Low MIC Values Research Articles

Sulfamethoxazole-phytochemical hybrid: A novel approach in current antibacterial drug development

Background: The Gram-positive (GP) bacterium, methicillin-resistant Staphylococcus aureus (MRSA) causes common infection, bacteremia at hospitals, and community sectors, with the simultaneous aggrandizement of resistance to several currently used antibacterials, resulting in additional morbidity and unexpected mortality. Since the last several decades, thousands of phytochemicals with antimicrobial potency have been recorded as alternate antibacterial agents; but, none of those have gone up to the pure-drug stage due to the lack of the desired drug-likeness values and the required pharmacokinetic properties. However, chemical modification of parent drug remains as the versatile approach in antibacterial drug development. Methods and materials: Based on the structural suitability of sulfamethoxazole (SMZ) and as a solution towards control of MRSA, proposed six new ‘SMZ-phytochemical’ hybrid entities followed by protocol of azo-coupling synthesis. PASS prediction, Lipinski rules of five, lethal-dose value, toxicity class, and molecular docking-simulation were employed before chemical synthesis. Due to the unavailability of the three-dimensional (3D) structure of the suitable target enzyme, MRSA-dihydropteroate synthases (DHPS), the 3D model of MRSA-DHPS was generated and validated by the Ramachandran plot for molecular docking-simulations study with designed hybrids. Based on the above computational analyses, the most effective hybrid, ‘SMZ-thymol,’ was synthesized and characterized by advanced spectral techniques such as UV, FTIR, LCMS, HPLC, NMR, and SEM. The zone of inhibition, MIC, and MBC values of the hybrid had determined against isolated MRSA strain from clinical samples, in vitro. Results: The synthesized ‘SMZ-thymol’ hybrid had the highest zone size inhibition on agar plates with 20 and 40 μg/mL as the lowest MIC and MBC values against MRSA, respectively, while the reference antibiotic ampicillin had the lower MIC and MBC values at 80 to 180 μg/mL. Additionally, from in vitro host-toxicity testing with cultured human lymphocytes from umbilical cord blood confirmed that the synthesized hybrid had broadly, non-toxic to human cells. Conclusion: Thus, newly synthesized ‘SMZ-thymol’ could be promoted as a newer antibacterial agent against gruesome MRSA and other MDR pathogenic bacteria. Indeed, the utilization of inactive antibacterials through suitable phytochemicals in the current antibacterial drug development module could be a prudent time-killing drug development approach using tools of medicinal chemistry and bioinformatics.

ANTI-CARIOGENIC POTENTIALS OF VITEX NEGUNDO LINN

Vitex negundo Linn. (Verbenaceae), is an ethnobotanical important shrub carrying a large array of pharmacologically active phytochemicals with diverse medicinal properties. Present study assessed the antibacterial activities of leaf and twig (without leaf) bioactives against common oral bacterial inhabitants viz., Staphylococcus aureus, Streptococcus oralis, Streptococcus gordonii, Streptococcus mutans, Lactobacillus brevis and Lactobacillus casei. Leaf and twig dried powdered samples of V. negundo were separately fractionated by five solvents in eluotropic series namely petroleum-ether, chloroform, absolute-ethanol, 80%-methanol and distilled-water. Extracts were further analyzed for total phenolic contents (TPC), flavonoids (TFC), tannins, alkaloids and terpenoids. Zone of inhibition, MIC, MBC and IC50 values of the fractionated extracts against oral bacterial pathogens were determined. The results demonstrated significantly higher antibacterial activity in ethanolic extracts (VnLEt) and chloroform (VnLCh) extracts of leaves as evident by their higher ZOI and lower MIC, MBC and IC50 values. VnLEt extracts showed bactericidal effects against all the tested six bacterial pathogens (L. casei>St. gordonii>Staphylococcus aureus>L. brevis>St. oralis=St. mutans). VnLCh showed notable bactericidal effects against five pathogens (L. casei>St. mutans>St. gordonii>Staphylococcus aureus) but remained ineffective against St. oralis and L. brevis. Among twig extracts, ethanolic extracts showed inhibition against Staphylococcus aureus, St. gordonii and St. mutans while chloroform extracts showed antibacterial effect only against Staphylococcus aureus. VnLEt extract showed abundance in TPC, TFC and tannins while VnLCh was rich in alkaloids and terpenoid suggesting their contribution in bactericidal effects against cariogenic bacterial pathogens. Hence, the present study successfully established V. negundo leaf extracts as an excellent natural remedy for oral-dental infections.

