Robust Antimicrobial Activity Research Articles

Investigating the Efficacy of Various Natural Products in Raw Form against Multidrug-Resistant Bacteria.

The alarming increase in antibiotic resistance urges alternative and efficacious antimicrobial solutions. Historically, medicinal plants have been used for therapeutic purposes, such as relieving pain and healing wounds. However, the evaluation of the natural therapeutic effects of medicinal plants in a manner that resembles how humans typically consume them is lacking. Therefore, in this study, many medicinal plants known to have some antimicrobial effects, including Frankincense, Garlic, Myrrh, and Ginger, were evaluated for their direct antibacterial activity in raw form. The direct antimicrobial activity of medicinal plants was evaluated against a variety of Gram-positive and Gram-negative bacterial strains, such as Staphylococcus aureus (S. Aureus), Acinetobacter baumannii and Klebsiella pneumoniae using agar well diffusion method and turbidity measurements in suspension culture. Out of all the tested medicinal plants, only raw garlic (Allium sativum) powder, when dissolved in water or vinegar, offered a straightforward antibacterial activity. A combination of garlic extract and vinegar increased antibacterial activity. Aqueous garlic extracts displayed robust antimicrobial activity against many resistant bacteria. Other medicinal plants used in this study had absent or minimal antibacterial effects. Only garlic in its raw form was effective against antibiotic-resistant bacteria. The increase in the antibacterial activity of garlic when combined with vinegar suggests the synergistic activity of garlic. The straightforward antibacterial action of raw garlic may be strategically harnessed to combat the continuous challenge of increasing antibiotic resistance. This work promotes additional testing of more natural products (in raw form) and assesses their therapeutic effects clinically.

Isolation, genomic analysis and functional characterization of Enterococcus rotai CMTB-CA6, a putative probiotic strain isolated from a medicinal plant Centella asiatica.

Probiotics and their derivatives offer significant health benefits by supporting digestive health, boosting the immune system, and regulating the microbiomes not only of the internal gastrointestinal track but also of the skin. To be effective, probiotics and their derivatives must exhibit robust antimicrobial activity, resilience to adverse conditions, and colonization capabilities in host tissues. As an alternative to animal-derived probiotics, plant-derived lactic acid bacteria (LAB) present promising advantages, including enhanced diversity and tolerance to challenging environments. Our study focuses on exploring the potential of plant-derived LAB, particularly from the medicinal plant Centella asiatica, in improving skin conditions. Through a bacterial isolation procedure from C. asiatica leaves, Enterococcus rotai CMTB-CA6 was identified via 16S rRNA sequencing, whole genome sequencing, and bioinformatic analyses. Based on genomic analysis, antimicrobial-resistance and virulence genes were not detected. Additionally, the potential functions of E. rotai CMTB-CA6 were characterized by its lysates' ability to regulate skin microbes, such as stimulating the growth of Staphylococcus epidermidis while inhibiting that of Cutibacterium acnes, to restore the viability of human dermal fibroblasts under inflammatory conditions, and to demonstrate effective antioxidant activities both in a cell-free system and in human dermal fibroblasts. Our investigation revealed the efficacy of E. rotai CMTB-CA6 lysates in improving skin conditions, suggesting its potential use as a probiotic-derived agent for skin care products. Considering the ecological relationship between plant-inhabited bacteria and their host plants, we suggest that the utilization of E. rotai CMTB-CA6 strain for fermenting its host plant, C. asiatica, could be a novel approach to efficiently enriching bioactive molecules for human health benefits.

Low Oxygen Concentration Reduces Neisseria gonorrhoeae Susceptibility to Resazurin.

Neisseria gonorrhoeae has developed resistance to every antibiotic currently approved for the treatment of gonorrhea, prompting the development of new therapies. The phenoxazine dye resazurin exhibits robust antimicrobial activity against N. gonorrhoeae in vitro but fails to limit vaginal colonization by N. gonorrhoeae in a mouse model. The lack of in vivo efficacy may be due to oxygen limitation as in vitro susceptibility assays with resazurin are conducted under atmospheric oxygen while a microaerophilic environment is present in the vagina. Here, we utilized broth microdilution assays to determine the susceptibility of N. gonorrhoeae to resazurin under low and atmospheric oxygen conditions. The minimal inhibitory concentration of resazurin for multiple N. gonorrhoeae clinical isolates was significantly higher under low oxygen. This effect was specific to resazurin as N. gonorrhoeae was equally susceptible to other antibiotics under low and atmospheric oxygen conditions. The reduced susceptibility of N. gonorrhoeae to resazurin under low oxygen was largely attributed to reduced oxidative stress, as the addition of antioxidants under atmospheric oxygen mimicked the reduced susceptibility to resazurin observed under low oxygen. Together, these data suggest oxygen concentration is an important factor to consider when evaluating the efficacy of new antibiotics against N. gonorrhoeae in vitro.

