Microdilution Method Research Articles

Evaluation of a simple method for testing aztreonam and ceftazidime-avibactam synergy in New Delhi metallo-beta-lactamase producing Enterobacterales.

NDM-producing carbapenem-resistant bacterial infections became a challenge for clinicians. Combination therapy of aztreonam and ceftazidime-avibactam is a prudent choice for these infections. However, there is still no recommendation of a practically feasible method for testing aztreonam and ceftazidime-avibactam synergy. We proposed a simple method for testing aztreonam and ceftazidime-avibactam synergy and compared it with reference broth micro-dilution and other methods. Carbapenem-resistant Enterobacterales clinical isolates were screened for the presence of the NDM gene by the Carba R test. NDM harbouring isolates were tested for aztreonam and ceftazidime-avibactam synergy by broth microdilution (reference method), E strip-disc diffusion, double disc diffusion, and disc replacement methods. In the newly proposed method, the MHA medium was supplemented with ceftazidime-avibactam (corresponding to an aztreonam concentration of 4μg/ml). The MHA medium was then inoculated with the standard inoculum (0.5 McFarland) of the test organism. An AZT disc (30 μg) was placed on the supplemented MHA medium, and the medium was incubated overnight at 37°C. Aztreonam zone diameter on the supplemented MHA medium (in the presence of ceftazidime-avibactam) was compared with that from a standard disc diffusion plate (without ceftazidime-avibactam), performed in parallel. Interpretation of synergy was based on the restoration of aztreonam zone diameter (in the presence of ceftazidime-avibactam) crossing the CLSI susceptibility breakpoint, i.e., ≥ 21 mm. Of 37 carbapenem-resistant NDM-producing isolates, 35 (94.6%) were resistant to aztreonam and tested synergy positive by the proposed method. Its sensitivity and specificity were 97.14% and 100%, respectively. Cohen's kappa value showed substantial agreement of the reference method with the proposed method (κ = 0.78) but no other methods. The proposed method is simple, easily interpretable, and showed excellent sensitivity, specificity, and agreement with the reference method. Therefore, the new method is feasible and reliable for testing aztreonam synergy with avibactam in NDM-producing Enterobacterales.

Antibacterial and Antibiofilm Potential of Bacterial Cellulose Hydrogel Containing Vancomycin against Multidrug-Resistant Staphylococcus aureus and Staphylococcus epidermidis.

The present study aimed to evaluate the in vitro antibacterial and antibiofilm activity of bacterial cellulose hydrogel produced by Zoogloea sp. (HYDROGEL) containing vancomycin (VAN) against bacterial strains that cause wound infections, such as multidrug-resistant (MDR) Staphylococcus aureus and Staphylococcus epidermidis. Initially, HYDROGEL was obtained from sugar cane molasses, and scanning electron microscopy (SEM) was performed to determine morphological characteristics. Then, VAN was incorporated into HYDROGEL (VAN-HYDROGEL). The antibacterial activity of VAN, HYDROGEL, and VAN-HYDROGEL was assessed using the broth microdilution method to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) against methicillin-sensitive S. aureus (MSSA) ATCC 25923, methicillin-resistant S. aureus (MRSA) ATCC 33591, S. epidermidis INCQS 00016 (ATCC 12228), five clinical isolates of MRSA, and nine clinical isolates of methicillin-resistant S. epidermidis, following the Clinical and Laboratory Standards Institute (CLSI) guidelines. Additionally, the antibacterial activity of VAN, HYDROGEL, and VAN-HYDROGEL was studied using the time-kill assay. Subsequently, the antibiofilm activity of VAN, HYDROGEL, and VAN-HYDROGEL was evaluated using crystal violet and Congo red methods, as well as SEM analysis. VAN and VAN-HYDROGEL showed bacteriostatic and bactericidal activity against MRSA and methicillin-resistant S. epidermidis strains. HYDROGEL did not show any antibacterial activity. Analysis of the time-kill assay indicated that HYDROGEL maintained the antibacterial efficacy of VAN, highlighting its efficiency as a promising carrier. Regarding antibiofilm activity, VAN and HYDROGEL inhibited biofilm formation but did not demonstrate biofilm eradication activity against methicillin-resistant S. aureus and S. epidermidis strains. However, it was observed that the biofilm eradication potential of VAN was enhanced after incorporation into HYDROGEL, a result also proven through images obtained by SEM. From the methods carried out in this study, it was possible to observe that HYDROGEL preserved the antibacterial activity of vancomycin, aside from exhibiting antibiofilm activity and enhancing the antibiofilm effect of VAN. In conclusion, this study demonstrated the potential of HYDROGEL as a candidate and/or vehicle for antibiotics against MDR bacteria that cause wound infections.

