Minimum Inhibitory Concentration Research Articles

Emilia sonchifolia (L.) DC. inhibits the growth of Methicillin-Resistant Staphylococcus epidermidis by modulating its physiology through multiple mechanisms

Bloodstream infections (BSIs) are a public health concern, causing substantial morbidity and mortality. Staphylococcus epidermidis (S. epidermidis) is a leading cause BSIs. Antibiotics targeting S. epidermidis have been the mainstay of treatment for BSIs, however their efficacy is diminishing in combating with drug-resistant bacteria. Therefore, alternative treatments for antibiotic-resistant infections are urgently required. Studies have demonstrated that certain traditional Chinese medicine (TCM) exhibit notable antimicrobial activity and can help mitigate bacterial resistance. Among these, The ethanol extract of Emilia sonchifolia (L.) DC (E. sonchifolia) (10 g crude drug/1 g extract ) exhibits a noteworthy anti-methicillin-resistant S. epidermidis (MRSE) effect. This study explores antibacterial activity and underlying mechanisms of E. sonchifolia against MRSE. The antibacterial activity of E. sonchifolia against MRSE was assessed in vitro by measuring the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The MRSE-induced mouse BSIs model was used to evaluate the antibacterial activity of E. sonchifolia in vivo. Proteomic and transcriptomic analyses were performed to elucidate the underlying antibacterial mechanisms. The MIC and MBC values of E. sonchifolia against MRSE were 5 mg/mL and 20 mg/mL, respectively. In vivo, E. sonchifolia effectively treated MRSE-induced BSIs. Additionally, proteomic and transcriptomic analyses revealed considerable down-regulation of purine metabolism, that were associated with oxidative stress and cell wall synthesis. The enzyme linked immunosorbent assay(ELISA) results showed decreased levels of inosine monophosphate (IMP), Adenosine monophosphate(AMP) and guanine monophosphate (GMP), indicating inhibited purine metabolism. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis confirmed bacterial cell wall damage. E. sonchifolia exerts antibacterial effects by inhibiting purine metabolism, promoting bacterial oxidative stress, and impairing cell wall synthesis. These findings provide novel insights into the mechanistic understanding of E. sonchifolia's efficacy against MRSE, offering potential strategies for managing MRSE infections.

Construction and Characterization of Polyethylene Glycol/Sodium Alginate Hydrogel Loaded With Zirconia Nanoparticles: Potential Antibacterial and Antibiofilm Agent to Inhibit Dental Caries InVitro and InVivo.

Biofilm formation on tooth surfaces is a primary contributor to dental caries and periodontal diseases. Streptococcus mutans is recognized for its role in biofilm production, significantly influencing the development of dental caries. Key virulence factors associated with S. mutans biofilms include acid production, acid tolerance, and the synthesis of exopolysaccharides (EPS). This study presents a novel approach by focusing on the loading of biosynthesized zirconia nanoparticles (ZrO2 NPs) onto polyethylene glycol/sodium alginate (PEG/SA) hydrogel nanocomposite, evaluating their effects on the biofilm-forming ability of S. mutans both invivo and invitro. ZrO2 NPs were biosynthesized using Citrus aurantifolia (C. aurantifolia) extract and incorporated into the PEG/SA hydrogel beads through a sol-gel process. The formation of ZrO2 NPs and the PEG/SA/ZrO2 NPs hydrogel nanocomposite was confirmed through diverse analyzes, including UV-visible spectroscopy, particle size measurement, morphology examination, spectral analysis, thermal gravimetric analysis (TGA) and hemolysis studies. The average particle size of the ZrO2 NPs was approximately 26 nm, while the PEG/SA/ZrO2 NPs hydrogel beads exhibited a highly porous, sheet-like surface structure. Invitro results demonstrated inhibition zones of 30 and 28 mm for ZrO2 NPs and PEG/SA/ZrO2 NPs hydrogel beads against S. mutans, respectively, with a minimum inhibitory concentration (MIC) of 12.5 mg/mL. The growth curve analysis indicated a complete decline in S. mutans growth with an 87% reduction in biofilm formation when treated with PEG/SA/ZrO2 NPs hydrogel beads. SEM analysis revealed that S. mutans cells appeared lysed or crumpled, losing their characteristic coccal shape after exposure to the hydrogel beads. Additionally, SEM images confirmed the effective prevention of S. mutans attachment to teeth when encapsulated with PEG/SA/ZrO2 NPs hydrogel, altering the morphology of mature biofilms that developed on the teeth after treatment. Finally, the incorporation of biosynthesized ZrO2 NPs into PEG/SA hydrogels demonstrates significant potential as an effective strategy for inhibiting S. mutans biofilm formation and may serve as a promising topical agent for reducing dental caries. Further studies could explore the long-term efficacy and potential clinical applications of this nanocomposite in oral health care.

