In vitro and in vivo activity of oxazolidinone candidate OTB-658 against Mycobacterium tuberculosis

In this work, we assess anti-tuberculosis activity of OTB-658 in vitro and in vivo . In vitro , OTB-658 showed bacteriostatic effectiveness with a lower minimum inhibitory concentration than linezolid against Mycobacterium tuberculosis . The minimal bactericidal concentrations and time-kill curves for OTB-658 indicated similar inhibition activity to that of linezolid. OTB-658 entered macrophages to inhibit of M. tuberculosis growth. OTB-658 had a low mutant frequency (10 −8 ), which would prevent drug-resistant mutations from emerging in combination regimens. In vivo , OTB-658 reduced colony-forming unit counts in the lungs and slightly inhibited bacterial growth in the spleen in the early stage and steady state in acute and chronic murine TB models. These results support the preclinical evaluation of OTB-658 and further clinical trials in China.

Drug-Lead Anti-tuberculosis Phytochemicals: A Systematic Review

Today, the occurrence and recurrence of multidrug-resistant tuberculosis (MDR-TB) strains and TB-comorbidity incidence are the main reasons for long-term morbidity and mortality from tuberculosis (TB) caused by the nasty acid-fast pathogen, Mycobacterium tuberculosis, globally. Therefore, discovering and developing well-tolerated and non-toxic anti-TB regimens are directly needed to defend the gruesome MDR-TB strains and support WHO’s ‘END-TB’ campaign. Alternatively, phytochemicals from various common and medicinal plants have always been vital therapeutic agents since the primitive era. Thus, to promote phytochemical-based anti-TB drug development, scientific documentation of biological activities, structural-cum-drug chemistry analyses are essential. In the present review, we have used some specific keywords such as ‘antituberculosis phytochemicals’, 'antituberculosis phytochemicals from plant source', ‘natural products against tuberculosis’ in Google, PubMed, ScienceDirect sites to get more appropriate research reports/ publications. Further, based on lower minimum inhibitory concentration (MIC) within 50 µg/mL, a total of two-hundred-twenty-one bioactive anti-TB phytochemicals were selected for critical drug-chemistry and structural activity relationship (SAR) analyses to accelerate the anti-TB drug development with most drug lead anti-TB candidates. Among all, abietane, ethyl-p-methoxycinnamate, ergosterol peroxide, mono-O-methyl curcumin isoxazole, 7-methyljuglone, 12-demethylmulticaulin, 12-methyl-5-dehy droacetylhorminone, tryptanthrin, etc. are some of the potential anti-TB phytochemicals display at the minimum concentration ≤ 1 µg/mL. Remarkably, existing and clinical drug pipelines for TB contain more than one phytochemical scaffold/ pharmacophores illustrated from the SAR analysis. Thus, updated experimental documentation and critical drug-chemistry analysis on isolated phytochemicals are more beneficial for drug developers, R & D centres and pharmaceutical companies to accelerate the anti-TB drug development.

SYNTHESIS OF A HIGH-PERFORMANCE ANTIMICROBIAL O-QUATERNIZED ALGINATE – A PROMISING POTENTIAL ANTIMICROBIAL AGENT

Three novel biologically active quaternized sodium alginates were synthesized via the reaction of sodium alginate (SA) with 3-chloro-2-hydroxypropyl trimethylammonium chloride, at room temperature for different time intervals (1, 3 and 6 h), to produce quaternized sodium alginates designated as QSA1, QSA3 and QSA6. The percentage degree of quaternization (DQ%) significantly increased with increasing the reaction time. Images from FTIR, 1H-NMR, XRD and SEM have confirmed the chemical structures of the QSA samples. Their antimicrobial activity was investigated against bacteria and fungi using XTT assay, and the results showed that all QSA samples displayed high growth inhibition capacity of the tested microorganisms, compared to zero inhibition for SA, as shown by their lower minimum inhibitory concentration (MIC). The QSA6 was the best antimicrobial composite, displaying the same MIC value as that of the used reference drugs. The developed composites were found to be safe on normal human fibroblast cells (WI-38 cell line), by evaluating them using cytotoxic activity measurement, which makes QSA a promising material in biomedical and food applications.

