Antibacterial Activity and Interaction Effects of Litsea Cubeba Fruit Essential Oil and Chitosan Against Food-Borne Bacteria

The aims of this study were to investigate the antibacterial activity and interaction effect of Litsea cubeba fruit essential oil (EO) and chitosan (CTS) against food-borne bacteria. The inhibition zone of EO, CTS and EO-CTS mixture against Escherichia coli ATCC 25922, Salmonella typhimurium ATCC 14028, Staphylococcus aureus ATCC 25923 and Bacillus cereus ATCC 13061 ranged from 39.0 - 57.3 mm; 11.7 - 15.5 mm and 29.7 - 39.3 mm, respectively. The minimum inhibitory concentration (MIC) of EO and CTS were 5.53 mg/mL and from 0.60 - 0.80 mg/mL, respectively. The synergistic effects were found when EO and CTS were used in combination with fractional inhibitory concentration values ranging from 0.62 - 0.67. The MIC of the EO and CTS combination was decreased from 6 to 8-fold and 2-fold compared to individual treatment by EO and CTS, respectively. The obtained results demonstrated the potential application of EO-CTS mixture in food preservation.

In vitro efficacy of gentamicin against multidrug-resistant Neisseria gonorrhoeae: synergy of three gentamicin antimicrobial combinations

ABSTRACTObjectivesTo determine in vitro activities of gentamicin alone and in combination with ceftriaxone, ertapenem and azithromycin against multidrug-resistant (MDR) N. gonorrhoeae isolates.Methods407 isolates from Nanjing, China, obtained in 2016 and 2017, had minimum inhibitory concentrations (MICs) determined for gentamicin using the agar dilution method. Antimicrobial combinations were also tested in 97 MDR strains using the antimicrobial gradient epsilometer test (Etest); results ranging from synergy to antagonism were interpreted using the fractional inhibitory concentration (FICI).ResultsAll 407 gonococcal isolates were susceptible to gentamicin. MICs ranged from 2 mg/L to 16 mg/L. Synergy was demonstrated in 16.5%(16/97), 27.8%(27/97) and 8.2%(8/97) MDR strains when gentamicin was combined with ceftriaxone [geometric mean (GM) FICI; 0.747], ertapenem (GM FICI; 0.662) and azithromycin (GM FICI; 1.021), respectively. No antimicrobial antagonism was observed with any combination. The three antimicrobial combinations were indifferent overall. The overall GM MICs of gentamicin were reduced by 2.63-, 3.80- and 1.98-fold when tested in combination with ceftriaxone, ertapenem and azithromycin, respectively. The GM MICs of the three antimicrobials by themselves were reduced by 3-, 2.57- and 1.98-fold respectively, when each was tested in combination with gentamicin. No antimicrobial antagonism was observed with any combination.ConclusionsGentamicin alone was effective in vitro against MDR N. gonorrhoeae and in combination with ceftriaxone, ertapenem or azithromycin. Combination testing of resistant strains, overall, showed lower effective MICs against gentamicin itself and each of the three antimicrobials when used in combination with gentamicin.

Synergistic activity of diclofenac sodium with oxacillin against planktonic cells and biofilm of methicillin-resistant Staphylococcus aureus strains

Aim: To evaluate the activity of diclofenac sodium and synergism with oxacillin against clinical strains of SARM in plactonic cells, antibiofilm and biofilm. Materials & methods: Synergism activity was assessed using the fractional inhibitory concentration index and its possible mechanism of action by flow cytometry. Results: The synergistic activity of diclofenac sodium with oxacillin was observed against plactonic cells, antibiofilm and in biofilm formed from clinical methicillin-resistant Staphylococcus aureusstrains. Conclusion: This combination caused damage to the integrity of the membrane and ruptures in the DNA of the cells, leading to apoptosis.