Comparative efficacy of eravacycline and tigecycline in addressing multidrug-resistant Gram-negative bacteria

The rise in antibiotic resistance among Gram-negative bacteria poses significant challenges to global health. This study evaluates the in vitro efficacy of tigecycline, omadacycline, and eravacycline against clinical isolates harboring the mobile tigecycline resistance genes tet(X4) and tet(A). A total of 175 clinical strains collected between 1999 and 2023 were analyzed. Resistance genes, including tet(X4) and tet(A), were determined using Polymerase chain reaction (PCR). Minimum inhibitory concentrations (MICs) were determined using the broth microdilution method. Eravacycline exhibited significantly lower MIC values than those of tigecycline for Escherichia coli carrying tet(X4) (P < 0.0001), despite similar resistance rates. Omadacycline consistently displayed the highest MIC values, indicating reduced potency. In contrast, Klebsiella pneumoniae carrying tet(A) showed higher MIC values for eravacycline than tigecycline. Universal resistance was observed in Enterobacter cloacae carrying tet(A). Eravacycline demonstrated superior in vitro efficacy, particularly against E. coli carrying tet(X4), underscoring its potential as a therapeutic option for multidrug-resistant infections. MIC values should complement resistance rates in clinical decision-making, and further studies are warranted to validate eravacycline’s clinical utility.

The combinational effect of avian IgY antibodies and broad-spectrum antibiotics (ciprofloxacin and chloramphenicol) in vitro reduces the incidence of Aeromonas hydrophila

ABSTRACT The frequent use of antibiotics in aquaculture to control bacterial diseases has led to the accumulation of antibiotic residues in the environment and biomagnification across various food chain trophic levels. This study examines the sustainable application of IgY antibodies to manage Aeromonas hydrophila infections. Formaldehyde-killed A. hydrophila were intramuscularly immunized in 22- to 24-week-old White Leghorn (Gallus gallus domesticus) chickens for the production of IgY antibodies. The purified egg yolk antibodies were analyzed, and a concentration of 11.88 mg/ml was found, with a specific protein concentration of 24%. High titers were observed using indirect enzyme-linked immunosorbent assay (ELISA) at dilutions greater than 1:10,000, demonstrating the efficacy of the IgY antibodies. The results confirmed that IgY remains stable under various conditions, including pH values ranging from 3 to 10, temperatures from freezing up to 70°C, molarity up to 50 mM using phosphate buffered saline, and solvent systems up to 30%. Using the serial dilution method, the minimum inhibitory concentrations (MICs) of IgY, ciprofloxacin, and chloramphenicol were 12.5 µg/ml, 0.77 µg/ml, and 3.1 µg/ml, respectively. The checkerboard method demonstrated synergistic effects between IgY and the antibiotics, with fractional inhibitory concentration (FIC) indices of 0.24 for ciprofloxacin and 0.37 for chloramphenicol. Combining IgY antibodies with these antibiotics shows synergism, significantly reducing the excessive use of antibiotics in fish farms and offering a sustainable solution to bacterial infections in aquaculture.