Activity of propyl-propane-thiosulfinate and propyl-propane-thiosulfonate against carbapenem-resistant Gram-negative bacteria.

Organosulfur compounds derived from plants of the Allium genus, such as propyl-propane-thiosulfinate (PTS) and propyl-propane-thiosulfonate (PTSO), have been proposed as an alternative in antibiotic resistance. The aim of this study was to compare the activity of these substances with other antibiotics against clinical isolates of carbapenem-resistant (CAR-R) and carbapenem-susceptible (CAR-S) Gram-negative bacteria. A total of 126 clinical isolates of CAR-R and 155 CAR-S bacteria were selected, including Enterobacterales, A. baumannii and P. aeruginosa. The antibiotic susceptibility of all isolates was assessed using the microdilution and Kirby-Bauer methods for PTS, PTSO, amoxicillin/clavulanate, piperacillin/tazobactam, cefotaxime, ceftazidime, cefepime, imipenem, ciprofloxacin, and amikacin. Both PTS and PTSO demonstrated in vitro bactericidal activity against CAR-R Enterobacteriaceae and A. baumannii, with no significant difference in activity compared to their response against CAR-S isolates. However, both compounds were less active against P. aeruginosa than against any of the other bacteria, regardless of their resistance to carbapenems. In all cases, the minimum inhibitory concentration values of PTSO were significantly lower than those of PTS. These findings offer valuable information about the potential antibacterial use of these substances, particularly against infections that currently have limited therapeutic options.

Comparative analysis of three methods for screening for colistin resistant <i>Escherichia coli</i>

The usage of colistin regarded as a drug of last resort has increased tremendously in recent years. This increase has been followed by an increase in the development of colistin resistant bacteria. Due the large size of colistin and its ability to adhere to plastic, the broth microdilution method using a special medium is the recommended testing method. Resource limited settings struggle with this method and employ alternate methods. This study therefore set out to determine colistin resistance in a group of Escherichia coli using three different methods comprised of colistin agar spot test (COL-AS), colistin drop test (COL-DT) and a disc diffusion method. A total of 51 Escherichia coli isolated from wound samples were screened for colistin resistance using the COLAS, COL-DT and colistin disc diffusion methods. Results showed a combined resistance rate of 96.1% among test isolates. Actual resistance rates varied between testing methods giving values of ranging from 37.3%, 66.0% and 88.2% for COL- DT, colistin disc diffusion methods and COL-A respectively. An assessment of test performance showed categorical agreement values and very major error values of 57.1%/36.7% for COL-DT and 63.3%/8.2% for COL-A. Results of this study show a high-level occurrence of colistin resistance among clinical Escherichia coli isolates. Furthermore, it demonstrates the superiority of the colistin agar test to the colistin drop test. It also points at a need to use higher concentrations of colistin in the screening tests.

Chemical Profile with Antibacterial and Modulatory Activity of Extracts from the Stem Bark of Cnidoscolus quercifolius Pohl.

Objective: The present study aimed to investigate the chemical profile and evaluate the antibacterial and antibiotic-modulating activity of the methanolic extract and ethyl acetate of the stem bark of C. quercifolius against standard and multiresistant strains. Methods: The Minimum Inhibitory Concentration was determined by the microdilution method, and the modulating potential of the extracts on aminoglycoside and β-lactam antibiotics was evaluated. Results: The classes of secondary metabolites identified from qualitative chemical prospecting were flavones, flavonols, xanthones, flavonones, flavonols, catechins and leucoanthocyanidins. The assays showed inhibition only for Klebsiella pneumoniae-producing extended-spectrum β- lactamase, Klebsiella pneumoniae carbapenemase and Escherichia coli ATCC 25922 with MICs of 256, 512 and 512 μg/mL, respectively. The extracts, when associated with gentamicin and amoxicillin, showed synergism against all standard and multiresistant strains, with the exception of Klebsiella pneumoniae carbapenemase and Klebsiella pneumoniae producing extendedspectrum β-lactamase, respectively. When combined with amikacin, they also demonstrated synergism against multidrug-resistant strains; however, only the ethyl acetate extract had a synergistic effect against E. coli ATCC 25922. The association of penicillin with methanolic extract showed synergism only for Klebsiella pneumoniae producing extended-spectrum β-lactamase and S. aureus ATCC 29213, while the ethyl acetate extracts demonstrated synergism against S. aureus and Klebsiella pneumoniae producing extended-spectrum β-lactamase. Conclusion: It was found that C. quercifolius extracts have antibacterial potential against gramnegative bacteria. However, the need for additional research using specific methods against bacteria carrying different resistance mechanisms, especially gram-positive ones, is highlighted, with the aim of elucidating their mechanism of action. conclusion: The species was found to have substances with potential against Gram-negative bacteria. However, the need for additional research using specific methods against bacteria carrying different resistance mechanisms, especially Gram-positive ones, is highlighted, with the aim of elucidating their mechanism of action.

