What’s old is new again: Insights into diabetic foot microbiome

Phenotypic and genotypic characteristics of macrolide, lacosamide, and streptogramin resistance in clinically resistant Streptococci and their correlation with reduced biocide susceptibility

BACKGROUND

Gram-positive Streptococci is a huge group of different species that are classified based on its hemolytic effect besides the C-substance in the cell wall. This study focuses on the investigation of the prevalence and genetic basis of resistance to macrolides, lincosamides, and streptogramins (MLS) in α- and β-hemolytic Streptococci.

METHODS

Streptococcal isolates were identified and their resistance was assessed to MLS antibiotics through phenotypic analysis and genotypic screening of resistance genes. Isolates were also tested for susceptibility to antiseptics/disinfectants. The correlation between high MLS antibiotic resistance and reduced susceptibility to biocides was assessed. Efflux pump activity in the most resistant isolates (to both MLS antibiotics and biocides) was investigated.

RESULTS

The susceptibility testing indicates an increasing resistance to MLS, particularly macrolides (erythromycin, azithromycin, and clarithromycin) and lincomycin. By screening the resistance, the most predominant phenotype is the constitutive (cMLS) one, while the erm genes, particularly ermB, are the most detected genotype. Furthermore, the esterase-encoding gene ereA is widely distributed in the streptococcal isolates. By evaluating the minimum inhibitory concentrations (MICs) to different biocides, there was a strong relation between the increased MIC values to both MLS antibiotics and tested biocides. This can be attributed mainly to the transferable ermB gene and the enhanced bacterial efflux.

CONCLUSIONS

A significant correlation exists between reduced biocide susceptibility and resistance to MLS antibiotics. Elevated efflux pump activity in MLS-resistant isolates suggests efflux mechanisms may contribute to dual resistance to antibiotics and biocides. However, cross-resistance is primarily driven by the horizontally transferable ermB gene, which confers resistance by targeting the 50S ribosomal subunit.

Repurposing Nitroimidazoles: A New Frontier in Combatting Bacterial Virulence and Quorum Sensing via In Silico, In Vitro, and In Vivo Insights

The global antibiotic resistance crisis demands innovative strategies targeting bacterial virulence rather than survival. Quorum sensing (QS), a key regulator of virulence and biofilm formation, offers a promising avenue to mitigate resistance by disarming pathogens without bactericidal pressure. This study investigates the repurposing of nitroimidazoles as anti-QS and anti-virulence agents at subminimum inhibitory concentrations (sub-MICs). In Silico analyses, including molecular docking and molecular dynamics (MD) simulations, were performed to investigate ligand-receptor interactions with structurally distinct Lux-type QS receptors and assess binding stability and conformational dynamics over time. In Vitro assays evaluated the effects of representative nitroimidazoles, metronidazole (MET) and secnidazole (SEC), on QS-controlled phenotypes, including violacein production in Chromobacterium violaceum and biofilm formation and protease activity in Pseudomonas aeruginosa, Acinetobacter baumannii, Salmonella enterica, and Proteus mirabilis. In Vivo efficacy was assessed using a murine infection model and HeLa cell invasion assays. Molecular docking revealed high-affinity binding to QS receptors, corroborating their mechanistic interference. Sub-MIC MET/SEC significantly suppressed violacein synthesis, biofilm biomass, and protease secretion in Gram-negative pathogens. Both compounds reduced bacterial invasiveness in HeLa cells and In Vivo protected mice from lethal P. aeruginosa infections. Crucially, nitroimidazoles attenuated virulence without affecting bacterial viability, preserving microbial ecology. These findings position nitroimidazoles as dual-function agents; antimicrobial at bactericidal doses and anti-virulence at sub-MICs. Their validated efficacy across In Silico, In Vitro, and In Vivo models underscores their potential as adjunctive therapies, bridging the gap between drug repurposing and next-generation anti-infective development.

Novel antimicrobial strategies for diabetic foot infections: addressing challenges and resistance

AIMS

This review examines the challenges posed by Diabetic Foot Infections (DFIs), focusing on the impact of neuropathy, peripheral arterial disease, immunopathy, and the polymicrobial nature of these infections. The aim is to explore the factors contributing to antimicrobial resistance and assess the potential of novel antimicrobial treatments and drug delivery systems in improving patient outcomes.

METHOD

A comprehensive analysis of existing literature on DFIs was conducted, highlighting the multifactorial pathogenesis and polymicrobial composition of these infections. The review delves into the rise of antimicrobial resistance due to the overuse of antimicrobials, biofilm formation, and microbial genetic adaptability. Additionally, it considers glycemic control, patient adherence, and recurrence rates as contributing factors to treatment failure. Emerging therapies, including new antimicrobial classes and innovative drug delivery systems, were evaluated for their potential efficacy.