Screening Resorufin Pentyl Ether Analogs for Enhanced Antimicrobial Activity Against Francisella tularensis and Neisseria gonorrhoeae.

Antibiotic resistance is an urgent public health threat. The CDC estimates there are approximately 2.8 million new cases of antibiotic-resistant infections annually resulting in 35,000 deaths and billions of dollars in health care costs. The development of new drugs is imperative to combat this crisis and prevent the loss of additional lives from once “curable” diseases. Resazomycins, a novel family of antibiotics, have bactericidal activity against Francisella tularensis and Neisseria gonorrhoeae. One resazomycin, resorufin pentyl ether (RPE), significantly reduces vaginal colonization by N. gonorrhoeae in a mouse model of infection. Repeated administration of RPE, however, fails to clear the infection, in contrast to a single dose of ceftriaxone, an antibiotic commonly used to treat gonorrhea, which clears the infection within 24 hours. Further characterization of resazomycins revealed the efficacy of these compounds is limited by interaction with serum albumin and reduced oxygen concentrations found within mammalian tissues. Therefore, we hypothesize that novel resazurin analogs that maintain antimicrobial activity in the presence of serum albumin and low oxygen will have improved therapeutic efficacy in vivo. Resazurin has been chemically modified to generate ether and deoxygenated compound derivatives. Six ether derivatives and two deoxygenated analogs exhibited robust antimicrobial activity against F. tularensis and N. gonorrhoeae. In the presence of serum albumin, however, reduced efficacy was observed in the six ether analogs yet activity was maintained in the deoxygenated analogs. We plan to screen the efficacy of additional ether and deoxygenated analogs against F. tularensis and N. gonorrhoeae.

Investigation of Antimicrobial Activity and Cytotoxicity of Silver Nanoparticle Synthesized using Dopamine as a Reducing and Capping Agent

AbstractWe present a study focused on the controlled fabrication of silver nanoparticles (AgNPs) through colloidal synthesis, employing dopamine as a reducing and capping agent. By manipulating the concentration of silver nitrate, the production of spherical AgNPs with distinct particle diameters (16, 24, 48, and 74 nm) was achieved. The investigation extended to the evaluation of AgNPs′ impact on human embryonic kidney cells, revealing a concentration‐dependent response. At lower AgNPs concentrations, cell viability remained nearly 100 %, progressively declining with rising AgNPs concentrations. Importantly, the cytotoxic thresholds observed were notably elevated, underscoring the relatively mild to moderate toxicity profile of the nanoparticles. Furthermore, the antimicrobial efficacy of these synthesized AgNPs was probed against E. coli and S. aureus bacterial strains. Notably, the AgNPs exhibited robust antimicrobial activity, with superior performance exhibited by smaller‐sized particles compared to larger ones. Impressively, the minimum inhibitory concentration reached as low as 3.5 μg/mL, indicating their potent antimicrobial potential. The achieved distinct particle diameters, concentration‐dependent cytotoxic responses, and potent antimicrobial efficacy against bacterial strains underscore the multifaceted potential of these nanoparticles. These findings contribute valuable insights for their application in diverse fields, from biomedicine to antimicrobial solutions.

Ureidopenicillins Are Potent Inhibitors of Penicillin-Binding Protein 2 from Multidrug-Resistant Neisseria gonorrhoeae H041.

