Minimum Inhibitory Concentration Measurements Research Articles

Adaptive cell wall thickening in Enterococcus faecalis is associated with decreased vancomycin susceptibility

ObjectivesEnterococcus faecalis can adopt both a commensal and a nosocomial lifestyle, resisting numerous antibiotics. In this study, we aim to investigate the relationship between the cell wall (CW) thickness and decreased susceptibility to vancomycin (VD) in van-gene negative clinical isolates of E. faecalis (nMIC 8 = 2, nMIC 4 = 3, ST30, ST40, and ST59). MethodsThe CW thickness was assessed in VD strains and compared with vancomycin susceptible isolates of the same sequence type (ST) (Vancomycin susceptible [VS]; nMIC 2 = 5). The VD and VS strains were subjected to serial passage (evolved [ev]) with and without vancomycin selection. Subsequent measurements of CW thickness and vancomycin MICs were performed. ResultsThe VD strains exhibited increased CW thickness when compared with ST-related VS strains (ΔCW thickness VD vs. VS ST30 25 nm, ST59 15 nm, and ST40 1 nm). Serial passages without vancomycin selection led to a decrease in CW thickness and vancomycin MIC in VD strains (ΔCW thickness VD vs. evVD ST30 22 nm, ST59 3 nm, and ST40 2 nm). Serial passages with vancomycin selection caused an increase in CW thickness and vancomycin MIC in ST-related VS strains (ΔCW thickness VS vs. evVS ST30 22 nm, ST59 16 nm, and ST40 1 nm). DiscussionAdaptive changes in CW thickness were observed in response to vancomycin exposure. Increased CW thickness correlated with decreased vancomycin susceptibility, whereas decreased CW thickness correlated with increased vancomycin susceptibility. Core single nucleotide polymorphisms in the evolved mutants were mostly found in genes encoding proteins associated with the cytoplasm or the cytoplasmic membrane. The potential relevance of these adaptive changes is underlined by the observed phenotypes in clinical isolates. Our findings emphasize the importance of monitoring adaptive changes, as vancomycin-resistant enterococci infections are a growing concern.

High antipersister activity of a promising new quinolone drug candidate in eradicating uropathogenic Escherichia coli persisters and persistent infection in mice.

To develop more potent drugs that eradicate persister bacteria and cure persistent urinary tract infections (rUTIs). We synthesized eight novel clinifloxacin analogs and measured minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), the time-kill curves in uropathogenic Escherichia coli (UPEC) UTI89, and applied the candidate drugs and combinations against biofilm bacteria in vitro and in mice. Transcriptomic analysis was performed for UPEC after candidate drug treatment to shed light on potential mechanism of action. We identified Compound 2, named Qingdafloxacin (QDF), which was more potent than clinafloxacin and clinically used levofloxacin and moxifloxacin, with an MIC of<0.04μg ml-1 and an MBC of 0.08∼0.16μg ml-1. In drug combination studies, QDF+gentamicin+nitrofuran combination but not single drugs completely eradicated all stationary phase bacteria containing persisters and biofilm bacteria, and all bacteria in a persistent UTI mouse model. Transcriptome analysis revealed that the unique antipersister activity of QDF was associated with downregulation of genes involved in bacterial stress response, DNA repair, protein misfolding repair, pyrimidine metabolism, glutamate, and glutathione metabolism, and efflux. QDF has high antipersister activity and its drug combinations proved highly effective against biofilm bacteria in vitro and persistent UTIs in mice, which may have implications for treating rUTIs.

Investigation of biofilm formation and the associated genes in multidrug-resistant Salmonella pullorum in China (2018-2022).