Anti-MRSA mechanism of spirostane saponin in Rohdea pachynema F.T.Wang & tang

Ethnopharmacology relevanceRohdea pachynema F.T.Wang & Tang (R. pachynema), is a traditional folk medicine used for the treatment of stomach pain, stomach ulcers, bruises, and skin infections in China. Some of the diseases may relate to microbial infections in traditional applications. However few reports on its antimicrobial properties and bioactive components.Aim of the study: To identify its bioactive constituents against methicillin-resistant Staphylococcus aureus (MRSA) in vitro and in vivo, and its mechanism. Materials and methodsThe anti-MRSA ingredient 6α-O-[β-D-xylopyranosyl-(1 → 3)-β-D-quinovopyranosyl]-(25S)-5α-spirostan-3β-ol (XQS) was obtained from R. pachynema by phytochemical isolation. Subsequently, XQS underwent screening using the broth microdilution method and growth inhibition curves to assess its antibacterial activity. The mechanism of XQS was evaluated by multigeneration induction, biofilm resistance assay, scanning electron microscopy, transmission electron microscopy, and metabolomics. Additionally, a mouse skin infection model was established in vivo. Results26 compounds were identified from the R. pachynema, in which anti-MRSA spirostane saponin (XQS) was reported for the first time with a minimum inhibitory concentration (MIC) of 8 μg/mL. XQS might bind to peptidoglycan (PGN) of the cell wall, phosphatidylglycerol (PG), and phosphatidylethanolamine (PE) of the cell membrane, then destroying the cell wall and the cell membrane, resulting in reduced membrane fluidity and membrane depolarization. Furthermore, XQS affected MRSA lipid metabolism, amino acid metabolism, and ABC transporters by metabolomics analysis, which targeted cell walls and membranes causing less susceptibility to drug resistance. Furthermore, XQS (8 mg/kg) recovered skin wounds in mice infected by MRSA effectively, superior to vancomycin (8 mg/kg). ConclusionsXQS showed anti-MRSA bioactivity in vitro and in vivo, and its mechanism association with cell walls and membranes was reported for the first, which supported the traditional uses of R. pachynema and explained its sensitivity to MRSA.

Design, Synthesis and Biological Evaluation of Novel Gypsogenin Derivatives as Potential Anticancer and Antimicrobial Agents.

Natural compounds are important sources for the treatment of chronic disorders such as cancer and microbial infectious disorders. In this research, Gypsogenin and its derivatives (2 a-2 f) have been tested against different cancer cell lines (MCF-7, HeLa, Jurkat and K562 cell lines) and further analyzed for cell proliferation, cell death type, and for act of the mechanism. Cell proliferation was determined by the MTT method and cell death types were analyzed with HO/PI staining. Fibroblast Growth Factor 1 (FGF-1), Interleukin 1 (IL-1), Interleukin 6 (IL-6), and Tumor Necrosis Factor Alpha (TNF-α), key players in breast cancer development and progression, were determined by Elisa kits. Results showed that compound 2 e inhibited the MCF-7 cell line proliferation with an IC50 value of 0.66±0.17 μM with 93.38 % apoptosis rate. Compound 2 e also decreased FGF-1, IL-1, IL-6, and TNF-α levels. Molecular docking studies performed in the binding site of FGFR-1 indicated that compound 2 e formed key hydrogen bonding with Arg627 and Asn568. Besides, compounds 2 a-2 f were evaluated for their antimicrobial activities against gram-negative and gram-positive bacteria and C. albicans via the microdilution method. Overall, compound 2 e stands out as a potential anticancer agent for future studies.

