Decrease In Minimum Inhibitory Concentration Research Articles

Analysis of the Antimicrobial Activity of Epigallocatechin-3-Gallate (EGCG).

We studied antimicrobial activity of epigallocatechin-3-gallate (EGCG), a green tea polyphenolic catechin, and its combined use with ceftazidime (CAZ) against bacterial strains of Klebsiella pneumoniae. EGCG exhibited no activity against strains of K. pneumoniae with a different sensitivity to CAZ. However, for a "sensitive" strain, a decrease in minimum inhibitory concentration (MIC) of CAZ (from 0.064 to 0.023 mg/liter) was revealed when CAZ was co-administered with EGCG. For a "resistant" stain, MIC of CAZ remained high, but activation of EGCG at its high concentrations was observed. Indirect evidence of antimicrobial effect of EGCG co-administered with CAZ on Klebsiella was obtained.

In vitro antimicrobial resistance of Escherichia coli, Serratia marcescens, Klebsiella oxytoca and Klebsiella pneumoniae on Bavarian dairy farms between 2014-2022

The objective of this study was to describe the prevalence of antimicrobial resistance of E. coli, K. oxytoca, K. pneumoniae, and S. marcescens from quarter milk samples submitted to the udder health laboratory of the Bavarian Animal Health Services (TGD) in Southern Germany between 2014 and 2022. All samples were tested with the California Mastitis Test and analyzed with a standard microbroth dilution to determine the minimum inhibitory concentrations (MIC). The antimicrobials tested were amoxicillin/clavulanate, cefazoline, kanamycin/cefalexin, cefoperazone, cefquinome, and marbofloxacin. Breakpoints were chosen in accordance with CLSI. Over the study period, E. coli, K. oxytoca, and K. pneumoniae showed only few resistances to all antimicrobials tested. For those pathogens MIC 50 and MIC 90 were below breakpoint for all antimicrobials except cefoperazone over the 9 years. A decrease in MIC could be seen for E. coli and K. oxytoca for all of the antimicrobials. While the MIC for K. pneumoniae stayed more stagnant, the prevalence of resistance still decreased overall. S. marcescens isolates were proven intrinsically resistant to amoxicillin/clavulanate and cefazolin and while in vitro resistances were low for all other antimicrobials tested, S. marcescens tended toward higher MIC for most of the antimicrobials over the years. Over time, there was also an overall increase in the number of isolates for all 4 pathogens per year. Starting 2018 there was steep increase in the number of isolates particularly from clinical cases. This jump in numbers coincided with a change of the regulation for veterinary drug prescriptions in Germany in 2018 that required, among other things, antimicrobial resistance testing before a change of antibiotics in the course of treatment and the use of critically important antimicrobials. Overall, while the pathogens increased in numbers, the prevalence of their antimicrobial resistance remained low.

Augmented antibacterial activity of cefazolin with silver nanoparticles against Staphylococcus aureus and Escherichia coli

Antibacterial drug resistance is a growing challenge that can be dealt with by introducing novel drugs or improving the efficacy of existing drugs. Combining nanomaterials with existing drugs to enhance drug effectiveness has garnered substantial research attention. Herein, we evaluated the synergistic antibacterial potential of cefazolin and silver nanoparticles (AgNPs) against two resistant strains of bacteria, Escherichia coli (ATCC35218) and Staphylococcus aureus (ATCC6538P). The broth macrodilution method and the Time-Kill assay were used to determine the antibacterial potential of the AgNP-Cefazolin combination. The Propidium Iodide Assay (PIA) and Bicinchoninic acid assay (BCA) were performed to examine the bacterial damage. Both strains showed the same minimum inhibitory concentration (MIC) of 400 μg/ml for cefazolin alone. When combined with AgNPs, both strains observed a significant MIC decrease. AgNPs to cefazolin ratio of 0.063:300 μg/ml exhibited the best antimicrobial activity against Staphylococcus aureus and Escherichia coli. PIA exhibited much fluorescence when cefazolin and AgNPs were used together, indicating significant damage to bacterial cell walls and membranes. Similarly, BCA showed leakage of a considerable amount of bacterial cytoplasmic protein in the media. Our results show that using AgNPs and cefazolin together could be a promising nano-drug against the two tested strains.

Evaluation of a Novel FKS1 R1354H Mutation Associated with Caspofungin Resistance in Candida auris Using the CRISPR-Cas9 System.