The study explored the biofilm (BF) formation capacity, BF-related gene profiles, and the trends in antimicrobial resistance (AMR) of Salmonella pullorum (SP) strains over several years. A total of 627 SP strains were isolated from 4,540 samples collected from chicken farms in Guangxi, China during 2018-2022. The BF-forming capacity of these isolates was assessed using crystal violet staining, and the presence of eight BF-related genes (csgA, csgB, csgD, ompR, bapA, pfs, luxS, and rpoS) in BF formation-positive strains was determined through Polymerase Chain Reaction (PCR) analysis. Antimicrobial susceptibility test was conducted to investigate the AMR of the isolates. Minimum Inhibitory Concentration (MIC) and Minimal Biofilm Eradication Concentration (MBEC) of nine SP-BF strains were determined using the broth microdilution method to assess the impact of BF formation on AMR. Additionally, the Optimal Biofilm Formation Conditions (OBFC) were investigated. The results indicated that 36.8% (231/627) of the strains exhibited a positive BF-formation capacity. Among these, 24.7% (57/231) were strong BF producers, 23.4% (54/231) were moderate BF producers, and 51.9% (120/231) were weak BF producers. Analysis of the eight BF-related genes in SP-BF strains revealed that over 90% of them were positive for all the genes. Antimicrobial susceptibility test conducted on the isolates showed that 100% (231/231) of them exhibited resistance to at least one antibiotic, with 98.3% (227/231) demonstrating multidrug resistance (MDR). Both MIC and MBEC measurements indicated varying degrees of increased AMR after BF formation of the bacteria. The optimal conditions for BF formation were observed at 37°C after 48 h of incubation, with an initial bacterial concentration of 1.2 × 106 CFU/mL. Notably, NaCl had a significant inhibitory effect on BF formation, while glucose and Trypticase Soy Broth (TSB) positively influenced BF formation. The results of the study emphasized the need for effective preventive and control strategies to address the challenges posed by the BF formation and MDR of SP in the field.

Antibacterial Activity of Honey Pineapple Peel Extract (Ananas comosus [L] Merr.) against MethicillinResistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) infection is a global health problem that needs to be answered by developing a synthetic or natural antibacterial to overcome the problem. The honey pineapple peel contains potentially antibacterial compounds such as bromelain and flavonoid. This study aims to determine the antibacterial activity of honey pineapple peel extract (Ananas comosus [L] Merr.) against MRSA. The design of this study was a true experimental study with a post-test control group design. This study examined the antibacterial activity of honey pineapple peel extract at concentrations of 100%, 50%, 25%, 12.5%, 6.25%, 3.125%, and 1.56% against MRSA bacteria by measuring minimum inhibitory concentration (MIC) with dilution method and minimum bactericidal concentration (MBC). The results of this study show that MIC was obtained at concentrations of 50 % and MBC at extract with a concentration of 100 %. There is an antibacterial activity of honey pineapple peel extract (Ananas comosus [L] Merr.) against MRSA.&#x0D; Keywords: Antibacterial Activity, Honey Pineapple Peel, MRSA

Exploring the Multifunctionality of Mechanochemically Synthesized γ-Alumina with Incorporated Selected Metal Oxide Species

γ-Alumina with incorporated metal oxide species (including Fe, Cu, Zn, Bi, and Ga) was synthesized by liquid-assisted grinding-mechanochemical synthesis, applying boehmite as the alumina precursor and suitable metal salts. Various contents of metal elements (5 wt.%, 10 wt.%, and 20 wt.%) were used to tune the composition of the resulting hybrid materials. The different milling time was tested to find the most suitable procedure that allowed the preparation of porous alumina incorporated with selected metal oxide species. The block copolymer, Pluronic P123, was used as a pore-generating agent. Commercial γ-alumina (SBET = 96 m2·g-1), and the sample fabricated after two hours of initial grinding of boehmite (SBET = 266 m2·g-1), were used as references. Analysis of another sample of γ-alumina prepared within 3 h of one-pot milling revealed a higher surface area (SBET = 320 m2·g-1) that did not increase with a further increase in the milling time. So, three hours of grinding time were set as optimal for this material. The synthesized samples were characterized by low-temperature N2 sorption, TGA/DTG, XRD, TEM, EDX, elemental mapping, and XRF techniques. The higher loading of metal oxide into the alumina structure was confirmed by the higher intensity of the XRF peaks. Samples synthesized with the lowest metal oxide content (5 wt.%) were tested for selective catalytic reduction of NO with NH3 (NH3-SCR). Among all tested samples, besides pristine Al2O3 and alumina incorporated with gallium oxide, the increase in reaction temperature accelerated the NO conversion. The highest NO conversion rate was observed for Fe2O3-incorporated alumina (70%) at 450 °C and CuO-incorporated alumina (71%) at 300 °C. The CO2 capture was also studied for synthesized samples and the sample of alumina with incorporated Bi2O3 (10 wt.%) gave the best result (1.16 mmol·g-1) at 25 °C, while alumina alone could adsorb only 0.85 mmol·g-1 of CO2. Furthermore, the synthesized samples were tested for antimicrobial properties and found to be quite active against Gram-negative bacteria, P. aeruginosa (PA). The measured Minimum Inhibitory Concentration (MIC) values for the alumina samples with incorporated Fe, Cu, and Bi oxide (10 wt.%) were found to be 4 µg·mL-1, while 8 µg·mL-1 was obtained for pure alumina.