Aniba rosaeodora (Var. amazonica Ducke) Essential Oil: Chemical Composition, Antibacterial, Antioxidant and Antitrypanosomal Activity

Aniba rosaeodora is one of the most widely used plants in the perfumery industry, being used as medicinal plant in the Brazilian Amazon. This work aimed to evaluate the chemical composition of A. rosaeodora essential oil and its biological activities. A. rosaeodora essential oil presented linalool (93.60%) as its major compound. The A. rosaeodora essential oil and linalool showed activity against all the bacteria strains tested, standard strains and marine environment bacteria, with the lower minimum inhibitory concentration being observed for S. aureus. An efficient antioxidant activity of A. rosaeodora essential oil and linalool (EC50: 15.46 and 6.78 µg/mL, respectively) was evidenced by the inhibition of the 2,2-azinobis- (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical. The antitrypanosomal activity of A. rosaeodora essential oil and linalool was observed at high concentrations against epimatigote forms (inhibitory concentration for 50% of parasites (IC50): 150.5 ± 1.08 and 198.6 ± 1.12 µg/mL, respectively), and even higher against intracellular amastigotes of T. cruzi (IC50: 911.6 ± 1.15 and 249.6 ± 1.18 µg/mL, respectively). Both A. rosaeodora essential oil and linalool did not exhibit a cytotoxic effect in BALB/c peritoneal macrophages, and both reduced nitrite levels in unstimulated cells revealing a potential effect in NO production. These data revealed the pharmacological potential of A. rosaeodora essential oil and linalool, encouraging further studies.

1600. Closing the gap on moxifloxacin breakpoints for Stenotrophomonas maltophilia

Background Moxifloxacin (MOX) has in vitro activity against Enterobacterales and Stenotrophomonas maltophilia (SM). Although MOX commonly displays lower minimum inhibitory concentration (MIC)50/90 values against SM when compared to levofloxacin, there are currently no established MOX breakpoints for treatment of SM. The Clinical and Laboratory Standards Institute (CLSI) has established interpretive categories and MIC breakpoints for levofloxacin (S ≤2µg/ml) against SM. The US Food and Drug Administration and European Committee on Antimicrobial Susceptibility Testing provide MOX breakpoints for Enterobacterales with susceptible MICs represented at ≤ 2 µg/mL and ≤ 0.25 µg/mL, respectively. The purpose of this study was to evaluate MOX MIC distribution against SM strains recovered from clinical specimens. Methods Clinical samples from patients with suspected infection during calendar year 2018 and 2019 were processed in the microbiology lab of Wake Forest Baptist Medical Center. After incubation, SM colonies were identified by MALDI-TOF system. MOX susceptibility testing was performed for these clinical isolates by gradient diffusion strip methodologies. Results were displayed as MIC (µg/mL) without interpretation. MIC50/90 and susceptibility rates at potential breakpoints were calculated. Results A total of 211 isolates were tested, 112 from 2018 and 99 from 2019. MOX MIC50 and MIC90 for all isolates was 0.25 µg/mL and 2 µg/mL, respectively. The range of MIC distribution was ≤ 0.006 µg/mL to ≥ 64 µg/mL. Percent susceptibilities at incremental MICs, including established MOX breakpoints against Enterobacterales and established levofloxacin breakpoints against SM, are represented in Table 1. MIC distribution was plotted in Figure 1. Table 1. Susceptibility rates of S. maltophilia to moxifloxacin at theoretical breakpoints Figure 1. Moxifloxacin MIC Distribution against All S. maltophilia Isolates Conclusion With no established breakpoint, these data represent one of the largest samples of MOX MICs against SM in the United States. Using the CLSI breakpoint for levofloxacin in SM (MIC of ≤2ug/ml) the overall susceptibility rate is 93%. This finding highlights the importance of performing susceptibility testing to this agent by the microbiology laboratory and the critical need for MOX breakpoints in SM. Disclosures Tyler J. Stone, PharmD, Paratek (Research Grant or Support) John Williamson, PharmD, Paratek (Research Grant or Support) Elizabeth Palavecino, MD, Paratek (Grant/Research Support)Paratek (Grant/Research Support)

Evaluation of a Bioengineered Honey and Its Synthetic Equivalent as Novel Staphylococcus aureus Biofilm-Targeted Topical Therapies in Chronic Rhinosinusitis

