Fractional Inhibitory Concentration Index Research Articles

Combining Fluconazole with Benzo[a]phenoxazine Derivatives as a Promising Strategy Against Fluconazole-Resistant Candida Species

The rise in non-albicans Candida species, exhibiting unpredictable antifungal resistance, complicates treatment and contributes to the growing threat of invasive, life-threatening infections. This study evaluates the antifungal activity of four benzo[a]phenoxazine derivatives (C34, C35, A42, and A44) against 14 Candida strains following EUCAST standards. Fluconazole interactions are analysed through fractional inhibitory concentration index (FICI) calculation and response surface analysis based on the Bliss model. Macrophage-like J774A.1 cells are used to assess Candida killing in the presence of synergistic compounds. The MIC values against the different strains vary, with C34 showing the strongest activity, followed by C35, while A42 has the highest MIC values, indicating lower efficacy. However, A42 demonstrates the best synergy with fluconazole against fluconazole-resistant Candida strains. Cytotoxicity assays reveal that the chloropropyl group present in C35 and A42 enhances cytocompatibility. Co-culture with macrophages shows significant yeast killing for C. albicans and C. auris when fluconazole and A42 are combined, requiring concentrations 4 and 16 times lower than their MIC values, enhancing antifungal activity. Given fluconazole’s fungistatic nature and the emergence of drug-resistant strains, benzo[a]phenoxazine derivatives’ ability to enhance fluconazole’s efficacy present a promising strategy to address antifungal resistance in critical pathogens. These findings align with global research priorities, offering new potential avenues for developing more effective antifungal therapies.

Cuminaldehyde in combination with tetracycline shows promising antibiofilm activity against drug-resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa, an opportunistic pathogen often causes biofilm-linked infections. A combinatorial approach involving tetracycline (antibiotic) and cuminaldehyde (phytochemical) was explored to combat this infectious pathogen. The results showed that both tetracycline and cuminaldehyde individually demonstrated antibacterial effects. However, when the compounds were applied together, there was a significant increase in their antimicrobial potential. The determined fractional inhibitory concentration index of 0.43 indicated a synergistic interaction between the two compounds. Furthermore, a series of experiments demonstrated that the combined application of cuminaldehyde and tetracycline could lead to a significant enhancement of their antibiofilm potential. This enhanced antibiofilm potential was attributed to the accumulation of reactive oxygen species and increased cell membrane permeability. Besides, this combinatorial application reduced the secretion of various virulence factors from P. aeruginosa. Therefore, this combined approach holds promise for effectively treating P. aeruginosa biofilms.

A Synergistic Interaction Between Citrus Hystrix Peel Essential Oil and Tetracycline and Evaluation of their Antibacterial Mechanism of Action in Vitro and in Silico Against Escherichia Coli.

Citrus hystrix essential oil (CHEO) have shown various pharmacological properties including antibacterial activity. This EO also possessed antibacterial effect against foodborne pathogens. There is less information available about the synergy interaction between CHEO and tetracycline, as well as their mechanism of action. Therefore, this study was conducted to evaluate the synergistic effect of CHEO and tetracycline against clinical isolate of Escherichia coli. Antibiofilm, bacteriolytic, and efflux pump inhibitor activities were also performed. The chemical composition of CHEO was analysed using GC-MS. Three major compounds, D-limonene (25.02 %), β-pinene (23.37 %), and β-sabinene (22.20 %) were identified. CHEO exhibited moderate antibacterial activity with MIC value of 250 μg/mL. The combination of CHEO (7.8 μg/mL) and tetracycline (62.5 μg/mL) produced a synergistic effect on E. coli with fractional inhibitory concentration index of 0.5. This mixture inhibited biofilm formation in E. coli. The combination of 7.8 μg/mL CHEO and 62.5 μg/mL tetracycline demonstrated bacteriolytic activity. In addition, the CHEO at 250 μg/mL showed a significant effect in inhibiting efflux pump. D-limonene has a binding free energy value of -20.13 kcal/mol with ompA transmembrane domain of E. coli. This finding indicates that CHEO has a potency to be developed as natural antibacterial against E. coli.

Antimicrobial activity of ceftibuten/polymyxin B combination against polymyxin/carbapenem-resistant Klebsiella pneumoniae.