FICI Value Determination of Combination of Aquilaria microcarpa Baill. Ethanolic Extract with Amoxicillin against Salmonella typhi

<p>Karas (<em>Aquilaria microcarpa</em> Baill.) adalah tanaman yang memiliki aktivitas antibakteri terhadap beberapa bakteri patogen. Tujuan dari penelitian ini untuk mengetahui nilai FICI dari kombinasi ekstrak etanol daun karas (<em>Aquilaria microcarpa</em> Baill.) dengan amoksisilin terhadap bakteri <em>Salmonella typhi</em>. Metode yang digunakan adalah metode difusi cakram Kirby-Bauer. Analisis data dilakukan secara deskriptif untuk mengetahui karakteristik kombinasi. Hasil penelitian menunjukkan bahwa nilai FICI kombinasi ekstrak etanol daun karas (<em>Aquilaria microcarpa</em> Baill.) dengan amoksisilin terhadap <em>Salmonella typhi</em> adalah 4. Sehingga dapat disimpulkan bahwa karakteristik kombinasi terhadap bakteri <em>Salmonella typhi</em> bersifat <em>indifferent</em> atau tak berbeda.</p><p><strong>Kata kunci :</strong> <em>Aquilaria microcarpa </em>Baill.<em>, </em>ekstrak etanol, amoksisilin, <em>Salmonella typhi</em> , <em>Fractional Inhibitory Concentration Index</em> (FICI)</p>

In vitro synergy of isavuconazole in combination with colistin against Candida auris

The in vitro interactions of isavuconazole with colistin were evaluated against 15 clinical Candida auris isolates by a microdilution checkerboard technique based on the EUCAST reference method for antifungal susceptibility testing and by agar diffusion using isavuconazole gradient concentration strips with or without colistin incorporated RPMI agar. Interpretation of the checkerboard results was done by the fractional inhibitory concentration index and by response surface analysis based on the Bliss model. By checkerboard, combination was synergistic for 93% of the isolates when interpretation of the data was done by fractional inhibitory concentration index, and for 80% of the isolates by response surface analysis interpretation. By agar diffusion test, although all MICs in combination decreased compared to isavuconazole alone, only 13% of the isolates met the definition of synergy. Essential agreement of EUCAST and gradient concentration strip MICs at +/− 2 log2 dilutions was 93.3%. Antagonistic interactions were never observed for any technique or interpretation model used.

Investigation of Copaifera genus as a new source of antimycobaterial agents

Aim: This paper reports on the antimycobacterial activity of the oleoresins and extracts obtained from Copaifera spp. Materials & methods: The minimum inhibitory concentration (MIC) and fractional inhibitory concentration index techniques helped to evaluate the effect of these oleoresins and extracts against six strains of mycobacteria that cause tuberculosis. Results & conclusion: Among the assayed oleoresins and plant extracts, the Copaifera langsdorffii, Copaifera duckei, Copaifera reticulata and Copaifera trapezifolia oleoresins provided the lowest MIC values against some of the tested strains. The combination of Copaifera spp. samples with isoniazid did not evidence any synergistic action. Some Copaifera spp. oleoresins may represent a future source for the discovery of new antimycobacterial drugs due to their low MIC values.

Quantifying synergy in the bioassay-guided fractionation of natural product extracts

Mixtures of drugs often have greater therapeutic value than any of their constituent drugs alone, and such combination therapies are widely used to treat diseases such as cancer, malaria, and viral infections. However, developing useful drug mixtures is challenging due to complex interactions between drugs. Natural substances can be fruitful sources of useful drug mixtures because secondary metabolites produced by living organisms do not often act in isolation in vivo. In order to facilitate the study of interactions within natural substances, a new analytical method to quantify interactions using data generated in the process of bioassay-guided fractionation is presented here: the extract fractional inhibitory concentration index (EFICI). The EFICI method uses the framework of Loewe additivity to calculate fractional inhibitory concentration values by which interactions can be determined for any combination of fractions that make up a parent extract. The EFICI method was applied to data on the bioassay-guided fractionation of Lechea mucronata and Schinus terebinthifolia for growth inhibition of the pathogenic bacterium Acinetobacter baumannii. The L. mucronata extract contained synergistic interactions (EFICI = 0.4181) and the S. terebinthifolia extract was non-interactive overall (EFICI = 0.9129). Quantifying interactions in the bioassay-guided fractionation of natural substances does not require additional experiments and can be useful to guide the experimental process and to support the development of standardized extracts as botanical drugs.