Synthesis, characterization and in silico studies of novel multifunctional imidazole-thiazole hybrids with potent antimicrobial and anticancer properties

Treating infections remains a significant challenge, driving the ongoing pursuit of novel drug candidates. Heterocyclic compounds, such as those containing imidazole and thiazole rings, are well-known for their diverse therapeutic and pharmaceutical applications. In this study, we designed, synthesized, and characterized a series of six novel compounds incorporating these two five-membered rings. The synthesis involved the reaction of different phenacyl bromides with imidazole-hydrazinecarbothioamide to produce imidazole-thiazole hybrid derivatives, which were confirmed through IR, 1H NMR, 13C NMR, and mass spectrometry analyses. The antimicrobial activities of the derivatives were evaluated against three bacterial strains and one fungal strain using the serial dilution method, with their minimum inhibitory concentrations (MICs) determined. Notably, all the derivatives exhibited moderate antimicrobial activity. Cytotoxicity assessment revealed that derivative 5a was particularly excellent, displaying significant inhibition with an IC50 value of 33.52 μM. Furthermore, molecular docking, ADME, and molecular dynamics simulations were conducted, focusing on the interaction between derivative 5a and the protein (PDB ID: 6LUD) to elucidate the stability of the interaction.

D-alanylation of lipoteichoic acids inhibitor provides anti-virulence and anti-resistance effects against methicillin-resistant Staphylococcus epidermidis.

Methicillin-resistant Staphylococcus epidermidis (MRSE) is an emerging multidrug-resistant pathogen responsible for numerous healthcare-associated infections. Most of them are resistant to all classes of antibiotics and thus lead to therapeutic impasse. For this reason, identifying new targets and characterizing new drugs are essential. We recently showed that methicillin-resistant Staphylococcus aureus strains deficient in D-alanylation of teichoic acids (TAs) lost resistance to various β-lactams. Here we explore if D-alanylation of TAs might be a druggable target to overcome β-lactam resistance of MRSE using a competitive DltA inhibitor. The binding affinity of a DltA inhibitor with the purified DltA protein was monitored by determining the half maximal inhibitory concentration (IC50). The efficiency of D-alanylation inhibition was determined by quantifying the ester-linked D-alanine content of purified TAs. Minimal inhibition concentrations (MICs) and bactericidal effects of several β-lactams were monitored in the absence or presence of the inhibitor against a panel of clinical MRSE isolates. Finally, the ability of inhibition of D-alanylation (i) to rescue MRSE-infected larvae of Galleria mellonella and (ii) to prevent or eradicate S. epidermidis biofilms was evaluated. The DltA inhibitor showed IC50 in the low µM range, drastically reduced the D-alanine esters content of TAs and re-sensitized MRSE to β-lactams. The most effective treatment was the DltA inhibitor/imipenem combination. Finally, inhibition of D-alanylation significantly reduced the virulence of MRSE in the G. mellonella infection model and strongly reduced the ability of S. epidermidis to form biofilms. All together, our results show the promising nature of the D-alanylation of TAs as a therapeutic target to fight against MRSE infections.

Identification of a novel aminoglycoside nucleotidyltransferase gene in Morganella morganii from farm sewage

BackgroundAminoglycosides are important broad-spectrum antimicrobial agents. When combined with β-lactam drugs, these agents can be used to treat severe infections such as those causing sepsis. Identifying additional resistance mechanisms will guarantee the successful application of aminoglycoside agents in clinical practice.MethodsThe isolate Morganella morganii A19 was obtained from a sewage sample from an animal farm by means of agar plate streaking. The agar dilution method was used to determine the minimum inhibitory concentrations (MICs) of the antimicrobial agents. Cloning of the predicted resistance gene was conducted, and its resistance function was assessed through MIC testing. The protein was expressed in E. coli, and the kinetic parameters were quantified. The analysis of novel resistance gene-related sequences, including their structures and evolutionary relationships, was performed using bioinformatic tools.ResultsIn Morganella morganii A19, a newly discovered chromosome-encoded aminoglycoside resistance gene named aadA37 was identified and characterized. The protein AadA37 exhibited the highest amino acid identity (57.14%) with the functionally characterized aminoglycoside adenylyltransferase AadA33. aadA37 confers resistance to spectinomycin, streptomycin and ribostamycin, and enzyme kinetic analysis also demonstrated that it had adenosine transfer activities against spectinomycin and streptomycin, with kcat/Km values of 0.66 × 103 M− 1 s− 1 and 1.63 × 103 M− 1 s− 1, respectively. The aadA37 gene and its homologs were not related to any mobile genetic element (MGE), and they were all found to be encoded on the chromosomes of the M. morganii strains.ConclusionA novel aminoglycoside resistance gene was identified from an environmental bacterium and characterized in this work. Identifying new resistance mechanisms will aid in the effective clinical use of antimicrobial agents for treating infectious diseases caused by pathogens harboring the same resistance genes.