To evaluate the synergistic effect of a ceftibuten and polymyxin B combination and to determine its capacity to overcome polymyxin B resistance in polymyxin/carbapenem-resistant (PC-R) Klebsiella pneumoniae. To investigate the combination's antibacterial efficacy, antimicrobial susceptibility tests using broth microdilution methods, chequerboard assays and time-kill testing were performed. Antibiofilm activity was also assessed. The treatment's effect on the bacterial cell membrane was examined by quantifying intracellular protein leakage and conducting scanning electron microscopy. Haemocompatibility tests were conducted to evaluate toxicity. Additionally, an infection model was established using Swiss mice to assess in vivo antimicrobial activity. The ceftibuten/polymyxin B combination demonstrated synergistic effects against several PC-R strains of K. pneumoniae, as determined by the FIC index (FICI) values, which ranged from 0.15 to 0.37. This combination was efficacious, exhibiting bactericidal activity at twice the MIC. Ceftibuten/polymyxin B also demonstrated antibiofilm activity. Additionally, ceftibuten/polymyxin B neither damaged the bacterial membrane nor exhibited haemolytic activity. Based on these findings, the in vivo therapeutic potential was investigated and it was found that ceftibuten/polymyxin B significantly decreased the bacterial load in the peritoneal lavage fluid of mice, revealing its effectiveness in treating infections caused by PC-R K. pneumoniae. The ceftibuten/polymyxin B combination exhibited synergistic effects in vitro and in vivo, and thus might be a promising therapeutic alternative for treating PC-R K. pneumoniae infections. As the combination was efficacious in preclinical models, researchers may further investigate its potential in clinical studies.

Isavuconazole and Amphotericin B Synergic Antifungal Activity: In Vitro Evaluation on Pulmonary Aspergillosis Molds Isolates

Background/Objectives. Pulmonary aspergillosis is a severe respiratory infection caused by Aspergillus spp., whose resistance profiles and invasive attitude complicate therapeutical strategies. Several aspergillosis cases emerged as superinfections during the SARS-CoV-2 pandemic when isavuconazole and amphotericin B became essential antifungal alternatives. The main purpose of the present study was to investigate a possible synergic activity between these molecules against Aspergillus spp. isolated from respiratory samples. Methods. The gradient test method detected isavuconazole and amphotericin B MIC values, prompting an arrangement of their combination into an R.P.M.I. agar medium. According to Liofilchem s.r.l. instructions, the FIC index was used to establish synergy, additivity, indifference, or antagonism. Results. Among 36 Aspergillus spp. isolates, only A. fumigatus strains showed both synergy and additivity episodes. A. niger reported the highest antagonism percentage, while A. terreus revealed several indifference episodes. Conclusions. Isavuconazole and amphotericin B remain fundamental therapeutical alternatives, including a possible synergic effect against A. fumigatus. On the basis of this species-related difference, further studies will be essential to investigate different antifungal drug combinations against filamentous fungi isolates.

New nano-chemotherapeutic chitosans- garlic oil - antibiotics against diabetic foot virulent Proteus spp

Background and Objectives: Diabetes foot ulcer is recognized to have a major side effect that raises the risk of amputation. Diabetic ulcer bacterial infections caused by virulent and resistant bacteria like Proteus mirabilis lead to serious wounds that are incurable with conventional medications. Materials and Methods: In this study, we evaluated the antibacterial activity of a natural product nanochitosan - garlic oil against ten diabetic foot isolates of Proteus mirabilis. Various chitosans (Crab (CScr) - shrimp (CSsh) - squilla (CSsq)) in nano form were prepared and coated with garlic oil (GO). GC-MS analysis was carried out to determine the main compo- nents of the essential garlic oil. The physicochemical properties of GO-NCSsq were analyzed using dynamic light scattering (DLS), zeta potentials (ZP) and subsequently scan electron microscope (SEM). Additionally, the minimum inhibitory con- centration (MIC) and fraction inhibitory concentration index (FICI) were determined. Results: GC-MS analysis revealed the presence of major palmitic fatty acid. (GO) loaded on nanochitosan squilla (NCSsq) showed high activity. Although SEM showed lower nano-size, average size of the GO-NCSsq was 330.8 nm by DLS and its zeta potential formulation was +39.6 mV. The final formulation represented by GO-NCSsq + Pipercillin (Pi) inhibited the virulence factor of P. mirabilis and reduced the MIC value (p-value > 0.001). Moreover, the killing time at 9 h was found to be significantly higher for GO-NCSsq + pipercillin (Pi) against P. mirabilis. Conclusion: In order to manage diabetic foot infections, GO-NCSsq is a legitimate antibacterial agent that can be coupled with other antibiotics.