Synthesis, biological evaluation and QSAR studies of new thieno[2,3-d]pyrimidin-4(3H)-one derivatives as antimicrobial and antifungal agents

A series of new thieno[2,3-d]pyrimidin-4(3H)-one derivatives were synthesized and evaluated for their activity against four gram-positive and four gram-negative bacterial and eight fungal species. The majority of the compounds exhibited excellent antimicrobial and antifungal activity, being more potent than the control compounds. Compound 22, bearing a m-methoxyphenyl group and an ethylenediamine side chain anchored at C-2 of the thienopyrimidinone core, is the most potent antibacterial compound with broad antimicrobial activity with MIC values in the range of 0.05–0.13 mM, being 6 to 15 fold more potent than the controls, streptomycin and ampicillin. Furthermore, compounds 14 and 15 which bear a p-chlorophenyl and m-methoxyphenyl group, respectively, and share a 2-(2-mercaptoethoxy)ethan-1-ol side chain showed the best antifungal activity, being 10–15 times more potent than ketoconazole or bifonazole with MIC values 0.013–0.026 and 0.027 mM, respectively. Especially in the case of compound 15 the low MIC values were accompanied by excellent MFC values ranging from 0.056 to 0.058 mM. Evaluation of toxicity in vitro on HFL-1 human embryonic primary cells and in vivo in the nematode C. elegans revealed no toxic effects for both compounds 15 and 22 tested at the MIC concentrations. Ligand-based similarity search and molecular docking predicted that the antibacterial activity of analogue 22 is related to inhibition of the topoisomerase II DNA gyrase enzyme and the antifungal activity of compound 15 to CYP51 lanosterol demethylase enzyme. R-Group analysis as a means of computational structure activity relationship tool, highlighted the compounds’ crucial pharmacophore features and their impact on the antibacterial and antifungal activity. The presence of a N-methyl piperidine ring fused to the thienopyrimidinone core plays an important role in both activities.

Design, synthesis, antimicrobial evaluation and in silico studies of symmetrical bis (urea-1,2,3-triazole) hybrids

In search of 1,2,3-triazole-based antimicrobials, some symmetrical bis(urea-1,2,3-triazole) hybrids were synthesized via clicked Huisgen cycloaddition. The structural characterization was done by different physical and spectral techniques like NMR, FTIR and HRMS. In vitro antimicrobial evaluation of all the synthesized compounds was performed against three bacterial strains (Staphylococcus epidermidis, Escherichia coli and Bacillus subtilis) and two fungal strains (Aspergillus niger and Candida albicans). All the synthesized urea-linked bis(1,2,3-triazole) hybrids (4a–4o) were found to exhibit higher potency than their alkyne precursors (3a–3c). Also, all the synthesized hybrids elicited better antifungal activity than the reference drug Fluconazole against both the fungal strains. Compound 4e and 4o were found to be more potent toward C. albicans with lowest MIC values 0.0112 µmol/mL and 0.0105 µmol/mL, respectively. The docking studies of compounds 4e and 4o and their respective alkynes 3b and 3c were carried out in the active site of sterol 14-α-demethylase of C. albicans.

Carbapenemase OXA-423: A Novel OXA-23 Variant in Acinetobacter baumannii.