Outbreaks of invasive infections, with high mortality rates, caused by multidrug-resistant Candida auris have been reported worldwide. Although hotspot mutations in FKS1 are an established cause of echinocandin resistance, the actual contribution of these mutations to echinocandin resistance remains unknown. Here, we sequenced the FKS1 gene of a caspofungin-resistant clinical isolate (clade I) and identified a novel resistance mutation (G4061A inducing R1354H). We applied the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system to generate a recovered strain (H1354R) in which only this single nucleotide mutation was reverted to its wild-type sequence. We also generated mutant strains with only the R1354H mutation introduced into C. auris wild-type strains (clade I and II) and analyzed their antifungal susceptibility. Compared to their parental strains, the R1354H mutants exhibited a 4- to 16-fold increase in caspofungin minimum inhibitory concentration (MIC) while the H1354R reverted strain exhibited a 4-fold decrease in caspofungin MIC. In a mouse model of disseminated candidiasis, the in vivo therapeutic effect of caspofungin was more closely related to the FKS1 R1354H mutation and the virulence of the strain than its in vitro MIC. The CRISPR-Cas9 system could thus aid in elucidating the mechanism underlying drug resistance in C. auris.

Acinetobacter baumannii under Acidic Conditions Induces Colistin Resistance through PmrAB Activation and Lipid A Modification.

Colistin is a last-resort antimicrobial agent for treating carbapenem-resistant Acinetobacter baumannii infections. The activation of PmrAB by several environmental signals induces colistin resistance in Gram-negative bacteria. This study investigated the molecular mechanisms of colistin resistance in A. baumannii under acidic conditions using wild-type (WT) A. baumannii 17978, ΔpmrA and ΔpmrB mutants, and pmrA-complemented strains. The pmrA or pmrB deletion did not affect the growth of A. baumannii under acidic or aerobic conditions. A. baumannii under acidic (pH 5.5) and high-iron (1 mM) conditions showed 32- and 8-fold increases in the minimum inhibitory concentrations (MICs) of colistin, respectively. The ΔpmrA and ΔpmrB mutants at pH 5.5 showed a significant decrease in colistin MICs compared to the WT strain at pH 5.5. No difference in colistin MICs was observed between WT and mutant strains under high-iron conditions. The pmrCAB expression significantly increased in the WT strain at pH 5.5 compared to the WT strain at pH 7.0. The pmrC expression significantly decreased in two mutant strains at pH 5.5 compared to the WT strain at pH 5.5. The PmrA protein was expressed in the ΔpmrA strain carrying ppmrA_FLAG plasmids at pH 5.5 but not at pH 7.0. Lipid A modification by the addition of phosphoethanolamine was observed in the WT strain at pH 5.5. In conclusion, this study demonstrated that A. baumannii under acidic conditions induces colistin resistance via the activation of pmrCAB operon and subsequent lipid A modification.

Effect of Carbonyl Cyanide M-chlorophenylhydrazone on Ciprofloxacin Resistance and Biofilm Formation in Hospital-acquired Uropathogenic Escherichia coli and Klebsiella pneumoniae

Antibiotic resistant and biofilm forming uropathogenic Enterobacteriaceae are rising. This study was conducted to evaluate the efflux pump and plasmid mediated efflux genes in ciprofloxacin (CIP) resistant hospital acquired uropathogenic Escherichia coli and Klebsiella pneumoniae. Also, to assess the anti-biofilm action of carbonyl cyanide m-chlorophenylhydrazone (CCCP). Uropathogenic E. coli and K. pneumoniae isolates were collected from Mansoura University Hospitals in Mansoura, Egypt. The effect of Sub- minimum inhibitory concentration (MIC) of CCCP on CIP MIC was evaluated and the MIC decrease factor (MDF) was calculated. The presence of oqxAB and qepA genes was detected by PCR. The effect CCCP on biofilm was detected in strong biofilm formers. 56 and 47 CIP-resistant uropathogenic E. coli and K. pneumoniae isolates respectively were detected. Significant MDF by CCCP was observed in 55.3% of these isolates. The qepA gene was only present in E. coli. However, oqxAB genes were found only in K. pneumoniae. Biofilm formation was detected in 58.9% and 72.3% of CIP-resistant E. coli and K. pneumoniae isolates, respectively. Biofilm formation was significantly decreased by CCCP. According to these findings, CIP resistance and plasmid-mediated efflux pumps in uropathogenic E. coli and K. pneumoniae are of rising concern. Efflux pump inhibitor CCCP represents a possible option to decrease the biofilm formation in these resistant urinary pathogens.