Repurposing of Chinese Medicine Extract against Staphylococcus Aureus: Assessing the Antibacterial and Anti-Transfer Activity of Plasmid in Drug-Resistant Bacteria.

Staphylococcus aureus is one of the most frequent human infections, which triggers various infectious diseases like soft tissue infection, lethal pneumonia, endocarditis, and bacteremia. The most common pathogen responsible for simple cystitis is E.coli; however, it also causes pneumonia, bacteremia, and abdominal infections, such as spontaneous bacterial peritonitis. Chinese medicines have been used effectively in the treatment of infectious disorders; thus, this study aimed to investigate the efficiency of Chinese medicine against S. aureus. An extract of traditional Chinese medicine was prepared using nine compounds: tongcao, talc, red peony root, fennel, guangui, lychee core, dry sunflower, dianthus, and purslane, to evaluate its antibacterial activity against Staphylococcus aureus RN450RF. The minimum inhibitory concentration (MIC) of the Chinese medicine measured by the consecutive double dilution technique was 200g/L. The drug-resistant plasmid was transferred equally well under controlled laboratory conditions with a median conjugation frequency of 1.1x106. The maximum activity of conjugated transfer of resistant drug plasmid of E. coli CP9 (R45) was observed at 2/1 MIC (100 g/L drug concentration), 32h time interval, with a bacterial concentration 108 CFU/ml. These results suggest that the secondary inhibitory concentration (1/2 MIC) of the Chinese medicine solution can promote the combination and transfer of the resistance plasmid of Chinese medicine (R45) between different strains. The drug concentration, binding time, and initial bacterial concentration have different degrees of positive promotion effects on the conjugation and transfer of drug-resistant plasmids. Traditional Chinese medicine might be a potentially huge disease management and infection control resource.

Antifungal resistance in yeasts from One Health perspective: A Brazilian study.

Antifungal resistance in yeasts from One Health perspective: A Brazilian study.

Detection of morphological variants of colistin-resistant Klebsiella pneumoniae associated with sepsis in Kerala, India.

Infections caused by colistin resistant Klebsiella pneumoniae are a major global health challenge linked to high mortality rates worldwide. Increased incidence of hypervirulent and drug-resistant Klebsiella causing life-threatening infections in young healthy individuals and asymptomatic carriage in the community has been largely reported in the Asian-Pacific Rim. This study conducted a molecular analysis of two morphologically distinct variants of K. pneumoniae that caused bacteremia and sepsis in a patient. Colony morphology of the isolates was characterized in various growth media, and the morphological variants differed in their mucoviscosity. The isolates were found to be serotype K2 (highly associated with hypervirulent Klebsiella) by molecular serotyping using specific PCR primers. The multidrug-resistant nature of the colony variants was evaluated by antibiotic susceptibility testing and it was found to have a similar antibiogram pattern in in vitro. An increased minimum inhibitory concentration (MIC) of colistin (>64 μg mL-1) was detected in both isolates using broth microdilution, and they were found to be highly resistant to colistin. Molecular analysis revealed that the isolates possessed a chromosomal mutation in mgrB, which causes colistin resistance. The increased incidence of infection caused by colistin-resistant K. pneumoniae requires continuous monitoring, and appropriate measures are necessary to control its adaptive evolution in healthcare settings.