RESULTS

DFIs present unique treatment challenges, with high rates of antimicrobial resistance and poor response to standard therapies. Biofilm formation and the genetic adaptability of pathogens worsen resistance, complicating treatment. Current antimicrobial therapies are further hindered by poor glycemic control and patient adherence, leading to recurrent infections. Novel antimicrobial classes and innovative delivery systems show promise in addressing these challenges by offering more targeted, effective treatments. These new approaches aim to reduce resistance and improve treatment outcomes.

CONCLUSION

DFIs remain a clinical challenge due to their multifactorial nature and antimicrobial resistance. The development of novel antimicrobials and drug delivery systems is crucial to improving patient outcomes and combating resistance. Future research should focus on enhancing treatment efficacy, reducing resistance, and addressing patient adherence to reduce the burden of DFIs.

Reprofiling lamivudine as an antibiofilm and anti-pathogenic agent against Pseudomonas aeruginosa

Resistance to antibiotics is a critical growing public health problem that needs urgent action to combat. To avoid the stress on bacterial growth that evokes the development of resistance, anti-virulence agents can be an attractive strategy as they do not target bacterial growth. There are FDA approved drugs have been screened for their anti-virulence activities. Lamivudine (LAM) is a synthetic nucleoside analogue used as an antiretroviral in treatment of HIV and can be used in treatment of HBV. The present study aimed to assess the anti-virulence activities of LAM against a clinically important pathogen Pseudomonas aeruginosa. The LAM's antibiofilm and anti-virulence activities were evaluated. The impact of LAM on the quorum sensing (QS) systems which control the production of these virulence factors was assessed virtually and by quantification of the expression of QS-encoding genes. Furthermore, in vivo mice protection assay was conducted to attest the LAM's anti-pathogenic activity. The current findings elaborated the promising anti-pathogenic and anti-QS activities of LAM. LAM interfered with biofilm formation in P. aeruginosa PAO1 strain. Moreover, swarming motility and production of pyocyanin and protease were significantly diminished. At the molecular level, LAM downregulated the QS-encoding genes LasI, LasR, RhlR, PqsA and PqsR. Additionally, the detailed in silico docking and molecular simulation studies showed the considered high LAM's ability to bind and hinder the QS receptors in the P. aeruginosa. In an agreement with in vitro and in silico, the in vivo results showed the LAM full protection of mice against P. aeruginosa. In conclusion, LAM could be repurposed to be employed as adjunct therapy with traditional antibiotics for treating serious pseudomonal infections.

Combating enteropathogenic and multidrug resistant Escherichia coli using the lytic bacteriophage vB_EcoM_ECO78, which disrupts bacterial biofilm formation and exhibits a remarkable environmental stability

AIM

The current study aimed to establish a phenotypic and genotypic characterization record of a novel lytic bacteriophage (phage) against multidrug-resistant (MDR) Escherichia coli (E. coli) infections.

METHODS AND RESULTS

Phenotypic characterization of the isolated phage included the assessment of phage morphology, host range, stability, and antibiofilm activity. The isolated phage vB_EcoM_ECO78 demonstrated a high lytic activity against MDR E. coli and E. coli serotypes O78: K80: H12 and O26: H11. Additionally, it showed a marked antibiofilm activity and high physical stability at a wide range of temperatures and pH. Genotypic investigations identified a double-stranded DNA genome of 165 912 base pairs (bp) spanning 258 open reading frames (ORFs), out of which 149 ORFs were identified and annotated. In vivo analysis further confirmed the therapeutic potential of vB_EcoM_ECO78 which effectively increased the survival of mice infected with MDR E. coli.

CONCLUSION

The isolated phage vB_EcoM_ECO78 exhibits considerable stability and antibiofilm activity against MDR E. coli isolates, supported by notable environmental fitness and in vivo antibacterial capability.

Piceatannol: a renaissance in antibacterial innovation unveiling synergistic potency and virulence disruption against serious pathogens

In the relentless battle against multi-drug resistant Gram-negative bacteria, piceatannol emerges as a beacon of hope, showcasing unparalleled antibacterial efficacy and a unique ability to disrupt virulence factors. Our study illuminates the multifaceted prowess of piceatannol against prominent pathogens-Proteus mirabilis, Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae. Notably, piceatannol demonstrated a remarkable ability to inhibit biofilm formation, reduce bacterial mobility, and diminish extracellular enzyme synthesis.Mechanistic insights into piceatannol's activity unraveled its impact on membrane potential, proton motive force, and ATP production. Furthermore, our study delved into piceatannol's anti-quorum sensing (QS) activity, showcasing its potential to downregulate QS-encoding genes and affirming its affinity to critical QS receptors through molecular docking. Crucially, piceatannol exhibited a low propensity for resistance development, positioning it as a promising candidate for combating antibiotic-resistant strains. Its mild effect on red blood cells (RBCs) suggests safety even at higher concentrations, reinforcing its potential translational value. In an in vivo setting, piceatannol demonstrated protective capabilities, significantly reducing pathogenesis in mice infected with P. aeruginosa and P. mirabilis. This comprehensive analysis positions piceatannol as a renaissance in antibacterial innovation, offering a versatile and effective strategy to confront the evolving challenges posed by resilient Gram-negative pathogens.