Chitosan-induced Synergy for Extended Antimicrobial Potency and Enhanced In Vitro Drug Release of Free Base Ciprofloxacin Nanoplexes

Background: Ciprofloxacin free base is practically insoluble in aqueous medium (0.0011 and 0.09 mg/mL at 25 and 37°C respectively). Its inorganic salt form (ciprofloxacin hydrochloride) is more soluble in water (1.35 mg/mL) however when administered orally, it exhibits decreased solubility in the stomach due to common ion effects. Ciprofloxacin free base was used in this study because of its greater hydrophobicity than its hydrochloride salt, which is required for effective permeability and potent antibacterial activity. Objective: The purpose of this study is to enhance oral solubility and bacterial cell permeability of the free base ciprofloxacin (CPX) using a single step CPX-chitosan (CT) selfassembly to form nanoplexes with organic counterions. It was envisioned that this would allow the delivery of larger amounts of active drug into the microorganisms. Methods: Ciprofloxacin-chitosan nanocomplex (nanoplex) was prepared using low energy electrostatic self-assembly technique previously described. Formation of eutectic nanoplex was confirmed using FTIR, DSC, TGA and SEM. The saturated solubility, in vitro release kinetics and mechanism of drug release were determined using mathematical models. Potency and synergism were determined from the inhibition zones, minimum inhibitory concentration (MIC) and Fractional Inhibitory Concentration (FIC) of the nanoplexes using Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. Results: Formation of CPX-CT eutectic adduct polymeric nanoplexes was confirmed with FT-IR and DSC and SEM revealed the conversion of rod-like crystals of CPX (117 μm long) into spherical nanostructures (23-503 nm) dictated by pH, ionic strength and concentration of CT. The solubility of free base CPX increased to a maximum of 32.77 mg/mL compared to 0.0011-0.09 mg/mL reported in literature and dissolution efficiency increased to a maximum of 100% within 72 h. The synergistic effect of CT on antimicrobial activity of CPX was quantified, for the first time, using Fractional Inhibitory Concentration (FIC) of the nanoplexes. FIC was less than 0.5 in both Gram positive (0.031-0.250) and Gram negative (0.036-0.281) microorganisms used in this study, confirming synergistic enhancement of antimicrobial efficacy of CPX. Conclusion: It is evident that the design of drug-polymer nanocomplex formulation provides a platform for the synergistic enhancement of therapeutic potency of antibiotics.

Prevention of Pseudomonas aeruginosa Biofilm Formation on Soft Contact Lenses by Allium sativum Fermented Extract (BGE) and Cannabinol Oil Extract (CBD)

Two natural mixtures, Allium sativum fermented extract (BGE) and cannabinol oil extract (CBD), were assessed for their ability to inhibit and remove Pseudomonas aeruginosa biofilms on soft contact lenses in comparison to a multipurpose Soft Contact Lens-care solution present on the Italian market. Pseudomonas aeruginosa (ATCC 9027 strain) and Pseudomonas aeruginosa clinical strains isolated from ocular swabs were tested. Quantification of the biofilm was done using the microtiter plate assay and the fractional inhibitory concentration index was calculated. Both forms of Pseudomonas aeruginosa generated biofilms. BGE at minimal inhibitory concentration (MIC) showed inhibition percentages higher than 55% for both strains, and CBD inhibited biofilm formation by about 70%. The care solution at MIC inhibited biofilm formation by about 50% for both strains tested. The effect of BGE on the eradication of the microbial biofilm on soft contact lenses at MIC was 45% eradication for P. aeruginosa ATCC 9027 and 36% for P. aeruginosa clinical strain. For CBD, we observed 24% biofilm eradication for both strains. For the care solution, the eradication MICs were 43% eradication for P. aeruginosa ATCC 9027 and 41% for P. aeruginosa clinical strain. It was observed that both the test soft contact lenses solution/BGE (fractional inhibitory concentration index: 0.450) and the test soft contact lenses solution/CBD (fractional inhibitory concentration index: 0.153) combinations exhibited synergistic antibiofilm activity against most of the studied bacteria. The study showed that BGE and CBD have good effect on inhibition of biofilm formation and removal of preformed biofilms, which makes them promising agents that could be exploited to develop more effective care solutions.