Hydroxypropyl chitosan nail lacquer of ciclopirox-PLGA nanocapsules for augmented in vitro nail plate absorption and onychomycosis treatment

Onychomycosis accounts for 90% of nail infections worldwide. Topical therapy provides localized effects with minimal adverse systemic actions, yet its effectiveness is limited by minimal drug permeation through the keratinized nail plate. Ciclopirox (CIX) is a FDA-approved broad-spectrum antimycotic agent. However, the complete cure with its nail lacquer (8% w/v) may continue for one year with a high cost. Therefore, poly lactide-co-glycolide (PLGA) nanocapsules (NCs) of CIX were prepared by nanoprecipitation and optimized through a 23 factorial design to be incorporated into hydroxypropyl chitosan (HPCH) based nail lacquer. Nail hydration, in vitro nail absorption, minimum inhibitory concentration (MIC), inhibition zones and ex vivo fungal growth on nail fragments were evaluated. The optimized NCs of CIX based on 100 mg PLGA 2 A and lipoid S75 showed a mean diameter of 174.77 ± 7.90 nm, entrapment efficiency (EE%) of 90.57 ± 0.98%, zeta potential (ZP) of −52.27 ± 0.40 mV and a prolonged drug release. Nail lacquer of the optimized NCs exhibited a higher stability than NCs dispersion. Compared to CIX solution (1% w/v), the respective decrease in MIC for NCs and their lacquer was four- and eight-fold. The lacquer superiority was confirmed by the enhancement in the nail hydration and absorption by 4 and 2.60 times, respectively, relative to CIX solution and the minimal ex vivo fungal growth. Therefore, HPCH nail lacquer of (1% w/v) CIX-PLGA-NCs can be represented as a potential topical delivery system for enhanced in vitro nail absorption and therapeutic efficacy against onychomycosis at a low dose.

Isolation and Identification of Flavones Responsible for the Antibacterial Activities of Tillandsia bergeri Extracts.

Plants are an everlasting inspiration source of biologically active compounds. Among these medicinal plants, the biological activity of extracts from some species of the Tillandsia genus has been studied, but the phytochemistry of the hardy species Tillandsia bergeri remains unknown. The aim of the present study was to perform the first phytochemical study of T. bergeri and to identify the compounds responsible for the antibacterial activity of T. bergeri extracts. Soxhlet extraction of predried and grinded leaves was first performed using four increasing polarity solvents. A bio-guided fractionation was performed using agar overlay bioautography as a screening method against 12 Gram-positive, Gram-negative, sensitive, and resistant bacterial strains. The results showed the inhibition of Gram-positive methicillin-sensitive Staphylococcus aureus ATCC 29213 (MSSA), methicillin-resistant S. aureus N-SARM-1 (MRSA), and Staphylococcus caprae ATCC 35538 by the dichloromethane fraction. A phytochemical investigation led to the isolation and identification by high-resolution mass spectrometry and nuclear magnetic resonance of the two flavones penduletin and viscosine, responsible for this antibacterial activity. For viscosine, the minimum inhibitory concentration (MIC) value is equal to 128 μg/mL against MSSA and is equal to 256 μg/mL against MRSA and S. caprae. The combination of these compounds with vancomycin and cloxacillin showed a decrease in MICs of the antibiotics. Penduletin showed synergistic activity when combined with vancomycin against MSSA (FICI < 0.258) and S. caprae (FICI < 0.5). Thus, unexplored Tillandsia species may represent a valuable source for potential antibiotics and adjuvants.