Enoxacin adversely affects Salmonella enterica virulence and host pathogenesis through interference with type III secretion system type II (T3SS-II) and disruption of translocation of Salmonella Pathogenicity Island-2 (SPI2) effectors

Salmonella enterica is a clinically significant oro-fecal pathogen that causes a wide variety of illnesses and can lead to epidemics. S. enterica expresses a lot of virulence factors that enhance its pathogenesis in host. For instance, S. enterica employs a type three secretion system (T3SS) to translocate a wide array of effector proteins that could change the surrounding niche ensuring suitable conditions for the thrive of Salmonella infection. Many antimicrobials have been recently introduced to overcome the annoying bacterial resistance to antibiotics. Enoxacin is member of the second-generation quinolones that possesses a considerable activity against S. enterica. The present study aimed to evaluate the effect of enoxacin at sub-minimum inhibitory concentration (sub-MIC) on S. enterica virulence capability and pathogenesis in host. Enoxacin at sub-MIC significantly diminished both Salmonella invasion and intracellular replication within the host cells. The observed inhibitory effect of enoxacin on S. enterica internalization could be attributed to its ability to interfere with translocation of the T3SS effector proteins. These results were further confirmed by the finding that enoxacin at sub-MIC down-regulated the expression of the genes encoding for T3SS-type II (T3SS-II). Moreover, enoxacin at sub-MIC lessened bacterial adhesion to abiotic surface and biofilm formation which indicates a potential anti-virulence activity. Importantly, in vivo results showed a significant ability of enoxacin to protect mice against S. enterica infection and decreased bacterial colonization within animal tissues. In nutshell, current findings shed light on an additional mechanism of enoxacin at sub-MIC by interfering with Salmonella intracellular replication. The outcomes presented herein could be further invested in conquering bacterial resistance and open the door for additional effective clinical applications.

Celastrol boosts fluconazole efficacy against vaginal candidiasis: in vitro and in vivo evidence

Candida albicans is a commensal fungus that naturally inhabits the vagina. However, overgrowth of C. albicans can result in vulvovaginal candidiasis (VVC), one of the most prevalent fungal infections affecting women. The rapid emergence of azole resistance in C. albicans, in addition to the limited available antifungal agents, complicates the treatment and emphasizes the urgent need for novel therapeutic options. Efflux-mediated azole resistance is a common resistance mechanism in fluconazole (FLZ)-resistant C. albicans. Combination therapy using natural compounds is a potential approach that can restore fluconazole's antifungal activity in azole-resistant isolates via efflux pump inhibition. This study aimed to evaluate the ability of celastrol, a natural triterpene, to retrieve FLZ antifungal activity against azole-resistant C. albicans in vitro and in vivo. Celastrol did not exhibit antifungal activity against the tested clinical isolates; however, the sub-MIC of celastrol inhibited rhodamine 6G (R6G) efflux and increased R6G accumulation inside celastrol-treated C. albicans cells. Synergy was spotted between celastrol and FLZ via a checkerboard assay. Quantification of m-RNA levels of efflux-mediated azole resistance genes within azole-resistant C. albicans demonstrated CDR1 overexpression. Upon celastrol treatment, a significant decline in ABC transporters transcript levels were detected. Moreover, molecular docking demonstrated that celastrol is a potential ABC efflux transporters blocker that successfully fits into target binding pockets. A negligible hemolytic effect of celastrol against human erythrocytes was observed. In the in vivo model of VVC, the combination of FLZ and celastrol in vaginal gel revealed a drastic reduction in the fungal burden with apparently normal vaginal tissue. Celastrol promising in vitro and in vivo findings strengthen its future use for the treatment of azole-resistant C. albicans.

Sulforaphane Is Not Only a Food Supplement: It Diminishes the Intracellular Survival and Colonization of Salmonella enterica

Sulforaphane is a main bioactive component in several edible cruciferous vegetables. It acquires several benefits to health in addition to its considered antibacterial and antivirulence activities. Herein, we aimed at evaluating the antivirulence activity of sulforaphane against the worldwide clinically important enteric pathogen Salmonella enterica serovar Typhimurium. The influence of sulforaphane on bacterial adhesion, invasion, biofilm formation, and intracellular replication was assayed. Additionally, the effect of sulforaphane on the type III secretion system (TTSS) in S. enterica was quantified. The outcome of the combination with different antibiotics was assessed, and an in vivo protection assay was conducted to assess the influence on S. enterica pathogenesis. The results showed the significant antibiofilm activity of sulforaphane at subinhibitory effect in addition to its significant reduction in bacterial invasion and intracellular replication inside the host cells. The in vivo findings emphasized the decreased capacity of S. enterica to induce pathogenesis in the presence of sulforaphane. Our finding attributed these antivirulence activities to the interference of sulforaphane with TTSS-type II and the downregulation of its encoding genes. In a nutshell, the edible cruciferous vegetable bioactive sulforaphane is a safe adjunct therapy that can be administrated alongside traditional antibiotics for treating clinically significant enteric pathogens as S. enterica.

