Lowest MIC Research Articles

Design, synthesis, and antibacterial activity of a new series of ciprofloxacin-thiadiazole hybrid

This study synthesized novel ciprofloxacin analogs bearing the 2-amino-1,3,4-thiadiazole ring, including tryptophan and different sulfonamides, to act as antimicrobial agents. Then, the activities of the synthesized hybrids were screened against 18 tested bacterial isolates from 4 standard strains (Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 25,923, Acinetobacter baumannii ATCC 19,606, and Pseudomonas aeruginosa PAO1) and 14 clinical strains (2 Enterobacter cloacae and 12 Klebsiella pneumonia isolates). Investigations revealed that compound 2 showed better antimicrobial activities among the synthesized compounds than the standard drug, ciprofloxacin, demonstrated by its lower MIC and MBC values. We also notably observed that compared to ciprofloxacin, compound 2 maintained its activity for a longer time without inducing resistance in the tested bacterium. Hence, we conducted a time-to-kill assay and compared the results with its parent drug, followed by a molecular modeling simulation study through the docking of compound 2 into E. coli DNA gyrase enzyme active site to elucidate its binding modes to the receptor. Then, we compared these results with ciprofloxacin and calculated the physicochemical descriptors, ADME parameters, pharmacokinetic properties, and drug-like nature profile of compound 2 as the most potent were also calculated. Based on our findings, we conclude that with further modifications of compound 2, the design of a new and optimized fluoroquinolone generation should be possible.

Antibacterial and antioxidant activities, lethality assay and chemical profile in crude extract of Biancaea sappan (L.) Tod. for anti-Vibrio agent

Background and objectivesThe bacterial infections are still an important cause of death for organisms leading to interesting finding the new antibacterial agent from natural source. The antimicrobial activity of Biancaea sappan extract (BSE) has been reported with a few mentions of anti-Vibrio efficiency. In this study, the heartwood extract from B. sappan was investigated for antibacterial activity, stability, toxicity, and anti-Vibrio in seawater. MethodsThe BSE was tested for antimicrobial activity to determine the minimum inhibitory concentration and minimum bactericidal concentration (MIC&MBC). The crude extract was evaluated an antioxidant activity through 2,2–diphenyl–1–picrylhydrazyl (DPPH) radical scavenging capacity and content of total phenolics according to Folin–Ciocalteu colorimetric method. Next, the BSE was determined thermal, diluent stabilities and Artemia salina toxicity before the time–kill study for anti-Vibrio in seawater. The major components in extract were analyzed using LC-Q-TOF-MS/MS. ResultsBSE was yielded at 9.56 %. The lowest MIC and MBC were 0.49 mg/mL for V. parahaemolyticus TISTR1596. The TPC in BSE was 31.46 GAE/g, and antioxidant activity with a 50 % inhibitory concentration (IC50) of 0.288 mg/mL. TPC in BSE was stable at high temperatures, and distilled water (>90 %).It was non-acute lethality toward A. salina for 24 h (LC50 = 7.374 mg/mL). At 3MIC and 4MIC of BSE were effective for killing V. parahaemolyticus within 2 h. ConclusionsThe BSE showed an effective inhibitory against V. parahaemolyticus with the lowest MIC and MBC. The TPC was stable with non-acute toxic effects on A. salina. It showed high potential anti-Vibrio activity in seawater that may be shown the usefulness in controlling Vibrio infection.

Lack of Association between YEASTONE Antifungal Susceptibility Tests and Clinical Outcomes of Cryptococcus Meningitis.

The relation between antifungal susceptibility and treatment outcomes is not well-characterized. There is paucity of surveillance data for cerebrospinal fluid (CSF) isolates of cryptococcus investigated with YEASTONE colorimetric broth microdilution susceptibility testing. A retrospective study of laboratory-confirmed cryptococcus meningitis (CM) patients was conducted. The antifungal susceptibility of CSF isolates was determined using YEASTONE colorimetric broth microdilution. Clinical parameters, CSF laboratory indices, and antifungal susceptibility results were analyzed to identify risk factors for mortality. High rates of resistance to fluconazole and flucytosine were observed in this cohort. Voriconazole had the lowest MIC (0.06 µg/mL) and lowest rate of resistance (3.8%). In a univariate analysis, hematological malignancy, concurrent cryptococcemia, high Sequential Organ Failure Assessment (SOFA) score, low Glasgow coma scale (GCS) score, low CSF glucose level, high CSF cryptococcal antigen titer, and high serum cryptococcal antigen burden were associated with mortality. In a multivariate analysis, meningitis with concurrent cryptococcemia, GCS score, and high CSF cryptococcus burden, were independent predictors of poor prognosis. Both early and late mortality rates were not significantly different between CM wild type and non-wild type species.

