Minimum Inhibitory Concentration Research Articles

Effects of Temperature on Resistance to Streptomycin in Xanthomonas arboricola pv. pruni

<i>Xanthomonas arboricola</i> pv. <i>pruni</i> (<i>Xap</i>) causes the shot hole disease of stone fruits and almonds. This bacterium is a damaging, widespread pathogen distributed across the major stone fruit producing regions of the world. To control shot hole disease, antibiotics such as streptomycin are mainly used. However, as concerns about antibiotic resistance increase, many restrictions are placed on the use of antibiotics. Additionally, it has been reported that the rise in temperature due to climate change affects disease occurrence and ecology. Therefore, in this study, we determined the minimum inhibitory concentration (MIC) of streptomycin for <i>Xap</i> at an optimal growth temperature of 28°C and investigated the changes in MIC and the occurrence frequency of resistant bacteria at 10°C, 25°C and 30°C. The results of this study showed that the MIC was 30 µg/ml at 28°C. In addition, when the change in streptomycin resistance concentration due to temperature was confirmed, we found that the resistance concentration decreased to 10 µg/ml at 30°C. When the occurrence of resistance according to concentration and temperature conditions was investigated, the occurrence frequency of resistant strains was found to be the highest at 50 µg/ml. In the case of temperature, the occurrence frequency of resistant strains was confirmed to be high at 30°C. These results provide basic data for further reducing the problem of antibiotic resistance by suggesting the possibility of changes in the occurrence of streptomycin-resistant strains depending on the antibiotic treatment environment.

Evaluation of antibiotic purchase data for ceftiofur and enrofloxacin and minimum inhibitory concentrations among Escherichia coli isolates from swine farms in the Midwestern United States using multiple statistical models.

Antimicrobial resistance is considered a global One Health threat. Controlling selection pressure by reducing antibiotic use in livestock is a significant component of the response to this threat. The science concerning use and resistance is complicated and affected by time from antibiotic exposure, changing bacterial fitness, and varies by drug and pathogen. From May 2020 through October 2023, we collected intestinal (substandard and sick pigs) and fecal swab (healthy pig) samples at breed-to-wean (BTW) and wean-to-market (WTM) swine production sites and isolated E. coli bacteria. Antibiotic susceptibility testing was performed on these isolates to determine minimum inhibitory concentrations (MIC) for ceftiofur and enrofloxacin. Monthly antibiotic purchase data were used to calculate the active milligrams of drug purchased and these were divided by the kilograms of pigs produced from a farm site to provide a mass-adjusted proxy metric for farm-level antibiotic use. The relationship between use and MIC was then evaluated using a variety of multivariable statistical models. Across multiple modeling approaches, both farm type (i.e., BTW versus WTM) and farm-level antibiotic use maintained statistically significant relationships relative to E. coli MIC values for each respective drug. Use of ceftiofur and enrofloxacin can lead to increased MIC values among E. coli over time. The reasons for antibiotic purchases were not tracked as part of this project. Future work should evaluate the age of the individual pig and the time from last treatment when sampling these animals to separate out the group from individual-level effects of antibiotic use.

Isolation and characterization of a broad-spectrum bacteriophage against multi-drug resistant Escherichia coli from waterfowl field.

Escherichia coli (E. coli) is a significant pathogen responsible for intestinal infections and foodborne diseases. The rise of antibiotic resistance poses a significant challenge to global public health. Traditional antibiotic therapy is becoming increasingly ineffective, highlighting the urgent need for innovative control strategies. This study explores the potential of bacteriophages as a sustainable alternative to traditional antibiotics. From 2021 to 2022, a total of 183 non-repetitive duck source fecal samples were collected from Mianyang City, Sichuan Province, and 126 strains of E. coli were isolated. The minimum inhibitory concentration (MIC) test showed that these strains exhibited high resistance to piperacillin (96.8%), tetracycline (88.9%), and chloramphenicol (86.5%). It is concerning that 93.7% of the isolates are classified as multidrug-resistant (MDR), posing a significant threat to existing treatment options. 20 bacteriophages were isolated from fecal and soil samples, among which 5 bacteriophages were selected for further analysis. Bacteriophage YP6 showed excellent lytic effects on MDR strains, especially strain MY104, as well as representative serotypes O1 (E. coli MY51) and O18 (E. coli MY106). The identification of YP6 as a member of the Myoviridae family was conducted using transmission electron microscopy, and it was found to have an optimal infection factor of 0.1. Bacteriophages exhibit significant thermal and pH stability, maintaining survival at temperatures up to 60 °C and pH ranges of 4 to 10. Whole genome sequencing confirmed that YP6 has a double stranded DNA genome of 139,323 base pairs (bp), and no antibiotic resistance or virulence genes were found, indicating a low possibility of horizontal gene transfer. In addition, YP6 effectively inhibits the formation of E. coli biofilm, which is a key factor in chronic infections. The in vivo experiments using Galleria mellonella (G. mellonella) larvae have shown that it has a significant protective effect against MDR E. coli infection. In summary, bacteriophage YP6 is expected to become a therapeutic agent against MDR E. coli infection due to its broad host range, environmental stability, and biofilm inhibition properties. Future research should optimize bacteriophage preparations, evaluate the safety and efficacy of animal models, and establish clinical application plans in the field of food safety.