Profiling of Antifungal Activities from the Leaf Extract of Selected Apiaceae Family Plants against &amp;lt;i&amp;gt;Aspergillus fumigates&amp;lt;/i&amp;gt;

Many ethnic plants are used as a source of traditional medicine to cure a variety of illnesses in both humans and animals. Developing secondary metabolites in plants with antifungal characteristics, offer alternative medications for reasonably priced and safe treatments. In the present study, methanolic, ethanolic, hexane and ethyl acetate leaves extracts of fifteen Apiaceae family plants were taken on the premise of their ethno botanical uses. The antifungal activity was assessed against significant fungal strain; Aspergillus fumigates by measuring minimum inhibitory concentration (MIC) and Zone of inhibition compared with standard drug fluconazole. Ethanol and methanol extracts of the plants were more effective than the hexane and ethyl acetate extracts against A. fumigates. Extracts of Cuminum cyminum, Pastinca sativa, Carum carvi, Dacus carota, Centella asiatica, Anthriscus cerefolium, Trachyspermum ammi, Pimpenella anisum and Apium graveolens showed relatively low inhibition effects between 3.5 to 8.5 mm. The MIC value of extracts was determined ranging between 0.8 to 0.43 μg/ml. The extract of Petroselinum crispum, Foeniculum vulgare, Ferula assaefoetida, Bunium persicum, Anethum graveolens and Coriander sativum could be considered as potential source of antifungal compounds for treating diseases in humans. Conclude remarks that these six extracts show astonishing fungicidal properties that can be used to discover drugs of very high potential.

Antioxidant and Antimicrobial Properties of Ethanolic Extract of Lemon Verbena

Background and Objectives: Chemical preservatives are commonly used to prevent food from quick spoiling and oxidizing. Despite their effect in increasing shelf life of foods, these compounds can have side effects. Residues of chemical compounds in foods increase microbial resistance. This study aims to investigate the antioxidant and antimicrobial properties of lemon verbena (Lippia citriodora L.) ethanolic extract against some gram-positive and gram-negative bacteria. Methods: In this experimental study, The soaking method and ethanol solvent was used for extraction. Antioxidant activities of different concentrations of extract were assessed using DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity test and compared with butylated hydroxyanisole (BHA) as a synthetic antioxidant. Antimicrobial effect of extract on Staphylococcus aureus, Listeria innocua, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa and Salmonella typhimurium was determined by disk diffusion and well diffusion methods and measuring minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Experimental data were analyzed in SPSS software, version 20 using analysis of variance and the mean values were compared using Duncan’s multiple range test. Results: The amounts of phenols and flavonoids in the ethanolic extract of were 96.47±0.35 mg of gallic acid/g of extract and 31.07±0.42 mg of quercetin/g of extract, respectively. The half-maximal inhibitory concentration of lemon verbena extract was 11.79±0.76 μg/mL, while it was 10.16±0.29 μg/mL for BHA. In both disk diffusion and well diffusion methods, with the increase of the concentration of extract, the inhibition zone diameter increased. The ethanolic extract of lemon verbena at the concentration of 12.5 mg/mL had no inhibitory effect on gram-negative bacteria growth. In both methods, the extract had the greatest effect on S. aureus. The MIC of ethanolic extract ranged from 8 to 128 mg/mL, depending on the type of bacteria (gram-positive or gram-negative). Conclusion: The ethanolic extract of lemon verbena has higher antimicrobial effects on gram-positive bacteria. Therefore, it can be used in food and pharmaceutical industries as a natural antimicrobial agent. Considering the increasing resistance of bacteria to chemical antibiotics, more studies on lemon verbena and its antibacterial compounds are needed for treating infections.

Anti-Bacterial Effect of Cannabidiol against the Cariogenic Streptococcus mutans Bacterium: An In Vitro Study.