In vitro susceptibility of carbapenem resistant Enterobacterales to meropenem-vaborbactam and ceftazidime-avibactam at a single academic medical centre

Background Carbapenem-resistant Enterobacterales (CRE) are considered an urgent threat. Ceftazidime-avibactam and meropenem-vaborbactam contain β-lactamase inhibitors active against CRE isolates including those that produce Klebsiella pneumoniae carbapenemases (KPC). Methods Retrospective chart review of CRE isolates from 1 January 2016 to 1 November 2018. Collected data includes a descriptive overview of measured MIC values, resistance mechanism via a polymerase chain reaction test (Xpert Carba-R, Cepheid, Sunnyvale CA), as well as clinical outcomes. Results Of 106 isolates reviewed, 86 isolates met the inclusion criteria from 85 individual subjects. The breakpoint:MIC ratio for ceftazidime-avibactam overall was 4, while for meropenem-vaborbactam this ratio was 32 (p < 0.0001). For KPC isolates, ceftazidime-avibactam MIC50/MIC90 in 2016, 2017, and 2018 were 2/4 mg/L (n = 32), 2/4 mg/L (n = 17), and 2/8 mg/L (n = 30), respectively. The meropenem-vaborbactam MIC50/MIC90, for KPC isolates in 2016, 2017, and 2018 were 0.06/0.125 mg/L (n = 32), 0.06/0.1 mg/L (n = 17), and 0.06/0.5 mg/L (n = 30), respectively. Microbiologic cure was 75% (n = 16) in ceftazidime-avibactam subjects and 58.3% (n = 12) in subjects treated with alternative agents (p = 0.43). The 14- and 30-day mortality was numerically higher in subjects treated with alternate agents when compared ceftazidime-avibactam 2/9 (22.2%) vs 3/17 (17.6%) (p = 1.00) and 4/9 (44.4%) vs 4/17 (28.6%) (p = 0.38), respectively. For ceftazidime-avibactam, 30-day mortality in 2016, 2017, and 2018 was 0/5 (0%), 0/2 (0%), and 4/10 (40%). Conclusion Selective pressure from the use of ceftazidime-avibactam at our institution may be decreasing its utility as a first-line agent for CRE infections. Meropenem-vaborbactam maintained low MIC values and may be a promising treatment option for CRE.

Functional Characterization of a Bacillus-Derived Novel Broad-Spectrum Antifungal Lipopeptide Variant against Candida tropicalis and Candida auris and Unravelling Its Mode of Action.

Limited treatment options, recalcitrance, and resistance to existing therapeutics encourage the discovery of novel antifungal leads for alternative therapeutics. Antifungal lipopeptides have emerged as potential candidates for developing new and alternative antifungal therapies. In our previous studies, we isolated and identified the lipopeptide variant AF4 and purified it to homogeneity via chromatography from the cell-free supernatant of Bacillus subtilis. AF4 was found to have broad-spectrum antifungal activity against more than 110 fungal isolates. In this study, we found that clinical isolates of Candida tropicalis and Candida auris exposed to AF4 exhibited low MICs of 4 to 8 mg/L. Time-kill assays indicated the in vitro pharmacodynamic potential of AF4. Biocompatibility assays demonstrated ~75% cell viability at 8 mg/L of AF4, indicating the lipopeptide's minimally cytotoxic nature. In lipopeptide-treated C. tropicalis and C. auris cells, scanning electron microscopy revealed damage to the cell surface, while confocal microscopy with acridine orange(AO)/propidium iodide (PI) and FUN-1 indicated permeabilization of the cell membrane, and DNA damage upon DAPI (4',6-diamidino-2-phenylindole) staining. These observations were corroborated using flow cytometry (FC) in which propidium iodide, 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA), and rhodamine 123 (Rh123) staining of cells treated with AF4 revealed loss of membrane integrity, increased reactive oxygen species (ROS) production, and mitochondrial membrane dysfunction, respectively. Membrane perturbation was also observed in the 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence study and the interaction with ergosterol was observed by an ergosterol binding assay. Decreased membrane dipole potential also indicated the probable binding of lipopeptide to the cell membrane. Collectively, these findings describe the mode of action of AF4 against fungal isolates by membrane disruption and ROS generation, demonstrating its antifungal potency. IMPORTANCE C. tropicalis is a major concern for candidiasis in India and C. auris has emerged as a resistant yeast causing difficult-to-treat infections. Currently, amphotericin B (AMB) and 5-flucytosine (5-FC) are the main therapeutics for systemic fungal infections; however, the nephrotoxicity of AMB and resistance to 5-FC is a serious concern. Antifungal lead molecules with low adverse effects are the need of the hour. In this study, we briefly describe the antifungal potential of the AF4 lipopeptide and its mode of action using microscopy, flow cytometry, and fluorescence-based assays. Our investigation reveals the basic mode of action of the investigated lipopeptide. This lipopeptide with broad-spectrum antifungal potency is apparently membrane-active, and there is a smaller chance that organisms exposed to such a compound will develop drug resistance. It could potentially act as a lead molecule for the development of an alternative antifungal agent to combat candidiasis.