PurposeA novel variant of OXA-23, named OXA-423, was identified in an Acinetobacter baumannii clinical isolate. The aim of this study was to analyse the resistance phenotype of OXA-423.MethodsThe A. baumannii strain WY-0713 was isolated from an intensive care unit patient. PCR was used to detect the blaOXA-23-like genes. Amplifying, cloning and sequencing were performed for the complete blaOXA-23-like. The novel blaOXA-423 and its ancestor blaOXA-23 were cloned into the expression vector pET-28b(+), and transformed into E. coli Rosetta (DE3) for antibiotic susceptibility testing. SDS-PAGE, modified Hodge test and CarbaNP test were used for detecting the expression of OXA-423 and OXA-23.ResultsPCR screening of A. baumannii WY-0713 was positive for blaOXA-23-like genes. Sequencing of the PCR product identified a novel blaOXA-23-like, named blaOXA-423 which encoding OXA-423. OXA-423 differed from OXA-23 by a crucial amino acid substitution (Val128Ala). The V128A substitution was located at the conserved active-site motifs SAV of OXA-23. Antibiotic susceptibility testing performed using isogenic E. coli showed that the MICs of E. coli Rosetta (pET-OXA-423) for penicillins and carbapenems were lower (reduced MICs 4-fold to 16-fold) than that of E. coli Rosetta (pET-OXA-23). The MICs of cefotaxime, ceftazidime and aztreonam for both transformants remained the same as the acceptor strain. Moreover, OXA-423 was slightly inhibited by sulbactam, clavulanic acid and tazobactam. SDS-PAGE analysis showed that OXA-423 and OXA-23 were conspicuously expressed. Modified Hodge test and CarbaNP test were positive demonstrated both of them were functional.ConclusionOXA-423, the first report of an amino acid substitution located at conserved active-site motifs of OXA-23, conferred lower MIC values of penicillins and carbapenems as compared with OXA-23, while without affecting the resistance profiles of expanded-spectrum cephalosporins and aztreonam.

Synthesis, Characterization and Antimicrobial Activity of Some Novel 1- substituted Benzimidazole Derivatives

Background: Benzimidazole derivatives are an important class of heterocyclic compounds in organic chemistry as they are related to a wide range of biological properties, including antimicrobial activity. Methods: A series of 1-naphthoyl and benzoyl benzimidazole derivatives were synthesised, identified and screened for their antimicrobial activities against a number of different test organisms such as Escherichia coli, Pseudomonas aureginosa, Klebsiella pneumoniae, Staphylococcus aureus, Enterococcus faecalis, Bacillus cereus, Salmonella typhimurium, Candida albicans (yeast). Results and Discussion: Benzimidazole derivatives (3a-d) were synthesised by using 4 different aminoacids. L-methionine, L-isoleucine, D-Phenylysine and L-Phenylamine as starting materials in the study. Experimental studies involve the use of benzimidazole derivatives (3a-d) of the selected amino acids to synthesize the benzoyl and naphthoyl derivatives of benzimidazole (4a-d, 5a-c). The structures of the synthesized compounds were confirmed by spectroscopic analyses (FTIR, 1HNMR, 13C-NMR) and elemental analysis. Conclusion: In this study, only one compound (5a) showed a low MIC value against the eukaryotic microorganism C. albicans. The other six compounds showed higher antimicrobial activities against the prokaryotes C. albicans which is a normal flora in the mouth but is one of the organisms that cause infections leading to the weakening of the human immune system. Compound 5a is a candidate for future alternative antimicrobial drugs against C. albicans infections. In addition, compound 5a has a potential to be used as an inhibitor against P. aureginosa for the treatment of cystic fibrosis.

Characterization of Streptomyces Isolates Associated with Estuarine Fish Chanos chanos and Profiling of Their Antibacterial Metabolites-Crude-Extract.