Dental caries is caused by biofilm-forming acidogenic bacteria, especially Streptococcus mutans, and is still one of the most prevalent human bacterial diseases. The potential use of cannabidiol (CBD) in anti-bacterial therapies has recently emerged. Here we have studied the anti-bacterial and anti-biofilm activity of CBD against S. mutans. We measured minimum inhibitory concentration (MIC) and minimum biofilm inhibitory concentration (MBIC). The bacterial growth and changes in pH values were measured in a kinetic study. The biofilm biomass was assessed by Crystal Violet staining and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) metabolic assay. Spinning Disk Confocal Microscopy (SDCM) was used to assess biofilm structure, bacterial viability and extracellular polysaccharide (EPS) production. CBD inhibited S. mutans planktonic growth and biofilm formation in a dose-dependent manner, with similar MIC and MBIC values (5 µg/mL). CBD prevented the bacteria-mediated reduction in pH values that correlated with bacterial growth inhibition. SDCM showed a decrease of 50-fold in live bacteria and EPS production. CBD significantly reduced the viability of preformed biofilms at 7.5 µg/mL with an 80 ± 3.1% reduction of metabolic activity. At concentrations above 20 µg/mL, there was almost no bacterial recovery in the CBD-treated preformed biofilms even 48 h after drug withdrawal. Notably, precoating of the culture plate surfaces with CBD prior to incubation with bacteria inhibited biofilm development. Additionally, CBD was found to induce membrane hyperpolarization in S. mutans. Thus, CBD affects multiple processes in S. mutans including its cariogenic properties. In conclusion, we show that CBD has a strong inhibitory effect against cariogenic bacteria, suggesting that it is a potential drug adjuvant for reducing oral pathogenic bacterial load as well as protecting against dental caries.

Ethylated analogue of Zingerone: A new and eco-respectful preservative in cosmetics.

This article describes the eco-design of a new preservative in cosmetics based on bio-inspiration of natural extracts from traditional medicines. In order to reach the multiple specification targets, various structures have been synthesized and evaluated to select the one demonstrating broad antimicrobial spectrum with favorable environmental profile and application potential to a wide variety of formulas. In order to evaluate the antimicrobial activity of the synthesized structures, the method of the challenge test consisting in an artificial contamination of the sample with collection microbial strains and evaluation of the number of revivable microorganisms was used to select the most promising candidate. Validation of its antimicrobial potential was later confirmed on Gram positive and Gram negative bacteria, yeast and mold with measurement of its Minimum Inhibitory Concentration (MIC) in comparison with known preservatives. Environmental impact assessment of the selected candidate was achieved with the help of ready biodegradability and aquatic ecotoxicity tests performed according to appropriate Organization tes a strfor Economic Co-operation and Development (OECD) and European Union (EU) guidelinesy. Bio-inspired from turmeric and ginger extracts, an ethylated analog of Zingerone (EZ) with the chemical name 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one demonstrates the strongest activity on Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa and Candida albicans. Moreover, EZ shows a solubility in water two times higher than that of Zingerone thus increasing its interest as a potential preservative. Finally, its assessment of ready biodegradability and aquatic ecotoxicity in OECD-EU tests with a favorable environmental profile confirms its unique interest and fully justifies its use in cosmetic formulas as an eco-respectful preservative. Bio-inspiration based on technologies without noteworthy side effects but also on eco-design, particularly through the use of measures of potential environmental impact very upstream of a development, are two fundamental elements for the launching of new eco-friendly cosmetic ingredients. This approach has thus validated the strong potential of EZ as a preservative of eco-respectful formulas. The selection of EZ is also a very good example of the achievement of two key objectives targeted by cosmetic companies for the development of a novel active ingredient: environmental performance and technical performance.

Potential Antibacterial of Binahong Leaf Extract Against Bacteria Enterococcus faecalis ATCC® 29212™ (in vitro)

Binahong is a plant widely found in Indonesia and has been used for generations, but only by inheritance without much optimal research. Enterococcus faecalis is bacteria that cause many problems in the oral cavity such as periradicular lesion. The purpose of this study was to determine the zone of inhibition, Minimum Bactericidal Concentration (MBC), and Minimum Inhibitory Concentration (MIC) of Binahong leaf extract against bacteria Enterococcus faecalis ATCC® 29212TM concentrations of 100%, 90%, 80%, 70%, and 60%, chlorhexidine 0,2% as positive control and DMSO as a negative control. The experimental method used for the research with a post-test only control group design, pure bacteria prepared in the microbiology laboratory, and Binahong leaf extract used in the chemical laboratory of the Faculty of Mathematics and Natural Sciences (FMIPA) at the University of North Sumatera. Five treatments of Binahong leaf extract concentration were tested as samples four times. MBC and MIC measurements of Binahong leaf extract against Enterococcus faecalis ATCC® 29212TM were exchanged for each concentration. Mueller Hinton Agar (MHA) and Nutrient Broth incubated for 24 hours at 37°C. The ANOVA test data is analysed, followed by the Post Hoc test. The average inhibition zone of 100% concentration was 14.19 mm, 90% was 12.25 mm, 80% was (10.19 mm), 70% was 8.81 mm, 60% was 0.00 mm, chlorhexidine 0,2% was 20.88 mm, and DMSO was 0.00 m). The conclusion is that the best inhibition zone has a concentration of 100%, MBC was at 100%, and MIC was at 60%.