Antifungal Resistance in Candida Species: A Bit from the Totality

: Resistance to antifungals is one of the natural protection processes developed by fungi to promote their persistence. Exposure of fungi to these agents over long periods due to improper prescription or a contaminated environment increases the resistance problem. Microbiology related to fungal species and clinical settings related to the therapeutic failure of antifungal drugs are two concepts used to define resistance. The minimum inhibitory concentration (MIC) measurement is the common criterion for determining antifungal resistance. Candida spp. is the most common group of fungi that has developed resistance to different antifungal agents. C. albicans has shown resistance to numerous antifungal agents from this genus, followed by non-albicans Candida (NAC). The majority of resistance is to the azole group of antifungal agents through various mechanisms. Resistance to echinocandins is also reported in many species of Candida, while resistance to polyene has been observed in rare cases. The mechanism of resistance action is generally related to a genetic mutation, which changes the mechanisms of diffusion, fungal structure, and drug degradation. Biofilm formation also contributes to antifungal resistance. Current information on the nature and mechanism of antifungal resistance in Candida spp. is briefly presented in this review.

Synthetic peptides bioactive against phytopathogens have lower impact on some beneficial bacteria: An assessment of peptides biosafety in agriculture.

The emergence of bacterial resistance and the increasing restrictions on the use of agrochemicals are boosting the search for novel, sustainable antibiotics. Antimicrobial peptides (AMPs) arise as a new generation of antibiotics due to their effectiveness at low doses and biocompatibility. We compared the antimicrobial activity of four promising AMPs (CA-M, BP100, RW-BP100, and 3.1) against a collection of notorious phytopathogens, and quantified their impact on plant beneficial bacteria. Plant growth promoters (PGP) and biological control agents (BCA) were also included to study the feasibility of integrating AMPs with bio-based strategies to mitigate diseases impacts and promote crop production. Flow cytometry and fluorescence microscopy revealed that the AMPs' effects on the membrane integrity of both gram-negative and gram-positive strains were time- and concentration-dependent. Bacterial strains were separated into three groups of susceptibility to the AMPs. Group 1 was represented by the most sensitive, gram-negative phytopathogenic belonging to Xanthomonadales and Pseudomonadales and the gram-positive C. michiganensis subsp. michiganensis. Group 2 encompassed bacteria showing intermediate susceptibility, namely P. carotovorum subsp. carotovorum, P. cerasi, both phytopathogens, as well as the plant growth promoters P. fluorescens and P. putida. Finaly, Group 3 was represented by the bacteria with the lowest susceptibility to AMPs. It included beneficial bacteria (B. zhangzhouensis, B. subtilis, B. safensis, P. azotoformans), a phytopathogen (R. solanacearum), and a strain reported as able to act as both (P. aeruginosa). This work demonstrates that the minimum inhibitory concentrations (MICs) needed to act against the beneficial Bacillus and Pseudomonas strains were higher than those needed to produce bacteriostatic or bactericidal effects on the phytopathogens tested, hence supporting that these AMPs might be environmentally safe antibiotics with low likeliness of disrupting the beneficial microbial communities. The possibility of mixing these AMPs with BCA/PGP, in a combined biocontrol strategy, is also discussed.

Antibacterial effect of Aloe Vera on Bacteria Isolated from Cases of Wound Infection.