Cefepime/sulbactam combination as a treatment alternative for extended spectrum beta-lacatmase producing Enterobacterales: A multicentric study from India

BackgroundPiperacillin/tazobactam has limited activity against Enterobacterales, which concurrently express ESBL/ampC/OXA-1 beta-lactamases, which are widely prevalent in India. Thus, there is a severe dearth for carbapenem sparing options that aggravate more dependent carbapenem therapy. In the Indian market, various cefepime/BLI combinations in diiferent fixed ratios were introduced to clinical practice. We investigated the activity of cefepime with increased sulbactam ratios against contemporary isolates of ESBL/OXA-1 expressing Enterobacterales. MethodsNon-duplicate contemporary ESBL and/or OXA-1 expressing E. coli (n = 117) and K. pneumoniae (n = 71) isolates were included in this study. The MIC of cefepime/sulbactam and its comparators were determined using a broth microdilution method. The presence of ESBL and OXA-1 genes were identified using multiplex PCR. ResultsAgainst ESBL and OXA-1 co-producing E. coli, cefepime combined with sulbactam at 8 mg/L, inhibited 82% of the isolates. Cefoperazone susceptibility against ESBL-E. coli increased from 52% at 4 mg/L to 77% at 8 mg/L with sulbactam. When tested against K. pneumoniae co-expressing ESBL and OXA-1, cefepime susceptibility was 77% at 4 mg/L sulbactam and 88% at 8 mg/L sulbactam. PTZ consistently showed limited activity against ESBL co-harbouring OXA-1 (E. coli, 43% and K. pneumoniae, 61%). ConclusionThe present study demonstrates that adding an increased sulbactam concentration enhances cefepime's activity against contemporary ESBL/OXA-1 expressing Enterobacterales. A reformulated cefepime/sulbactam (2 g/2 g) combination may be the best carbapenem sparing option until cefepime/tazobactam and cefepime/enmetazobactam become available in the future.

Characterization of linezolid- and methicillin-resistant coagulase-negative staphylococci in a tertiary hospital in China

BackgroundRecently, linezolid-resistant staphylococci have become an emerging problem worldwide. Understanding the mechanisms of resistance, molecular epidemiology and transmission of linezolid-resistant CoNS in hospitals is very important.MethodsThe antimicrobial susceptibilities of all isolates were determined by the microdilution method. The resistance mechanisms and molecular characteristics of the strains were determined using whole-genome sequencing and PCR.ResultsAll the strains were resistant to oxacillin and carried the mecA gene; 13 patients (36.1%) had prior linezolid exposure. Most S. epidermidis and S. hominis isolates were ST22 and ST1, respectively. MLST typing and evolutionary analysis indicated most linezolid-resistant CoNS strains were genetically related. In this study, we revealed that distinct CoNS strains have different mechanisms of linezolid resistance. Among ST22-type S. epidermidis, acquisition of the T2504A and C2534T mutations in the V domain of the 23 S rRNA gene, as well as mutations in the ribosomal proteins L3 (L101V, G152D, and D159Y) and L4 (N158S), were linked to the development of linezolid resistance. In S. cohnii isolates, cfr, S158Y and D159Y mutations in the ribosomal protein L3 were detected. Additionally, emergence of the G2576T mutation and the cfr gene were major causes of linezolid resistance in S. hominis isolates. The cfr gene, G2576T and C2104T mutations, M156T change in L3 protein, and I188S change in L4 protein were found in S. capitis isolates.ConclusionThe emergence of linezolid-resistant CoNS in the environment is concerning because it involves clonal dissemination and frequently coexists with various drug resistance mechanisms.

Evaluation of Mediterranean Tree Leaves as Valuable Biomass of Digestive Enzymes and Bacterial Inhibitors in the Concept of Circular Bioeconomy