Assessment of Diversity of Antimicrobial Resistance Phenotypes and Genotypes of Mannheimia haemolytica Isolates From Bovine Nasopharyngeal Swabs.

The threat of bovine respiratory disease (BRD) for cattle operations is exacerbated by increasing prevalence of antimicrobial resistance (AMR) in Mannheimia haemolytica, a leading cause of BRD. Characterization of AMR in M. haemolytica by culture and susceptibility testing is complicated by uncertainty regarding the number of colonies that must be selected to accurately characterize AMR phenotypes (antibiograms) and genotypes in a culture. The study objective was to assess phenotypic and genotypic diversity of M. haemolytica isolates on nasopharyngeal swabs (NPS) from 28 cattle at risk for BRD or with BRD. NPS were swabbed onto five consecutive blood agar plates; after incubation up to 20 M. haemolytica colonies were selected per plate (up to 100 colonies per NPS). Phenotype was determined by measuring minimum inhibitory concentrations (MIC) for 11 antimicrobials and classifying isolates as resistant or not. Genotype was indirectly determined by matrix-assisted laser desorption/ionization time of flight mass spectroscopy (MALDI-TOF MS). NPS from 11 of 28 cattle yielded at least one M. haemolytica isolate; median (range) of isolates per NPS was 48 (1–94). NPS from seven cattle yielded one phenotype, 3 NPS yielded two, and 1 NPS yielded three; however, within a sample all phenotypic differences were due to only one MIC dilution. On each NPS all M. haemolytica isolated were the same genotype; genotype 1 was isolated from three NPS and genotype two was isolated from eight. Diversity of M. haemolytica on bovine NPS was limited, suggesting that selection of few colonies might adequately identify relevant phenotypes and genotypes.

The Monte Carlo Simulation of Three Antimicrobials for Empiric Treatment of Adult Bloodstream Infections With Carbapenem-Resistant Enterobacterales in China.

Introduction: The aim of this study was to predict and evaluate three antimicrobials for treatment of adult bloodstream infections (BSI) with carbapenem-resistant Enterobacterales (CRE) in China, so as to optimize the clinical dosing regimen further.Methods: Antimicrobial susceptibility data of blood isolates were obtained from the Blood Bacterial Resistance Investigation Collaborative Systems in China. Monte Carlo simulation was conducted to estimate the probability target attainment (PTA) and cumulative fraction of response (CFR) of tigecycline, polymyxin B, and ceftazidime/avibactam against CRE.Results: For the results of PTAs, tigecycline following administration of 50 mg every 12 h, 75 mg every 12 h, and 100 mg every 12 h achieved > 90% PTAs when minimum inhibitory concentration (MIC) was 0.25, 0.5, and 0.5 μg/mL, respectively; polymyxin B following administration of all tested regimens achieved > 90% PTAs when MIC was 1 μg/mL with CRE; ceftazidime/avibactam following administration of 1.25 g every 8 h, 2.5 g every 8 h achieved > 90% PTAs when MIC was 4 μg/mL, 8 μg/mL with CRE, respectively. As for CFR values of three antimicrobials, ceftazidime/avibactam achieved the lowest CFR values. The highest CFR value of ceftazidime/avibactam was 77.42%. For tigecycline and ceftazidime/avibactam, with simulated regimens daily dosing increase, the CFR values were both increased; the highest CFR of tigecycline values was 91.88%. For polymyxin B, the most aggressive dosage of 1.5 mg/kg every 12 h could provide the highest CFR values (82.69%) against CRE.Conclusion: This study suggested that measurement of MICs and individualized therapy should be considered together to achieve the optimal drug exposure. In particular, pharmacokinetic and pharmacodynamic modeling based on local antimicrobial resistance data can provide valuable guidance for clinicians for the administration of empirical antibiotic treatments for BSIs.