In Vitro Synergistic Activity of Ceftazidime-Avibactam and Aztreonam against New Delhi Metallo-β-Lactamase-Producing Clinical Enterobacterales Isolates

Background: Carbapenemase-producing-Enterobacterales (CPE) infections are on the rise and associated with increased morbidity and mortality, due to a limited number of therapeutic options. The goal of this study was to assess the synergistic activity of ceftazidime-avibactam (CZA) and aztreonam (ATM) combination against phenotypically and genetically characterized blaMBL-producing Enterobacterales.Methods: In this study, forty (n=40) non-repeat, CPE clinical isolates, including: n=35 Klebsiella pneumoniae, n=2 each of Escherichia coli and Klebsiella oxytoca, and n=1 Enterobacter cloacae isolates were identified and susceptibilities were assessed using the Vitek-II compact (bioMérieux, Inc., France) and Microscan Walkaway (Beckman Coulter) systems. Genotypic analysis of clinically relevant carbapenemases was performed by using Xpert-Carba-R assay on GeneXpert (Cepheid, USA). The minimum inhibitory concentrations (MICs) and synergy testing of CZA and ATM, were tested by the Etest fixed ratio method (bioMérieux, Inc., France). The fractional inhibitory concentration index (FICI) was calculated for each antibiotic.Results: Our results showed that 97.5% of blaMBL-producing Enterobacterales isolates were susceptible to an in-vitro CZA + ATM combination regimen. The fractional inhibitory concentration index (FICI) ranged from 0.001 to 1.001. Among the tested CPE isolates, Synergy was observed in 36/40 (90%), an additive effect was observed in 5% (n=2)’ while two (5%) isolates showed indifference. There was no antagonism observed in our study.Conclusion: Our study exhibited a potent activity of CZA and ATM combination synergy against clinical CPE metallo- β-lactamase producers. More extensive studies involving a variety of Gram-negative pathogens with different resistance mechanisms are required to determine the efficacy of this combination regimen.Keywords: Synergy; Aztreonam; Ceftazidime-Avibactam; Carbapenem-Resistant Enterobacterales; Etest

Antibacterial activity and mechanism of colistin-loaded polymeric nanoparticles for combating multidrug-resistant Pseudomonas aeruginosa biofilms: A synergistic approach

Multidrug-resistant P. aeruginosa (MDR-P. aeruginosa), associated with elevated morbidity, mortality, and readmission rates, presents a formidable challenge to eradication due to its robust resistance to antimicrobial agents and biofilm formation. Herein, self-assembling nanoparticles (NO-PE/PLL NPs) comprised of NO donor-conjugated γ-polyglutamic acid (GSNO-PGA), epsilon-poly-l-lysine (PLL) and colistin were fabricated. The negatively charged NO-PE/PLL NPs exhibited effective penetration through airway mucus, reaching the infection site where GSNO-PGA released NO in response to glutathione within biofilm. PLL worked synergistically with colistin (fractional inhibitory concentration index: 0.281), reducing the minimum inhibitory concentration (MIC) of colistin from 2 to 0.5 μg/mL. Benefiting from this synergistic antibacterial action and NO-mediated biofilm disruption, NO-PE/PLL NPs achieved a 99.99 % eradication rate against MDR-P. aeruginosa biofilms. Additionally, NO-PE/PLL NPs efficiently inhibited endotoxins-stimulated inflammation response. In a chronic pulmonary infection model, NO-PE/PLL NPs displayed the highest eradication efficiency (99.78 %) to infected mice, while having no adverse effects on their major organs or pulmonary functions. These results highlight NO-PE/PLL NPs as a promising therapeutic strategy for treating recalcitrant infections caused by MDR-P. aeruginosa biofilms.

Synthesis and antibacterial potential of novel thymol derivatives against methicillin-resistant Staphylococcus aureus and P. aeruginosa pathogenic bacteria.