Background Chronic rhinosinusitis (CRS) is a common condition which affects the quality of life of millions of patients worldwide and has a significant impact on health-care resources. While Staphylococcus aureus bacterial biofilms play an important role in this disease, antimicrobial therapy is rarely effective and may promote antibiotic resistance. Thus, development of novel biofilm-targeting and antibiotic-sparing therapies is highly desirable and urgently required. Objective This in vitro study evaluated the antimicrobial activity of a novel synthetic honey-equivalent product which was designed to have the same reactive oxygen release profile as the engineered honey SurgihoneyRO™. Methods Treatment efficacy was investigated by assessment of planktonic growth, biofilm viability, thickness, and biomass using 12 CRS-related S. aureus mucosal bacterial strains. Results Both SurgihoneyRO™ and the synthetic honey-equivalent product inhibited growth of planktonic methicillin-resistant and methicillin-sensitive S. aureus strains, with the synthetic honey-equivalent product exhibiting a lower minimum inhibitory concentration. Treatment of established S. aureus biofilms reduced biofilm viability with 24-hour treatment resulting in a 2-log reduction in viability of biofilms formed by methicillin-resistant strains and a 1-log reduction in biofilms formed by methicillin-sensitive strains. Conclusions This preliminary study shows that the synthetic honey-equivalent product provides marked antimicrobial activity against S. aureus biofilms, with the potential for development in the clinical setting as an adjunctive biofilm-targeted therapy in CRS. The ultimate aim of such a product would be to reduce the need for antibiotics, steroids, and invasive surgical procedures in CRS patients as well as improving clinical outcomes following endoscopic sinus surgery.

Systematical Analysis of the Protein Targets of Lactoferricin B and Histatin-5 Using Yeast Proteome Microarrays

Antimicrobial peptides (AMPs) have potential antifungal activities; however, their intracellular protein targets are poorly reported. Proteome microarray is an effective tool with high-throughput and rapid platform that systematically identifies the protein targets. In this study, we have used yeast proteome microarrays for systematical identification of the yeast protein targets of Lactoferricin B (Lfcin B) and Histatin-5. A total of 140 and 137 protein targets were identified from the triplicate yeast proteome microarray assays for Lfcin B and Histatin-5, respectively. The Gene Ontology (GO) enrichment analysis showed that Lfcin B targeted more enrichment categories than Histatin-5 did in all GO biological processes, molecular functions, and cellular components. This might be one of the reasons that Lfcin B has a lower minimum inhibitory concentration (MIC) than Histatin-5. Moreover, pairwise essential proteins that have lethal effects on yeast were analyzed through synthetic lethality. A total of 11 synthetic lethal pairs were identified within the protein targets of Lfcin B. However, only three synthetic lethal pairs were identified within the protein targets of Histatin-5. The higher number of synthetic lethal pairs identified within the protein targets of Lfcin B might also be the reason for Lfcin B to have lower MIC than Histatin-5. Furthermore, two synthetic lethal pairs were identified between the unique protein targets of Lfcin B and Histatin-5. Both the identified synthetic lethal pairs proteins are part of the Spt-Ada-Gcn5 acetyltransferase (SAGA) protein complex that regulates gene expression via histone modification. Identification of synthetic lethal pairs between Lfcin B and Histatin-5 and their involvement in the same protein complex indicated synergistic combination between Lfcin B and Histatin-5. This hypothesis was experimentally confirmed by growth inhibition assay.

Analysis of glycosylated flavonoids extracted from sweet-cherry stems, as antibacterial agents against pathogenic Escherichia coli isolates

The aim of this study was to evaluate the bioactivity of flavonoids extracted from sweet-cherry stems, which is often used by traditional medicine to treat infections from gastro-intestinal and urinary but without any consistent scientific evidences, moreover the information about the class of phenolics, their content and the potential bioactivity of such material is very scarce. Thus, in this context, we set a research study in which we evaluate the profile and content of phenolics extracted from sweet-cherry stems through a conventional (70ºC and 20 minutes) and ultrasound assisted extraction (40 kHz, room temperature and 20 minutes) methods. After, the extracts were phytochemical characterized by HPLC-DAD-UV/VIS, and assayed trough the in vitro minimum inhibitory concentration (MIC) bioassay, against Escherichia coli isolates. Simultaneously the total antioxidant activity were measured using the assay of 2,2′-azinobis-3-ethylbenzothiazoline-6-sulphonate (ABTS●+) radical cation. Our results showed that sweet-cherry stems presented higher content of sakuranetin, ferulic acid, p-coumaric acid, p-coumaroylquinic acid, chlorogenic acid and it´s isomer neochlorogenic acid. Their average levels were highly affected by the extraction method (p<0.001) used. The same trend was observed for total antioxidant activity and MIC values. The extracts produced under ultrasound presented both higher total antioxidant activity and lower minimum inhibitory concentration. The statistical analyses of our results showed a significant correlation (p<0.01) of total antioxidant activity and minimum inhibitory concentration with phenolics in the extracts studied. Thus, we can conclude that cherry stems can be further exploited to purify compounds and produced coproducts with enhanced biological added valuefor pharmaceutical industry.