MIC Range Research Articles

From Synergy to Monotherapy: Discovery of Novel 2,4,6-Trisubstituted Triazine Hydrazone Derivatives with Potent Antifungal Potency In Vitro and In Vivo.

Invasive fungal infections pose a serious threat to public health and are associated with high mortality and incidence rates. The development of novel antifungal agents is urgently needed. Based on hit-to-lead optimization, a series of 2,4,6-trisubstituted triazine hydrazone compounds were designed, synthesized, and biological evaluation was performed, leading to the identification of compound 28 with excellent in vitro synergy (FICI range: 0.094-0.38) and improved monotherapy potency against fluconazole-resistant Candida albicans and Candida auris (MIC range: 1.0-16.0 μg/mL). Moreover, 28 exhibited broad-spectrum antifungal activity against multiple pathogenic strains. Furthermore, 28 could inhibit hyphal and biofilm formation, which may be related to its ability to disrupt the fungal cell wall. Additionally, 28 significantly reduced the CFU in a mouse model of disseminated infection with candidiasis at a dose of 10 mg/kg. Overall, the triazine-based hydrazone compound 28 with low cytotoxicity, hemolysis, and favorable ADME/T characteristics represents a promising lead to further investigation.

Mapping pathogenic bacteria resistance against common antibiotics and their potential susceptibility to methylated white kidney bean protein.

As antibiotics cannot inhibit multidrug-resistant bacteria (MDR), continuous research is mandatory to find other antibacterials from natural resources. Native legume proteins and their modified forms exhibited broad spectra of high antimicrobial activities. Sixteen bacterial isolates were mapped for antibiotic resistance, showing resistance in the range of (58-92%) and (42-92%) in the case of the Gram-negative and Gram-positive bacteria, respectively. White native Phaseolus vulgaris protein (NPP) was isolated from the seeds and methylated (MPP). The MIC range of MPP against 7 MDR bacteria was 10-25 times lower than NPP and could (1 MIC) considerably inhibit their 24h liquid growth. MPP showed higher antibacterial effectiveness than Gentamycin, the most effective antibiotic against Gram-positive bacteria and the second most effective against Gram-negative bacteria. However, MPP recorded MICs against the seven studied MDR bacteria in the 1-20µg/mL range, the same for Gentamycin. The combination of Gentamycin and MPP produced synergistic effects against the seven bacteria studied, as confirmed by the Transmission Electron Microscopic images. The antimicrobial activity of MPP against the seven MDR bacteria remained stable after two years of cold storage at 8-10°C as contrasted to Gentamycin, which lost 20-72% of its antimicrobial effectiveness.

Bromelain-loaded silver nanoparticles: Formulation, characterization and biological activity

Bromelain (BL), a type of proteolytic enzymes from Ananas comosus (pineapple), has a variety of therapeutic potentials; nevertheless, its low bioavailability has restricted the clinical applications. The main aim of the current research was to develop a green synthesized Ag-BL nanoparticles via a cost-effective route to improve the physicochemical and antimicrobial characteristics as a novel agent for medical applications. In the present study, Bromelain was loaded on the silver nanoparticle surface via covalent bonds through green synthesis method. The physicochemical properties of Ag-BL nanoparticles characterized by following a detailed analysis over scanning electron microscopy, zeta potential, ultraviolet–visible absorption spectroscopy, transmission electron microscopy, fourier transform infrared spectroscopy, and X-ray diffraction studies. The antifungal and antibacterial activity were investigated by the Clinical and Laboratory Standards Institute methods and the results were compared with Ag NPs and plain bromelain. The cytotoxicity of Ag-BL nanoparticles was investigated by MTT assay. The TEM and XRD techniques revealed the successful biosynthesis of Ag-BL nanoparticles in spherical shape with the mean size of 7 to 24 nm and FTIR analysis pattern proved the attachments of bromelain and Ag nanoparticles in the fabricated nanostructure. The negative zeta value of the Ag-BL nanoparticles (−50 to –32 mV) indicates their high stability in the suspension. The Ag-BL nanoparticles demonstrated significant antimicrobial activity against various types of fungi and bacteria strains with a MIC range of 4–32 and 4–64 μg/mL, respectively. The MTT assay analysis determined the acceptable cell safety of Ag-BL nanoparticles. Generally, the results confirmed that Ag-BL nanoparticles could develop a new insight to produce antimicrobial products for biomedical applications.