Antimicrobial resistance exhibited by bacteria against the majority of antibiotics has resulted in research on alternative methods of treatment. Aloe vera has a strong tradition as a medical plant with a wide range of therapeutic uses. The objective of this study is to determine the antibacterial activity of gel and crude ethanol leaf extract of Aloe vera against Staphylococcus aureus and Enterobacterales isolated from wound infections. It is a cross-sectional study conducted over a period of 7 months. Antibacterial effect of the ethanol leaf extract and gel was determined by the punch well method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the ethanol leaf extract were determined by macro broth dilution technique. Aloe vera ethanol leaf extract induced a mean zone size of 13.0 ± 6.0 mm and 16.7 ± 8.4 mm, respectively, for S. aureus and Enterobacterales by Punch Well method (p≤0.002). Whereas Aloe vera gel failed to induce any zone of inhibition for all the isolates p<0.001. Mean MIC of Aloe vera leaf extract against 74 S. aureus was 94 ± 41.23 mg/ml and against 73 Enterobacterales, it was 45.6 ± 20 mg/ml p < 0.001. Mean MBC of Aloe vera leaf extract against 74 S.aureus isolates was 188 ± 82.46 mg/ml and against 73 Enterobacterales was 91.18±40 mg/ml p < 0.001. Aloe vera ethanol leaf extract showed a good antibacterial effect against the different strains of bacteria causing wound infection. The present article shows the possibility of future use of natural products for the treatment of wound infections.

Anti-biofilm activity of carvacrol-thymoquinone nanocarriers on vulvovaginal candidiasis isolates.

Given the recurrent nature of vulvovaginal candidiasis (VVC), the restricted availability of effective antifungal agents, and the recent rise in drug resistance, this study sought to assess the antifungal efficacy of carvacrol-thymoquinone delivered via a nanocarrier on Candida isolates obtained from patients with VVC. Isolates were identified using phenotypic and genotypic methods. Nanocarriers were synthesized using the thin-film hydration method. The antifungal activity of carvacrol-thymoquinone was evaluated using the broth microdilution method (CLSIM27-A3). The impact of nanocarriers on the biofilm formation capabilities of Candida isolates was assessed using the MTT assay. Data were analyzed using the Mann-Whitney U test. The nanocarrier exhibited a spherical morphology with a diameter measuring 50 nm. The nano-formulated drug combination could inhibit biofilm formation in C. albicans at half the minimum inhibitory concentration and in C. glabrata at the minimum inhibitory concentration. Our results suggest that the carvacrol-thymoquinone nanocarrier can be studied further in vivo for potential use in the treatment of recurrent VVC.

Spoilage investigation of pasteurized apple juice with visual defects identifies a potentially novel Acetobacter species as the primary spoilage agent.

Jellified materials were observed in spoiled pasteurized apple juice that contained dimethyl dicarbonate (DMDC). Microbiological analysis showed a high microbial load (4-5 log CFU/mL) in the sample. Acetobacter spp. was identified as the spoilage microorganism by 16S rRNA gene sequencing. Metataxonomic analysis showed Acetobacter represented 99% of the bacterial community. Three Acetobacter isolates (LX5, LX9 and LX16) were selected for whole genome sequencing and characterized for their susceptibility to DMDC. Genome-based phylogeny supported the species-level classification of LX5 as A. fabarum. It also suggested LX9 and LX16 are the same microorganisms from a potentially novel species closely related to A. lovaniensis. The minimum inhibitory concentrations (MICs) of DMDC for Acetobacter isolates in sterile apple juice (pH ∼3) at 30°C were 46ppm and 329ppm for A. fabarum LX5 and Acetobacter LX9/LX16, respectively. The minimum bactericidal concentrations (MBCs) were 250 and 500ppm for A. fabarum LX5 and Acetobacter LX9/LX16, respectively. The inoculum concentration for the MIC assay was approximately 6 log10 CFU/mL, representing the "worst-case" scenario. When the contamination level was reduced to 500CFU/mL per US federal regulation (21 CFR 172.133) and the apple juice was refrigerated, Acetobacter isolates did not grow and were completely inhibited by 238ppm DMDC. Pangenome analysis identified gene clusters that potentially play a role in biofilm development, carbohydrate metabolism, and oxidative stress tolerance, but it also ruled out the involvement of Acetobacter in apple juice gel formation. The investigation concluded that post-pasteurization contamination, high microbial load and ambient storage were factors leading to this spoilage incident.