Plant-Based Copper Oxide Nanoparticles; Biosynthesis, Characterization, Antibacterial Activity, Tanning Wastewater Treatment, and Heavy Metals Sorption

Herein, the aqueous extract of Portulaca oleracea has been used as a safe, cheap, eco-friendly, and applicable scale-up method to bio-fabricate copper oxide nanoparticles (CuO-NPs). The character of CuO-NPs were determined using UV-vis spectroscopy, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energy dispersive X-ray(EDX), Dynamic light scattering (DLS), and zeta potential. Spherical and crystalline CuO-NPs with a size range of 5–30 nm at a maximum surface plasmon resonance of 275 nm were successfully fabricated. The main components of the green-synthesized particles were Cu and O with weight percentages of 49.92 and 28.45%, respectively. A Zeta-potential value of −24.6 mV was recorded for CuO-NPs, indicating their high stability. The plant-based CuO-NPs showed promising antimicrobial and catalytic activity in a dose-dependent manner. Results showed that the synthesized CuO-NPs had the efficacy to inhibit the growth of pathogens Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans with low MIC values in the ranges of 6.25–25 µg/mL. The highest decolorization percentages of tanning wastewater were attained under sunlight irradiation conditions at a concentration of 2.0 mg/mL after 200 min with percentages of 88.6 ± 1.5% compared to those which were recorded under dark conditions (70.3 ± 1.2%). The physicochemical parameters of tanning wastewater including total suspended solids (TSS), total dissolved solids (TDS), chemical oxygen demand (COD), biological oxygen demand (BOD), and conductivity under optimum conditions were significantly decreased with percentages of 95.2, 86.7, 91.4, 87.2, and 97.2%, respectively. Interestingly, the heavy metals including cobalt (Co), lead (Pb), nickel (Ni), cadmium (Cd), and chromium (Cr (VI)) decreased with percentages of 73.2, 80.8, 72.4, 64.4, and 91.4%, respectively, after treatment of tanning wastewater with CuO-NPs under optimum conditions. Overall, the plant-synthesized CuO-NPs that have antimicrobial and catalytic activities are considered a promising nano-catalyst and environmentally beneficial to wastewater treatment.

Polyphenolic and Flavonoids Contents and Antibacterial Activity of Hydro-Ethanolic and Aqueous Extract of Fresh Leaves of Gardenia Aqualla Staph and Hutch (Rubiaceae)