Spectrum of Candida auris infections in a tertiary care hospital, South India

<i>Candida auris</i> is a globally emerging multi-drug resistant yeast, causing bloodstream, wound, urinary and respiratory tract infections. Understanding the epidemiology and risk factors associated with <i>C. auris</i> infection, would help in early diagnosis and instituting appropriate antifungal therapy. In this retrospective observational study, we analyzed the clinical and epidemiological data of twelve cases of <i>C. auris</i> from our institute for a period of 3 years from 2018 to 2020. The demographic, clinical and microbiological data were collected and analyzed. Identification was done by Vitek 2C and antifungal susceptibility testing by broth microdilution for all the isolates. Of the total 217 patients diagnosed with invasive candidiasis,<i> C. auris</i> was the causative species in 12 (5.5%) patients. <i>C.auris</i> was isolated from blood in 10/12 (83.3%) of these patients and from pus and tissue in one patient each with surgical site infection (SSI). Risk factors identified were the presence of invasive devices, surgical procedures, neutropenia, prolonged ICU stay, previous hospitalization, previous bacterial and fungal infections, prior use of broad-spectrum antimicrobials and antifungals. High MIC to amphotericin B (MIC range 8-16µg/ml) and fluconazole (MIC range 32-64µg/ml) were noted in 11 of 12 isolates. Seven patients with sepsis expired before <i>C.auris</i> infection was reported. In the present study, the isolates of <i>C.auris</i> were multidrug resistant which is a matter of concern. Presence of risk factors that might have led to the nosocomial acquisition of <i>C.auris</i> infection.

Daptomycin MICs by Broth Microdilution Method Against Staphylococcus aureus in Clinical Specimens: A Cross-Sectional Study from Pakistan.

To explore the distribution of daptomycin (DAP) minimum inhibitory concentrations (MICs) in Staphylococcus aureus isolated from complicated skin, soft tissue, and bloodstream infections collected from the Pakistani population using broth microdilution (BMD). Descriptive, cross-sectional study. Place and Duration of the Study: Department of Pathology and Laboratory Medicine, The Aga Khan University Hospital, from May to October 2021. Through consecutive sampling techniques, 169 Staphylococcus aureus (S. aureus) isolated from clinical specimens including pus, tissue, and blood were collected. Patients' data including age, gender, geographical location, specimen site, and methicillin susceptibility were collected from the laboratory data. BMD was used to determine MICs of clinical isolates and S. aureus ATCC 29213. DAP MIC ≤1.0 µg/ml was considered susceptible according to the Clinical and Laboratory Standards Institute M100. Among all the clinical isolates, 144 (85%) and 25 (15%) were from skin and soft tissue and blood, respectively. All isolates were susceptible to DAP with MIC50, MIC90, and MIC range of 0.25 µg/ml, 0.5 µg/ml, and 0.06 - 0.5 µg/ml, respectively. These study findings demonstrated low in-vitro MICs for DAP against S. aureus in tested isolates from a diverse variety of patient specimens from across Pakistan. Daptomycin, Staphylococcus aureus, Broth microdilution, Minimum inhibitory concentrations.

IN VITRO ACTIVITY OF BEDAQUILINE AGAINST MYCOBACTERIUM FORTUITUM COMPLEX

The activity of bedaquiline (Bdq), a drug that is effectively used for the treatment of tuberculosis, including those with multiple (MDR) and extensively drug resistant (XDR) pathogen, was studied against rapidly growing non-tuberculous mycobacteria (NTM) belonging to Mycobacterium fortuitum complex (MFC). Methods. А total 154 strains of MFC (78 of M. fortuitum and 76 of M. peregrinum) were examined. In addition, the drug susceptibility (DS) of these strains to 15 antibacterial drugs (ABD) was studied using the Sensitititre RapMyco test system. Results. Тhe Bdq MIC range for M. fortuitum was found to be 0.0015–1.0 μg/mL, M. peregrinum – 0.0015–2.0 μg/mL. The MIC50 for M. fortuitum was 0.015 µg/mL, MIC90 was 0.25 µg/mL, and ECOFF was 0.5 µg/mL. For M. peregrinum, the corresponding values were 0.007, 0.06 and 2.0 µg/mL. As a result, only 1 (1.3%) resistant strain of M. fortuitum was detected, no resistant strains of M. peregrinum were found. When the DS of these NTM species to other ABDs were studied, it was found that M. fortuitum and M. peregrinum were highly resistant to most of them. Conclusion. Bdq was found to be active against MFC in vitro and is likely to be effective in the chemotherapy of mycobacteriosis caused by these NTM species