Synthesis, Antibacterial Activity and In Silico Study of 1-(2-ethyl acetate)-2-styryl 5-nitroimidazole Derivatives

Background: For more than six decades, the use of metronidazole has been limited to anaerobic microorganisms. However, there are accounts of metronidazole derivatives exhibiting strong effectiveness against facultative anaerobic bacteria, suggesting that there may be another mechanism of action for metronidazole. Recent studies have shown that the enzyme FabH (β-ketoacyl-acyl carrier protein synthase III), responsible for the first step of fatty acid biosynthesis (FAB), is a promising target for nitroimidazole derivatives that can be used as an effective anti-infective agent. Objective: This study aimed to synthesize 1-(2-ethyl acetate)-2-styryl nitroimidazole derivatives and evaluate their in vitro and in silico antibacterial activity Methods: We synthesized 2-styryl 5-nitroimidazole derivatives by first condensing metronidazole with benzaldehydes and then carrying out an acetylation reaction. We evaluated the antimicrobial activity of the synthesized compounds against three Gram-positive bacterial strains (Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus agalactiae) and three Gram-negative bacterial strains (Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae) using a two-fold serial dilution MTT (3-(4,5-dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide) assay. Results: Compounds 2 and 4 exhibited the highest level of antibacterial effectiveness, with minimum inhibitory concentrations (MIC) of 1.56 μg/mL against S. agalactiae and 3.13 μg/mL against P. aeruginosa. Compounds 2 and 4 also exhibited potent activity against K. pneumonia, with an MIC value of 6.25 μg/mL and 12.5 μg/mL, respectively. Molecular docking studies revealed that both compounds have favorable hydrophobic and electrostatic interactions with conserved residues in the binding site of the E. coli β-Ketoacyl-acyl carrier protein synthase III (FabH) complex. Conclusion:: Acetylation of 2-styryl-5-nitroimidazoles improved both their biological activity and binding interaction with the target protein

Synthesis of tetra-substituted thiophene derivatives as potential Hits combating antibiotic resistant bacteria ESKAPE.

The escalating prevalence of antibiotic-resistant bacteria has led to a serious global public health problem; therefore, there is an urgent need for the development of structurally innovative antibacterial agents. In our study, different series of tetra-substituted thiophene derivatives were designed and synthesized by multi-component reactions (MCRs) in moderate to excellent yields. Some of the designed final compounds were synthesized by both microwave assisted method and traditional synthesis. Thirteen compounds were evaluated against antibiotic resistance bacteria ESKAPE, among which compounds 11, 13 and 17 showed the most potent inhibitory activities against multidrug-resistant Enterococcus faecalis with MIC (minimum inhibitory concentration) values as low as 15.62, 7.61 and 15.62µg/mL, respectively. Two potent candidates 11 and 13 not only showed rapid bactericidal properties and impeded E. faecalis biofilm formation to effectually relieve the development of drug resistance, but also performed low toxicity toward human normal cells. Moreover, time dependent killing assay was performed that showed the reduction of the concentration of bacteria by 5.0 Log (CFU/mL) within 6h, stronger than reference drug, ampicillin at the same concentration. Additionally, mechanistic investigation demonstrated that both compounds 11 and 13 could exert inhibitory activity against DHPS with IC50 value of 1.73 and 4.67µM, respectively and against DNA gyrase enzyme with IC50 value of 0.07 and 0.04µM, respectively. Moreover, the cytotoxic activity of the most active compound was crucial to be determined that showed IC50 value of 75.42µM. Molecular docking indicated that the binding of both compounds 11 and 13 to DHPS and DNA gyrase enzymes could hinder their function. These results can provide novel structures of antibacterial drugs chemically different from currently known antibiotics and broaden prospects for the development of effective antibiotics against antibiotic-resistant bacteria.