Wound-Healing and Antibacterial Activity of the Quercetin–4-Formyl Phenyl Boronic Acid Complex against Bacterial Pathogens of Diabetic Foot Ulcer

Complications of diabetic foot can be prevented using a naturally occurring, efficient, and newly synthesized antimicrobial agent. The purpose of the study was to improve wound healing and antibacterial effects of quercetin and its esterified complex with 4-formyl phenyl boronic acid (4FPBA–Q) compared with phenytoin. The formation of the 4FPBA–Q complex was confirmed by thin-layer chromatography (TLC), Fourier transform infrared (FTIR) spectroscopy, and mass spectrometry (MS). The prepared 4FPBA–Q complex was used against Gram-positive bacteria along with Gram-negative bacteria, and more than 2-fold decrease in minimum inhibitory concentrations (MIC) was observed compared to pure quercetin. Scanning electron microscopic images of Pseudomonas aeruginosa and Staphylococcus aureus showed their complete destruction after incubation with the 4FPBA–Q complex even after 3 h. Interestingly, wound-healing properties of the 4FPBA–Q complex in infected diabetic rats increased from 64 to 99% as compared to phenytoin, which were increased from those of noninfected diabetic rats. Furthermore, histopathological evaluations showed significantly enhanced wound healing, re-epithelialization, fibroblasts, and angiogenesis in wounds of diabetic rats after 10 days. Conclusively, reduction in the primary irritation index (PDII) and improved antibacterial and wound-healing properties render the 4FPBA–Q complex ideal for diabetic foot ulcer treatment.

Hydrogel composite containing azelaic acid and tea tree essential oil as a therapeutic strategy for Propionibacterium and testosterone-induced acne

Azelaic acid (AzA) is a USFDA bioactive prescribed against acne vulgaris. It possesses delivery challenges like poor aqueous solubility, low skin-penetrability, and dose-dependent side effects, which could be overcome by its synergistic combination with tea tree oil (TTO) as a microemulsion (ME)-based hydrogel composite. AzA-TTO ME was prepared to employ pseudo-ternary phase diagram construction. The best AzA-TTO ME was of uniform size (polydispersity index < 0.7), nano-range (~357.4 ± 2% nm), transmittance (> 90%), and negative zeta potential (−1.42 ± 0.25% mV) values. ME hydrogel composite with optimum rheological and textural attributes showed better permeation, retention, and skin-compliant characteristics, vis-a-vis marketed formulation (Aziderm™) when evaluated in Wistar rat skin. In vitro antibacterial efficacy in bacterial strains, i.e., Staphylococcus aureus, Propionibacterium acne, and Staphylococcus epidermidis, was evaluated employing agar well plate diffusion and broth dilution assay. ME hydrogel has shown an increase in zone of inhibition by two folds and a decrease in minimum inhibitory concentration (MIC) by eightfold against P. acnes vis-a-vis AzA. Finally, ME hydrogel composite exhibited a better reduction in the papule density (93.75 ± 1.64%) in comparison to Aziderm™ 72.69 ± 4.67%) on acne as developed in rats by inducing testosterone. Thus, the developed AzA-TTO ME hydrogel composite promises an efficacious and comparatively safer drug delivery system for the topical therapy of acne vulgaris.Graphical abstract

PHENOTYPIC DETECTION OF EFFLUX MECHANISM IN AMIKACIN-RESISTANT ACINETOBACTER ISOLATES FROM TWO DIFFERENT STATES IN SOUTH INDIA

Acinetobacter has already gained resistance to the majority of antibiotics available. Aminoglycosides are commonly used to treat invasive infections. Aminoglycoside resistance is associated with decreased drug absorption, aminoglycoside modification, and aminoglycoside efflux. The aim of this study was to detect the presence of an efflux mechanism in amikacin-resistant Acinetobacter isolated from hospital wards using Carbonyl Cyanide 3- Chlorophenylhydrazone (CCCP). One hundred isolates of Acinetobacter were isolated from tertiary care hospitals in two distinct South Indian states. Antibacterial susceptibility patterns were discovered between 2017 and 2019. Amikacin minimum inhibitory concentration (MIC) for resistant Acinetobacter isolates was determined using Clinical and Laboratory Standards Institute (CLSI) standards. The efflux system activity was determined using CCCP. Among 100 Acinetobacter baumannii isolates, 49 isolates with amikacin resistance were found. The MIC’s of Acinetobacter ranged between 2 – 1024 μg/mL for the amikacin studied. After treatment with the efflux pump inhibitor, 38.77% of isolates became less resistant to amikacin, as determined by phenotypic detection of efflux pumps, showing a decrease in antibiotic MICs of at least four fold. The data demonstrated the importance of efflux pump activity conferring amikacin resistance on Acinetobacter clinical isolates.