This study aspires to evaluate the antibacterial and inhibitory effects of carbohydrate digestive enzymes in tree leaves that are widely distributed in the Mediterranean region. Leaves were sequentially extracted with solvents of increasing polarity. The results demonstrated a wide range of phenolic (3.5–770.7 mg gallic acid equivalent g−1) and flavonoid (0.2–321.3 mg catechin equivalent g−1) contents in leaf extracts. The minimum inhibitory and bactericidal concentration of leaf extracts was determined for six bacteria using the broth microdilution method. The polar extracts of carob, lentisk, and white mulberry leaves exerted strong antibacterial potency against Gram-positive bacteria, while the susceptibility of Escherichia coli on relative apolar extracts of carob, fig, and olive leaves was also observed. In parallel, the inhibitory effects of leaf extracts on carbohydrate digestive enzymes were evaluated. A robust inhibition of α-glucosidase was found for carob and lentisk leaf extracts, followed by extracts produced by white mulberry and olive leaves. Carob and lentisk leaves also act as a-amylase inhibitors at high concentrations. Overall, this study provides valuable data for the nutraceutical value of the “forgotten” treasure of Mediterranean tree leaves and assesses these plants as potential sources of antibacterial and carbohydrate digestive enzyme inhibitory agents for drug discovery.

Phenotypic and genomic characterization of a multidrug-resistant Salmonella enterica serovar Kentucky ST198 isolated from a patient in China

ObjectivesThe objective of this study was to investigate the resistance mechanisms of a multidrug-resistant Salmonella Kentucky ST198 FJ-2064 isolated from a patient in China. MethodsThe antimicrobial susceptibility of FJ-2064 was determined by the standard disc dilution and broth microdilution methods. The complete genome of FJ-2064 was sequenced using PacBio and Illumina MiSeq platforms. Polymerase chain reaction (PCR) and S1-PFGE were utilized to confirm the mutation sites and the genomic plasmids, respectively. ResultsIsolate FJ-2064 belongs to sequence type ST198 and harboured no visible large plasmids, but was concurrent resistant to 22 detected antimicrobial agents including cefotaxime, ciprofloxacin, and azithromycin. The complete genome sequence identified 20 acquired antibiotic resistance genes (ARGs) and five chromosomal mutations in the gyrA and parC genes of the quinolone resistance determining regions (QRDRs) in FJ-2064. In addition, PCR sequencing confirmed that most of the ARGs were clustered on one multidrug-resistant region and a variant of SGI1-K. In particular, the bla-TEM-1 and bla-CTX−M-55, qnrS1, mph(A) genes, which confer resistance to cephalosporins, quinolones, and macrolides respectively, were all located on the multidrug-resistant region. ConclusionsWe have demonstrated one multidrug-resistant region and a variant of SGI1-K in a Salmonella Kentucky ST198 that is co-resistant to cefotaxime, ciprofloxacin, and azithromycin.

Oral candidiasis in liver transplant patients: species identification and antifungal susceptibility profile.

This study aimed to verify oral candidiasis, identify the causative species, and investigate the antifungal susceptibility of yeasts isolated from liver transplant patients. A descriptive analysis of 97 patients who underwent liver transplantation was conducted at a hospital. Two clinical examinations (Collections A and B) of the oral cavity were performed. Oral material was collected from all patients, inoculated in Sabouraud Dextrose Agar, and incubated at 35℃ for 48 hours. Samples were identified by molecular sequencing of the internal trascribed space region of rDNA. An antifungal susceptibility test with fluconazole, amphotericin B, and micafungin was performed using the Clinical and Laboratory Standards Institute yeast broth microdilution method. Among the patients, 15 presented with oral candidiasis: eight in Collection A and seven in Collection B. The primary type of candidiasis was atrophic, followed by pseudomembranous candidiasis. The most prevalent species was Candida albicans (nine), followed by Candida glabrata (three), Candida tropicalis (two), and Candida dubliniensis (one). Regarding susceptibility to fluconazole, of the 15 samples, 11 were susceptible, three were susceptible in a dose-dependent manner, and one was resistant. The most commonly identified type of candidiasis was atrophic, with C. albicans and C. glabrata being the most prevalent causative species. One fluconazole-resistant isolate each of C. tropicalis and C. albicans were identified.

A novel antifungal nanoemulsion based on reuterin-assisted synergistic essential oils: Preparation and in vitro/in vivo characterization