Effective treatment of gonorrhea is threatened by the increasing prevalence of Neisseria gonorrhoeae strains resistant to the extended-spectrum cephalosporins (ESCs). Recently, we demonstrated the promise of the third-generation cephalosporin cefoperazone as an antigonococcal agent due to its rapid second-order rate of acylation against penicillin-binding protein 2 (PBP2) from the ESC-resistant strain H041 and robust antimicrobial activity against H041. Noting the presence of a ureido moiety in cefoperazone, we evaluated a subset of structurally similar ureido β-lactams, including piperacillin, azlocillin, and mezlocillin, for activity against PBP2 from H041 using biochemical and structural analyses. We found that the ureidopenicillin piperacillin has a second-order rate of acylation against PBP2 that is 12-fold higher than cefoperazone and 85-fold higher than ceftriaxone and a lower MIC against H041 than ceftriaxone. Surprisingly, the affinity of ureidopenicillins for PBP2 is minimal, indicating that their inhibitory potency is due to a higher rate of the acylation step of the reaction compared to cephalosporins. Enhanced acylation results from the combination of a penam scaffold with a 2,3-dioxopiperazine-containing R1 group. Crystal structures show that the ureido β-lactams overcome the effects of resistance mutations present in PBP2 from H041 by eliciting conformational changes that are hindered when PBP2 interacts with the weaker inhibitor ceftriaxone. Overall, our results support the potential of piperacillin as a treatment for gonorrhea and provide a framework for the future design of β-lactams with improved activity against ESC-resistant N. gonorrhoeae.

Chemical Composition, Antioxidant, and Antibacterial Activity of Ruta chalepensis L. Ethanolic Extract.

Ruta chalepensis L. is a versatile herb used in culinary arts and traditional medicine. The study aimed to determine the chemical composition of an ethanolic extract from R. chalepensis and the total phenolic and flavonoid content. Additionally, the extracts' antimicrobial and antioxidant activities were tested. The disc diffusion method and minimum inhibitory concentration (MIC) were used to test the antibacterial properties on four types of bacteria: Escherichia coli, Proteus penneri, Bacillus cereus, and Staphylococcus aureus. A colorimetric assay was used to evaluate the total phenolic and flavonoid content, and the DPPH method was used to assess the antioxidant activity. The phytochemical constituents were determined using LC-MS/MS. The results indicated that R. chalepensis ethanolic extract had 34 compounds, and the predominant compounds were quercetin (9.2 %), myricetin (8.8 %), and camphene (8.0 %). Moreover, the extract had a good level of polyphenols and flavonoids, as demonstrated by inhibiting free radicals (DPPH) (IC50 was 41.2±0.1). Also, the extract exhibited robust antimicrobial activity against P. penneri and S. aureus with an MIC of 12.5 and 25.0 μg/mL, respectively. In conclusion, the results suggest that the R. chalepensis ethanolic extract has good antioxidant and antibacterial properties that could be utilized to develop new antibacterial agents.

Exploiting the synergistic antibacterial activity of shikimic acid and ceftiofur against methicillin-resistant Staphylococcus aureus.

Efforts to curtail the escalating health threat posed by methicillin-resistant Staphylococcus aureus (MRSA), a formidable superbug, necessitate the development of innovative treatment strategies. Leveraging potential compounds from natural sources in tandem with antibiotics has emerged as a promising approach against MRSA. These strategies should enhance the antibiotic efficacy, reduce dosage and toxicity, and bypass MRSA resistance. In this study, we used a checkerboard assay to illustrate the significant synergistic anti-MRSA effect of shikimic acid (SA), a naturally occurring compound, and ceftiofur (CF). Time-kill curves further revealed that a combination of 1/4 of the minimum inhibitory concentration (MIC) of SA and 1/8 MIC of the sodium CF eradicated MRSA within 2h, with no noticeable toxicity observed with these concentrations. In vivo experiments confirmed that this combination therapy demonstrated robust antimicrobial activity against MRSA-induced bacteremia in mice, significantly reducing bacterial loads in the kidneys, liver, and spleen, attenuating inflammatory cell infiltration, and alleviating pathological damage. This study not only offers a compelling strategy, capitalizing on the synergistic potential of SA and CF, to rapidly address antibiotic resistance but also contributes significantly to the refinement of antimicrobial therapeutic strategies.

Chitosan-Polyvinyl Alcohol Nanocomposites for Regenerative Therapy.