Microbial profile of diabetic foot osteomyelitis from the northwest of England

BACKGROUND

Osteomyelitis of the diabetic foot is a common and challenging complication affecting patients with diabetic foot ulcers and infections. The complexity of these infections lies in their polymicrobial nature, high rates of persistence and recurrence. This study examined the microbiological profile of diabetic foot osteomyelitis from a teaching hospital in Northwest England and their resistance patterns to understand its impact on infection persistence and to direct effective treatment.

METHODS

A retrospective review of 105 patients who underwent surgical management for diabetic foot osteomyelitis between 2019 and 2024. We analysed three consecutive culture samples for each patient to assess for the microbiological profile and resistance patterns of these infections and to monitor infection recurrence and persistence rates.

RESULTS

A total of 105 patients were identified. Infection eradication was noted in 42% of the cohort, infection persistence in 18%, and late infection recurrence in 40%. Polymicrobial growth was evident in 72% of our study sample. Gram-positive bacteria made up the majority of the bacterial isolates in all 3 culture samples, 74.81% in sample 1, 69.31% in sample 2, and 55.1% in sample 3. Staphylococcus aureus was the most prevalent gram-positive bacteria, at 52.38% in sample 1, 36.19% in sample 2, and 18.09% in sample 3, followed by Haemolytic Streptococcus, Enterococcus and Corynebacterium. The frequently identified gram-negative bacteria were Pseudomonas in sample 1 (7.61%), E. coli and Proteus in sample 2 (5,71%), Pseudomonas and Proteus in sample 3 (2.85%). Gram-positive bacteria were resistant to penicillin and macrolides with resistance of staphylococcus aureus to clarithromycin identified among all 3 culture samples. Gram-negative bacteria were most resistant to amoxicillin. Staphylococcus aureus was responsible for infection persistence in most of our cohort (12/19) 63.15%. Among those patients, Staphylococcus was resistant to clarithromycin in 6 of the cases. The 5-year mortality rate for our study sample was 32.38%.

CONCLUSION

This study highlights the prevalence of polymicrobial growth and multi-drug resistant pathogens in the scope of diabetic foot osteomyelitis. It highlights the predominance of Staphylococcus aureus and its resistant strains among patients affected by diabetic foot osteomyelitis in Greater Manchester.

Bacteriophage-cocktail hydrogel dressing to prevent multiple bacterial infections and heal diabetic ulcers in mice

Bacteriophage (phage) has been reported to reduce the bacterial infection in delayed-healing wounds and, as a result, aiding in the healing of said wounds. In this study we investigated whether the presence of phage itself could help repair delayed-healing wounds in diabetic mice. Three strains of phage that target Salmonella enterica, Escherichia coli, and Pseudomonas aeruginosa were used. To prevent the phage liquid from running off the wound, the mixture of phage (phage-cocktail) was encapsulated in a porous hydrogel dressing made with three-dimensional printing. The phage-cocktail dressing was tested for its phage preservation and release efficacy, bacterial reduction, cytotoxicity with 3T3 fibroblast, and performance in repairing a sterile full-thickness skin wound in diabetic mice. The phage-cocktail dressing released 1.7%-5.7% of the phages embedded in 24 h, and reduced between 37%-79% of the surface bacteria compared with the blank dressing (p <.05). The phage-cocktail dressing exhibited no sign of cytotoxicity after 3 days (p <.05). In vivo studies showed that 14 days after incision, the full-thickness wound treated with a phage-cocktail dressing had a higher wound healing ratio compared with the blank dressing and control (p <.01). Histological analysis showed that the structure of the skin layers in the group treated with phage-cocktail dressing was restored in an orderly fashion. Compared with the blank dressing and control, the repaired tissue in the phage-cocktail dressing group had new capillary vessels and no sign of inflammation in its dermis, and its epidermis had a higher degree of re-epithelialization (p <.05). The slow-released phage has demonstrated positive effects in repairing diabetic skin wounds.