This research aimed to develop, optimize, and evaluate a new antifungal nanoemulsion system based on the crude reuterin-synergistic essential oils (EOs) hybrid to overcome the EOs application limits. At first, the antifungal effects of the Lactobacillus plantarum and Lactobacillus reuteri cell-free extracts (CFE) were tested against the Botrytis cinerea, Penicillium expansum, and Alternaria alternata as indicator fungus using broth microdilution method. The L. reuteri CFE with the MIC of 125 μL/mL for B. cinerea and 250 μL/mL for P. expansum and A. alternata showed more inhibitory effects than L. plantarum. Next, reuterin as a significant antibacterial compound in the L. reuteri CFE was induced in glycerol-containing culture media. To reach a nanoemulsion with maximum antifungal activity and stability, the reuterin concentration, Tween 80 %, and ultrasound time were optimized using response surface methodology (RSM) with a volumetric constant ratio of 5 % v/v oil phase including triple synergistic EOs (thyme, cinnamon, and rosemary) at MIC concentrations. Based on the Box-Behnken Design, the maximum antifungal effect was observed in the treatment with 40 mM reuterin, 1 % Tween 80, and 3 min of ultrasound. The growth inhibitory diameter zones of B. cinerea, P. expansum, and A. alternata were estimated 6.15, 4.25, and 4.35 cm in optimum nanoemulsion, respectively. Also, the minimum average particle size diameter (16.3 nm) was observed in nanoemulsion with reuterin 40 mM, Tween 80 5 %, and 3 min of ultrasound treatment. Zeta potential was relatively high within −30 mV range in all designed nanoemulsions which indicates the nanoemulsion's stability. Also, the prepared nanoemulsions, despite initial particle size showed good stability in a 90-d storage period at 25 °C. In vivo assay, showed a significant improvement in the protection of apple fruit treated with reuterin-EOs nanoemulsions against fungal spoilage compared to free reuterin nanoemulsion. Treatment of apples with nanoemulsion containing 40 mM reuterin showed a maximum inhibitory effect on B. cinerea (5.1 mm lesion diameter compared to 29.2 mm for control fruit) within 7 d at 25 °C. In summary, the present study demonstrated that reuterin-synergistic EOs hybrid with boosted antifungal activities can be considered as a biopreservative for food applications.

Assessment of antimicrobial and anti-biofilm activities of lemongrass and bay leaf extracts on microorganisms from fermented cereal-based porridges in northern Benin

Lemongrass (Cymbopogon citratus) and bay leaf (Laurus nobilis) are condiments in food processing. This study aimed to assess the antimicrobial and anti-biofilm activities of lemongrass and bay leaf extract on the microorganisms isolated from cereal-based fermented porridges produced in northern Benin. The phytochemical components of lemongrass and bay leaf extracts were analyzed qualitatively using two solvents: water and alcohol. The antimicrobial activity of the extracts was tested using the solid media diffusion method, and the minimum concentration was determined using the microdilution method. The extracts were also evaluated for their ability to inhibit biofilm formation using qualitative assays. The two plants have different phytochemical profiles. Tannins, flavonoids, mucilage, and alkaloids were detected in both plants. Cyanogenic derivatives, O-heterosides, and genin-reduced O-heterosides were absent. L. nobilis contained anthocyanins, quinone derivatives, saponosides, reducing compounds, and free anthracenes, absent in C. citratus. The inhibition diameters ranged from 4.4 to 26.3, depending on the strains and extracts, and varied significantly. The MICs for Escherichia coli ranged from 4.5 mg/ml to 7 mg/ml, staphylococci from 3.75 mg/ml to 10 mg/ml, and lactic bacteria from 2.5 mg/ml to 4.44 mg/ml. The CMB varied between 8.125 mg/ml and 14 mg/ml for E. coli, 7.5 mg/ml to 20 mg/ml for staphylococci, and 6 mg/ml to 10 mg/ml for lactic bacteria. It is worth noting that staphylococci are the most biofilm-producing strains (80%), followed by E. coli (60%), and lactic bacteria produce less biofilm (30%). The findings of this research confirm the presence of a wide range of biological activities, including antibacterial and anti-biofilm, in the aqueous and ethanolic extracts of these two aromatic plants. Further research is required to identify and isolate the active components responsible for their medicinal properties and ascertain their operation mode.