First detection in Spain of NDM-1-producing Pseudomonas aeruginosa in two patients transferred from Ukraine to a university hospital

ObjectivesCarbapenemase-mediated carbapenem resistance in Pseudomonas aeruginosa is a relevant health problem. We detected for the first time in Spain two clinical NDM-producing P. aeruginosa (NDM-Pa) isolates in two Ukrainian patients admitted to our hospital between April and August 2022. MethodsAntimicrobial susceptibility was studied by microdilution and MIC gradient strips (EUCAST-2022 criteria). Carbapenemase genes were detected by the Xpert Carba-R and immunochromatography assays. WGS (Illumina and Oxford-Nanopore) was also performed. ResultsIn May 2022, we detected an NDM-Pa in a sternotomy wound in a patient. In June-2022, a second NDM-Pa along with an OXA-48-Klebsiella pneumoniae (OXA-48-Kp) isolate was detected in a mandibular abscess from an unrelated patient. Moreover, an NDM+OXA-48-K. pneumoniae (NDM+OXA-48-Kp) was also found in a rectal sample of this patient. Both patients had undergone surgery in Ukraine before their transfer to our hospital. NDM-Pa isolates were resistant to all tested antimicrobials with the exception of aztreonam (MIC = 8 mg/L), colistin (MIC =2 mg/L) and cefiderocol (MIC range = 0.75–2 mg/L). WGS confirmed that both P. aeruginosa isolates were NDM-1 producers, belonged to ST773 and shared an identical resistome. blaNDM-1 was located on a ∼117-Kb chromosomally integrated integrative conjugative element (ICE). OXA-48-Kp and NDM+OXA-48-Kp belonged to ST147 and contained blaOXA-48 on an identical ∼300-Kb IncHIB-plasmid. blaNDM-1 was located on a 51-Kb IncFIB-plasmid only found in NDM+OXA-48-Kp. ConclusionsThis is the first description of NDM-Pa in Spain. We highlight the threat of further cross-border dissemination of NDM-1 through P. aeruginosa along with K. pneumoniae high-risk clones also carrying OXA-48, which draws a complex epidemiological scenario.

Evaluation of Equisetin as an Anti-Microbial and Herbicidal Agent from Endophytic Fungus Fusarium sp. JDJR1

Equisetin was isolated from endophytic fungus Fusarium sp. JDJR1 via bioassay-guided isolation, and it was evaluated as an anti-microbial and herbicidal agent. Bioactivity assessments revealed that equisetin exhibited a broad spectrum of fungicidal and anti-bacterial activity against various plant pathogens. The EC50 values against Botrytis cinerea, Fusarium graminearum, Sclerotinia sclerotiorum, and Rhizoctonia solani ranged from 10.7 to 21.0 μg/mL. Notably, equisetin demonstrated activity against Xanthomonas oryzae pv. oryzicola, Xanthomonas oryzae pv. oryzae and Pseudomonas solanacearum with an MIC range of 4–16 μg/mL, surpassing the efficacy of the positive control: streptomycin sulfate. Equisetin, at a concentration of 100 μg/mL, could completely inhibit the spore germination of F. graminearum. In in vivo protection experiments, the protective efficacy of equisetin against B. cinerea on tomato fruits at 200 μg/mL reached 72.9%. Furthermore, in herbicidal activity tests that use the Petri dish bioassay method, equisetin had a good inhibitory effect on the root growth of weeds. At a concentration of 100 μg/mL, the inhibition rates for Echinochloa crusgalli and Eclipta prostrata root were 98.8 and 94.4%, respectively.