Material Technologies for Improved Diabetic Foot Ulcer (DFU) Treatment: A Questionnaire Study of Healthcare Professionals' Needs

Background/Objectives: Diabetic foot ulcers (DFUs) are a common and severe complication of diabetic patients, with significant global prevalence and associated health burdens, including high recurrence rates, lower-limb amputations, and substantial associated economic costs. This study aimed to understand the user needs of healthcare professionals treating diabetic foot ulcers for newly developed material technologies. Methods: An open-ended questionnaire was used to identify user needs, identify the limitations of current treatments, and determine the specific requirements for ideal treatment. This information was used to develop a list of key considerations for creating innovative material technologies to improve diabetic wound treatment results. Results: Most respondents indicated that they followed published treatment guidelines for DFUs but noted that treatment often required a case-specific approach. Antibiotics and surgical debridement were commonly used for infection control. The participants showed a strong preference for wound dressings with lasting antibacterial properties. Respondents identified ideal properties for new products, including ease of use, enhanced antibacterial properties, affordability, and targeted biological activity. The respondents also highlighted the importance of a holistic approach to DFU management, integrating product development with comprehensive care strategies and patient education. Conclusions: This study highlights the complexity of DFU care, emphasizing that no single product can address all treatment needs. Future materials could focus on combination therapies and specific use cases. Additionally, understanding global variations in treatment practices and educating users on the proper application of newly developed material technologies is crucial for improving the management of DFUs and patient outcomes.

Arctigenin from Burdock Root Exhibits Potent Antibacterial and Anti-Virulence Properties against Pseudomonas aeruginosa

Arctium lappa (Burdock) root is used in various culinary applications especially in Asian Cuisine. Arctigenin (ARC) is a polyphenolic compound abundant in the roots of the burdock plant from which it derives its name. The emergence of bacterial resistance is a growing global worry, specifically due to the declining availability of new antibiotics. Screening for the antibacterial candidates among the safe natural products is a promising approach. The present study was aimed to assess the antibacterial activity of ARC against Pseudomonas aeruginosa exploring its effect on the bacterial cell membrane. Furthermore, the anti-virulence activities and anti-quorum sensing (QS) activities of ARC were in vitro, in vivo and in silico assessed against P. aeruginosa. The current results showed the ARC antibacterial activity was owed to its disruption effect of the cell membrane. ARC at sub-MIC significantly decreased the formation of biofilm, motility, production of extracellular enzymes and in vivo protected mice against P. aeruginosa. These anti-virulence activities of ARC are owed to its interference with bacterial QS and its expression. Furthermore, ARC showed mild effect on mammalian erythrocytes, low probability to induce resistance and synergistically combined with antibiotics. In summary, the promising anti-virulence properties of ARC indicate its potential as an effective supplement to conventional antibiotics for treating severe P. aeruginosa infections.

Surveillance of Enterobacteriaceae from Diabetic Foot Infections in a Tunisian Hospital: Detection of E. coli-ST131-blaCTX-M-15 and K. pneumoniae-ST1-blaNDM-1 Strains

The study determined the prevalence, antimicrobial resistant (AMR) determinants, and genetic characteristics of Escherichia coli and Klebsiella pneumoniae isolates from patients with diabetic foot infection (DFI) in a Tunisian hospital. A total of 26 Escherichia spp. and Klebsiella spp. isolates were recovered and identified by MALDI-TOF-MS. Antimicrobial susceptibility testing, the detection of AMR determinants and Shiga-like toxin genes, phylogenetic grouping, and molecular typing were performed. Twelve E. coli, 10 K. pneumoniae, 3 K. oxytoca, and 1 E. hermanii were isolated. A multidrug-resistant phenotype was detected in 65.4% of the isolates. About 30.8% of isolates were extended-spectrum β-lactamase (ESBL) producers and mainly carried blaCTX-M-15 and blaCTX-M-14 genes. One blaNDM-1-producing K. pneumoniae-ST1 strain was identified. Class 1 integrons were detected in 11 isolates and 5 gene cassette arrangements were noted: dfrA1+aadA1 (n = 1), dfrA12+aadA2 (n = 3), and dfrA17+aadA5 (n = 1). Other non-β-lactam resistance genes detected were as follows (number of isolates): aac(3')-II (3), aac(6')-Ib-cr(8), qnrB (2), qnrS (4), cmlA (2), floR (4), sul1 (11), sul2 (11), and sul3 (2). The phylogroup B1 was the most frequent (41.7%) among E. coli, and two ESBL-producing isolates corresponded to the ST131-B2 lineage. The ESBL- and carbapenemase-producing Enterobacteriaceae in DFIs are described for the first time in Tunisia.

Cilostazol is a promising anti-pseudomonal virulence drug by disruption of quorum sensing