The Chemical Profiling of Essential Oils from Different Tissues of Cinnamomum camphora L. and Their Antimicrobial Activities.

Cinnamomum camphora L. is grown as an ornamental plant, used as raw material for furniture, as a source of camphor, and its essential oil can be used as an important source for perfume as well as alternative medicine. A comparative investigation of essential oil compositions and antimicrobial activities of different tissues of C. camphora was carried out. The essential oils were extracted by hydrodistillation with a Clevenger apparatus and their compositions were evaluated through gas chromatography-mass spectrometry (GC-MS), enantiomeric composition by chiral GC-MS, and antimicrobial properties were assayed by measuring minimum inhibitory concentrations (MICs). Different plant tissues had different extraction yields, with the leaf having the highest yield. GC-MS analysis revealed the presence of 18, 75, 87, 67, 67, and 74 compounds in leaf, branch, wood, root, leaf/branch, and leaf/branch/wood, respectively. The significance of combining tissues is to enable extraction of commercial quality essential oils without the need to separate them. The oxygenated monoterpene camphor was the major component in all tissues of C. camphora except for safrole in the root. With chiral GC-MS, the enantiomeric distributions of 12, 12, 13, 14, and 14 chiral compounds in branch, wood, root, leaf/branch, and leaf/branch/wood, respectively, were determined. The variation in composition and enantiomeric distribution in the different tissues of C. camphora may be attributed to the different defense requirements of these tissues. The wood essential oil showed effective antibacterial activity against Serratia marcescens with an MIC of 39.1 μg/mL. Similarly, the mixture of leaf/branch/wood essential oils displayed good antifungal activity against Aspergillus niger and Aspergillus fumigatus while the leaf essential oil was notably active against Trichophyton rubrum. C. camphora essential oils showed variable antimicrobial activities against dermal and pulmonary-borne microbes.

Assessment of the Effects of a High Amikacin Dose on Plasma Peak Concentration in Critically Ill Children.

This study aimed to assess the incidence of amikacin plasma peak concentration (Cmax) below 60 mg·L-1 in critically ill children receiving an amikacin dosing regimen of 30 mgkg-1·day-1. Secondary objectives were to identify factors associated with low Cmax and to assess the incidence of acute kidney injury (AKI). A retrospective observational study was performed in two French pediatric intensive care units. All admitted children who received 30 mg·kg-1 amikacin and had a Cmax measurement were eligible. Clinical and biological data, amikacin dose, and concentrations were collected. In total, 30 patients were included, aged from 3 weeks to 7 years. They received a median amikacin dosage of 30 mgkg-1·day-1 (range 29-33) based on admission body weight (BW), corresponding to 27 mgkg-1·day-1 (range 24-30) based on actual BW. Cmax was < 60 mg·L-1 in 21 (70%) children and none had a Cmax ≥ 80 mg·L-1. Among the 15 patients with a measured minimum inhibitory concentration (MIC), 13 (87%) had a Cmax/MIC ratio > 8. Univariate analysis showed that factors associated with Cmax < 60 mg·L-1 were high estimated glomerular filtration rate (p = 0.015) and low blood urea concentration (p = 0.001). AKI progression or occurrence was observed after amikacin administration in two (7%) and six (21%) patients, respectively. Despite the administration of the maximal recommended amikacin dose, Cmax was below the pharmacokinetic target in 70% of our pediatric population. Further studies are needed to develop a pharmacokinetic model in a population of critically ill children to optimize target attainment.

An automated and portable antimicrobial susceptibility testing system for urinary tract infections.

Urinary tract infections (UTIs) are bacterial infections that 1) commonly affect females, 2) can pose high risks to impair kidney function, 3) are often treated with broad-spectrum antibiotics, and 4) are associated with high recurrence rates due to the evolution of drug-resistant strains. To choose the appropriate antibiotic, the minimum inhibitory concentration (MIC) among a panel of antibiotics should be determined before administration to avoid inadequate dosing or use of wrong antibiotics. To meet with the unmet needs, we developed a bead-based method for bacterial preconcentration with capture rates ranging from 20-50% and then automatically performed on-chip AST on an automated device which was composed of a pneumatic control module, a temperature control module and a chip image processing module. The developed portable system was capable of automatically conducting AST and MIC measurements using urine samples (via image analysis) in only 4.5-9 h and tested on four common UTIs bacterial strains. This compact system may therefore be promising for point-of-care personalized medicine in the near future.