Antibacterial, Resistance Modulation, Anti-Biofilm Formation, and Efflux Pump Inhibition Properties of Loeseneriella africana (Willd.) N. Halle (Celastraceae) Stem Extract and Its Constituents.

This study investigated the antibacterial, resistance modulation, biofilm inhibition, and efflux pump inhibition potentials of Loeseneriella africana stem extract and its constituents. The antimicrobial activity was investigated by the high-throughput spot culture growth inhibition (HT-SPOTi) and broth microdilution assays. The resistance modulation activity was investigated using the anti-biofilm formation and efflux pump inhibition assays. Purification of the extract was carried out by chromatographic methods, and the isolated compounds were characterized based on nuclear magnetic resonance, Fourier transform infrared and mass spectrometry spectral data and comparison with published literature. The whole extract, methanol, ethyl acetate, and pet-ether fractions of L. africana all showed antibacterial activity against the test bacteria with MICs ranging from 62.5 to 500.0 µg/mL The whole extract demonstrated resistance modulation effect through strong biofilm inhibition and efflux pump inhibition activities against S. aureus ATCC 25923, E. coli ATCC 25922 and P. aeruginosa ATCC 27853. Chromatographic fractionation of the ethyl acetate fraction resulted in the isolation of a triterpenoid (4S,4αS,6αR,6βS,8αS,12αS,12βR,14αS,14βR)-4,4α,6β,8α,11,11,12β,14α-Octamethyloctadecahydropicene-1,3(2H,4H)-dione) and a phytosterol (β-sitosterol). These compounds showed antibacterial activity against susceptible bacteria at a MIC range of 31-125 µg/mL and potentiated the antibacterial activity of amoxicillin (at ¼ MIC of compounds) against E. coli and P. aeruginosa with modulation factors of 32 and 10, respectively. These compounds also demonstrated good anti-biofilm formation effect at a concentration range of 3-100 µg/mL, and bacterial efflux pump inhibition activity at ½ MIC and ¼ MIC against E. coli and P. aeruginosa. Loeseneriella africana stem bark extracts and constituents elicit considerable antibacterial, resistance modulation, and biofilm and efflux pump inhibition activities. The results justify the indigenous uses of L. africana for managing microbial infections.

Target identification, and optimization of dioxygenated amide derivatives as potent antibacterial agents with FabH inhibitory activity

The enzyme FabH plays a critical role in the initial step of fatty acid biosynthesis, which is vital for the survival of bacteria. As a result, FabH has emerged as an appealing target for the development of novel antibacterial agents. In this study, employing the chemical proteomics method, we validated the previously identified skeleton amide derivatives bearing dioxygenated rings, potentially formed through metabolic processes. Building upon the proteomics findings, we then synthesized and evaluated 32 compounds containing N-heterocyclic amides for their antimicrobial activity for future optimizing the deoxygenated amides. Several compounds demonstrated potent antimicrobial properties with low toxicity, particularly compound 25, which exhibited remarkable potential as an agent with an MIC range of 1.25–3.13 μg/mL against the tested bacterial strains and an IC50 of 2.0 μM against E. coli-derived FabH. Furthermore, we evaluated nine analogues with relatively low MIC values through cytotoxicity and hemolytic activity assessments, Lipinski's rule-of-five criteria, and in silico ADMET predictions to ascertain their druggability potential. Notably, a detailed docking simulation was performed to investigate the binding interactions of compound 25 within the binding pocket of E. coli FabH, which encouragingly revealed strong binding interactions. Based on our findings, compound 25 emerges as the optimal candidate for in vivo therapy aimed at treating infected skin defects. Remarkably, the application of compound 25 demonstrated a significant reduction in the duration of wound infection and notably accelerated the healing process of infected wounds, achieving an impressive 94 % healing rate by day 10.

Anticandidal Activity of In Situ Methionine γ-Lyase-Based Thiosulfinate Generation System vs. Synthetic Thiosulfinates.