Exploring the antibacterial efficacy of Opuntia monacantha in combatting methicillin-resistant Staphylococcus aureus

Public health is seriously threatened by the rise of antibiotic-resistant strains of bacteria, especially methicillin resistant Staphylococcus aureus (MRSA). This study investigated the phytochemical compounds, and possible antibacterial effects of a methanolic extract of the cactus species Opuntia monacantha Haw. against MRSA. The powdered substance was extracted with methanol and filtered, and the filtrate was partitioned with n-hexane, chloroform and ethyl acetate. The fractions with higher percentage yields such as the n-hexane and chloroform fractions went through GC-MS analysis. They consist of various compounds that are known to have strong antioxidant and antimicrobial activities. The antimicrobial activity of the plant was measured via a diffusion assay. On the basis of these results, the Opuntia monacantha crude methanolic extract, and the n-hexane and chloroform fractions significantly inhibited all the MRSA strains used in the test at 100, 75 and 50 mg/mL. Furthermore, the minimum inhibitory concentrations of various fractions of the methanolic extract of Opuntia monacantha were also examined. Therefore, Opuntia could be a promising candidate for strengthening the existing formulations in pharmaceutical science for the treatment of MRSA. However, additional research is necessary before its therapeutic use is recommended. The results are intended to provide important new information for the creation of sustainable and alternative antimicrobial agents.

Antimicrobial Resistance and Mortality in Carbapenem-Resistant Pseudomonas aeruginosa Infections in Southern Thailand

Background/Objectives: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) is an important pathogen associated with high mortality and treatment failure rates. We aimed to assess the susceptibility of CRPA to antipseudomonal agents, identify its resistance mechanisms, and evaluate clinical outcomes in a sample of CRPA isolates. Methods: This was an in vitro study of a clinical isolate of CRPA from hospitalized patients with CRPA infection and a retrospective observational study of these patients, who were diagnosed between 14 February 2021 and 10 August 2023 at Songklanagarind Hospital in Songkhla, Thailand. In vitro experiments were conducted to determine the minimum inhibitory concentrations (MICs) of the antipseudomonal agents using the broth microdilution method. Resistance mechanisms were assessed using the modified carbapenem inactivation method, combined disk tests, and quantitative real-time reverse transcription polymerase chain reaction. Results: A total of 140 CRPA isolates were analyzed. Both traditional and novel β-lactams had high MICs. The most common resistance mechanism was the upregulation of the MexAB-OprM efflux pump (81.3%), followed by the downregulation of the OprD porin (48.9%) and metallo-β-lactamase (MBL) production (45.0%), and the overexpression of blaAmpC (41.0%). The 30-day all-cause mortality rate was 30.5%. The risk factors associated with 30-day mortality included a Charlson Comorbidity Index of ≥5 (OR: 3.43; 95% CI: 1.07–10.99; p = 0.03), sepsis (OR: 10.62; 95% CI: 1.26–89.44; p = 0.03), and septic shock (OR: 4.39; 95% CI: 1.67–11.55; p &lt; 0.01). In contrast, receiving active documented therapy was significantly associated with reduced mortality (OR: 0.17; 95% CI: 0.04–0.74; p = 0.01). Conclusions: This study revealed higher MIC values of all β-lactams for CRPA, while colistin and amikacin remained effective. The resistance mechanisms included MexAB-OprM overexpression, OprD downregulation, MBL production, and blaAmpC overexpression, with a higher prevalence of MBL than in other regions of Thailand. High 30-day mortality was associated with comorbidities, sepsis, and septic shock, but active therapy reduced mortality.

TROJAN-MDR: in vitro activity of cefiderocol and comparators against multidrug-resistant Enterobacterales and Pseudomonas aeruginosa strains in Southern France, evaluation of available testing methods performances