Limited antimicrobial efficacy of oral care antiseptics in microcosm biofilms and phenotypic adaptation of bacteria upon repeated exposure

ObjectivesThe aims of this study were to investigate the antimicrobial efficacy of antiseptics in saliva-derived microcosm biofilms, and to examine phenotypic adaption of bacteria upon repeated exposure to sub-inhibitory antiseptic concentrations.MethodsSaliva-derived biofilms were formed mimicking caries- or gingivitis-associated conditions, respectively. Microbial compositions were analyzed by semiconductor-based 16S rRNA sequencing. Biofilms were treated with CHX, CPC, BAC, ALX, and DQC for 1 or 10 min, and colony forming units (CFU) were evaluated. Phenotypic adaptation of six selected bacterial reference strains toward CHX, CPC, and BAC was assessed by measuring minimum inhibitory concentrations (MICs) over 10 passages of sub-inhibitory exposure. Protein expression profiles were investigated by SDS-PAGE.ResultsBoth biofilms showed outgrowth of streptococci and Veillonella spp., while gingivitis biofilms also showed increased relative abundances of Actinomyces, Granulicatella, and Gemella spp. Antiseptic treatment for 1 min led to no relevant CFU-reductions despite for CPC. When treated for 10 min, CPC was most effective followed by BAC, ALX, CHX, and DQC. Stable adaptations with up to fourfold MIC increases were found in E. coli toward all tested antiseptics, in E. faecalis toward CHX and BAC, and in S. aureus toward CPC. Adapted E. coli strains showed different protein expression as compared with the wildtype strain.ConclusionAntiseptics showed limited antimicrobial efficacy toward mature biofilms when applied for clinically relevant treatment periods. Bacteria showed phenotypic adaptation upon repeated sub-inhibitory exposure.Clinical relevanceClinicians should be aware that wide-spread use of antiseptics may pose the risk of inducing resistances in oral bacteria.

Enhanced Antibacterial Activity of Silver Nanoparticles Combined with Hydrogen Peroxide Against Multidrug-Resistant Pathogens Isolated from Dairy Farms and Beef Slaughterhouses in Egypt.

PurposeThe last few decades have witnessed a rapid and global increase in multidrug-resistant bacteria (MDR) emergence.MethodsThe aim of the current study is to isolate the most common MDR bacteria from dairy farms and beef slaughterhouses followed by evaluation of their antimicrobial resistance pattern and assessment of the antibacterial activity of AgNPs-H2O2 as an alternative to conventional antibiotics. In this regard, 200 samples were collected from two dairy farms and one beef slaughterhouse located in Dakhliya Governorate, Egypt.ResultsInterestingly, out of 120 collected samples from dairy farms, the prevalence of the isolated strains was 26.7, 23.3, 21.7, 16.7, and 11.7% for S. typhimurium, E. coli O157:H7, L. monocytogenes, K. pneumoniae and P. aeruginosa, respectively. Meanwhile, the overall prevalence was 30, 25, 22.5, 17.5, and 5% for E. coli O157:H7, L. monocytogenes, S. typhimurium, P. aeruginosa, and K. pneumoniae, respectively, for the 80 samples collected from a beef slaughterhouse. The antimicrobial susceptibility pattern elucidated that all isolated strains exhibited resistance to at least four of the tested antimicrobials, with multiple-antibiotic resistance index values (MAR) ranging between 0.44 and 0.88. Furthermore, the commercial AgNPs-H2O2 product was characterized by transmission electron microscopy (TEM) and zeta potential that showed spherical particles with a surface charge of −0.192 mV. The antimicrobial activity of synergized nano-silver (AgNP) with H2O2 product toward MDR strains was assessed via measuring minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill curve.ConclusionThe present data report high prevalence rates of MDR pathogens in dairy farms and abattoirs. More importantly, AgNPs-H2O2 exerted broad-spectrum bactericidal activity toward MDR bacterial strains, suggesting their promising usage as safe, ecofriendly, cost-effective antibacterial agents. To our knowledge, this study is a pioneer in investigating the potential alternative antimicrobial role of silver nanoparticles for control of multiple drug-resistant pathogens in Egypt.