Tissue accidents provide numerous pathways for pathogens to invade and flourish, causing additional harm to the host tissue while impeding its natural healing and regeneration. Essential oils (EOs) exhibit rapid and effective antimicrobial properties without promoting bacterial resistance. Clove oils (CEO) demonstrate robust antimicrobial activity against different pathogens. Chitosan (CS) is a natural, partially deacetylated polyamine widely recognized for its vast antimicrobial capacity. In this study, we present the synthesis of four membrane formulations utilizing CS, polyvinyl alcohol (PVA), and glycerol (Gly) incorporated with CEO and nanobioglass (n-BGs) for applications in subdermal tissue regeneration. Our analysis of the membranes' thermal stability and chemical composition provided strong evidence for successfully blending polymers with the entrapment of the essential oil. The incorporation of the CEO in the composite was evidenced by the increase in the intensity of the band of C-O-C in the FTIR; furthermore, the increase in diffraction peaks, as well as the broadening, provide evidence that the introduction of CEO perturbed the crystal structure. The morphological examination conducted using scanning electron microscopy (SEM) revealed that the incorporation of CEO resulted in smooth surfaces, in contrast to the porous morphologies observed with the n-BGs. A histological examination of the implanted membranes demonstrated their biocompatibility and biodegradability, particularly after a 60-day implantation period. The degradation process of more extensive membranes involved connective tissue composed of type III collagen fibers, blood vessels, and inflammatory cells, which supported the reabsorption of the composite membranes, evidencing the material's biocompatibility.

Current Perspectives and Challenges of MAIT Cell-Directed Therapy for Tuberculosis Infection.

Mucosal-associated invariant T (MAIT) cells are a distinct population of non-conventional T cells that have been preserved through evolution and possess properties of both innate and adaptive immune cells. They are activated through the recognition of antigens presented by non-polymorphic MR1 proteins or, alternately, can be stimulated by specific cytokines. These cells are multifaceted and exert robust antimicrobial activity against bacterial and viral infections, direct the immune response through the modulation of other immune cells, and exhibit a specialized tissue homeostasis and repair function. These distinct characteristics have instigated interest in MAIT cell biology for immunotherapy and vaccine development. This review describes the current understanding of MAIT cell activation, their role in infections and diseases with an emphasis on tuberculosis (TB) infection, and perspectives on the future use of MAIT cells in immune-mediated therapy.

Confronting the Threat: Designing Highly Effective bis-Benzimidazolium Agents to Overcome Biofilm Persistence and Antimicrobial Resistance.

The objective of this study is to take the initial steps toward developing novel antibiotics to counteract the escalating problem of antimicrobial and bacterial persistence, particularly in relation to biofilms. Our approach involves emulating the structural characteristics of cationic antimicrobial peptides. To circumvent resistance development, we have designed a library of bis-benzimidazolium salts that selectively target the microbial membranes in a nonspecific manner. To explore their structure-activity relationship, we conducted experiments using these compounds on various pathogens known for their resistance to conventional antibiotics, including Gram-positive methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecium (VRE), and Gram-negative Escherichia coli (E. coli). Notably, two bis-benzimidazolium salts exhibited robust antimicrobial activity while maintaining a high level of selectivity compared with mammalian cells. Our investigations revealed significant antibiofilm activity, as these compounds rapidly acted against established biofilms. In addition, bis-benzimidazolium compounds exhibited consistent results in resistance development and cross-resistance studies. Consequently, amphiphilic bis-benzimidazolium salts hold promise as potential candidates to combat resistance-associated infections.

Synthesis and application of Ag-doped TiO2 nanoparticles with antifungal activity and ethylene inhibition in postharvest of avocado cv. Hass

Avocado is highly susceptible to postharvest diseases and rapid ripening, making it challenging to maintain its quality and shelf life. One potential solution is the use of nanoparticles that can act as both antimicrobial agents and ethylene inhibitors. In this study, we synthesized Ag-doped TiO2 nanoparticles through a solution combustion method and subjected them to various characterization techniques, including X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. These nanoparticles were then tested for their effectiveness in combating common avocado pathogens and their ability to inhibit ethylene production. To apply our findings practically, we treated Hass avocado fruits in the postharvest stage with a suspension of Ag-doped TiO2 nanoparticles and stored them under controlled conditions to simulate the ripening process. The Ag-doped TiO2 nanoparticles formed agglomerates within the nanometric range and exhibited oxidation-reduction characteristics, effectively inhibiting ethylene production and degrading Rhodamine-B dye. Moreover, these nanoparticles displayed robust antimicrobial activity, significantly suppressing the growth of Colletotrichum gloeosporioides sensu lato pathogens. Treated fruits in the postharvest phase showed reduced microbial growth, decreased incidence of anthracnose, stem and root diseases, and an extended shelf life compared to the control group, due to ethylene inhibition. Ag-doped TiO2 nanoparticles, with their dual capabilities of antimicrobial activity and ethylene inhibition, show promise in improving postharvest management of Hass avocados. They have the potential to enhance fruit quality, reduce postharvest losses, and improve marketability. Further research and field trials are essential to fully explore the practical applications of these nanoparticles in commercial avocado production and distribution.