Streptomyces has been reported as an essential producer of bioactive substances, including antibiotics and other types of antimicrobials. This study investigated antibacterial-producing Streptomyces isolated from the gut of estuarine fish Chanos chanos, emphasizing screening for the producer of peptide-containing antibacterial compounds. Eighteen isolates were found during preliminary screening, in which four isolates showed the best antibacterial activities. Based on the morphological, physiological, and biochemical characterization, as well as 16S rRNA partial sequencing, all of the four isolates belonged to Streptomyces. Three isolates were suspected as novel isolate candidates based on homology presentations and phylogenetic tree analysis. Disk-diffusion assay of the metabolite-crude-extract from the isolates showed broad-spectrum inhibitory activities against Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 10876, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa InaCC B52 with minimum inhibitory concentration and minimum bactericidal concentration ranging from 2.5–10 mg/mL and 5–10 mg/mL, respectively. The highest antibacterial activity with low MIC and MBC values was shown by isolate AIA-10. Qualitative HPLC profiling revealed that the metabolic-crude-extracts showed many peaks with intensive area at 210 and 214 nm, especially from SCA-11 and AIA-10, indicating the presence of peptide groups in the structure of the constituent compound. The results also suggested that crude extracts SCA-11 and AIA-10 had higher hydrophobicity properties than the other extracts. Further characterization of the active compound was needed to find out which compounds were responsible for the antibacterial activity. The results of this study indicated that some Streptomyces isolated from new environmental niches, i.e., gut of estuarine fish Chanos chanos, produce promising peptide-containing bioactive compounds.

Characterization of the Bacteriophage-Derived Endolysins PlySs2 and PlySs9 with In Vitro Lytic Activity against Bovine Mastitis Streptococcus uberis.

Bovine mastitis, an infection of the cow’s mammary gland, is frequently caused by Streptococcus uberis and causes major economic losses in the dairy industry. The intramammary administration of antibiotics currently remains the predominant preventive and therapeutic measure. These antimicrobial compounds, of which some are considered critical in human health care, are frequently applied as dry therapy resulting in their consistent overuse. Therefore, the use of antibiotics in the dairy sector is being questioned. We here identified two endolysins, i.e., PlySs2 and PlySs9, respectively derived from Streptococcus suis serotype-2 and -9 prophages, with lytic activity against S. uberis in an in vitro setting. Both endolysins gave clear lysis zones in spot-on-plate assays and caused a reduction of the optical density in a turbidity reduction assay. In depth characterization identified PlySs9 as the more potent endolysin over PlySs2 with a lower MIC value and about one additional log of killing. PlySs2 and PlySs9 were challenged to a panel of subclinical and clinical S. uberis milk isolates and were both able to lyse all strains tested. Molecular dissection of these endolysins in catalytic and cell wall binding subdomains resulted in major loss of killing and binding activity, respectively. Taken together, we here propose PlySs2 and PlySs9 as candidate compounds to the current antimicrobial arsenal known against bovine mastitis-causing S. uberis as future add-on or replacement strategy to the currently used intramammary antibiotics.

HPLC-DAD phenolic profiles, antibiofilm, anti-quorum sensing and enzyme inhibitory potentials of Camellia sinensis (L.) O. Kuntze and Curcuma longa L.

This study aimed at investigating phenolic composition, anti-quorum sensing and enzyme inhibitory potential of Camellia sinensis and Curcuma longa. HPLC-DAD identified and quantified curcumin (398.67 ± 0.34 mg/g), demethoxycurcumin (261.39 ± 0.27 mg/g) and bisdemethoxycurcumin (173.32 ± 0.46 mg/g) in C. longa extract and eight phenolics in C. sinensis with major components epigallocatechin (365.53 ± 0.49 mg/g), epicatechin (324.05 ± 0.37 mg/g) and epicatechin gallate (94.48 ± 0.27 mg/g). Seven pathogenic microorganisms (Escherichia coli, Listeria monocytogenes, Enterococcus faecalis, Salmonella typhi, Staphylococcus aureus, Candida albicans, Pseudomonas aeruginosa) were subjected to antimicrobial and antibiofilm assays and lowest MIC values were 0.3125 mg/mL exhibited by Camellia sinensis on S. aureus and Curcuma longa on P. aeruginosa. At MIC and sub-MIC concentrations, extracts displayed excellent antibiofilm activities especially at MIC concentrations and S. aureus was most susceptible to extracts of C. sinensis (80.56 ± 1.16%) and C. longa (75.79 ± 0.58%). Extracts exhibited concentration-dependent percentage inhibitions of motility and violacein production but only C. longa displayed good antiquorum sensing activity at MIC (18.6 ± 3.0 mm) and MIC/2 (14.5 ± 0.2 mm). C. longa extract disrupted signal reception by CV026 of externally supplied acyl homoserine lactone within revealed anti-quorum sensing zones. Extracts displayed moderate anticholinesterase, anti-urease and anti-tyrosinase activities. Both food extracts can control foodborne infections.