Antifungal Activity of 3-Hydrazinoquinoxaline-2-Thiol, a Novel Quinoxaline Derivative against Candida Species

Candida ranks as among the most frequently encountered fungal infections that associated with high morbidity and mortality. Quinoxaline derivatives are a group of small molecules that showed a promising antimicrobial activity. This study aimed to investigate the fungicidal effects of 3-hydrazinoquinoxaline-2-thiol against Candida in comparison with Amphotericin B in vitro as a reference. Also, we aim to assess the efficacy of 3-hydrazinoquinoxaline-2-thiol in vivo using mice oral candidiasis model. Fifty-six Candida isolates were subjected to susceptibility testing by broth microdilution method for 3-hydrazinoquinoxaline-2-thiol and Amphotericin B. Therefore, Minimal inhibitory concentrations (MIC) were assessed and compared. The oral candidiasis mice model was used to evaluate the activity of 3-hydrazinoquinoxaline-2-thiol in vivo. Microbiological evaluation of progression and ELISA were used in this study. 3-hydrazinoquinoxaline-2-thiol was more effective than Amphotericin B against most clinical isolates of Candida albicans. Higher effectiveness was seen against Candida glabrata and Candida parapsilosis isolates. However, the efficiency against Candida tropicalis isolates varies. 3-hydrazinoquinoxaline-2-thiol was also effective against Pichia kudriavzevii and Clavispora lusitaniae. 3-hydrazinoquinoxaline-2-thiol showed a good efficacy in mice model against C. albicans cells ATCC 10231. 3-hydrazinoquinoxaline-2-thiol has shown promising antifungal and anti-inflammatory activity against different Candida species. More tests and experiments are needed.

Solidago virgaurea L.: Chemical composition, antibacterial, and antileishmanial activity of essential oil from aerial part

Solidago virgaurea L. popularly called Goldenrod is a member of the Asteraceae family. S. virgaurea sample were obtained from Binsar, Almora (Indian state of Uttarakhand). The essential oil from the aerial part was distilled out using steam distillation, and GC and GC-MS were employed for analysis. A total of 27 constituents from aerial part were identified constituting 92.92% of total oil composition. The aerial parts of S. virgaurea were found to contain limonene (25.57%), α-humulene (12.19%), linalool oxide (8.65%), benzyl salicylate (6.40%), 1,4-cineole (6.22%) and humulene epoxide (II) (5.93%). The antibacterial activity of this essential oil was studied using disk diffusion and broth microdilution methods on five human pathogen bacteria and six plant pathogenic bacteria. There was moderate to good antibacterial activity in the oil sample extracted from the entire aerial portion of the plant. We did the antileishmanial activity of essential oils with Leishmania donovani (Dd8) promastigotes and intracellular amastigotes. EO was safer on the J774.A1 macrophages and lethal to promastigotes and intracellular amastigotes at different concentrations (10, 50, and 100 μg/ mL). These findings support the traditional uses of S. virgaurea and suggest its potential as a natural remedy for bacterial infections and leishmaniasis.

Abundance of Colistin-Resistance Genes in Retail Meats in Vietnam.

The degree of contamination of retail meat with colistin-resistant bacteria and its potential contribution to dissemination within communities remains to be determined. Thus, we aimed to elucidate the contamination status of colistin-resistance genes, indicative of colistin-resistant bacteria, in retail meats in Vietnam. In total, 46 chicken and 49 pork meats from stores in Vietnam and Japan were examined. Multiplex real-time polymerase chain reaction with TaqMan probes was performed for detecting mcr-1, mcr-3, and Escherichia coli 16S rRNA. Colistin-resistant bacteria in meats were isolated using selective media. The minimum inhibitory concentrations of colistin were determined using the broth microdilution method. The results showed that 70.7% of chicken meats in Vietnam were contaminated with both mcr-1 and mcr-3. Meanwhile, mcr-1 and mcr-3 were detected in 15.9% and 40.9% of pork meat, respectively. Only mcr-3 was detected in 40% of chicken in Japan. In addition, mcr-1-harboring E. coli and mcr-3-harboring Aeromonas were isolated from chicken meats in Vietnam. Some of these isolates showed colistin resistance. These results showed that most retail meats were highly contaminated with colistin-resistance genes. Notably, our results suggest that mcr-3 is more prevalent in the contaminated samples compared with mcr-1.