Synthesis of novel Fe3O4@gly@Indole@CuNO3 magnetic nanoparticle as high-performance antibiotic absorbent, antimicrobial agent, and reusable magnetic Nano catalyst

The synthesis of nanoparticles has gained attention for their broad applications. Our research focused on developing a novel material, Fe3O4@gly@Indole (FGI), and exploring its diverse uses. FGI was synthesized in two steps using FeCl2.4H2O, FeCl3.6H2O, glycine, and indole-3-carboxaldehyde. Its structure was confirmed via FT-IR, XRD, VSM, SEM, TGA, and EDAX. Antimicrobial tests revealed FGI exhibited higher activity than some antibiotics, with a Minimum Inhibitory Concentration (MIC) of 1µg/mL against Staphylococcus aureus. To enhance its properties, a magnetic nanocatalyst (FGICu) was synthesized by combining FGI with Cu(NO3)2. FGICu proved effective in synthesizing chromeno[4,3-b]chromen-6-one derivatives, achieving 95% yield in 20minutes at 50°C. Additionally, FGICu outperformed FGI in antibacterial tests, showing a lower MIC of 0.5µg/mL and stronger bactericidal activity (MBC of 2-8µg/mL). FGICu also demonstrated significant potential as an adsorbent, with a maximum adsorption capacity of 500.8mg/g for tetracycline (TC). The adsorption mechanism involved electrostatic interactions, hydrogen bonding, and π-π stacking, with the SIPS model best fitting the isotherm and pseudo-second-order model describing the kinetics. FGICu maintained over 70% efficiency after five adsorption cycles, showing excellent stability and reusability. These findings suggest FGICu is a promising material for antimicrobial applications and pollutant removal from wastewater.

Integration of transcriptomics and metabolomics reveals the mechanism of enrofloxacin resistance in Aeromonas schubertii.

Aeromonas schubertii infections has caused severe economic losses in aquaculture in China. In this study, we first induced enrofloxacin (ENR) resistance in A. schubertii strains and then analyzed the mechanisms of drug resistance using transcriptomics and metabolomics. We found that the minimal inhibitory concentration (MIC) was 0.03125 μg/mL for the sensitive strain (WL23S) and 32 μg/mL for the resistant strain (WL23R), which is a 1,024-fold increase. After 40 serial passages, the WL23R strain maintained a MIC of 32 μg/mL, even in the absence of ENR-induced stress. Notably, it had also developed resistance to several other antibiotics, such as neomycin sulfate and flumequine. There was no significant difference in the growth rates of the two strains, highlighting the strong adaptability and growth characteristics of the WL23R strain. Comparison of the transcriptome data between the WL23R and WL23S strains identified 579 differentially expressed genes. Expression of the efflux pump-related genes (e.g., acrA, acrB, pstB, pstC, pstS) was significantly upregulated in the WL23R strain (P < 0.05). The highest enrichment of differential genes in the Gene Ontology analysis was in the catabolism of various amino acids, and that in the Kyoto Encyclopedia of Genes and Genomes pathway was in ATP-binding cassette (ABC) transport. Comparison of the metabolomics data between the WL23R and WL23S strains revealed 1, 059 differentially expressed metabolites. Metabolomics analysis revealed the impact of drug resistance on the levels of amino acids, the activity of amino acid biosynthesis/metabolism pathways, and the ABC transport protein pathway, which confirmed the transcriptomics results. The joint analysis results showed that ABC transporters were most prominent in the shared pathways between enriched differentially expressed genes and metabolites. To further validate the resistance mechanism of A. schubertii, we exposed the WL23R strain to the efflux pump inhibitor carbonyl cyanide 3-chlorophenylhydrazone. The minimal inhibitory concentration of the induced resistant strain decreased by 4-fold after the addition of the inhibitor, indicating the overexpression of active efflux pumps in WL23R. Our results indicate that the efflux system and ABC transporters play crucial roles during the development of multidrug resistance in A. schubertii. This study will serve as an important reference for understanding bacterial resistance to quinolones and multidrug resistance in aquatic environments.

Antimicrobial and anti-biofilm effects of dihydroartemisinin-loaded chitosan nanoparticles against methicillin-resistant Staphylococcus aureus.