Cloning and sequencing of lsaE efflux pump gene from MDR Enterococci and its role in erythromycin resistance

Enterococci are opportunistic members of intestinal microbiota with notable ability to transmit antimicrobial resistance genes. Among the different resistance mechanisms, multidrug efflux is evolving as a huge problem in conferring multidrug resistance to bacterial cells because these pumps extrude a broad range of antimicrobials. Therefore, the aim of this work was to evaluate role of efflux pumps in the development of multi-drug resistance in Enterococci through studying the antimicrobial resistance profiles of Enterococci isolates, phenotypically and genotypically investigating the role of active efflux pumps in development of resistance, in addition to characterizing the most common efflux pump genes. The study involved the recovery of 149 Enterococci isolates from specimens of patients suffering infections in some hospitals in Egypt. Antimicrobial resistance profiles of isolates showed that only 1.3% of the isolates were resistant to each of linezolid, daptomycin, and fosfomycin. The highest resistance was to ampicillin (60.4%) while 47 of the isolates (31.54%) were found to be multidrug-resistant. Efflux pumps have shown to have a significant role in erythromycin resistance in 11 isolates (23.4% of MDR isolates) as indicated by an 8 or more fold decrease in minimum inhibitory concentration in the presence of the efflux pump inhibitor, carbonyl cyanide m- chlorophenylhydrazone (CCCP). End point PCR was used to detect efflux pump genes lsaE, msrC, and mefA in the 11 isolates at which efflux pumps were found to play a significant role in resistance. Nine out of the 11 isolates (81.8%) were found to carry lsaE gene. This gene was inserted into pUC21 vector and cloned into DH5α E. coli resulting in successful transformation and expression of erythromycin resistance in this host. Finally, sequencing of the lsaE gene was carried out. To the best of our knowledge, this is the first report on the cloning of lsaE gene from MDR Enterococcus isolates.

Effect of hybrid combinations of Erythroxylum revolutum Mart. leaf ethanolic extract or alkaloid-enriched fraction with antibiotic drugs against multidrug-resistant bacteria strains

Background The combination between antibiotic drugs and extracts derived from medicinal plants is one of the promising strategies against multidrug-resistant (MDR) bacterial strains to overwhelm the antimicrobial resistance.Hypothesis/Purpose We aimed to evaluate the antibacterial effect of hybrid combinations of ethanolic extract (EREE) or alkaloid-enriched fraction (ERAF) obtained from Erythroxylum revolutum leaves and conventional antibiotic drugs.Methods We tested the antimicrobial activity of EREE and ERAF in vitro against gram-positive (Staphyloccocus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) standard and MDR strains. Additionally, we performed phytochemical studies using GC/MS, 1H, 13C NMR spectra, and two-dimensional techniques.Results Although the minimum inhibitory concentration (MIC) values of EREE or ERAF alone against bacterial growth were ≥ 1024 µg/ml, we denoted a total synergism effect in the hybrid combinations ERAF + gentamicin, ERAF + norfloxacin, and ERAF + erythromycin against MDR S. aureus strain, with a significant MIC reduction of 84.7%, 75.0%, and 89.85%, respectively. Although EREE demonstrated a total synergism effect in the hybrid combination gentamicin + EREE (with a significant decrease of MIC of 68.8%), on the contrary, EREE also elicited a strong antagonist effect in some hybrid combinations against the MDR bacteria strains tested. Phytochemical studies revealed in ERAF the presence of two tropane alkaloids described for the first time in the family Erythroxylaceae: 6-(2’-methylbutyryloxy)-3-hydroxytropane (87.07%) and 6-butyryloxy-3-hydroxytropane (12.93%).Conclusion Together, these data can highlight the first evidence of enriched-alkaloid fractions of E. revolutum in hybrid combinations with antibiotics, and propose tropane alkaloids from E. revolutum as new potential candidates in drug combinations for the treatment of infections caused by MDR S. aureus, which is one of the main agents causing infections with death worldwide.