Candida albicans and non-albicans Candida species are a common cause of human mucosal infections, as well as bloodstream infections and deep mycoses. The emergence of resistance of Candida spp. to antifungal drugs used in practice requires the search for new antimycotics. The present study unravels the antifungal potential of the synthetic dialk(en)ylthiosulfinates in comparison with an enzymatic in situ methionine γ-lyase-based thiosulfinate generation system (TGS). The kinetics of the TGS reaction, namely, the methionine γ-lyase-catalyzed β-elimination of S-alk(en)yl-L-cysteine sulfoxides, was investigated via 1H NMR spectroscopy for the first time, revealing fast conversion rates and the efficient production of anticandidal dialk(en)ylthiosulfinates. The anticandidal potential of this system vs. synthetic thiosulfinates was investigated through an in vitro assay. TGS proved to be more effective (MIC range 0.36-1.1 μg/mL) than individual substances (MIC range 0.69-3.31 μg/mL). The tested preparations had an additive effect with the commercial antimycotics fluconazole, amphotericin B and 5-flucytosine demonstrating a fractional inhibitory coefficient index in the range of 0.5-2 μg/mL. TGS can be regarded as an attractive candidate for the targeted delivery of antimycotic thiosulfinates and for further implementation onto medically implanted devices.

Design, synthesis, evaluation and optimization of novel azole analogues as potent antifungal agents

In order to develop antifungal drugs, a series of novel azole analogues were designed and synthesized based on our previous work. Most of the target compounds had broad-spectrum antifungal activity, which showed excellent to moderate inhibitory activity against the tested strains, except A. fum 0504656. Among these, compounds B3, B7, B8, B11, B12 and E9 showed excellent activity against C. alb Y0109 and C. alb SC5314 (with the MIC80: 0.0156 ug/mL). In addition, compound B3 showed the best inhibitory activity against fluconazole-resistant strains C. alb 901 and C. alb 904, and had low toxicity against NIH/3T3 cells at the effective MIC range against fungi. Structure-activity relationship and docking studies of the derivatives suggest that the presence of the 2-fluoro-4-hydroxyphenyl and 1,2,3-triazole group enhance the antifungal activity of the compounds, which may be related to the interaction of the key groups with the amino acids surrounding the target enzyme.

2128. In Vitro Activity of Ceftibuten-Avibactam and Comparator Agents Against Resistant Enterobacterales from UTIs Collected Globally as Part of the ATLAS Surveillance Program, 2022

Abstract Background Increasing resistance among agents commonly prescribed to treat urinary tract infections (UTIs) indicate that new orally bioavailable agents are needed. Ceftibuten (CTB) is an orally administered third-generation cephalosporin and is in early clinical development being combined with an oral prodrug of avibactam (AVI). AVI is a non-β-lactam inhibitor of Ambler class A β-lactamases, including ESBLs and KPCs, class C (AmpC) β-lactamases, and some class D (OXA-48) β-lactamases. Ceftibuten-avibactam prodrug (CBA) is in early clinical development as a potential oral treatment for complicated urinary tract infections. This study evaluated the in vitro activity of CBA and oral comparators against Enterobacterales from UTIs with drug-resistant phenotypes collected globally as part of the 2022 Antimicrobial Testing Leadership and Surveillance (ATLAS) program. Methods 4,265 non-duplicate clinical isolates from UTIs were collected in 2022 in 55 countries. Susceptibility testing with CBA tested at a fixed concentration of 4 µg/mL AVI and comparators was performed by CLSI broth microdilution and interpreted using CLSI 2023 breakpoints. Nonsusceptible (NS)/resistant (R) phenotypes were based on 2023 CLSI breakpoints. MDR was defined as R to ≥1 agent from ≥3 drug classes. Results CBA was the most active compound tested against all Enterobacterales, with the MIC90 value decreasing from 32 µg/mL to 0.12 µg/mL. A total of 96% of all isolates were inhibited at a CBA MIC of ≤1 µg/mL. Percent susceptible of oral comparators ranged from 63.4% to 76.8%. CBA maintained activity against NS/R subsets of Enterobacterales (MIC90 range, 0.25 to 4 µg/mL; 85.0% to 93.2% inhibited at ≤1 µg/mL), including MDR isolates (MIC90, >64 µg/mL; 81.7% inhibited at ≤1 µg/mL). Conclusion Ceftibuten-avibactam demonstrated potent in vitro activity against multidrug-resistant Enterobacterales collected globally. Ceftibuten -avibactam prodrug could be an effective oral therapy for difficult-to-treat infections caused by multidrug-resistant Enterobacterales. Disclosures Meredith Hackel, PhD, Pfizer Inc.: Honoraria|Venatorx: Paid fees for conducting the study and abstract preparation Gregory Stone, PhD, Pfizer: Stocks/Bonds Daniel F. Sahm, PhD, Merck & Co., Inc.: Honoraria|Pfizer Inc.: Honoraria|Venatorx: Paid fees for conducting the study and abstract preparation