Antibacterial Activity of Non-Cytotoxic, Amino Acid-Modified Polycationic Dendrimers against Pseudomonas aeruginosa and Other Non-Fermenting Gram-Negative Bacteria.

Due to the rapid increase of antimicrobial resistance with ensuring therapeutic failures, the purpose of this study was to identify novel synthetic molecules as alternatives to conventional available, but presently ineffective antibiotics. Variously structured cationic dendrimers previously reported have provided promising outcomes. However, the problem of their cytotoxicity towards eukaryotic cells has not been completely overcome. We have now investigated the antibacterial activities of three not cytotoxic cationic dendrimers (G5Ds: G5H, G5K, and G5HK) against several multidrug-resistant (MDR) clinical strains. All G5Ds displayed remarkable activity against MDR non-fermenting Gram-negative species such as P. aeruginosa, S. maltophilia, and A. baumannii (MICs = 0.5–33.2 µM). In particular, very low MIC values (0.5–2.1 µM) were observed for G5K, which proved to be more active than the potent colistin (2.1 versus 3.19 µM) against P. aeruginosa. Concerning its mechanism of action, in time-killing and turbidimetric studies, G5K displayed a rapid non-lytic bactericidal activity. Considering the absence of cytotoxicity of these new compounds and their potency, comparable or even higher than that provided by the dendrimers previously reported, G5Ds may be proposed as promising novel antibacterial agents capable of overcoming the alarming resistance rates of several nosocomial non-fermenting Gram-negative pathogens.

Semi-synthesis of antibacterial dialkylresorcinol derivatives.

Dialkylresorcinols are a class of antimicrobial natural products produced by a range of bacterial species. Semi-synthetic derivatization of two microbial dialkylresorcinols isolated from a Pseudomonas aurantiaca strain has yielded 21 derivatives, which were tested for antimicrobial activity, revealing several trends in their activity. The presence of aromatic and phenolic hydrogen atoms was crucial for activity, with all derivatives lacking these features possessing greatly reduced activity. On the other hand, derivatives with shorter alkyl chains at C-5 possessed lower MIC values, while one mono-fluorosulfated derivative showed significantly improved activity against several of the test strains.

1,3-Disubstituted urea derivatives: Synthesis, antimicrobial activity evaluation and in silico studies

The development of new antimicrobial compounds is in high demand to overcome the emerging drug resistance against infectious microbial pathogens. In the present study, we carried out the extensive antimicrobial screening of disubstituted urea derivatives. In addition to the classical synthesis of urea compounds by the reaction of amines and isocyanates, we also applied a new route including bromination, oxidation and azidination reactions, respectively, to convert 2-amino-3-methylpyridine to 1,3-disubstituted urea derivatives using various amines. The evaluation of antimicrobial activities against various bacterial strains, Candida albicans as well as Mycobacterium tuberculosis resulted in the discovery of new active molecules. Among them, two compounds, which have the lowest MIC values on Pseudomonas aeruginosa, were further evaluated for their inhibition capacities of biofilm formation. In order to evaluate their potential mechanism of biofilm inhibition, these two compounds were docked into the active site of LasR, which is the transcriptional regulator of bacterial signaling mechanism known as quorum sensing. Finally, the theoretical parameters of the bioactive molecules were calculated to establish their drug-likeness properties.