Investigation of the Rv3065, Rv2942, Rv1258c, Rv1410c, and Rv2459 efflux pump genes expression among multidrug-resistant Mycobacterium tuberculosis clinical isolates

BackgroundDifferent resistance mechanisms for multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) have been reported. Although mutations in target genes are the main cause of drug resistance, efflux pumps (Eps) also play an important role in this process. Here, we investigated the overexpression of five putative EP genes plus gene mutations in MDR-TB clinical isolates. MethodsA total of 27 M. tuberculosis (Mtb) clinical isolates including, 22 MDR and 5 sensitive isolates were analyzed. Minimum inhibitory concentrations (MIC) were determined in the absence and presence of efflux inhibitor. The expression level of 5 EP genes (Rv3065, Rv2942, Rv1258c, Rv1410c, Rv2459) was investigated by quantitative real time PCR (RT-qPCR). DNA sequencing of rpoB, katG, and inhA promoter was done. ResultsAmong the 22 MDR-TB isolates, 13 (59.1%) showed significant overexpression (>4-fold) for at least one EP gene. The expression levels of 5 genes were significantly higher (P < 0.05) in MDR-TB isolates than sensitive isolates. The Rv3065 (22.7%), and Rv1410c (18.2%) were found to be the most commonly overexpressed EPs. The observed MICs were as follows: RIF (2 to >128 μg/ml) and INH (2–32 μg/ml). After efflux pump inhibitor exposure, 10/22 (45.45%) isolates showed a decrease in MIC of INH, and 17/22 (77.27%) isolates showed a decrease in MIC of RIF. Of the isolates that overexpressed, 4 isolates lacked mutation in inhA, rpoB, and katG genes and 10 ones lacked mutation in inhA and katG. ConclusionThe results showed that overexpression of EP genes in Mtb isolates, besides target gene mutations can contribute to the development of MDR phenotype.

Antibacterial and Antifungal Activities and Toxicity of the Essential Oil from Callistemon viminalis Complexed with β-Cyclodextrin.

The essential oil from Callistemon viminalis (EOC) is rich in monoterpenes, with a variety of biological properties: antibacterial, antifungal, insecticide, and antioxidant. Inclusion complexes (ICs) with cyclodextrins (CDs) is an alternative to prevent toxicity, improve the activity, and reduce the concentration to be used. Thus, the objective of this work was to prepare an IC (EOC/β-CD) and evaluate the antibacterial, antifungal and phospholipase activities, as well as the toxicity. Antimicrobial activity used the agar diffusion test and antifungal activity the disc diffusion test. Toxicity tests were carried out using Lactuca sativa L. The inhibition of phospholipase activity using the venom of Bothrops atrox as an inducer was performed. Antibacterial and antifungal tests demonstrated a decrease in the minimum inhibitory concentration (MIC) of the IC. It was most significantly observed for the bacterium Listeria monocytogenes, for which there was a decrease in the MIC from 250µgmL-1 to 62.5µgmL-1 after complexation, and for the fungus Aspergillus flavus, with a decrease in MIC from 125µgmL-1 to 62.5µgmL-1 after complexation. Toxicity tests with Lactuca sativa showed a decrease in toxicity after complexation in all parameters analyzed, with no statistical difference from the negative control. Inhibition of phospholipase activity induced by Bothrops atrox venom was more expressive in the highest proportion studied (1:10m:m), exerting 23% inhibition. The assays demonstrated that the complexation between the EOC and β-CD is a promising alternative for use in different branches, especially in food industry, to fully exploit its application potential.

Guar gum micro-vehicle mediated delivery strategy and synergistic activity of thymoquinone and piperine: An in vitro study on bacterial and hepatocellular carcinoma cells

This study reports the observed synergy in antimicrobial and anticancer activity of thymoquinone and piperine, encapsulated in porous guar gum micro-vehicle. Natural therapeutics like piperine and thymoquinone showed less effectivity in human medical trials due to their hydrophobicity leading to poor clinical efficacy. To overcome this problem, we have developed a delivery strategy by using guar gum, a natural biodegradable biopolymer. The successful encapsulation of phytochemicals and the microstructures of gum micro-vehicles were confirmed by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) and UV–Vis spectra analysis. We also report here a significant decrease in minimum inhibitory concentration (MIC) value and synergistic bactericidal activity against four different bacterial strains and observed remarkably low median lethal dose (LD50) value against human hepatocellular carcinoma cell lines along with pH-responsive delivery of therapeutic in the case of combinatorial therapy. In our overall study, we analyze and discuss the structure, efficacy, and delivery of our designed natural therapeutic amalgamation to pave the way for augmenting the use of phytochemicals in medical applications.