Background Cefiderocol, a newly introduced siderophore cephalosporin, exhibits activity against various multidrug-resistant (MDR) Gram-negative bacilli (GNB), including producers of Ambler class A, B and D carbapenemases. The TROJAN-MDR study aimed to (i) compare the in vitro activity of cefiderocol with other last-resort antibiotics against a well-characterized collection of Enterobacterales and Pseudomonas aeruginosa strains from Southern France, and (ii) assess the performance of available cefiderocol antimicrobial susceptibility testing (AST) methods.MethodsThe collection comprised 127 Enterobacterales from various clones, including 119 carbapenemase producers (93.7%), and 53 MDR P. aeruginosa. The minimum inhibitory concentrations (MICs) of cefiderocol were determined using the UMIC® broth microdilution method (BMD) as the reference. Comparators MICs were measured using Sensititre™ EUMDRXXF plates and Liofilchem strips for aztreonam-avibactam. Results were interpreted according to EUCAST breakpoints, with CLSI breakpoints also used for cefiderocol. The performance of the ComASP® BMD and disk diffusion on two different Mueller–Hinton media (Bio-Rad and BD) were evaluated according to ISO 20776-2:2007 and 2021.ResultsCefiderocol demonstrated potent activity on Enterobacterales (81.9% susceptible) and P. aeruginosa (84.9%) using EUCAST breakpoints. Among Enterobacterales, the most effective comparators were colistin, aztreonam-avibactam, meropenem-vaborbactam, and amikacin, with susceptibility rates of 99.2%, 98.4%, 85%, and 76.4%, respectively. For P. aeruginosa, only colistin exhibited better activity (100%). The disk diffusion method showed superior performance on BD medium compared to Bio-Rad. The ComASP® method did not provide sufficient performance to be considered reliable.ConclusionsCefiderocol was highly active against a large collection of MDR GNB, including high-risk clones. It is crucial to assess susceptibility to this last-resort antibiotic using a validated method when considering clinical use.

South African Propolis: Anti-Helicobacter pylori Activity, Chemistry, and Toxicity.

Propolis, a resin-like substance produced by bees, has previously shown antimicrobial activity against the ulcer-causing gut pathogen, Helicobacter pylori. South African propolis, however, was yet to be investigated. This study aimed to investigate a comprehensive range of South African propolis for its antimicrobial activity against H. pylori and to investigate toxicity. A total of 51 samples were collected from around South Africa, and comparatively analysed with three Brazilian samples. The antimicrobial broth microdilution assay was used to determine the minimum inhibitory concentration (MIC) of ethanolic propolis extracts against three clinical H. pylori strains. A total of 27 South African propolis extracts presented antimicrobial activity better than that of the Brazilian samples (MIC ≤ 0.51 mg/mL). Samples with the best anti-H. pylori activity were selected for chemical analysis using ultra performance liquid chromatography-mass spectrometry. The compounds pinocembrin, 3-O-acetylpinobanksin, and pinobanksin were found to be most abundant. All propolis extracts investigated in this study were considered non-toxic (mortality < 50%) when investigated using the brine shrimp lethality assay. This study demonstrates the in vitro potential of utilizing propolis for treating H. pylori infections and highlights the possible compounds responsible for the activity observed.

Characterization, antifungal activity and possible action mechanism of Melissa officinalis essential oil against Candida spp. and Cryptococcus neoformans strains.

This study aimed to characterize Melissa officinalis essential oil (EOMO) from a region in Northeast Brazil and evaluate its antifungal activity against Candida and Cryptococcus neoformans, by analyzing its action mechanism. EOMO was characterized using gas chromatography-mass spectrometry and the main chemical compounds were Geranial (14.10%) and (Z)-Nerolidol (17.75%). The broth microdilution assay was used to determine the minimum inhibitory concentration (MIC) against strains of Candida albicans, Candida parapsilosis, Candida krusei, Candida auris (MIC raging from 256 to 26.7 µg ml-1) and C. neoformans (MIC ranging from 64 to 32 µg ml-1). Flow cytometry and comet assays were employed to investigate EOMO's mechanism of action, which might be related to an increase in the production of reactive oxygen species and damage to fungal DNA. The chemical composition of EOMO from Northeast Brazil showed a higher content of (Z)-Nerolidol and has significant antifungal potential.