Antibacterial, Antifungal and Anti-tubercular Activities of Chloroform Fraction of the Leaf Extract of Irvingia Gabonensis (African Bush Mango)

Background: The prevalence of anti-drug resistance by disease causing microorganisms has necessitated the search for alternative sources of drugs for the treatment of the ailments caused by these microorganisms. This study examines the biological properties of extracts from the leaves of Irvingia gabonensis (bush mango). Objective: The objective of this study is to determine the anti-microbial activity of chloroform fraction of the leaf extract and compare it with that of clinical reference. Methods: Antimicrobial activity of the chloroform fraction of the leaf extract of Irvingia gabonensis was evaluated against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Shigella dysenteriae, Salmonella typhi, Klebsiella pneumonia, Salmonella paratyphi, Candida albicans and Trichophyton rubrum by using the agar well diffusion method and Mycobacterium tuberculosis using agar proportion method on Lowenstein–Jensen medium. Preliminary phytochemical screening of the chloroform leaf fraction was done using qualitative standard methods. Results: This showed the presence of saponins, flavonoids, tannins, coumarin, phenol and alkaloids. Organisms were susceptible to chloroform fraction at different concentrations. The lowest MIC value obtained was 0.625mg/mL for S. aureus and S. typhi. While, five out of seven mycobacterial strains that were used, were susceptible. Conclusion: The antimicrobial activity is a result of the phytochemicals present in leaf. Therefore, we conclude that Irvingia gabonensis leaves can be used in the development of new pharmaceuticals research activities such as drug production.

Brominated plastoquinone analogs: Synthesis, structural characterization, and biological evaluation

A series of brominated PQ analogs (BrPQ1-13) was synthesized by employing two different routes: 1) dibromination followed by oxidation and amination of dimethyl hydroquinone, respectively, 2) oxidation of dimethyl hydroquinone followed by amination and bromination, respectively. In addition to the single-crystal X-ray structural characterization of two analogs (BrPQ2 and BrPQ3), the structures of all analogs were determined based on spectral (FTIR, 1H NMR, 13C NMR, and HRMS) data. We evaluated the analogs for in vitro antibacterial and antifungal activity against ATCC® strains (panel of seven bacterial strains with three Gram-positive and four Gram-negative bacteria and three fungi) using the broth microdilution method. The structure–activity relationship of brominated PQ analogs indicated that the electron-withdrawing group (EWG) on the phenyl ring (-CF3, trifluoromethyl group) has a positive effect on antibacterial activity. These in vitro data show that brominated analogs, especially for BrPQ1, BrPQ2, and BrPQ3, have the potential to be developed as new antibacterial agents against S. aureus and/or S. epidermidis with low MIC values.

ISONIAZID - MONORESISTANT TUBERCULOSIS IN BULGARIA

Background. Isoniazid is a common drug in the treatment regimens for TB infection. Monoisoniazid resistance reduces the probability of a successful treatment outcome and increases the risk of acquiring additional drug resistance.
 Material and methods. For the period 2015-2016 a total of 36 TB cases were confirmed in NRL TB, Sofia, as isoniazid-monoresistant Mycobacterium tuberculosis complex. Minimum inhibitory concentration testing for isoniazid was conducted with BАСТЕС MGIT 960 System in the following concentrations of the drug: 0.1 μg/ml, 0.15μg/ml, 0.2μg/ml, 0.3μg/ml, 0.4μg/ml. Molecular testing was performed with GenoType ® MTBDRplus in order to detect the most common mutations associated with resistance to isoniazid.
 Results. Only 25% of the tested M. tuberculosis complex isolates with phenotypic isoniazid monoresistance had the S315T1 mutation in katG; all isolates were with MIC over 0.4 μg/ml. C15T in the promoter region of inhA was detected in 22.22% of cases and only 1 of them showed MIC below 0.4 μg/ml. No mutations were detected in nearly half of the cases (n=19, 52.78%) and most of these isolates were with lower MIC values (n=12). Conclusion. The rapid testing with GenoType ® MTBDRplus can be used as a screening procedure indicating whether further examination of isoniazid MIC is relevant in resistant M. tuberculosis and whether higher doses could be considered.