Supramolecular self-assembled drug delivery system (SADDs) of vancomycin and tocopherol succinate as an antibacterial agent: in vitro, in silico and in vivo evaluations

In this study self-assembled drug delivery system (SADDs) composed of a hydrophobic d-α-tocopherol succinate (TS) and a hydrophilic vancomycin (VCM) were formulated, and its potential for enhancing the antibacterial activity of VCM against Staphylococcus aureus (SA) and Methicillin-resistant Staphylococcus aureus (MRSA) were explored. The SADDs were synthesized via supramolecular complexation, then characterized for in silico, in vitro and in vivo studies. In silico studies confirmed the self-assembly of VCM/TS into NPs. The size, surface charge and drug loading of the SADDs was ˂100 nm, −27 mV and 68%, respectively. The SADDs were non-hemolytic and biosafe. A sustained release of VCM from SADDs was noted, with 52.2% release after 48 hr. The in vitro antibacterial test showed a twofold decrease in Minimum inhibitory concentration (MIC) against SA and MRSA, and a significantly higher reduction in MRSA biofilms compared to bare VCM. Further, in silico studies confirmed strong and stable binding of TS to MRSA efflux pumps. The in vivo study using mice skin infection models showed a 9.5-fold reduction in bacterial load after treatment with SADDs, in comparison with bare VCM. These findings affirmed that VCM/TS NPs as a promising novel nano-delivery for treating bacterial infections.

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.

Inhibitory effects of aptamer targeted teicoplanin encapsulated PLGA nanoparticles for Staphylococcus aureus strains.

Emergence of resistance to traditional antibiotic treatments necessitates alternative delivery systems. Teicoplanin is a glycopeptide antibiotic used in the treatments of serious infections caused by Gram-positive bacteria, including Methicillin Resistant Staphylococcus aureus (MRSA). One strategy to keep up with antibiotic resistance development is to limit dose and amount during treatments. Targeted delivery systems of antibiotics have been suggested as a mechanism to slow-down the evolution of resistance and to increase efficiency of the antimicrobials on already resistant pathogens. In this study, we report teicoplanin delivery nanoparticles of Poly Lactic-co-Glycolic Acid (PLGA), which are functionalized with S. aureus specific aptamers. A 32-fold decrease in minimum inhibitory concentration (MIC) values of teicoplanin for S. aureus was demonstrated for susceptible strains and about 64-fold decline in MIC value was achieved for moderately resistant clinical isolates of MRSA upon teicoplanin treatment with aptamer-PLGA nanoparticles. Although teicoplanin delivery in PLGA nanoparticles without targeting demonstrated eightfold decrease in MIC of susceptible strains of S. aureus and S. epidermidis and twofold in MIC of resistant strains, the aptamer targeting specifically decreased MIC for S. aureus, but not for S. epidermidis. Therefore, aptamer-targeted PLGA delivery of antibiotic can be an attractive alternative to combat with some of the multi-drug resistant bacterial pathogens.

Azithromycin Exerts Bactericidal Activity and Enhances Innate Immune Mediated Killing of MDR Achromobacter xylosoxidans.

Azithromycin (AZM), the most commonly prescribed antibiotic in the United States, is thought to have no activity against multidrug-resistant Gram-negative pathogens such as Achromobacter xylosoxidans (AX) per standard minimum inhibitory concentration testing in cation-adjusted Mueller Hinton Broth. Here we provide the first report of AZM bactericidal activity against carbapenem-resistant isolates of AX, with a multifold decrease in minimum inhibitory concentration across 12 clinical isolates when examined under physiologic testing conditions that better recapitulate the in vivo human environment. This pharmaceutical activity, evident in eukaryotic tissue culture media, is associated with enhanced AZM intracellular penetration and synergistic killing with human whole blood, serum, and neutrophils. Additionally, AZM monotherapy inhibited preformed AX biofilm growth in a dose-dependent manner together with a reduction in viable bacteria. In an illustrative case, AZM in combination with piperacillin-tazobactam exerted clear therapeutic effects in a patient with carbapenem-resistant AX mediastinitis, sternal osteomyelitis, and aortic graft infection. Our study reinforces how current antimicrobial testing practices fail to recapitulate the host environment or host-pathogen interactions and may misleadingly declare complete resistance to useful agents, adversely affecting patient outcomes. We conclude that AZM merits further exploration in the treatment of drug-resistant AX infections. Novel approaches to antimicrobial susceptibility testing that better recapitulate the host environment should be considered, especially as infections caused by multidrug-resistant Gram-negative bacterial pathogens are expanding globally with high morbidity and mortality.