forthcoming experimental studies will focus on these recent therapeutic strategies that may lead to the development of effective biofilm inhibitors than conventional treatments.

Quercetin Inhibits Biofilm Formation by Decreasing the Production of EPS and Altering the Composition of EPS in Staphylococcus epidermidis

Staphylococcus epidermidis is an opportunistic pathogen, and its biofilm formation ability is an important virulent factor. Quercetin, a typical flavonoid ubiquitously used in dietary supplementation, is known for its antioxidant property, but its anti-biofilm activity against S. epidermidis remains unknown. In this study, the anti-biofilm activity of quercetin was investigated using S. epidermidis ATCC35984, a strong biofilm-positive strain. An attempt was made to disclose the mechanisms of the anti-biofilm activity of quercetin. S. epidermidis exhibited a less cell surface hydrophobicity after quercetin treatment. Also, quercetin effectively inhibited S. epidermidis cells from adhering to the glass slides. Quercetin downregulated the intercellular adhesion (ica) locus and then polysaccharide intercellular adhesin (PIA) production was reduced. Therefore, S. epidermidis cells became less hydrophobic, which supported quercetin’s anti-biofilm effect. Our study suggests that quercetin from plants be given further attention as a potential anti-biofilm agent against the biofilm formation of S. epidermidis, even biofilm infections of other bacteria.