Resistance to antibiotics is a critical growing public health problem that desires urgent action to combat. To avoid the stress on bacterial growth that evokes the resistance development, anti-virulence agents can be an attractive strategy as they do not target bacterial growth. Quorum sensing (QS) systems play main roles in controlling the production of diverse virulence factors and biofilm formation in bacteria. Thus, interfering with QS systems could result in mitigation of the bacterial virulence. Cilostazol is an antiplatelet and a vasodilator FDA approved drug. This study aimed to evaluate the anti-virulence activities of cilostazol in the light of its possible interference with QS systems in Pseudomonas aeruginosa. Additionally, the study examines cilostazol's impact on the bacterium's ability to induce infection in vivo, using sub-inhibitory concentrations to minimize the risk of resistance development. In this context, the biofilm formation, the production of virulence factors and influence on the in vivo ability to induce infection were assessed in the presence of cilostazol at sub-inhibitory concentration. Furthermore, the outcome of combination with antibiotics was evaluated. Cilostazol interfered with biofilm formation in P. aeruginosa. Moreover, swarming motility, biofilm formation and production of virulence factors were significantly diminished. Histopathological investigation revealed that liver, spleen and kidney tissues damage was abolished in mice injected with cilostazol-treated bacteria. Cilostazol exhibited a synergistic outcome when used in combination with antibiotics. At the molecular level, cilostazol downregulated the QS genes and showed considerable affinity to QS receptors. In conclusion, Cilostazol could be used as adjunct therapy with antibiotics for treating Pseudomonal infections. This research highlights cilostazol's potential to combat bacterial infections by targeting virulence mechanisms, reducing the risk of antibiotic resistance, and enhancing treatment efficacy against P. aeruginosa. These findings open avenues for repurposing existing drugs, offering new, safer, and more effective infection control strategies.

Investigating Sulforaphane's anti-virulence and anti-quorum sensing properties against Pseudomonas aeruginosa

Background

P. aeruginosa, a significant bacterium, can cause severe illness and resistance to antibiotics. Quorum sensing (QS) systems regulate virulence factors production. Targeting QS could reduce bacteria pathogenicity and prevent antibiotic resistance. Cruciferous vegetables contain sulforaphane, known for its anti-inflammatory, antioxidant, anticancer, and antimicrobial properties.

Aim

We aimed to examine the inhibitory influences of sulforaphane, at a sub-inhibitory concentration (¼ minimum inhibitory concentration, MIC), on virulence and QS in P. aeruginosa.

Materials and methods

The sulforaphane's anti-virulence actions at sub-inhibitory concentrations were explored in vitro and in vivo. A sub-MIC concentration of sulforaphane was combined with anti-pseudomonal drugs, and the results of this combination were assessed. The virtual affinity of sulforaphane for the receptors of QS was studied, and its effect on the expression of QS genes was quantified.

Results

Sulforaphane significantly decreased the biofilm formation, motility, ability to withstand oxidative stress, and the synthesis of virulence extracellular enzymes such as proteases, hemolysins, and elastase, as well as other virulence factors like pyocyanin. In addition, sulforaphane lessened the severity of P. aeruginosa infection in mice. Sulforaphane reduced the antipseudomonal antibiotics' MICs when used together, resulting in synergistic effects. The observed anti-virulence impacts were attributed to the ability of sulforaphane to inhibit QS via suppressing the QS genes' expression.

Conclusion

Sulforaphane shows promise as a potent anti-virulence and anti-QS agent that can be used alongside conventional antimicrobials to manage severe infections effectively. Furthermore, this study paves the way for further investigation of sulforaphane and similar structures as pharmacophores for anti-QS candidates.

Overview of Proteus mirabilis pathogenicity and virulence. Insights into the role of metals

Proteus mirabilis is a Gram-negative bacterium with exclusive molecular and biological features. It is a versatile pathogen acclaimed for its distinct urease production, swarming behavior, and rapid multicellular activity. Clinically, P. mirabilis is a frequent pathogen of the human urinary system where it causes urinary tract infections (UTIs) and catheter-associated urinary tract infections (CAUTIs). This review explores the epidemiology, risk factors, clinical manifestations, and treatment of P. mirabilis infections, emphasizing its association with UTIs. The bacterium's genome analysis revealed the presence of resistance genes against commonly used antibiotics, an antibiotic-resistant phenotype that poses a serious clinical challenge. Particularly, the emergence of extended-spectrum β-lactamases (ESBLs) and carbapenemases resistant P. mirabilis strains. On a molecular level, P. mirabilis possesses a wide array of virulence factors including the production of fimbriae, urease, hemolysins, metallophores, and biofilm formation. This review thoroughly tackles a substantial gap in understanding the role of metallophores in shaping the virulence factors of P. mirabilis virulence. Siderophores, iron metal chelating and transporting metallophores, particularly contribute to the complex pathogenic strategies, displaying a potential target for therapeutic intervention.