2747. Aztreonam-Avibactam Susceptibility Testing Program for Metallo-β-Lactamase-Producing Enterobacterales collected through the Antimicrobial Resistance Laboratory Network, March 2019 to April 2023

Abstract Background Metallo-β-lactamase-producing Enterobacterales (MBL-E) are a major public health concern as they cause infections with few effective treatment options. Aztreonam-avibactam (AZA) is a β-lactam/β-lactamase inhibitor combination agent in the drug development pipeline that is active against MBL-E. Though clinical studies are ongoing, the effective components can be administered by combining two FDA-approved drugs: aztreonam and ceftazidime-avibactam. In 2019, CDC initiated a program in the Antimicrobial Resistance Laboratory Network (AR Lab Network), the Expanded Antimicrobial Susceptibility Testing Program for Hard-to-Treat Infections, to provide antimicrobial susceptibility testing (AST) of MBL-E for AZA. We provide a summary of the program’s results. Methods Seven AR Lab Network laboratories validated the use of a digital dispenser to create custom broth microdilution panels for AZA AST. Testing requests must be for clinical decision-making purposes. Isolates must be an Enterobacterales and have laboratory results positive for an MBL gene (i.e., blaNDM, blaVIM, or blaIMP), or be not susceptible to all β-lactams tested. AZA testing results for confirmed MBL-E were reported back to submitters within 3 working days from receipt of the isolate and shared with CDC. Results From March 2019 through April 2023, AZA AST was performed for 250 isolates: 103 Escherichia coli, 86 Klebsiella pneumoniae, 46 Enterobacter cloacae complex, 8 K. oxytoca, 2 Providencia rettgeri, 1 K. aerogenes, 1 Morganella morganii, 1 Proteus mirabilis, 1 E. hormaechei, and 1 Citrobacter amalonaticus. Carbapenemase genes detected were: 206 blaNDM, 24 blaNDM/blaOXA-48-like, 14 blaKPC/blaNDM, 2 blaIMP, 2 blaKPC/blaIMP, and 2 blaNDM/blaIMP. All isolates were resistant to ceftazidime-avibactam; 227/250 (90.8%) were not susceptible to aztreonam (≥8 µg/mL). For isolates not susceptible to aztreonam, the addition of avibactam resulted in a median 128-fold MIC reduction of aztreonam. The MIC range of AZA was ≤0.03/4 - >64/4 µg/mL. Overall, the MIC50 and MIC90 of AZA were 0.5/4 µg/mL and 8/4 µg/mL, respectively; the MIC50 and MIC90 for E. coli were higher than other species, 4/4 µg/mL and 16/4 µg/mL. Conclusion Our data suggest that AZA has potent in vitro activity against MBL-E collected in the United States. Disclosures All Authors: No reported disclosures

In vitro and ex vivo anti-Pythium insidiosum potential of ozonated sunflower oil.

This study sought to evaluate the in vitro and ex vivo susceptibility of Pythium insidiosum to ozonized sunflower oil (OSO) and verify the morphological alterations of OSO-exposed hyphae. Susceptibility assays were performed according to the broth microdilution protocol M38-A2/CLSI, and the minimal inhibitory (MIC) and minimal oomicidal (MOC) concentrations were also determined. Non-ozonated sunflower oil (SO) was used as the oil control. Additionally, kunkers from equine pythiosis were exposed to OSO. Damages caused by OSO and SO on P. insidiosum hyphae ultrastructure were verified using scanning electron microscopy. The MIC range for OSO was 7000 to 437.5mg/mL, and the values for SO were higher, ranging from 56000 to 14000mg/mL. The MOC was equal to MIC for both oil formulations. The OSO fully inhibited the oomycete growth from kunkers, although there was P. insidiosum growth in the kunker control in 24h of incubation. The SEM analyses showed that both OSO and SO caused morphological alterations in P. insidiosum hyphae, highlighting the presence of cavitation along the hyphae with loss of continuity of the cell wall, which was more evident in the OSO-treated hyphae. The OSO had the best oomicidal activity, leading us to believe that our findings may support future research containing this formulation to be applied in integrative medicine protocols to control pythiosis in animals and humans.