The formation of biofilms enhances bacterial antibiotic resistance, posing significant challenges to clinical treatment. Methicillin-resistant Staphylococcus aureus (MRSA) is a primary pathogen in biofilm-associated infections. Its high antibiotic resistance and incidence rates make it a major clinical challenge, underscoring the urgent need for novel therapeutic strategies. Building on previous research, this study employs nanotechnology to fabricate dihydroartemisinin-chitosan nanoparticles (DHA-CS NPs) and, for the first time, applies them to the treatment of MRSA biofilm infections. The antibacterial and anti-biofilm activities of these compounds were evaluated, and their potential mechanisms of action were preliminarily explored. The results demonstrated that the DHA-CS NPs exhibited a minimum inhibitory concentration (MIC) of15μg/mLand a minimum bactericidal concentration (MBC) of 30μg/mL. At 15μg/mL, the DHA-CS NPs significantly inhibited MRSA biofilm formation (P<0.001),while at 7.5μg/mL, they dispersed 67.4±3.77% of the preformed biofilms (P<0.001). Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) confirmed the disruption of MRSA biofilms. Mechanistic studies, including phenol-sulfuric acid assays, static biofilm microtiter plate assays, and RT-qPCR, revealed that the DHA-CS NPs inhibited the synthesis of extracellular polymeric substances (EPS), suppressed the release of extracellular DNA (eDNA), and downregulated key biofilm-related genes (icaA, sarA, cidA, and agrA). These findings suggest that DHA-CS NPs hold significant promise for inhibiting and eradicating MRSA biofilms, providing a theoretical basis for the development of novel antibiofilm therapies.

The first Ranatuerin antimicrobial peptide with LPS-neutralizing and anti-inflammatory activities in vitro and in vivo.

Pelophylax nigromaculata, common traditional Chinese medicinal material used for several hundreds of years, is one of the most widely distributed amphibians in China. In this study, a novel Ranatuerin-2 family antimicrobial peptide, Rana-2PN, was identified and characterized from its skin, and its structural characteristics and functional activities were studied extensively. First, Rana-2PN exhibited a broad spectrum of antimicrobial activity, displaying minimum inhibitory concentration (MIC) values ranging from 12.5 to 100 μM against all strains tested. Mechanistically, Rana-2PN exerted its bacteriostatic effects by binding to bacterial cells and inducing bacterial membrane rupture and subsequent bacterial death. Secondly, Rana-2PN effectively inhibited the inflammatory response in RAW264.7 cells induced by lipopolysaccharide (LPS) and reduced inflammation induced by carrageenan in mouse toes. Thus, Rana-2PN with LPS-neutralizing, anti-inflammatory, and antimicrobial properties, represents the first member of the Ranatuerin antimicrobial peptide family, and its discovery offers a promising therapeutic candidate for addressing inflammatory disorders resulting from bacterial infections.

Antimicrobial efficacy of alternative root canal disinfection strategies: An evaluation on multiple working models.

Researching disinfection strategies is pivotal because effectively eliminating bacteria and their byproducts during root canal treatment (RCT) remains a challenge. This study investigated the antimicrobial efficacy of natural antimicrobial compounds, propolis (PRO) and copaiba oil-resin (COR), compared to conventional agents in Endodontics. Antimicrobials were tested against endodontic pathogens via macrodilution with standardized inoculums to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). Biofilm killing efficacy were performed using two dual-species biofilms: Enterococcus faecalis (ATCC 29212) and Streptococcus mutans (ATCC 20523) and Streptococcus oralis (J22) and Actinomyces naeslundii (T14V-J1) grown on dentine discs. At the intratubular level (dentine cylinders), dentine tubule contamination was performed with E. faecalis and S. mutans. The specimens were exposed to antimicrobials to simulate their use at different sets of RCT and bacterial viability was quantified using Live/Dead staining via confocal laser scanning microscopy (CLSM). Biofilm characteristics and immediate removal of S. oralis and A. naeslundii biofilm model were evaluated employing optical coherence tomography (OCT) and CFU/mL counting. Statistical tests were applied according to data distribution for each analysis (α=0.05). Macrodilutions showed different effects against endodontic pathogens. Direct contact and intratubular analysis showed that PRO and COR promoted disinfection like conventional agents (p > 0.05). According to OCT analysis, PRO and COR showed similar biofilm reduction after immediate contact (p < 0.05). CFU/mL counting showed decontamination (p < 0.05) after using natural and conventional agents. PRO and COR showed antimicrobial effects, indicating their suitability as complementary approaches in RCT to eliminate as much microbial load as possible.

Development and Evaluation of the Antibacterial Properties of an Experimental Herbal Gel Against Cariogenic Bacteria.