Thymoquinone is a natural antibiofilm and pathogenicity attenuating agent in Pseudomonas aeruginosa

Pseudomonas aeruginosa belongs to the critical pathogens that represent a global public health problem due to their high rate of resistance as listed by WHO. P. aeruginosa can result in many nosocomial infections especially in individuals with compromised immune systems. Attenuating virulence factors by interference with quorum sensing (QS) systems is a promising approach to treat P. aeruginosa-resistant infections. Thymoquinone is a natural compound isolated from Nigella sativa (black seed) essential oil. In this study, the minimum inhibitory concentration of thymoquinone was detected followed by investigating the antibiofilm and antivirulence activities of the subinhibitory concentration of thymoquinone against P. aeruginosa PAO1. The effect of thymoquinone on the expression of QS genes was assessed by quantitative real-time PCR, and the protective effect of thymoquinone against the pathogenesis of PAO1 in mice was detected by the mouse survival test. Thymoquinone significantly inhibited biofilm, pyocyanin, protease activity, and swarming motility. At the molecular level, thymoquinone markedly downregulated QS genes lasI, lasR, rhlI, and rhlR. Moreover, thymoquinone could protect mice from the pathologic effects of P. aeruginosa increasing mouse survival from 20% to 100%. In conclusion, thymoquinone is a promising natural agent that can be used as an adjunct therapeutic agent with antibiotics to attenuate the pathogenicity of P. aeruginosa.

Redirecting pantoprazole as a metallo-beta-lactamase inhibitor in carbapenem-resistant Klebsiella pneumoniae

The development of resistance to carbapenems in Klebsiella pneumoniae due to the production of metallo-β-lactamases (MBLs) is a critical public health problem because carbapenems are the last-resort drugs used for treating severe infections of extended-spectrum β-lactamases (ESBLs) producing K. pneumoniae. Restoring the activity of carbapenems by the inhibition of metallo-β-lactamases is a valuable approach to combat carbapenem resistance. In this study, two well-characterized clinical multidrug and carbapenem-resistant K. pneumoniae isolates were used. The sub-inhibitory concentrations of pantoprazole and the well-reported metallo-β-lactamase inhibitor captopril inhibited the hydrolytic activities of metallo-β-lactamases, with pantoprazole having more inhibiting activities. Both drugs, when used in combination with meropenem, exhibited synergistic activities. Pantoprazole could also downregulate the expression of the metallo-β-lactamase genes bla NDM and bla VIM. A docking study revealed that pantoprazole could bind to and chelate zinc ions of New Delhi and Verona integron-encoded MBL (VIM) enzymes with higher affinity than the control drug captopril and with comparable affinity to the natural ligand meropenem, indicating the significant inhibitory activity of pantoprazole against metallo-β-lactamases. In conclusion, pantoprazole can be used in combination with meropenem as a new strategy for treating serious infections caused by metallo-β-lactamases producing K. pneumoniae.

The anti-staphylococcal fusidic acid as an efflux pump inhibitor combined with fluconazole against vaginal candidiasis in mouse model

BACKGROUND

Candida albicans is the most common fungus that causes vaginal candidiasis in immunocompetent women and catastrophic infections in immunocompromised patients. The treatment of such infections is hindered due to the increasing emergence of resistance to azoles in C. albicans. New treatment approaches are needed to combat candidiasis especially in the dwindled supply of new effective and safe antifungals. The resistance to azoles is mainly attributed to export of azoles outside the cells by means of the efflux pump that confers cross resistance to all azoles including fluconazole (FLC).

OBJECTIVES

This study aimed to investigate the possible efflux pump inhibiting activity of fusidic acid (FA) in C. albicans resistant isolates and the potential use of Fusidic acid in combination with fluconazole to potentiate the antifungal activity of fluconazole to restore its activity in the resistant C. albicans isolates.

METHODS

The resistance of C. albicans isolates was assessed by determination of minimum inhibitory concentration. The effect of Fusidic acid at sub-inhibitory concentration on efflux activity was assayed by rhodamine 6G efflux assay and intracellular accumulation. Mice model studies were conducted to evaluate the anti-efflux activity of Fusidic acid and its synergistic effects in combination with fluconazole. Impact of Fusidic acid on ergosterol biosynthesis was quantified. The synergy of fluconazole when combined with Fusidic acid was investigated by determination of minimum inhibitory concentration. The cytotoxicity of Fusidic acid was tested against erythrocytes. The effect of Fusidic acid on efflux pumps was tested at the molecular level by real-time PCR and in silico study. In vivo vulvovaginitis mice model was used to confirm the activity of the combination in treating vulvovaginal candidiasis.

RESULTS

Fusidic acid showed efflux inhibiting activity as it increased the accumulation of rhodamine 6G, a substrate for ABC-efflux transporter, and decreased its efflux in C. albicans cells. The antifungal activity of fluconazole was synergized when combined with Fusidic acid. Fusidic acid exerted only minimal cytotoxicity on human erythrocytes indicating its safety. The FA efflux inhibitory activity could be owed to its ability to interfere with efflux protein transporters as revealed by docking studies and downregulation of the efflux-encoding genes of both ABC transporters and MFS superfamily. Moreover, in vivo mice model showed that using fluconazole-fusidic acid combination by vaginal route enhanced fluconazole antifungal activity as shown by lowered fungal burden and a negligible histopathological change in vaginal tissue.

CONCLUSION

The current findings highlight FA's potential as a potential adjuvant to FLC in the treatment of vulvovaginal candidiasis.