An Alternative Approach Using Nano-garlic Emulsion and its Synergy with Antibiotics for Controlling Biofilm-Producing Multidrug-Resistant Salmonella in Chicken

Surface-growing antibiotic-resistant pathogenic Salmonella is emerging as a global health challenge due to its high economic loss in the poultry industry. Their pathogenesis, increasing antimicrobial resistance, and biofilm formation make them challenging to treat with traditional therapy. The identification of antimicrobial herbal ingredients may provide valuable solutions to solve this problem. Therefore, our aim is to evaluate the potency of nano garlic as the alternative of choice against multidrug-resistant (MDR) Salmonella isolates using disc diffusion and microdilution assays. Then, checkerboard titration in trays was applied, and FIC was measured to identify the type of interaction between the two antimicrobials. A disc diffusion assay revealed that neomycin was the drug of choice. The range of nano garlic MIC was 12.5–25 μg/ml, while the neomycin MIC range was 32–64 μg/ml. The FIC index established a synergistic association between the two tested drugs in 85% of isolates. An experimental model was used including nano garlic and neomycin alone and in combination against Salmonella infection. The combination therapy significantly improved body productivity and inhibited biofilm formation by more than 50% down regulating the CsgBAD, motB, and sipA operons, which are responsible for curli fimbriae production and biofilm formation in Salmonella serotypes.

In vitro activity of tebipenem and comparator agents against bacterial pathogens isolated from patients with cancer

Abstract Background Tebipenem is a broad-spectrum orally administered carbapenem antibiotic that could be an alternative to IV carbapenems. The current study evaluated in vitro activity of tebipenem against bacterial isolates recovered from patients with cancer. Methods A total of 611 bacterial pathogens recently isolated from patients with cancer were tested for susceptibility to tebipenem and comparators. CLSI-approved broth microdilution methods were used. MIC50, MIC90, MIC range and percentage susceptibility calculations were made using FDA breakpoints when available. Results Tebipenem had a low MIC90 for most Gram-positive and Enterobacterales isolates. Tebipenem MIC90 ranged from 0.06 to 0.25 mg/L for all tested Enterobacterales. Conclusions Oral tebipenem has promising activity against clinically significant bacterial pathogens isolated from patients with cancer. Further clinical evaluation of tebipenem for the treatment of bacterial infections in patients with cancer is warranted.

Population pharmacokinetics of enrofloxacin and florfenicol in the giant danio (Devario aequipinnatus) following oral administration of both antibiotics and bath administration of enrofloxacin

The lack of pharmacokinetic and drug exposure data, even for commonly utilized antibiotics, in freshwater ornamental teleost fish species magnifies the difficulties in treating bacterial pathogens. This study aimed to determine the population pharmacokinetics of enrofloxacin and florfenicol and to predict their probability of target attainment for giant danio (Devario aequipinnatus), a close relative of the commercially and biomedically important zebra danio (Danio rerio). Enrofloxacin was dosed orally at 8 mg/kg or via bath at 10 mg/L in 95 fish, and florfenicol orally at 60 mg/kg in 56 fish. Informative sampling times were identified by optimal design analysis. Drug concentrations in blood and muscle homogenate were quantified by LC-MS/MS and modelled by population pharmacokinetics. Monte Carlo simulations were used to predict the probability of pharmacokinetic/pharmacodynamic (PK/PD) target attainment. The apparent total clearance was 1.17 mL/h (33.9% coefficient of variation [CV] for between animal variability) for enrofloxacin and 1.89 mL/h (20.9% CV) for florfenicol. The ratio of drug exposure in muscle homogenate compared to that in plasma was 1.61 (33.3% CV) for enrofloxacin and 0.782 (19.4% CV) for florfenicol. Oral florfenicol at 60 mg/kg robustly covered MICs up to 2 to 4 mg/L, depending on the PK/PD target. While oral enrofloxacin (8 mg/kg) robustly covered MICs up to 0.125 to 0.5 mg/L, bath dosing at 10 mg/L for 5 or 10 h only covered MICs up to 0.0156 to 0.125 mg/L. These Monte Carlo simulations provided guidance on the range of MICs that result in high probabilities of successful treatment.