Erectile dysfunction has become for two decades, a real public health problem. Its prevalence is estimated at 322 million in 2025. Its management is based on the administration of phosphodiesterase inhibitors alone or in combination. Infections have been rarely mentioned although <i>E coli</i>, <i>Staphylococcus aureus</i>, <i>Klebsiella pneumoniae </i>or <i>Serratia marcescens</i> are recognized as factors of erectile dysfunction. The purpose of this study was to evaluate the phytochemical profile of the aqueous (AE) and hydroethanolic (HE) extracts of the fresh leaves of <i>Gardenia aqualla</i> and to determine their antibacterial potential on bacteria involved in male accessory gland infections. The aim of this study was to evaluate phytochemical profile of aqueous (AE) and hydroethanolic (HE) extracts of fresh leaves of <i>Gardenia aqualla</i> and to determine their antibacterial potential on bacteria involved in male accessory gland infections. Phytochemical profile highlighted the presence of alkaloids, polyphenols with concentrations of 434.5 ± 14.5 mgEq Tannic acid/g of dried extract greater than 249.5±18.3 mgEq Tannic acid/g of dried extract found in AE including flavonoids whose concentrations is 184.9 ± 6.3 μgEqRutin/g of dry extract in HE against 183.0±9.1 μgEqRutin/g of dried extract in AE. Antibacterial tests showed equivalence of activity on <i>E coli</i> and S aureus strains with MICs of 100 mg/mL and 50mg/mL respectively and only HE showed activity on <i>Klebsiella pneumoniae</i> and<i> Serratia marcescens</i> which had the lowest MIC 6.25 mg/mL.

Coagulase-Negative Staphylococci in Neonatal Blood: How Concerning?

Objective Coagulase-negative staphylococci (CoNS) are being implicated as one of the leading causes of bloodstream infection (BSI). To study the spectrum, prevalence, and antimicrobial susceptibility of CoNS causing BSI in neonates. Materials and Methods A cross-sectional study was done in level III neonatal intensive care unit (NICU). Blood samples in automated culture bottles were processed as per the standard technique. Previously validated methods were followed for the characterization of CoNS and for AST of standard antibiotics by Kirby Bauer disk diffusion and vancomycin by agar dilution. The prevalence of causative organisms and susceptibility of CoNS were statistically analyzed. Categorical variables were compared by chi-square or Fisher's exact probability tests. Result In total, 1,365 blood samples (1,365 neonates) were studied, of which 383 (28.05%) were positive and 982 (71.94%) were negative. Gram-positive organisms (GPC) predominated ( n = 238; 62.14%) ( p < 0.001) with 41.77% (160/383) S. aureus and 13.83% (53/383) CoNS. CoNS included S. epidermidis (19, 38%), S . haemolyticus (7, 14%), S. hominis (6, 12%), S. simulans (6,12%), S. capitis (5,10%), S. cohnii (4, 8%), S. warneri (1, 2%), and S. xylosus (1, 2%). The susceptibility to netilmicin, linezolid, and vancomycin was 100% ( p ≤ 0.001), and 54% ( n = 27) had vancomycin MIC of 0.125 μg/mL but methicillin-resistant CoNS (MRCoNS) was 70%. Methicillin-susceptible (MS) CoNS had lower MIC of vancomycin ( p < 0.05) than MRCoNS. Conclusion The spectrum of pathogens causing BSI in neonates is changing with predominance of GPC and among CoNS, S. epidermidis . Considerable proportion of MRCoNS with the emergence of MIC creep for vancomycin requires immediate attention.

Carvacrol and Cinnamaldehyde as Next Generation Antimicrobial Agents against Foodborne Pathogens: Antibacterial Efficacy and Synergistic Interaction with Nisin

Foodborne infections cause substantial issues all around the world, hence food safety is a major public health concern. The goal of this research is to provide information to the scientific community on the possible application of two plant essential oil molecules, Carvacrol (CAR) and Cinnamaldehyde (CN), as next-generation antimicrobials in the fight against foodborne pathogens. CAR and CN demonstrated outstanding dose-dependent antibacterial efficacy against 10 foodborne pathogens. Both Gram-positive and Gram-negative bacteria were suitably inhibited by the drugs. Antimicrobial activity of 10% v/v CAR and CN was much higher than that of the conventional antibiotic azithromycin (15g/disc). The study discovered that CAR and CN have very low MIC values (0.08% to 0.31% v/v), indicating that the compounds are efficacious even at very low concentrations. Even at 0.16% concentration, combining CAR and CN with Nisin (a widely available natural preservative) exhibited substantial synergism, with inhibition zones ranging from 8.5- 12.38 mm, decreasing the dose required to produce sufficient antimicrobial action. The findings imply that CAR and CN combined with nisin can be used as a natural antibacterial agent to limit the growth of foodborne pathogens and as a natural food preservative.&#x0D; Bangladesh J Microbiol, Volume 39, Number 1, June 2022, pp 7-14

Phytochemical Characterization and Efficacy of Artemisia judaica Extract Loaded Chitosan Nanoparticles as Inhibitors of Cancer Proliferation and Microbial Growth