The increasing threat of antibiotic resistance has created an urgent need for new antibacterial agents, particularly plant-based natural compounds and their derivatives. Thymol, a natural monoterpenoid phenolic compound derived from Monarda citriodora, is known for its aromatic and therapeutic properties, including antibacterial activity. This study focuses on synthesizing dihydropyrimidinone and dihydropyridine derivatives of thymol and exploring their antibacterial properties. The synthesized compounds were tested for their in vitro antibacterial potential against pathogenic microorganisms, specifically Pseudomonas aeruginosa (Gram-negative) and methicillin-resistant Staphylococcus aureus (MRSA) (Gram-positive). Among the synthesized derivatives, compound 3i (ethyl 4-(4-hydroxy-5-isopropyl-2-methylphenyl)-2-imino-6-methyl-1,2,3,4-tetrahydropyrimidine-5-carboxylate) exhibited the most promising antibacterial activity, with minimum inhibitory concentration (MIC) values of 12.5µM against P. aeruginosa and 50.0µM against MRSA. Additionally, compound 3i demonstrated a synergistic effect when combined with vancomycin, enhancing its antibacterial efficacy. The optimum fractional inhibitory concentration index (FICI) observed was 0.10 and 0.5 for MRSA and P. aeruginosa, respectively, in combination with vancomycin. In silico analysis of the physiochemical properties of 3i indicated compliance with all drug-likeness rules. Furthermore, molecular docking studies revealed that compound 3i has a stronger binding affinity to the target protein than thymol, providing valuable insights into its potential mechanism of action.

Zidovudine in synergistic combination with nitrofurantoin or omadacycline: in vitro and in murine urinary tract or lung infection evaluation against multidrug-resistant Klebsiella pneumoniae.

Limited treatment options and multidrug-resistant (MDR) Klebsiella pneumoniae present a significant therapeutic challenge, underscoring the need for novel approaches. Drug repurposing is a promising tool for augmenting the activity of many antibiotics. This study aimed to identify novel synergistic drug combinations against K. pneumoniae based on drug repurposing. We used the clinically isolated GN 172867 MDR strain of K. pneumoniae to determine the reversal resistance activity of zidovudine (AZT). The combined effects of AZT and various antibiotics, including nitrofurantoin (NIT) and omadacycline (OMC), were examined using the checkerboard method, growth curves, and crystal violet assays to assess biofilms. An in vitro combination activity testing was carried out in 12 isolates of K. pneumoniae. In vivo murine urinary tract and lung infection models were used to evaluate the therapeutic effects of AZT + NIT and AZT + OMC, respectively. The fractional inhibitory concentration index and growth curve demonstrated that AZT synergized with NIT or OMC against K. pneumoniae strains. In addition, AZT + NIT inhibited biofilm formation and cleared mature biofilms. In vivo, compared with untreated GN 172867-infected mice, AZT + NIT and AZT + OMC treatment decreased colony counts in multiple tissues (P < 0.05) and pathological scores in the bladder and kidneys (P < 0.05) and increased the survival rate by 60% (P < 0.05). This study evaluated the combination of AZT and antibiotics to treat drug-resistant K. pneumoniae infections and found novel drug combinations for the treatment of acute urinary tract infections. These findings suggest that AZT may exert significant anti-resistance activity.

Synergistic invitro antimicrobial activity of polyherbal combination of Morinda lucida fruit and Pterocarpus santalinoides seed against multi-drug resistant clinical bacterial isolates