Understanding and predicting ciprofloxacin minimum inhibitory concentration in Escherichia coli with machine learning

It is important that antibiotics prescriptions are based on antimicrobial susceptibility data to ensure effective treatment outcomes. The increasing availability of next-generation sequencing, bacterial whole genome sequencing (WGS) can facilitate a more reliable and faster alternative to traditional phenotyping for the detection and surveillance of AMR. This work proposes a machine learning approach that can predict the minimum inhibitory concentration (MIC) for a given antibiotic, here ciprofloxacin, on the basis of both genome-wide mutation profiles and profiles of acquired antimicrobial resistance genes. We analysed 704 Escherichia coli genomes combined with their respective MIC measurements for ciprofloxacin originating from different countries. The four most important predictors found by the model, mutations in gyrA residues Ser83 and Asp87, a mutation in parC residue Ser80 and presence of the qnrS1 gene, have been experimentally validated before. Using only these four predictors in a linear regression model, 65% and 93% of the test samples’ MIC were correctly predicted within a two- and a four-fold dilution range, respectively. The presented work does not treat machine learning as a black box model concept, but also identifies the genomic features that determine susceptibility. The recent progress in WGS technology in combination with machine learning analysis approaches indicates that in the near future WGS of bacteria might become cheaper and faster than a MIC measurement.

Reduced susceptibility mechanism to cefiderocol, a siderophore cephalosporin, among clinical isolates from a global surveillance programme (SIDERO-WT-2014)

ObjectiveTo investigate possible mechanistic factors to explain cefiderocol (CFDC) non-susceptibility, we characterized 38 clinical isolates with a CFDC minimum inhibitory concentration (MIC) of >4μg/mL from a multi-national surveillance study. MethodsThe MIC measurement in the presence of β-lactamase inhibitors and whole genome sequencing were performed. ResultsThe MIC decrease of CFDC by β-lactamase inhibitors was observed against all of the test isolates. Among the 38 isolates, NDM and PER genes were observed in 5 and 25 isolates, respectively. No other β-lactamases responsible for high MIC were identified in the other eight isolates. The MIC of CDFC against Escherichia coli isogenic strains introduced with NDM and PER β-lactamase increased by ≥16-fold, suggesting the contribution of NDM and PER to the non-susceptibility to CFDC. Against NDM producers, a ≥8-fold MIC increase was observed only when both serine- and metallo-type β-lactamase inhibitors were added. In addition, many of the PER or NDM producers remained susceptible to CFDC. These results suggested that the presence of only NDM or PER would not lead to non-susceptibility to CFDC and that multiple factors would be related to CFDC resistance. ConclusionMultiple factors including NDM and PER could be related to reduced susceptibility to CFDC.

Functional Identification and Evolutionary Analysis of Two Novel Plasmids Mediating Quinolone Resistance in Proteus vulgaris.

Plasmid-mediated quinolone resistance (PMQR) remains one of the main mechanisms of bacterial quinolone resistance and plays an important role in the transmission of antibiotic resistance genes (ARGs). In this study, two novel plasmids, p3M-2A and p3M-2B, which mediate quinolone resistance in Proteus vulgaris strain 3M (P3M) were identified. Of these, only p3M-2B appeared to be a qnrD-carrying plasmid. Both p3M-2A and p3M-2B could be transferred into Escherichia coli, and the latter caused a twofold change in ciprofloxacin resistance, according to the measured minimum inhibitory concentration (MIC). Plasmid curing/complementation and qRT-PCR results showed that p3M-2A can directly regulate the expression of qnrD in p3M-2B under treatment with ciprofloxacin, in which process, ORF1 was found to play an important role. Sequence alignments and phylogenetic analysis revealed the evolutionary relationships of all reported qnrD-carrying plasmids and showed that ORF1–4 in p3M-2B is the most conserved backbone for the normal function of qnrD-carrying plasmids. The identified direct repeats (DR) suggested that, from an evolutionary perspective, p3M-2B may have originated from the 2683-bp qnrD-carrying plasmid and may increase the possibility of plasmid recombination and then of qnrD transfer. To the best of our knowledge, this is the first identification of a novel qnrD-carrying plasmid isolated from a P. vulgaris strain of shrimp origin and a plasmid that plays a regulatory role in qnrD expression. This study also sheds new light on plasmid evolution and on the mechanism of horizontal transfer of ARGs encoded by plasmids.