Despite the advanced development in the field of drug discovery and design, fighting infectious and non-infectious diseases remains a major worldwide heath challenge due to the limited activity of currently used drugs. Nevertheless, in recent years, the approach of designing nanoparticles for therapeutic applications has gained more interest and promise for future use. Thus, the current study is focused on the evaluation of A. judaica extract and chitosan nanoparticles loaded extract (CNPsLE) for potential antimicrobial and anticancer activities. The HPLC analysis of the extract has shown the presence of various phenolic and flavonoid compounds, including kaempferol (3916.34 µg/mL), apigenin (3794.32 µg/mL), chlorogenic acid (1089.58 µg/mL), quercetin (714.97 µg/mL), vanillin (691.55 µg/mL), naringenin (202.14 µg/mL), and rutin (55.64 µg/mL). The extract alone showed higher MIC values against B. subtilis, E. coli, S. aureus, K. pneumonia, and C. albicans (62.5, 15.65, 15.62, 31.25, and 31.25 µg/mL, respectively), whereas lower MIC values were observed when the extract was combined with CNPsLE (0.97, 1.95, 3.9, 4.1, and 15.62 µg/mL, respectively). The extract exhibited low cytotoxicity against normal Vero cells with IC50 173.74 µg/mL in comparison with the cytotoxicity of the CNPsLE (IC50, 73.89 µg/mL). However, CNPsLE showed more selective toxicity against the human prostate cancer cell line (PC3) with IC50 of 20.8 µg/mL than the extract alone with 76.09 µg/mL. In the docking experiments, kaempferol and apigenin were revealed to be suitable inhibitors for prostate cancer (2Q7L). Overall, the obtained data highlighted the promising potential therapeutic use of CNPsLE as an anticancer and antimicrobial agent.

Letter to the Editor: In Vitro Activity of Oxazolidinone Against Nontuberculous Mycobacteria in China.

Letter to the Editor: In Vitro Activity of Oxazolidinone Against Nontuberculous Mycobacteria in China.

Determination of Chemical Composition and Investigation of Biological Activities of Ocimum basilicum L.

This study aimed to determine the chemical composition of the essential oils (EOs) of Ocimum basilicum L., as well as to evaluate the antibacterial, antidiabetic, dermatoprotective, and anti-inflammatory properties, and the EOs and aqueous extracts of O. basilicum. The antibacterial activity was evaluated against bacterial strains, Gram-positive and Gram-negative, using the well diffusion and microdilution methods, whereas the antidiabetic activity was assessed in vitro using two enzymes involved in carbohydrate digestion, α-amylase and α-glucosidase. On the other hand, the dermatoprotective and anti-inflammatory activities were studied by testing tyrosinase and lipoxygenase inhibition activity, respectively. The results showed that the chemical composition of O. basilicum EO (OBEO) is dominated by methyl chavicol (86%) and trans-anethol (8%). OBEO exhibited significant antibacterial effects against Gram-negative and Gram-positive strains, demonstrated by considerable diameters of the inhibition zones and lower MIC and MBC values. In addition, OBEO exhibited significant inhibition of α-amylase (IC50 = 50.51 ± 0.32 μg/mL) and α-glucosidase (IC50 = 39.84 ± 1.2 μg/mL). Concerning the anti-inflammatory activity, OBEO significantly inhibited lipoxygenase activity (IC50 = 18.28 ± 0.03 μg/mL) compared to the aqueous extract (IC50 = 24.8 ± 0.01 μg/mL). Moreover, tyrosinase was considerably inhibited by OBEO (IC50 = 68.58 ± 0.03 μg/mL) compared to the aqueous extract (IC50 = 118.37 ± 0.05 μg/mL). The toxicological investigations revealed the safety of O. basilicum in acute and chronic toxicity. The finding of in silico analysis showed that methyl chavicol and trans-anethole (main compounds of OBEO) validate the pharmacokinetics of these compounds and decipher some antibacterial targets.