Antibacterial activity of Sarcocephalus latifolius and Acacia sieberiana, and the effect of their association with antibiotics against multidrug-resistant Staphylococcus aureus

Background: Infectious diseases continue to wreak havoc around the world causing directly or indirectly 17 million deaths per year. The present study was carried out to evaluate the in vitro antibacterial activity of the methanol extracts from the root of Sarcocephalus latifolius and from the leaves of Acacia siberiana, and their ability to potentiate the action of antibiotics against multidrug-resistant (MDR) Staphylococcus aureus. Methods: The antibacterial assays were performed using the broth microdilution method, and the extracts were screened for phytochemicals using standard qualitative methods. The effect of Sarcocephalus latifolius root extract on the functioning of H+/ATPases proton pumps of ATCC25923 Staphylococcus aureus was determined using a standard qualitative method. Results: The extracts of Sarcocephalus latifolius and Acacia siberiana had minimum inhibitory concentrations (MIC) ranging from 16 to 1024 µg/mL and 32 to 1024 µg/mL, respectively, with action spectra of 93.75% and 87.5% against the 16 strains of Staphylococcus aureus tested. The S. latifolius root extract contained alkaloids, phenols, and terpenoids as the main classes of secondary metabolites. In contrast, the A. siberiana leaf extract contained phenols and terpenoids as the major classes of secondary metabolites. The S. latifolius extract enhanced the activity of penicillin against 100% of the isolates tested. On the other hand, the A. siberiana extract enhanced the activity of Cefixime against 85.71% of the isolates tested with a 128-fold increase in activity. Conclusion: The results obtained in this study provide significant data that could potentially support the use of Sarcocephalus latifolius and Acacia siberiana in combating bacterial infections caused by multidrug-resistant Gram-positive Staphylococcus aureus.

Synthesis, characterization, and biological activity of novel 1,2,4-triazole moieties: Antileishmanial, antimicrobial effects, and molecular docking studies

In this study; new 1,2,4-triazole derivatives, (E)-4-(((3-methyl-5-oxo-1,5-dihydro-4H-1,2,4-triazol-4-yl)imino)methyl)phenyl 4-methoxybenzoate (3a), (E)-4-(((3-benzyl-5-oxo-1,5-dihydro-4H-1,2,4-triazol-4-yl)imino)methyl)phenyl 4-methoxybenzoate (3b) and (E)-4-(((3-(4-fluorobenzyl)-5-oxo-1,5-dihydro-4H-1,2,4-triazol-4-yl)imino)methyl)phenyl 4‑methoxy benzoate methoxy benzoate (3c) were synthesized and characterized by FTIR and NMR (1H- and 13C-) spectroscopic methods. Structural and spectral parameters were calculated by DFT/B3LYP/6–311++G(d,p) methods. The newly synthesized compounds 3a–3c were evaluated for their antimicrobial activities against eight pathogenic microorganisms. Standard commercial drugs ampicillin and fluconazole were used as references for bacteria and yeast, respectively. The leishmanicidal activity of three different synthesized compounds against Leishmania infantum promastigotes was investigated using the microdilution method. In addition, the study attempted to investigate the interactions crucial for the antileishmanial activity of compound 3b by molecular docking analysis targeting trypanothione reductase (TRe).

In vitro efficacy of combinations of antibiotics used in clinical practice on clinical isolates of Helicobacter pylori.

The main antibiotics used against Helicobacter pylori have been chosen empirically over time, with few preclinical studies to provide support. The rise in resistance to some of these antibiotics is prompting a reassessment of their use. This work aimed to evaluate the invitro efficacy of 2 × 2 combinations of the most widely used antibiotics against H. pylori. J99 reference strains and 19 clinical isolates of H. pylori with various antibiotic resistance phenotypes were used. Minimum inhibitory concentrations were carried out using the microdilution method in 96-well plates. The activity of 15 possible combinations of two antibiotics including amoxicillin, clarithromycin (CLA), levofloxacin, rifampicin, tetracycline, and metronidazole was determined for all strains by the checkerboard method. A mean fractional inhibitory concentration index (FICmean) was calculated for each combination and strain and the type of pharmacodynamic interaction was considered as synergic if FICmean ≤ 0.5, additive if 0.5 < FICmean ≤ 1, indifferent if 1 < FICmean < 4 or antagonistic if FICmean ≥ 4. Most of the 285 pharmacodynamic interactions tested with clinical strains were close to additivity (average FICmean = 0.89 [0.38-1.28]). No interaction was found to be antagonistic. When two antibiotics to which a strain was resistant were combined, the concentrations required to inhibit bacterial growth were higher than their respective breakpoints. The present results have shown that invitro, the different antibiotics used in therapeutics have additive effects. The addition of the effects of two antibiotics to which a strain was resistant was not sufficient to inhibit bacterial growth. In probabilistic treatment, the choice of antibiotics to combine should therefore be based on the local epidemiology of resistance, and on susceptibility testing in the case of CLA therapy, so that at least one antibiotic to which the strain is susceptible is used.