Coupling solvent-mediated modulations with the morphological, optical, and antimicrobial attributes of solvothermally synthesized multifunctional Cu2ZnSnS4 nanoparticles

In this study, two distinct reaction media- water (CZTS1) and ethylene glycol (EG) (CZTS2) were used to synthesize nanocrystalline Cu2ZnSnS4 (CZTS) samples using the facile solvothermal method. X-ray diffraction (XRD) analysis indicated the presence of a tetragonal kesterite phase in both samples with CZTS2 exhibiting broader peaks and smaller crystallite size (6.04 nm) compared to CZTS1 (8.78 nm). Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray (EDX) analysis revealed the superior surface morphology and better stoichiometric composition of CZTS2 nanoparticles. In terms of optical properties, the direct bandgap values of CZTS1 and CZTS2 show variation from 1.45 eV to 1.50 eV, as determined from the Tauc plot. Furthermore, the antimicrobial assay of samples was identified by their zone of inhibition of a bacterial (Bacillus subtilis) and a fungal (Tilletia indica) strain demonstrating CZTS1 exhibited more robust antimicrobial activity compared to CZTS2 suggesting its potential in agriculture, food safety, and healthcare.

Exploring Traditional Uses, Phytochemical Composition, and Antimicrobial Potential of Latex-Producing Plants in the Euphorbia Genus: A Comprehensive Review

The Euphorbia genus, ranking as the third largest among angiosperm plants, encompasses nearly 2026 species. The latex derived from these plants contains irritants to the skin and finds application in wart removal. Additionally, it serves as a source for crafting fish and arrow poisons. Literature substantiates the utilization of these plants in the treatment of diverse ailments including menstrual issues, diarrhea, colds, fevers, as well as an array of skin conditions such as warts, sores, boils, dermatitis, psoriasis, eczema, and sunburn. Moreover, they contribute to wound healing. Certain species within the Euphorbia genus, classified under Euphorbiaceae, exhibit properties as anti-herpetic and antitumor agents against polio, rhinoviruses, and coxsackievirus. In the realm of Ayurveda, specific plant latex from select species is employed in the preparation of surgical threads for Kshara sutra therapy. This Ayurvedic approach serves as a minimally invasive para-surgical procedure in the management of anorectal piles or fistula. Remarkably, various di- and tri-terpenes obtained from the latex exhibit robust antimicrobial activity against both bacterial and fungal strains. Moreover, the di-terpenoids sourced from Euphorbia species display anti-inflammatory properties along with noteworthy cytotoxic and anticancer activities. The focal objective of this review is to present a contemporary overview encompassing traditional applications, phytochemical constituents, and the antimicrobial potential of ten latex-producing plants within the Euphorbia genus.

Optimization of Bis-anthraquinones Production from Endophytic Fungi Diaporthe sp. GNBP-10

Bis-anthraquinones with a unique molecular backbone, (+)-2,2’-epicytoskyrin A (epi) and (+)-1,1′-bislunatin (bis), was produced by endophytic fungi Diaporthe sp GNBP-10 associated with Gambir plant (Uncaria gambier). Epi and bis possess robust antimicrobial activity toward various pathogens. This study focus on knowing the optimum condition of epi and bis production from Diaporthe sp GNBP-10. A series of culture media with various nutrient compositions was investigated in epi and bis production. The content of epi and bis was determined by measuring the area under the curve from TLC-densitometric (scanner) experiment. The linear regression analysis was then applied to obtain the results. The optimized epi and bis production was observed in liquid media 3 containing potato starch and dextrose with the amount of epi produced is 0.484mg while bis content is 0.163mg. The presence of carbohydrates, whether simple sugar or carbohydrate complex, plays an essential role in the bis-anthraquinones production from Diaphorthe sp culture. The presence of minerals and excessive protein sources did not significantly affect bis-anthraquinones production. 
 Keywords: bis-anthraquinone, Diaporthe sp, culture media, regression, TLC scanner