Design, synthesis, molecular dynamic simulation studies, and antibacterial evaluation of new spirocyclic aminopyrimidines

The rise of new bacterial pathogens that ascribed as multi-drug resistant became a major concern, particularly in the medical sectors. In the current study, we designed novel molecular hybrids based on spirocyclic pyrimidine which feature either triazolo ring or various functionalities such as alkyl, hydrazino, azomethine motifs. The newly synthesized spirocyclic pyrimidines were screened for their bactericidal activities against some bacterial pathogens such as Salmonella typhimurium and Proteus vulgaris in addition to the multi-drug resistant Pseudomonas aeruginosa and Staphylococcus aureus (MRSA). Compounds coded 4, 6, and 8e were found to possess potent bactericidal activities compared to the standard drugs (Ciprofloxacin and Cephradine). Interestingly, compound 6 exhibited the highest antibacterial activity with low MIC value close to that obtained for ciprofloxacin. Molecular dynamic simulations and docking studies were investigated to check the performance of our compounds upon binding to the protein active sites as well as their interactions and stabilities through the simulation process.

Determination of Antibacterial Activities of Stinging Nettle (Urtica dioica) Ethanol Extract at Different Bacterial Concentrations

The study evaluated the antibacterial effect of stinging nettle extract by the liquid microdilution method to obtain quantitative results. Unlike other studies in the literature, MIC and MBC values showing bacteriostatic and bactericidal effects were investigated for four different bacterial concentrations. Six pathogen strains were studied, including Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, Streptococcus pneumoniae ATCC 45615, Klebsiella pneumoniae ATCC 70063, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 and different levels of antimicrobial effects were determined. While the extract does not affect the Klebsiella pneumoniae ATCC 70063 strain at any level, Pseudomonas aeruginosa ATCC 27853 in strains 1.5x105 and 1.5x104 MIC values were found at concentrations, no effect was observed at the MBC level. While MIC and MBC values were found at the concentrations of Staphylococcus aureus ATCC 29213 except for the 1.5x107 concentration, the remaining standard strains had different MIC and MBC values at all concentrations. The standard strain Streptococcus pneumoniae ATCC 45615 was the most effective with the extract's lowest MIC and MBC values. This study showed that nettle extract (Urtica dioica) would contribute to the research results in the scientific literature on its antimicrobial effect.

Antimicrobial and Cytotoxic Activity of Endophytic Fungi from Lagopsis supina.

In this study, five endophytic fungi belonging to the Aspergillus and Alternaria genera were isolated from Lagopsis supina. The antimicrobial activity of all fungal fermented extracts against Staphylococcus and Fusarium graminearum was tested using the cup-plate method. Among them, Aspergillus ochraceus XZC-1 showed the best activity and was subsequently selected for large-scale fermentation and bioactivity-directed separation of the secondary metabolites. Four compounds, including 2-methoxy-6-methyl-1,4-benzoquinone (1), 3,5-dihydroxytoluene (2), oleic acid (3), and penicillic acid (4) were discovered. Here, compounds 1 and 4 displayed anti-fungal activity against F. graminearum, F. oxysporum, F. moniliforme, F. stratum, Botrytis cinerea, Magnaporthe oryzae, and Verticillium dahliae with diverse MIC values (128-512 μg/ml), which were close to that of the positive control antifungal, actidione (64-128 μg/ml). Additionally, compounds 1 and 4 also exhibited moderate antibacterial activity against S. aureus, Listeria monocytogenes, Escherichia coli, and Salmonella enterica, with low MIC values (8-64 μg/ml). Moreover, compounds 1 and 4 displayed selective cytotoxicity against cancer cell lines as compared with the normal fibroblast cells. Therefore, this study proposes that the endophytic fungi from L. supina can potentially produce bioactive molecules to be used as lead compounds in drugs or agricultural antibiotics.

Scedosporium apiospermum isolated from a skin wound in a dog and in vitro activity of eleven antifungal drugs

Scedosporium apiospermum, an emerging opportunistic fungus, is increasingly implicated with serious invasive mycoses in immunocompromised patients. Rare occurrence and difficulty in identification of this species complicate the management of infection in dogs. In the present report, the characterization of a Scedosporium apiospermum isolate obtained from a dog’s skin wound is described. Identification was obtained through macroscopic and microscopic examination of the cultured isolate and by sequencing the internal transcribed spacer (ITS) gene of the rRNA region. Numerous hyaline septate hyphae along with conidia were observed histologically. The isolate exhibited low MIC values for voriconazole, itraconazole and isavuconazole while high MIC/MEC values were recorded for the remaining antifungals. To the best of the authors’ knowledge, this is the first reported case of isolation of S. apiospermum from a skin wound in a dog.

Synergistic Combinations of FDA-Approved Drugs with Ceftobiprole against Methicillin-Resistant Staphylococcus aureus.