Comparison of antimicrobial susceptibility of Glaesserella parasuis from different pig production systems in Taiwan between 2015 and 2020

BackgroundGlässer’s disease, caused by Glaesserella parasuis (G. parasuis), is a widespread bacterial infection in swine that leads to significant economic losses. G. parasuis, a member of the normal microbiota within the Pasteurellaceae family, exhibits horizontal resistance gene exchange and intracellular invasion capabilities, increasing the risk of developing resistant isolates. Accurate antimicrobial therapy is essential for controlling Glässer’s disease. The production systems for exotic crossbred pigs and Taiwan black pigs differ considerably. To inform Glässer disease control and monitor antimicrobial resistance, we assessed the antimicrobial susceptibilities of G. parasuis isolates, analyzed them using normalized resistance interpretation (NRI), and compared findings between the two production systems.ResultsA total of 154 G. parasuis isolates from 106 exotic crossbred pig herds and 48 Taiwan black pig herds were tested against 16 antimicrobial agents between 2015 and 2020. Due to the absence of specific breakpoints for G. parasuis, NRI was utilized to define non-wild-type (non-WT) populations based on minimum inhibitory concentration (MIC) distributions. Non-WT subpopulations of isolates for amoxicillin, ampicillin, ceftiofur, gentamicin, kanamycin, and tiamulin were observed. The highest MIC90 (the concentration at which 90% of isolates were inhibited) was > 256 µg/mL for several antimicrobials, including gentamicin, kanamycin, lincomycin, lincospectin, spectinomycin, and tylosin. In contrast, the lowest MIC90 was observed for ceftiofur (0.5 µg/mL). The MIC values for cephalothin were significantly higher in exotic crossbred pigs than in Taiwan black pigs (p = 0.0016). Conversely, MIC values for florfenicol were significantly higher in Taiwan black pigs than in exotic crossbred pigs (p = 0.003).ConclusionsThis study provides the susceptibility profile of G. parasuis isolates for both exotic crossbred pigs and Taiwan black pigs in Taiwan and highlights potential antimicrobial resistance for aminocyclitol, aminoglycosides, beta-lactams, lincosamides, macrolides, and pleuromulin. Ceftiofur, cephalothin, doxycycline, and florfenicol could be most suitable for treating early-stage Glässer’s disease. Nonetheless, increased attention should be paid to the responsible use of antimicrobials in light of the growing threat of antimicrobial resistance.

A Novel Benzopyrone Derivative from Streptomyces chrestomyceticus ADP4 Inhibits Growth and Virulence Factors of Candida albicans.

Antimicrobial resistance (AMR) poses a serious threat to human health globally. Expeditious discovery and development of new drugs has become indispensable for addressing this challenge. In this context, a novel benzopyrone derivative, designated as 82B1, has been isolated from S. chrestomyceticus strain ADP4. This compound exhibited significant inhibitory activity against different Candida species including C. albicans, C. tropicalis, C. krusei, C. parapsilosis and C. auris with minimum inhibitory concentration (MIC90) values in the concentration range of 25-125µg/mL. The structure of 82B1 was elucidated through analyses of the spectral data obtained using liquid chromatography-tandem mass spectrometry (LCMS/MS), Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FTIR) and Ultraviolet (UV) spectroscopy, that led to its identity as 7, 13, 14-trihydroxy-6H-benzo-[c]-chromen-6-one8-[1'β-carboxycyclopentanyl]-2'β-[8'β-ethylcyclopentane]. It significantly inhibited the major virulence factors of C. albicans such as yeast to hyphae transition, biofilm formation, and secretion of hydrolytic enzymes at its subinhibitory concentrations. It did not display cytotoxicity on human hepatoblastoma cell line (HepG2 cells), signifying its potential as a candidate for anti-Candida drug development.

Biogenic mediated synthesis, characterization, antimicrobial and radical scavenging studies of iron oxide nanoparticles (Fe3O4-NPs) using Eichhornia crassipes leaves extract