The Molecular Identification and Antifungal Susceptibility of Clinical Isolates of Aspergillus Section Flavi from Three French Hospitals.

(1) Background: Aspergillus flavus is a cosmopolitan mold with medical, veterinary, and agronomic concerns. Its morphological similarity to other cryptic species of the Flavi section requires molecular identification techniques that are not routinely performed. For clinical isolates of Aspergillus section Flavi, we present the molecular identification, susceptibility to six antifungal agents, and clinical context of source patients. (2) Methods: One hundred forty fungal clinical isolates were included in the study. These isolates, recovered over a 15-year period (2001-2015), were identified based on their morphological characteristics as belonging to section Flavi. After the subculture, sequencing of a part of the β-tubulin and calmodulin genes was performed, and resistance to azole antifungals was screened on agar plates containing itraconazole and voriconazole. Minimum inhibitory concentrations were determined for 120 isolates by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) broth microdilution method. (3) Results: Partial β-tubulin and calmodulin sequences analysis showed that 138/140 isolates were A. flavus sensu stricto, 1 isolate was A. parasiticus/sojae, and 1 was A. nomiae. Many of the isolates came from samples collected in the context of respiratory tract colonization. Among probable or proven aspergillosis, respiratory infections were the most frequent, followed by ENT infections. Antifungal susceptibility testing was available for isolates (n = 120, all A. flavus ss) from one hospital. The MIC range (geometric mean MIC) in mg/L was 0.5-8 (0.77), 0.5-8 (1.03), 0.125-2 (0.25), 0.03-2 (0.22), 0.25-8 (1.91), and 0.03-0.125 (0.061) for voriconazole, isavuconazole, itraconazole, posaconazole, amphotericin B, and caspofungin, respectively. Two (1.67%) isolates showed resistance to isavuconazole according to current EUCAST breakpoints with MICs at 8 mg/L for isavuconazole and voriconazole. One of these two isolates was also resistant to itraconazole with MIC at 2 mg/L. (4) Conclusions: The present characterization of a large collection of Aspergillus belonging to the Flavi section confirmed that A. flavus ss is the predominant species. It is mainly implicated in respiratory and ENT infections. The emergence of resistance highlights the need to perform susceptibility tests on section Flavi isolates.

Pyrano-coumarin hybrids as potential antimicrobial agents against MRSA strains: Design, synthesis, ADMET, molecular docking studies, as DNA gyrase inhibitors

Due to their various pharmacological effects, several substituted nitrogen heterocycles containing coumarin have recently attracted a great deal of attention. Acetyl-coumarin was used in reactions with p-methoxy-benzaldehyde, malononitrile, and ordinary heating to produce compound 1, which contains cyano-amine, allowing for the one-pot and speedy synthesis of coumarin derivatives. Ethyl cyanoacetate, triethyl orthoformate, phenyl isothiocyanate, carbon disulfide, and benzaldehyde, were used to condense compound 1 to get the corresponding chromene derivatives 2–15. Elemental and spectroscopic evidence was used to characterize every freshly synthesized hits. S. aureus (MRSA), P. aeruginosa, E. coli, and C. albicans were the standard strains employed in this investigation. Most of the compounds displayed moderate to high activity against all the tested species, according to the early screening results with a MIC range of 0.25 to 1024 μg/mL. When compared to the positive control, compounds 3, 6, 9, and 12 showed the greatest declining reduction in the bulk of the bacterial species' biofilm. The findings of subsequent testing on the three most powerful compounds against E. coli DNA gyrase inhibitory activity revealed that all these derivatives block DNA gyrase and hence prevent cell proliferation. Additionally, successful in silico investigations for the most active compounds were conducted.