New strategies are urgently needed to address the public health threat of antimicrobial resistance. Synergistic agent combinations provide one possible pathway toward addressing this need and are also of fundamental mechanistic interest. Effective methods for comprehensively identifying synergistic agent combinations are required for such efforts. In this study, an FDA-approved drug library was screened against methicillin-resistant Staphylococcus aureus (MRSA) (ATCC 43300) in the absence and presence of sub-MIC levels of ceftobiprole, a PBP2a-targeted anti-MRSA β-lactam. This screening identified numerous potential synergistic agent combinations, which were then confirmed and characterized for synergy using checkerboard analyses. The initial group of synergistic agents (sum of the minimum fractional inhibitory concentration ∑FICmin ≤0.5) were all β-lactamase-resistant β-lactams (cloxacillin, dicloxacillin, flucloxacillin, oxacillin, nafcillin, and cefotaxime). Cloxacillin-the agent with the greatest synergy with ceftobiprole-is also highly synergistic with ceftaroline, another PBP2a-targeted β-lactam. Further follow-up studies revealed a range of ceftobiprole synergies with other β-lactams, including with imipenem, meropenem, piperacillin, tazobactam, and cefoxitin. Interestingly, given that essentially all other ceftobiprole-β-lactam combinations showed synergy, ceftaroline and ceftobiprole showed no synergy. Modest to no synergy (0.5 < ∑FICmin ≤ 1.0) was observed for several non-β-lactam agents, including vancomycin, daptomycin, balofloxacin, and floxuridine. Mupirocin had antagonistic activity with ceftobiprole. Flucloxacillin appeared particularly promising, with both a low intrinsic MIC and good synergy with ceftobiprole. That so many β-lactam combinations with ceftobiprole show synergy suggests that β-lactam combinations can generally increase β-lactam effectiveness and may also be useful in reducing resistance emergence and spread in MRSA. IMPORTANCE Antimicrobial resistance represents a serious threat to public health. Antibacterial agent combinations provide a potential approach to combating this problem, and synergistic agent combinations-in which each agent enhances the antimicrobial activity of the other-are particularly valuable in this regard. Ceftobiprole is a late-generation β-lactam antibiotic developed for MRSA infections. Resistance has emerged to ceftobiprole, jeopardizing this agent's effectiveness. To identify synergistic agent combinations with ceftobiprole, an FDA-approved drug library was screened for potential synergistic combinations with ceftobiprole. This screening and follow-up studies identified numerous β-lactams with ceftobiprole synergy.

661. In vitro Activity of Omadacycline and Comparator Antibiotics against Clostridioides difficile

Abstract Background Omadacycline was approved for the treatment of community acquired bacterial pneumonia (CABP) and acute bacterial skin and skin structure infections (ABSSSI) in 2018. Previous studies demonstrate that omadacycline has in vitro activity against Clostridioides difficile. We determined the in vitro activity of omadacycline and of comparator antimicrobials for the approved indications, CABP and ABSSSI, towards a contemporary and clinically relevant collection of C. difficile isolates. Methods Antimicrobial agar dilution was performed on 200 clinical C. difficile isolates collected from 2014 – 2021. Isolates were selected based on the most prevalent restriction endonuclease analysis (REA) groups locally and nationally. Omadacycline was compared to 8 standard of care antimicrobials for CABP and ABSSSI: amoxicillin-clavulanate, azithromycin, ceftriaxone, clindamycin, doxycycline, linezolid, moxifloxacin, and trimethoprim-sulfamethoxazole. Results Omadacycline demonstrated in vitro activity against all C. difficile isolates tested. The geometric mean MIC of omadacycline was 0.07 μg/ml and the MIC50 and MIC90 were 0.0625 μg/ml and 0.125 μg/ml, respectively. Among the comparator antibiotics, 52% of isolates were resistant to ceftriaxone and 37% of isolates were resistant to clindamycin. The majority of REA group BI isolates were resistant to clindamycin (77.7%, 28/36) and the clindamycin geometric mean MICs were higher for group BI compared to all other REA group strains (32 µg/ml and 5.33 µg/ml, respectively, p &amp;lt; 0.005). REA group BI also had elevated azithromycin and moxifloxacin geometric MICs (335.2 and 17.3 µg/ml, respectively). REA group DH isolates had higher trimethoprim-sulfamethoxazole geometric MICs compared to all other REA group strains (17.28 µg/ml and 8.14 µg/ml, respectively p &amp;gt;0.001). Nearly half of REA group BK isolates (47%) had MICs ≥2 µg/ml which did not correspond to elevated omadacycline MICs for the same isolates. Conclusion Omadacycline demonstrated consistently low MICs against C. difficile when compared to approved antimicrobials for CABP and ABSSI which varied in activity among particular C. difficile strains. Omadacycline may reduce the risk of developing a C. difficile infection and requires further study. Disclosures Stuart Johnson, M.D., Ferring Pharmaceuticals: Membership on Ferring Publication Steering Committee|Ferring Pharmaceuticals: Employee|Summit Plc: Advisor/Consultant.