ANTIMICROBIAL ACTIVITY OF LANTANA CAMARA AGAINST PSEUDOMONAS AERUGINOSA, SERRATIA MARCESCENS AND STAPHYLOCOCCUS AUREUS TO DEVELOP OINTMENT BASED THERAPY

Plant extract (Lantana camara) and earthworm (Pheretima posthuma) extract have been used to treat many illnesses for centuries; they have been reported to suppress the growth of many pathogenic bacteria and are specially used for wound healing. We analyzed the antibacterial activity of the different organic extracts obtained from these species against pathogenic strains of bacteria and compared them to know which is more potent for developing antiseptic ointment. Ethanol and acetone solvents were used for the extraction and analyzed for their antibacterial activity by the disk diffusion and shake flask test. Then we identified the minimum inhibitory concentration of extracts against gram-positive and gram-negative strains. Lantana camara showed the largest growth inhibitory zone against Pseudomonas aeruginosa, followed by Serratia marcescens, and Staphylococcus aureus. MIC for plant extract was 150μg/ml, while earthworm extract inhibited growth at a minimum dose of 200μg/ml. We found that the plant's ethanol extract (L. camara) exhibited robust antimicrobial activity compared to the worm extract. Current investigation reinforces the application of Lantana camara extract to develop ointment to treat wound infections.

Impact of Hypoalbuminemia on Ceftriaxone Treatment Failure in Patients With Enterobacterales Bacteremia: A Propensity-Matched, Retrospective Cohort Study.

Ceftriaxone is frequently prescribed due to its convenience of dosing and robust antimicrobial activity. However, patients with hypoalbuminemia may experience suboptimal ceftriaxone exposure due to the high degree of protein binding. We aimed to evaluate the impact of hypoalbuminemia on treatment failure among hospitalized adults with Enterobacterales bacteremia who received ceftriaxone therapy. We conducted an observational cohort study among patients with Enterobacterales bacteremia who received >72 hours of ceftriaxone initiated within 48 hours of index culture. A propensity-score model was used to match and compare patients with hypoalbuminemia. The primary outcome was treatment failure, defined as a composite of (1) escalation from ceftriaxone to ertapenem or an intravenous antibacterial agent with activity against Pseudomonas aeruginosa, or (2) inpatient death. Secondary outcomes included hospital length of stay, duration of antibiotic therapy, and time to infection resolution. Of 260 patients included, the majority developed bacteremia from a urinary source (71.5%), and Escherichia coli was the most common pathogen identified (72.3%). Patients with hypoalbuminemia experienced numerically higher rates of treatment failure, although not reaching statistical significance (12.3% vs 7.7%; P = .21). Among patients receiving care in the intensive care unit, the impact of hypoalbuminemia on treatment failure was more pronounced (24.4% vs 7.3%; P = .07). Hypoalbuminemia may not have a significant impact on clinical outcomes among patients with Enterobacterales bacteremia treated with ceftriaxone. However, critically ill patients may be subject to higher incidence of treatment failure in the presence of hypoalbuminemia.

Antibacterial activity of 18β-glycyrrhetinic acid against Neisseria gonorrhoeae in vitro

Gonorrhea is the second most common sexually transmitted diseases worldwide. Chronic infection of Neisseria gonorrhoeae (N. gonorrhoeae) can lead to severe complications. Presently, N. gonorrhoeae has developed resistance to almost all antibiotics used for the treatment of gonorrhea. Thus, it's urgent to explore new approaches to treat gonorrhea. Presently, nontraditional treatment method as an alternative to antibiotic use is getting more and more attention. Here we demonstrated that 18β-glycyrrhetinic acid (GRA) exhibited robust antimicrobial activity against N. gonorrhoeae in vitro. GRA led to a significant decline in viable N. gonorrhoeae in a dose dependent manner compared with DMSO treatment (P < 0.001). Addition of GRA resulted in a significant reduction in viable bacteria within 2 h post-inoculation (P < 0.001). Minimum inhibitory concentrations (MICs) to GRA ranged from 3.9 to 62.5 μg/ml overall, with MIC50 and MIC90 values of 31.25 μg/ml and 62.5 μg/ml, respectively. There was no significant difference of MIC 50 and MIC90 between multi-drug resistant (MDR) strains and non-MDR strains. Minimum bactericidal concentration (MBC) ranges were 3.9–125 μg/ml, basically consistent with MIC values. GRA inhibited biofilm formation and diminished pre-formed biofilm. These data suggested that GRA could be a candidate for gonorrhea treatment.