The plant Eichhornia crassipes (commonly known as water hyacinth) was obtained from Lake Geriyo, Yola, Adamawa State, Nigeria. The sampled leaves were gently washed with deionized (DI) water and air-dried at room temperature (25–30 °C). Iron nanoparticles were synthesized using Eichhornia crassipes (water hyacinth extract) and characterized using XRD, SEM, TEM, SEM-EDX, and FTIR. The antioxidant activity of the iron nanoparticles was analyzed using DPPH scavenging activity. The plant extracts and iron nanoparticles were tested for antibacterial efficiency against Escherichia coli, Staphylococcus aureus, Streptococcus pneumoniae, Salmonella typhi, and Klebsiella pneumoniae. The results revealed the proximate composition of the water hyacinth plant, including moisture content, ash content, fiber, fat content, protein, and carbohydrates. The proximate composition followed the order: carbohydrates &gt; lipids &gt; fiber &gt; moisture &gt; protein &gt; ash content. Qualitative phytochemical screening of the leaf revealed the presence of carbohydrates, terpenoids, phenolics, and saponins, while amino acids, terpenes, alkaloids, steroids, and flavonoids were absent. SEM-EDX, TEM, XRD, and FTIR confirmed the formation of iron nanoparticles. The iron nanoparticles exhibited higher percentage inhibition with varied concentrations of 25% FeNPs, 50/50 FeNPs, and 25/75 FeNPs, with 25/75 FeNPs showing significant scavenging activity of 24%, 39%, 47%, 55%, and 73% at 10, 20, 30, 40, and 50 µl/ml, respectively. The minimum inhibitory concentration (MIC) of 25% FeNPs for Klebsiella pneumoniae and Staphylococcus aureus showed that the extract had a higher inhibitory effect on Klebsiella pneumoniae compared to Staphylococcus aureus. The inhibition sequence showed similar inhibition for all pathogens except Salmonella typhi and Klebsiella pneumoniae, which exhibited the least inhibition among all FeNP concentrations. An increase in material concentration resulted in higher inhibition for four organisms, while Klebsiella pneumoniae showed a different trend, with the highest inhibition observed at a 200 µg/L concentration.

Friedelin: A natural compound exhibited potent antibacterial, anti-inflammatory, and wound healing properties against MRSA-infected wounds.

Methicillin-resistant Staphylococcus aureus (MRSA) is primarily recognized as a pathogen responsible for skin, soft tissue, and multiple organs infection. The colonization of the skin and mucous membranes by hypervirulent resistant bacteria like MRSA during hospitalization significantly contributes to life-threatening conditions. Friedelin (FRN) is a pentacyclic triterpene (C30H50O) isolated from Euphorbia grantii Oliv. The current work aims to determine the efficacy of FRN against MRSA-infected wounds in mice besides the in vitro study to evaluate its bactericidal activity. The in vitro study revealed that FRNwas strongly active against MRSA which had a wide zone of MRSA growth inhibition and promising minimum inhibitory concentration (MIC). Moreover, FRN downregulated the major virulence genes seb and icaD, responsible for the production of staphylococcal enterotoxin SED and biofilm formation, respectively in contrast to the untreated group. The dressing of MRSA-infected wound with 40 ppm FRN significantly reduced the wound size and bacterial count and accelerated the process of wound healing which had a higher immune expression of both VEGF (vascular endothelial growth factor) and α-SMA (alpha smooth muscle actin) compared with other treated groups. Additionally, FRN could reduce the inflammatory response of MRSA in a dose-dependent manner by downregulating the TNF-α (tumor necrosis factor-α) and PGS-2 (prostaglandin synthase-2) gene expression levels. FRN is effective against MRSA-infected wounds via its potent bactericidal and anti-inflammatory activities that accelerate angiogenesis and wound maturation.

Synthesis and Evaluating the Anticandidal Activities of Triazino[4,3-a]quinolinecarboxylate Derivatives: A Promising Approach to Combat Candida Infections.

Novel triazino[4,3-a]quinolinecarboxylate compounds (4, 6, 8 and 10) were synthesized and investigated for their antifungal activity against Candida species. Compound 8 was a standout candidate which displayed impressive anticandidal activity against various Candida species with low minimum inhibitory concentrations (MIC = 32-45 µg/ml) compared to the reference drug Miconazole (MIC = 50-60 µg/ml). Furthermore, the induced both morphological and ultra-structural changes by compound 8 on Candida cells are analyzed by light and transmission electron microscopy (L/TEM). Significant alterations in the viability and the architecture of Candida cells highlight the potential of compound 8 as a lead for further use as antifungal drug. Molecular docking study of the most active compounds 8 and 10 was conducted inside 14α-demethylase (CYP51) to predict binding mode of these compounds as antifungal.