Green Synthesis of Gold Nanoparticles by Aqueous Extract of Zingiber officinale: Characterization and Insight into Antimicrobial, Antioxidant, and In Vitro Cytotoxic Activities

The main challenge for researchers in the biomedical sectors concerns the development of new active compounds through cost-effectiveness, rapid, simple, and ecofriendly methods to overcome antibiotic resistance to pathogenic microbes. Herein, gold nanoparticles (AuNPs) were fabricated by a green approach through the reduction of chloroauric acid (HAuCl4) by harnessing the metabolites present in the aqueous extract of Zingiber officinale rhizome. UV-Vis spectroscopy, FT-IR, XRD, TEM, DLS, and zeta potential were used to characterize phytosynthesized AuNPs. In addition, the antimicrobial effect was investigated against Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli), unicellular fungi (Candida albicans), and multicellular fungi (Aspergillus brasiliensis). Antioxidant and in vitro cytotoxic activities were assessed. TEM and XRD showed the successful formation of spherical and crystalline structures, with sizes in the range of 5–53 nm (average size: 15.11 ± 8.5 nm). The zeta potential value (i.e., –28.8 mV) explains the high stability of synthesized AuNPs. AuNPs exhibit promising activity against prokaryotic and eukaryotic microorganisms with variable inhibition zones and low MIC values in the range of 25–6.25 µg mL−1. Phytosynthesized AuNPs exhibit DPPH scavenging activity with percentages of 87.6 ± 0.5% at a maximum concentration (1000 µg mL−1), which can be compared with ascorbic acid (97.3 ± 0.2%). Moreover, the AuNPs displayed a target-oriented effect for cancer cell lines HepG2 and MCF7 at low IC50 concentrations of 131.9 ± 9.34 and 288.23 ± 31.39 µg mL−1 compared to the normal oral epithelial OEC cell line (487.612 ± 3.53 µg mL−1). Overall, the phytosynthesized AuNPs show wide activities that enable their use in various biomedical and biotechnological applications.

New thiadiazole modified chitosan derivative to control the growth of human pathogenic microbes and cancer cell lines

The emergence of multidrug-resistant microbes and the propagation of cancer cells are global health issues. The unique properties of chitosan and its derivatives make it an important candidate for therapeutic applications. Herein, a new thiadiazole derivative, 4-((5-(butylthio)-1,3,4-thiadiazol-2-yl) amino)-4-oxo butanoic acid (BuTD-COOH) was synthesized and used to modify the chitosan through amide linkages, forming a new thiadiazole chitosan derivative (BuTD-CH). The formation of thiadiazole and the chitosan derivative was confirmed by FT-IR, 1H/13C-NMR, GC–MS, TGA, Elemental analysis, and XPS. The BuTD-CH showed a high antimicrobial effect against human pathogens Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, and Candida albicans with low MIC values of 25–50 μg ml−1 compared to unmodified chitosan. The in-vitro cytotoxicity of BuTD-CH was evaluated against two cancer cell lines (MCF-7 and HepG2) and one normal cell (HFB4) using the MTT method. The newly synthesized derivatives showed high efficacy against cancerous cells and targeted them at low concentrations (IC50 was 178.9 ± 9.1 and 147.8 ± 10.5 μg ml−1 for MCF-7 and HepG2, respectively) compared with normal HFB4 cells (IC50 was 335.7 ± 11.4 μg ml−1). Thus, low concentrations of newly synthesized BuTD-CH could be safely used as an antimicrobial and pharmacological agent for inhibiting the growth of human pathogenic microbes and hepatocellular and adenocarcinoma therapy.