Effects of stabilized hypochlorous acid on oral biofilm bacteria

BackgroundCaries and periodontitis are amongst the most prevalent diseases worldwide, leading to pain and loss of oral function for those affected. Prevention relies heavily on mechanical removal of dental plaque biofilms but for populations where this is not achievable, alternative plaque control methods are required. With concerns over undesirable side-effects and potential bacterial resistance due to the use of chlorhexidine gluconate (CHX), new antimicrobial substances for oral use are greatly needed. Here we have investigated the antimicrobial effect of hypochlorous acid (HOCl), stabilized with acetic acid (HAc), on oral biofilms and compared it to that of CHX. Possible adverse effects of stabilized HOCl on hydroxyapatite surfaces were also examined.MethodsSingle- and mixed-species biofilms of six common oral bacteria (Streptococcus mutans, Streptococcus gordonii, Actinomyces odontolyticus, Veillonella parvula, Parvimonas micra and Porphyromonas gingivalis) within a flow-cell model were exposed to HOCl stabilized with 0.14% or 2% HAc, pH 4.6, as well as HOCl or HAc alone. Biofilm viability was assessed in situ using confocal laser scanning microscopy following LIVE/DEAD® BacLight™ staining. In-situ quartz crystal microbalance with dissipation (QCM-D) was used to study erosion of hydroxyapatite (HA) surfaces by stabilized HOCl.ResultsLow concentrations of HOCl (5 ppm), stabilized with 0.14% or 2% HAc, significantly reduced viability in multi-species biofilms representing supra- and sub-gingival oral communities, after 5 min, without causing erosion of HA surfaces. No equivalent antimicrobial effect was seen for CHX. Gram-positive and Gram-negative bacteria showed no significant differential suceptibility to stabilized HOCl.ConclusionsAt low concentrations and with exposure times which could be achieved through oral rinsing, HOCl stabilized with HAc had a robust antimicrobial activity on oral biofilms, without causing erosion of HA surfaces or affecting viability of oral keratinocytes. This substance thus appears to offer potential for prevention and/or treatment of oral biofilm-mediated diseases.

Visualization and elimination of polymicrobial biofilms by a combination of ALA-carvacrol-blue light.

Chronic wound infections caused by multidrug-resistant (MDR) bacteria are one of the serious threats to public health due to limited therapeutic options and lengthy care. This investigation combines 5-aminolevulinic acid (ALA), blue light (BL), and phytochemical carvacrol, named ABC cocktail or trio-therapy, to efficiently eliminate wound-related MDR pathogens. Both planktonic cells and biofilms of blue light-refractory Escherichia (E.) coli and Klebsiella (K.) pneumoniae succumbed to the trio-therapy partly due to porphyrin accumulations following ALA incubation. ALA either alone or alongside carvacrol could vigorously trigger bursts of reactive oxygen species (ROS) upon blue light irradiation in K. pneumoniae, but not in mammalian cells. The robust antimicrobial activity was extended to polymicrobial biofilms composed of five MDR pathogens (Staphylococcus aureus, E. coli, K. pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa) in vitro and in vivo. Strikingly, polymicrobial biofilm in mouse wounds became readily visible in the presence of ALA owing to the increasing generation of porphyrins that exhibited bright red fluorescence in response to blue light. Thus, ALA not only enhances killing efficacy, but also helps to pinpoint the infections for guiding debridement, precise phototherapy, and timely assessment of treatment effectiveness. Featuring a broadened antimicrobial spectrum and advantages of bacterial/biofilm imaging, the trio-therapy can be used either alone or adjunctive to other wound management modalities to effectively combat MDR bacteria in wounds.