Background: Synergistic drug combination has been shown to be a way of bypassing drug resistance and reducing the amounts of antimicrobials consumed. As infections caused by multi-drug resistant organisms (MDROs) continue to pose global threat, it is important to search for new antimicrobial combinations of plant origin that are safe and readily available. The objective of this study is to evaluate the synergistic antimicrobial activity of extracts of Morinda lucida fruit and Pterocarpus santalinoides seed against multi-drug resistant (MDR) bacterial isolates Methodology: Morinda lucida and P. santalinoides fruits were plucked and washed clean, and the fruits of P. santalinoides were deseeded to remove the seeds. They were cut into smaller pieces and dried under shade before being milled into smooth powder and extracted with methanol. The clinical bacterial isolates used were MDR Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus. The phytochemical constituents of the extracts were determined using the standard method. The invitro antimicrobial assay of the extracts was done at a concentration of 50 to 400 mg/ml using the agar well diffusion technique. The minimum inhibitory concentration (MIC) and fractional inhibitory concentration (FIC) of each extract were determined using the Checker-board micro-titration method, and the FIC result obtained for each isolate was used to calculate the fractional inhibitory concentration index (FICI) of the combined extracts. The time kill assay was performed to confirm the synergistic and bactericidal activities from the MIC values obtained. Results: The phytochemical analysis revealed that the extracts of both herbal plants contained alkaloids, phenol, tannin, saponin, glycosides, and terpenoids. The antimicrobial assay results showed that the polyherbal combination of the extracts was active against all the MDR bacterial isolates tested with varying zones of inhibition. The mean inhibition zone diameters of individual M. lucida and P. santalinoides ranged from 18.0±0.9mm to 26.0±1.4mm and 17.0±0.1mm to 24.0±0.2mm respectively, while the MIC ranged from 6.25mg/ml to 12.5mg/ml for M. lucida and 12.5 mg/ml for P. santalinoides. The mean inhibition zone diameter of the polyherbal combination of the two plant extracts ranged from 25.00±00mm to 34.0±0.4mm, which compared favorably with that of levofloxacin control (28.0±0.0mm to 32.00±0.0mm), while their MIC ranged from 0.39mg/ml to 1.56mg/ml. The FIC of M. lucida extract ranged from 0.06mg/ml to 0.25mg/ml while that of P. santalinoides ranged from 0.03mg/ml to 0.13mg/ml. The FICI of combined extracts ranged from 0.09mg/ml to 0.38 mg/ml for all the MDR isolates, which is less than 0.5mg/ml, indicating synergism against all the isolates. The time of kill assay confirmed the synergistic and bactericidal activities with a 3log10 CFU/ml decrease in the number of viable cells within 6 hours of incubation.Conclusion: Our findings showed synergistic antibacterial actions of extracts of M. lucida fruit and P. santalinoides seed against MDR clinical bacterial isolates, comparable to levofloxacin. Combination of these herbal plants may serve as alternative sources of antimicrobial agents for the treatment of infections caused by MDR bacterial pathogens.

Synergistic Effect Antibacterial Activity of The Combination of Andaliman (Zanthoxylum acanthopodium DC) Fruit Essential Oil and Erythromycin against Streptococcus mutans and Streptococcus pyogenes

Background: The concept of synergism is one of the approaches taken to combat the problems related to antibiotic resistance. Objectives: The goal of this study was to determine the synergistic effect of antibacterial activity of a combination of essential oil of Zanthoxylum acanthopodium DC fruit and erythromycin against Streptococcus mutans and Streptococcus pyogenes. Methods: The broth microdilution assay was used to determine the Minimum Inhibitory Concentration (MIC) of Z. acanthpodium DC fruit essential oil and erythromycin. The synergistic effects were assessed using the checkerboard method. Results: MIC value of Z. acanthopodium DC fruit essential oil against both bacteria was 2500 mg/mL. The combination of Z. acanthopodium DC fruit essential oil and erythromycin had a synergistic effect against S. mutans and S. pyogenes with fractional inhibitory concentration index (FICI) values of 0.375 and 0.0872, respectively. Conclusions: These results suggest that a combination of herbal plants and conventional antibiotics could be used as an alternative therapy for bacterial infections.

In vitro bio-activity of Rosa rubiginosa L. (sweet briar) rosehip fixed oil combined with essential oils for acne vulgaris

Cutibacterium acnes, Staphylococcus epidermidis, and Staphylococcus aureus proliferate within accumulated sebum and produce localised inflammation thereby inducing acne vulgaris. Essential oils are one of the leading natural products used for acne and are diluted in fixed oils to reduce irritation and toxicity. This study investigated the in vitro antimicrobial, anti-inflammatory, cytotoxicity, and skin retention properties of Rosa rubiginosa rosehip fixed oil in combination with essential oils having activity against acne vulgaris. The broth microdilution assay was used to determine the minimum inhibitory concentration (MIC), and the sum of the fractional inhibitory concentration index (ΣFIC) was calculated for the interactions. The lipopolysaccharide (LPS) induced inflammatory pathway in RAW 264.7 macrophages was used to assess anti-inflammatory activity. A dual-staining method in A549 epithelial cells was used to assess cytotoxicity. Qualitative Fourier Transform Infrared spectroscopy analysis was used for initial skin retention determination. Rosa rubiginosa oil combined with Cinnamomum zeylanicum essential oil displayed antimicrobial synergy (MIC = 0.42 mg/ mL; ΣFIC = 0.45) against three acne-inducing strains. Rosa rubiginosa fixed oil combined with Styrax benzoin essential oil suppressed LPS-induced nitrite production by 33.80%. Rosa rubiginosa oil combined with Melaleuca quinquenervia essential oil exhibited the lowest cytotoxicity (84.32% cell viability). Rosa rubiginosa oil combined with either C. zeylanicum, Eugenia caryophyllata, Rosa damascena or S. benzoin essential oil was retained within the porcine skin. Rosa rubiginosa fixed oil serves as an ideal carrier oil that can potentiate selected essential oils for the treatment of acne vulgaris.