The Anti-Virulence Activities of the Antihypertensive Drug Propranolol in Light of Its Anti-Quorum Sensing Effects against Pseudomonas aeruginosa and Serratia marcescens

The development of bacterial resistance is an increasing global concern that requires discovering new antibacterial agents and strategies. Bacterial quorum sensing (QS) systems play important roles in controlling bacterial virulence, and their targeting could lead to diminishing bacterial pathogenesis. In this context, targeting QS systems without significant influence on bacterial growth is assumed as a promising strategy to overcome resistance development. This study aimed at evaluating the anti-QS and anti-virulence activities of the β-adrenoreceptor antagonist propranolol at sub-minimal inhibitory concentrations (sub-MIC) against two Gram-negative bacterial models Pseudomonas aeruginosa and Serratia marcescens. The effect of propranolol on the expression of QS-encoding genes was evaluated. Additionally, the affinity of propranolol to QS receptors was virtually attested. The influence of propranolol at sub-MIC on biofilm formation, motility, and production of virulent factors was conducted. The outcomes of the propranolol combination with different antibiotics were assessed. Finally, the in vivo protection assay in mice was performed to assess propranolol's effect on lessening the bacterial pathogenesis. The current findings emphasized the significant ability of propranolol at sub-MIC to reduce the formation of biofilms, motility, and production of virulence factors. In addition, propranolol at sub-MIC decreased the capacity of tested bacteria to induce pathogenesis in mice. Furthermore, propranolol significantly downregulated the QS-encoding genes and showed significant affinity to QS receptors. Finally, propranolol at sub-MIC synergistically decreased the MICs of different antibiotics against tested bacteria. In conclusion, propranolol might serve as a plausible adjuvant therapy with antibiotics for the treatment of serious bacterial infections after further pharmacological and pharmaceutical studies.

The Metabolic Characteristics of Patients at the Risk for Diabetic Foot Ulcer: A Comparative Study of Diabetic Patients with and without Diabetic Foot

Backgrounds and Objective

Diabetic foot is a relatively severe complication in patients with type 2 diabetes (T2D), with peripheral neuropathy and angiopathy frequently serving as risk factors. However, it is unknown how the other major systemic metabolic factors impacted the profile of these patients, besides glucose management. Thus, we investigated the distinct characteristics of patients with diabetic foot ulcers and their relationships with angiopathy.

Materials and Methods

We obtained the laboratory data of 334 diabetic patients at Shanghai Pudong Hospital from 2020 to 2023. The comparisons were performed between the groups with or without diabetic foot, including glucose metabolism, lipids profile, liver and kidney function, thyroid function, and serum iron. The association between metabolic factors and lower extremity computed tomography angiography (CTA) was analyzed.

Results

We found significant disparities between groups in relation to age, serum protein content, liver transferase, serum creatinine, estimated glomerular filtration rate (eGFR), serum uric acid (UA), small dense low-density lipoprotein (sdLDL), lipoprotein A (LP(a)), apolipoprotein A1 (APOA1), thyroid function, serum iron, and hemoglobin (Hb) (p<0.05). The Spearman correlational analyses showed that the severity of CTA, categorized by the unilateral or bilateral plaque or occlusion, was positively significantly correlated with UA (r=0.499), triglyceride (TG) (r=0.751), whereas inversely correlated with serum albumin (r=-0.510), alanine aminotransferase (r=-0.523), direct bilirubin (DBil) (r=-0.494), total bilirubin (TBil) (r=-0.550), Hb (r=-0.646).

Conclusion

This cross-section investigation showed that compared to T2D only, the patients with diabetic foot ulcer (DFU) might display similar glucose metabolic control context but adverse metabolic profiles, and this profile is associated with macrovascular angiopathy characteristics and their severity.

Relocating Glyceryl Trinitrate as an Anti-Virulence Agent against Pseudomonas aeruginosa and Serratia marcescens: Insights from Molecular and In Vivo Investigations

The problem of antibiotic resistance is a global critical public health concern. In light of the threat of returning to the pre-antibiotic era, new alternative approaches are required such as quorum-sensing (QS) disruption and virulence inhibition, both of which apply no discernible selective pressure on bacteria, therefore mitigating the potential for the development of resistant strains. Bearing in mind the significant role of QS in orchestrating bacterial virulence, disrupting QS becomes essential for effectively diminishing bacterial virulence. This study aimed to assess the potential use of sub-inhibitory concentration (0.25 mg/mL) of glyceryl trinitrate (GTN) to inhibit virulence in Serratia marcescens and Pseudomonas aeruginosa. GTN could decrease the expression of virulence genes in both tested bacteria in a significant manner. Histopathological study revealed the ability of GTN to alleviate the congestion in hepatic and renal tissues of infected mice and to reduce bacterial and leukocyte infiltration. This study recommends the use of topical GTN to treat topical infection caused by P. aeruginosa and S. marcescens in combination with antibiotics.