Antimicrobial activity of oregan and clove essential oils against some foodborne pathogens

The tendency to replace synthetic antimicrobials for natural ones in food industry and an increase in bacterial resistance to antibiotics resulted in a necessity to find new alternatives, and essential oils are emerging as promising substitutes for synthetic chemicals in food preservation. The objective of this work was to test the antimicrobial activity of oregano (OEO) and clove (CEO) essential oils over a range of bacteria, molds and yeast of importance as pathogens or food spoilage. The antimicrobial activity of oregano and clove essential oils were analyzed by disk diffusion method and broth microdilution test (MIC) of OEO and CEO were determined for each tested microorganism. OEO and CEO were evaluated in natura (IN) and after thermal processing (TP) at 120 o C for 5 min. Both OEO and CEO presented the same inhibition zones for IN and TP samples, for all tested microorganisms, indicating that these oils can be thermally processed maintaining their antimicrobial activity. For OEO and CEO, the more sensitive microorganisms were the fungi (Aspergillus niger, Penicillium citrinum and Candida albicans), followed by Staphylococcus aureus, Bacillus cereus and Methicillin - resistant Staphylococcus aureus (MRSA); the lowest antimicrobial activities were observed against Streptococcus mutans and Enterococcus faecalis. In general, OEO resulted in higher inhibition zones and lower MIC values for all tested microorganisms, suggesting that it was more effective as an antimicrobial agent than CEO

Exploring how structural changes to new Licarin A derivatives effects their bioactive properties against rapid growing mycobacteria and biofilm formation

Several species of rapidly growing mycobacteria (RGM) have been associated with biofilms in areas such as biomedical devices, water distribution systems, cosmetic surgery, and catheter-related blood infections. Biofilms which exhibit antimicrobial resistance such as those formed by the genus Mycobacterium pose a significant risk to health and are of particular interest to researchers. Licarin A (a neolignan found in numerous plant species e.g. nutmeg) has been reported to show a wide range of biological actions including anti-inflammatory, antioxidant, and antibacterial properties. The aim of this study was to prepare a set of Licarin A derivatives and investigate the impact of specific structural changes on its antimycobacterial ability, and its effect on the biofilm formation of RGM species. Initially, the phenolic sub-unit and alkenyl side chain of Licarin A were modified to create derivatives with a higher partition coefficient; as the activity of a compound against mycobacteria seems to be strongly influenced by its hydrophobicity. Further, polar groups were inserted into the side chain to change the hydrophilic-lipophilic profile of the molecules. Results showed variability in the susceptibility profile of mycobacteria against the Licarin A derivatives under analysis. A number of the derivatives showed significant inhibitory activity of planktonic growth of the three strains of mycobacteria used, with even lower MIC values than those observed with reference drugs and Licarin A itself. Cytotoxicity assays showed they also have low toxicity, confirming that structural modifications to the Licarin A have made improvements to its antimycobacterial properties.

Antimicrobial susceptibility of multi-drug and extensively-drug-resistant Escherichia coli to ceftolozane-tazobactam and ceftazidime-avibactam: An in vitro study*

Aim: <i>Escherichia coli</i> is one of the Gram-negative bacteria, known to cause many nosocomial infections. Multi-drug (MDR) and extensively-drug resistant (XDR). <i>E. coli</i> are of particular note, due to significant limitations in antibiotic therapy. Ceftolozane-tazobactam and ceftazidime-avibactam are novel therapeutic options against Gram-negative bacteria; hence the aim of this study was to evaluate and compare the <i> in vitro </i> activity of ceftolozane-tazobactam and ceftazidime-avibactam against MDR and XDR clinical <i>E. coli</i> isolates. Material/Methods: The study included 100 non-replicate <i>E. coli</i> isolates derived from clinical samples of patients hospitalized in teaching hospitals. Bacteria were identified by applying mass spectrometry in the MALDI Biotyper system (Bruker). ESBL (bla<sub>CTX-M-1group</sub>, bla<sub>CTX-M-9group</sub>) and carbapenemase (bla<sub>KPC</sub>, bla<sub>VIM</sub>, bla<sub>NDM</sub>, bla<sub>OXA-48</sub>, bla<sub>OXA-181</sub>) genes were detected using the eazyplex® SuperBug CRE test, based on a loop-mediated isothermal amplification (LAMP). The in vitro susceptibility to ceftolozane-tazobactam and ceftazidime-avibactam was tested using validated MIC Test strips (Liofilchem). Results: All 84 extended-spectrum β-lactamase-producing (ESBL) <i>E. coli</i> isolates were susceptible to ceftazidime-avibactam and 83 to ceftolozane-tazobactam. Among 17 <i>E. coli</i> isolates with resistance to at least one of the carbapenems, three (17.6%) were susceptible to ceftolozane-tazobactam and ceftazidime-avibactam. All 14 blaVIM gene-positive <i>E. coli</i> isolates were resistant to both ceftolozane-tazobactam and ceftazidime-avibactam. Both antibiotics were active against bla<sub>CTX-M-9group</sub> and bla<sub>OXA-48</sub> gene-positive <i>E. coli</i> isolates, but they were not active against bla<sub>CTX-M-1group</sub> and bla<sub>VIM</sub> gene-positive isolates. Conclusions: Ceftolozane-tazobactam and ceftazidime-avibactam are alternative, non-carbapenem therapeutic options for ESBL-positive <i>E. coli</i> strains, and they are promising in the treatment of carbapenem-resistant <i>E. coli</i> strains, but not for those carrying the metallo-β-lactamase enzymes. Both drug combinations have comparable activity against ESBL, however, lower MIC values were found for ceftazidime-avibactam.