Antibacterial activity and mechanism of combination natural essential oils from oregano and cinnamon against enterotoxigenic Escherichia coli K99

Essential oils from oregano (OEO) and cinnamon (CEO) have been reported an excellent antibacterial activity, but their synergistic antibacterial effect is rarely studied. In this study, the chemical compositions of OEO, CEO and mixed OEO with CEO (MEO) and their antibacterial activities were analyzed, the mode of MEO action against enterotoxigenic Escherichia coli K99 (ETEC K99) were investigated. Results showed that MEO had the synergistic antibacterial effect, which was proven by fractional inhibitory concentration index of 0.375. The inhibition zone diameter measured varying with volume ratio of OEO and CEO showed that the best synergistic effect was at a ratio 2:8. Meanwhile, the antibacterial mechanism of MEO demonstrated that the MEO changed the morphology of ETEC K99 by scanning and transmission electron microscopy, and disrupted the cell membrane integrity that were proved by the leakage of intracellular nucleic acid and lower alkaline phosphatase activity of ETEC K99. In addition, the MEO also inhibited DNA biosynthesis, biofilm formation and scavenged mature biofilm of ETEC K99. These results confirm the synergistic effect on improvement of antibacterial activity and elucidate a variety of mechanisms through which the ETEC K99 was inactivated, and support the application of MEO to against ETEC K99.

Synergistic combinations of novel polymyxins and rifampicin with improved eradication of colistin-resistant Pseudomonas aeruginosa biofilms

BackgroundIncreased prevalence of antimicrobial resistance coupled with a lack of new antibiotics against Gram-negative bacteria emphasize the imperative for novel therapeutic strategies. Colistin-resistant Pseudomonas aeruginosa constitutes a challenge, where conventional treatment options lack efficacy, in particular for biofilm-associated infections. Previously, synergy of colistin with other antibiotics was explored as an avenue for the treatment of colistin-resistant infections, and recently we reported our efforts towards colistin analogs capable of combating planktonic colistin-resistant strains. AimsThe aim of the present study was to investigate whether analogs of polymyxin B with improved potency in wild-type and moderate resistant Gram-negative pathogens would retain similarly increased activity in highly colistin-resistant clinical P. aeruginosa isolates (in planktonic and biofilm growth) when applied alone and in combination with rifampicin. Materials and methodsIn this in vitro study, we tested three analogs of polymyxin B prepared by solid-phase peptide synthesis. Antimicrobial susceptibility testing was performed by measurement of minimum inhibitory concentrations via the broth microdilution method. Interactions between two antimicrobials was quantified in a checkerboard broth microdilution assay by calculating the fractional inhibitory concentration index for each combination. For testing of antibiofilm activity a previously described model with alginate beads encapsulating a biofilm culture was applied. The minimum biofilm eradication concentrations (MBECs) were evaluated, and the fractional biofilm eradication concentration indices were calculated. Three recently identified colistin analogs (CEP932, CEP936 and CEP938) were tested against three isogenic pairs of colistin-susceptible and colistin-resistant P. aeruginosa clinical isolates as well as the reference strain PAO1. ResultsFor bacteria in planktonic growth CEP938 retained almost full potency in all three resistant isolates, while exhibiting similar activity as colistin in susceptible isolates. Against biofilms CEP938 was slightly more potent against PAO1 as compared to colistin, while also retaining activity against a biofilm of the colistin-resistant strain 41,782/98. Next, synergy between CEP938 and the antibiotic rifampicin was explored. Interestingly, CEP938 did not exhibit synergy with rifampicin in planktonic cultures. Importantly, for colistin-resistant biofilms the CEP938-rifampicin combination demonstrated activity superior to that found for the colistin-rifampicin combination. ConclusionsThe present study showed in vitro efficacy of CEP938 against both colistin-susceptible and colistin-resistant P. aeruginosa biofilms as well as an ability of CEP938 to synergize with rifampicin in biofilm eradication.