Recently, products with antibacterial properties derived from medicinal plants have increased as an alternative to conventional drugs. Thus, this study aimed to formulate and evaluate the antibacterial activity of an experimental gel based on Grindelia tarapacana essential oil in a bacterial consortium. The composition of the essential oil (EO) was determined using gas chromatography-mass spectrometry (GC-MS). The antibacterial activity of the EO against Streptococcus mutans ATCC 25175, Streptococcus sanguinis ATCC 10556, and Streptococcus salivarius ATCC 13419 was evaluated using an Agar disc diffusion and minimum inhibitory concentration methods. Five formulations of the experimental gel were prepared at 0.25%, 0.5%, 1%, 1.5%, and 2% (v/v). The antibacterial susceptibility test was evaluated using an Agar-Well diffusion assay against a bacterial consortium of S. mutans, S. sanguinis, and S. salivarius. The physical properties, pH, spreadability, gel morphology, phase separation, and drug release were evaluated. The experimental gels were compared with a chlorhexidine gel. Data were analyzed with one-way ANOVA and Kruskal-Wallis tests with a significant level of 5%. The major components of the EO were bornyl acetate, α-isomethyl-E-nerolidol, germacrene B, E-nerolidol, α-cedrene-epoxide, fokienol, and 10-epi-γ-eudesmol. All formulations were effective in inhibiting bacterial growth. The 2% concentration presented inhibition zones (18.14 ± 1.01 mm) similar to those observed for the chlorhexidine gel (p > 0.05). All formulations were stable, without signs of separation, with adequate physical properties, and no significant differences were observed regarding the drug content with the chlorhexidine gel (p > 0.05). The experimental gels based on G. tarapacana EO presented good physicochemical properties and were highly effective in inhibiting the growth of a cariogenic bacterial consortium.

Antimicrobial resistance and epidemiological patterns of Streptococcus pyogenes in Türkiye.

Drug-resistant Group A beta-hemolytic streptococci remain significant infectious agents globally. This study investigated the major S. pyogenes strains responsible for infections in Türkiye and their susceptibility to beta-lactam and macrolide antibiotics. We determined the minimum inhibitory concentration using the penicillin gradient test and performed emmtyping and DNA fingerprinting via pulsed-field gel electrophoresis (PFGE) to analyze the clonal spread of 92 S. pyogenes strains isolated from two hospitals in Türkiye between 2020 and 2022. Our findings revealed the predominant S. pyogenes strains causing infections in the population and provided insights into the epidemiological relatedness of these drug-resistant strains. This study also evaluated the correlation between emm typing and PFGE in tracking S. pyogenes epidemiology. In this study, the current resistance patterns of S. pyogenes strains in Türkiye identified erythromycin resistance in a few strains, but no resistance to penicillin was detected. This study revealed that emm types 1, 12 and 89 as S. pyogenes strain genotypes were responsible for epidemic infections in Türkiye. PFGE genotyping and emm typing were found to provide better phylogenetic classification in the investigation of S. pyogenes epidemiology.

Multiple mechanisms mediate aztreonam-avibactam resistance in Klebsiella pneumoniae: Driven by KPC-2 and OmpK36 mutations.

Aztreonam-avibactam (ATM-AVI) is a promising β-lactam/β-lactamase inhibitor combination with an antimicrobial spectrum covering serine carbapenemase- or metallo-β-lactamase-producing Enterobacterales. Although ATM-AVI has not been widely used in clinical practice, resistance to it in Escherichia coli has been widely reported. In this study, we investigated an ATM-AVI-resistant Klebsiella pneumoniae strain, designated as 1705R, derived from K. pneumoniae ATCC BAA-1705 by induction, with a minimal inhibitory concentration of 128 µg/mL. The 1705R strain contained two copies of the blaKPC-2 variant, which encodes for a K. pneumoniae carbapenemase (KPC) variant with a Ser109Pro substitution, as well as a premature termination in OmpK36 and OmpK35 porins. This KPC variant decreased susceptibility to ATM-AVI by four-fold and demonstrated a reduced affinity for ATM and AVI in molecular docking analysis. In porin-deficient strains harbouring this KPC variant, ATM-AVI susceptibility was further diminished, exhibiting a 32-fold reduction. Whole-genome sequencing revealed that the transposition of Tn4401 carrying blaKPC from the IncFIB/FIIK plasmid into the ColRNAI plasmid produced a second copy of blaKPC. Quantitative polymerase chain reaction revealed that the copy number of blaKPC and its carrier plasmid increased, which significantly up-regulated their mRNA expression. Overexpression of the AcrAB-TolC efflux pump may also be associated with high levels of ATM-AVI resistance. Furthermore, collateral susceptibility and costs of growth and biofilm formation developed after the acquisition of ATM-AVI resistance. This study demonstrates that multiple molecular mechanisms collectively contribute to ATM-AVI resistance in K. pneumoniae 1705R strain, which may represent a mode of resistance to ATM-AVI.