Quantification of 2- and 3-isopropylmalic acids in forty Italian wines by UHPLC-MS/MS triple quadrupole and evaluation of their antimicrobial, antioxidant activities and biocompatibility

2-Isopropylmalic acid (2-IPMA) and 3-isopropylmalic acid (3-IPMA), recently discovered in wines, were simultaneously quantified in forty wines by UHPLC-MS/MS triple quadrupole. Principal component analysis displayed that red wines were more correlated with high amounts of 2-IPMA (average content 31.60 mg/L); white wines were mostly characterized by low levels of both organic acids. No correlation of theirs levels to other wine features (wine ageing or alcoholic content) were found. 2-IPMA and 3-IPMA showed MICs values of 4096 mg/L and MBCs values of 8192 mg/L or higher against several food borne pathogens. In association, an interesting lower MIC and MBC values (2048 mg/L and 4096 mg/L respectively) were observed against Y. enterocolitica. Interestingly, 3-IPMA showed a mild antioxidant activity by DPPH assay (EC50 = 3940 mg/L), higher than that of 2-IPMA (EC50 > 4800 mg/L). No toxicity of these compounds against human colorectal and liver cells (TB assay) was observed.

Teasaponin suppresses Candida albicans filamentation by reducing the level of intracellular cAMP.

BackgroundCandidiasis has long been a threat to human health, but cytotoxicity and resistance always block the usefulness of antifungal agents. The ability to switch between yeast and hypha is one of the most discussed virulence trait attributes of the human pathogenic fungus Candida albicans. The morphological transition provides a novel target for developing antifungal drugs. The aim of the present study was to explore the activity and mechanism of teasaponin (TS), a generally regarded as safe natural product, in inhibiting filamentation of C. albicans, hoping to provide an experimental basis for its clinical application.MethodsThe effect of TS on filamentation and biofilm formation of C. albicans was evaluated by XTT reduction assay and microscopy. The level of intracellular cAMP was measured to further explore the underlying mechanism. In addition, cytotoxicity of TS was evaluated by using MTT assay in vitro and Caenorhabditis elegans model in vivo. The potential of TS-resistance induction was tested by a serial passage experiment.ResultsTS displayed a moderate antifungal activity against the wild type, efflux pump mutant and multi-resistance C. albicans strains, and could effectively retard filamentation and biofilm formation with a low MIC value. Further mechanism investigation revealed that the reduced cAMP level inhibited filamentation and biofilm formation. In addition, TS showed no significant cytotoxicity in vitro or in vivo, and had little potential to develop resistance during long-time induction.ConclusionsOur work evaluated the antifungal activity of TS against filamentation and biofilms formation of C. albicans and disclosed the underlying mechanism, which might provide useful clues for the potential clinical application of TS in fighting clinical fungal infections by targeting the virulence factors.