Unveiling the therapeutic significance of shikimate pathway-derived phenolic acids against penicillin-binding protein 3 of Pseudomonas aeruginosa

ABSTRACT This study investigated the modulatory potential of Shikimate pathway-derived phenolic acids against penicillin-binding protein 3 (PBP3) of Pseudomonas aeruginosa using computational and in vitro methods. The binding and inhibitory capabilities of 22 phenolic acids against the catalytic site of PBP3 were evaluated and revealed ellagic and chlorogenic acids as the top inhibitors, showing superior docking scores of −8.4 kcal/mol each compared to the standard, cefotaxime (−7.5 kcal/mol). Dynamics simulation of their PBP3 complexes indicated chlorogenic acid’s efficacy in inhibiting PBP3 (−33.65 kcal/mol) relative to cefotaxime (−30.10 kcal/mol), while interacting with key catalytically relevant residues. The quantum features analysis using DFT/B3LYP suggested chlorogenic acid’s superior reactivity and compatibility with the PBP3 active site. In vitro evaluation revealed an MIC of 200 mg/ml for chlorogenic acid and 0.8 mg/ml for cefotaxime against Pseudomonas aeruginosa ATCC 27,853, while their combination showed a synergistic action mechanism (FIC index of 0.5). These observations were validated in time-kill kinetics (gradual decrease in viable cells over 24 h). The study concludes chlorogenic acid as promising PBP3 inhibitor. Nonetheless, further studies could focus on the structural modification of chlorogenic acid to improve its pharmacokinetic properties and potential as an antibacterial drug candidate in vivo.

Combination of Intracanal Medicines with Zinc Oxide Nanoparticles for Effective Eradication of Enterococcus faecalis

Background: Intracanal-resistant infections are the most important reason for root canal treatment failure. Therefore, cleaning the root canals is crucial. The efficiency of nanomedicines in eliminating intracanal contaminations and preventing bacterial attachment to surfaces are new strategies in this field. This study aimed to evaluate the effect of intracanal medicines, including calcium hydroxide (CH), zinc oxide nanoparticles (nZnO), pantoprazole (PP), and chlorhexidine (CHX) on Enterococcus faecalis (E. faecalis) in the individual and combinatorial form in an in vitro design in order to introduce an effective medicine for the eradication of E. faecalis. Sterilized water and sodium hypochlorite (NaOCl) 5.25% were used as the negative and positive control of antimicrobial activity, respectively. Methods: E. faecalis (ATCC 29212) was used for bacterial assays. The powder and the gel forms of the tested compounds were used in the analysis. The antibacterial and antibiofilm activities of the medicines were evaluated by the Minimum Inhibitory Concentration (MIC) determination using the broth microdilution method. The anti-biofilm effect of the tested compounds was assessed by Minimum Biofilm Inhibitory Concentration (MBIC). The antibacterial and antibiofilm effects of antimicrobial agent combinations were detected using the checkerboard assay and determination of the Fractional Inhibitory Concentration Index (FICI). Time-kill kinetics were conducted at zero, 2, 4, 6, 8, 10, 12, and 24 h. Results: Except for the MIC of the NaOCl, which was significantly lower than CH, there was no statistically significant difference between groups in MIC and MBIC. Only the mixture of CHX and nZnO and the mixture of PP and nZnO had a synergic effect against the planktonic and biofilm form of E. faecalis. Except for CHX and ZnO nanoparticles in gel form, other medicines did not show significant anti-biofilm effects against E. faecalis. Furthermore, the gel for CHX and nZnO showed stronger anti-biofilm effects. Conclusion: Combination therapy of common intracanal medicines with zinc oxide nanoparticles would lead to higher antibacterial and anti-biofilm effects against E. faecalis compared to conventional intracanal medicaments.