Standardization, Characterization and Potential Biological Activity of Ozonized Sunflower Vegetable Oil

Objective: The ozone molecule, composed of three oxygen atoms, possesses high oxidizing power and is widely utilized for various applications, including therapeutic treatments involving the administration of medicinal ozone to combat various diseases. The standardization of ozonized oil is essential to ensure patient safety. The objective of this study was to develop protocols for the standardization and characterization of ozonized oil using analytical techniques such as gas chromatography-mass spectrometry (GC-MS) and to evaluate its biological activity through microbiological and cytotoxic assays. Methods: Standardization and characterization were carried using gas chromatography coupled to mass spectrometry (CG-MS), and microbiological tests including agar diffusion, time-kill and MIC and cytotoxic tests were employed in bacterial cells. Results: The obtained results indicated that after 480 minutes of ozonization in 100 mL of sunflower oil (OG), a significant antimicrobial potential was observed, leading to the formation of ozonides. Antibacterial and antifungal activity assays, conducted using the ‘time kill’ method, agar diffusion, and Minimum Inhibitory Concentration (MIC) tests, demonstrated activity against Staphylococcus aureus, Escherichia coli, Salmonella choleraesuis, Pseudomonas aeruginosa, Candida albicans, Aspergillus brasiliensis, and Malassezia furfur. Conclusion: Results demonstrate the therapeutic potential of the application of ozonized oil in the treatment of topic infectious diseases. In summary, the standardization of the ozonization process of sunflower oil showed to be promising, providing a product exerting antimicrobial activity and therapeutic potential, opening perspectives for its application in various areas of medicine.

Antibiotic resistance phenotypes of different species belonging to Staphylococcus genus isolated at the China-Guinea Friendship Hospital of Kipé in Conakry

Introduction: Staphylococcal infections constitute a worldwide public health problem, particularly in hospitals. This is a retrospective study from July 1, 2012 to December 31, 2016 carried out at the Biomedical Laboratory of the China-Guinea Friendship Hospital (HASIGUI) in Kipé/Conakry. The aim of this study was to determine the antibiotic resistance phenotypes of species of the genus Staphylococcus isolated from various biological secretions. Material and methods: A total of 226 strains belonging to genus of Staphylococcus isolated from 226 patients were studied. Cultures were made on agar media. Bacterial identifications and antibiograms were done by Vitek2 automated system and by the API method (bioMérieux France). Minimum inhibitory concentrations (MIC) were determined by Vitek 2 Compact. Results: Male were predominant and sex ratio (Male/Female) was 1.45. The mean age of the patients was 47.5% ± 21years [1-91years] and the most prominent age group (34.51%) was 60 years and over. The majority of staphylococci were isolated from urine (68.58%), pus (13.72%). Vaginal secretions (5.75%) and semen (5.31%). Fifteen Staphylococcus species were identified with a predominance of Staphylococcus aureus (26.11%), followed by Staphylococcus epidermidis (15.49%), Staphylococcus xylosus (15.04%), Staphylococcus haemolyticus (13.72%). The majority of strains were sensitive to nitrofurantoin (97.10%), tobramycin (92.86%), moxifloxacin (92.75%), tigecycline (91.30%) and gentamicin (85.51%), ciprofloxacin (73.85%), quinupristin/dalfopristin (75.36%) levofloxacin (53.62%). On the other hand, the majority of these strains were resistant to benzylpenicillin (98.55%), to the combination trimethoprim/sulfamethoxazole (81.16%), oxacillin (79.71%) and tetracycline (78.26%), erythromycin (62.32%), clindamycin (62.32%), rifampicin (62.32%) and vancomycin (62.32%). Conclusion: All of these results show that many species of the genus Staphylococcus are involved in human infections, sometimes with multidrug resistance to many families of antibiotics.