Characterization and applications of iron oxide nanoparticles synthesized from Phyllanthus emblica fruit extract

Nanotechnology is a treasure trove of diversified themes which are endowed with broad applications. Herein, iron oxide (Fe2O3) nanoparticles were synthesized using Phyllanthus emblica aqueous fruit extract. The UV-Visible spectrum exhibited a surface plasmon resonance peak at 295nm. Fourier Transform Infrared Spectroscopy provided insight into the functional groups responsible for capping. X-ray diffraction analysis authenticated the crystalline nature of nanoparticles, while energy dispersive X-ray spectroscopy divulged that iron and oxygen comprised 54% of the nanoparticles’ weight. Scanning electron microscopy established irregular morphology and agglomeration of nanoparticles. The Fe2O3 nanoparticles validated potent antimicrobial activity against 11 bacterial and 1 fungal isolates. The biggest zone of inhibition (23mm) was measured against S. enterica, whereas the smallest zone of inhibition (12mm) was documented against C. albicans and E. coli. The values for minimum inhibitory concentration ranged between 10 and 15μg/ml for all microbes. Nevertheless, no synergy was exhibited by the nanoparticles with any of the selected antibiotics (Fractional Inhibitory Concentration Index &gt; 1). The photocatalytic dye degradation capability of Fe2O3 nanoparticles was assessed and the observations implied a significant increase in degradation of methyl red although, not of methylene blue. Furthermore, the nanoparticles were in possession of substantial antioxidant (34–38%) and anti-inflammatory (31–38%) capacities. Consequent upon the robust activities of P. emblica-mediated nanoparticles, these can be scrutinized for biomedical and environmental implementations in future.

Polymyxin combined with Ocimum gratissimum essential oil: one alternative strategy for combating polymyxin-resistant Klebsiella pneumoniae.

Introduction. Multidrug-resistant infections present a critical public health due to scarce treatment options and high mortality. Ocimum gratissimum L. essential oil (O.geo) is a natural resource rich in eugenol known for its antimicrobial activity.Hypothesis/Gap Statement. O.geo may exert effective antimicrobial activity against polymyxin-resistant Klebsiella pneumoniae and, when combined with Polymyxin B (PMB), may exhibit a synergistic effect, enhancing treatment efficacy and reducing antimicrobial resistance.Aim. This study aims to investigate the antimicrobial activity of O.geo against polymyxin-resistant K. pneumoniae using in vitro tests and an in vivo Caenorhabditis elegans model.Methodology. The O.geo was obtained by hydrodistillation followed by gas chromatography. The MIC and antibiofilm activity were determined using broth microdilution. Checkerboard and time-kill assays evaluated the combination of O.geo and polymyxin B (PMB), whereas a protein leakage assay verified its action.Results. Eugenol (39.67%) was a major constituent identified. The MIC of the O.geo alone ranged from 128 to 512 µg ml-1. The fractional inhibitory concentration index (0.28) and time-kill assay showed a synergism. In addition, O.geo and PMB inhibited biofilm formation and increased protein leakage in the plasma membrane. The treatment was tested in vivo using a Caenorhabditis elegans model, and significantly increased survival without toxicity was observed.Conclusion. O.geo could be used as a potential therapeutic alternative to combat infections caused by multidrug-resistant bacteria, especially in combination with PMB.

&lt;i&gt;Iv vitro&lt;/i&gt; synergistic antimicrobial interactions between the extract of &lt;i&gt;Azadirachta indica&lt;/i&gt; and antibiotics against &lt;i&gt;Bacillus subtilis&lt;/i&gt;

This study aims to investigate the in vitro antimicrobial interactions between crude aqueous extract of Azadirachta indica and standard antibiotics, including ciprofloxacin, and norfloxacin. Using checkerboard techniques with Bacillus subtilis as the test microorganism, the synergistic effect of Azadirachta indica and antibiotics (ciprofloxacin and norfloxacin), was determined. The checkerboard assay presented FIC indices indicative of synergy, particularly notable with the combination of A. indica extract and the antibiotics. Specifically, with the 4:6, 8:2, and 9:1 ratios of ciprofloxacin and 1.9 to 9:1 of norfloxacin. These results suggest a potentiation of antibacterial effects when the plant extract is used in conjunction with conventional antibiotics. The synergistic interaction could potentially reduce the required doses of antibiotics, thereby minimizing side effects and the risk of antibiotic resistance.