Anthelmintic Activity of Nine Varieties of Cajanus cajan (L.) Millsp on Haemonchus contortus from Sheep

Background: Internal parasitosis is the most important parasitism in small ruminants in tropical region. Synthetic anthelmintics are usually used for their control. Due to the emergence of resistance in worm population, the use of alternative methods such as plants bioactive molecules are developed. This study aimed at assessing anthelmintic activity of nine varieties of Cajanus cajan, a taniferous plant cultivated in West Africa. Methods: Leaves of the nine varieties of Cajanus cajan were dried, ground and hydroacetonic extracts were obtained by cold maceration at a concentration of 60 mg/ml. Live adult of Haemonchus contortus were obtained from sheep’s stomach and exposed, in triplicate, to the following solutions: hydroacetonic extracts (60 mg/ml), hydroacetonic extracts (60 mg/ml) associated with polyvinylpyrrolidone (PVP) (50 mg/ml), Levamisole (20 mg/ml) and phosphate buffered saline (PBS) solution. Worm death time was recorded for each treatment. Result: Worms exposed to Levamisole recorded the shortest death time about 9.73±1.77 min. The potent of the extracts induced worm death time of 64.83±4.73 min while the least efficient induced a death time of 156.50±23.20 min. Worms in the PBS solution were still alive after 24 hours of exposure. These results indicated that the four varieties of C. cajan used in this study have promising wormicidal. Besides that, the effect of tannins were not the only compound responsible for the anthelmintic activity.

Raltegravir 1200 mg once daily as maintenance therapy in virologically suppressed HIV-1 infected adults: QDISS open-label trial

Background Raltegravir (RAL) has favorable tolerability and safety profile, with few and manageable drug interactions. The use of RAL 1200 mg once daily (qd) for first-line therapy is well established. We assessed efficacy and safety of RAL 1200 mg qd, as part of triple combined antiretroviral therapy (cART), for maintenance strategy. Methods The QDISS trial (NCT03195452) was a 48-week multicenter, single-arm, open-label study designed to evaluate the ability of 2 NRTIs + RAL 1200 mg qd to maintain virological suppression in HIV-1 infected subjects on a stable cART with 2 NRTIs and a third agent for at least 6 months. The primary endpoint was the proportion of participants with HIV-1 RNA < 50 copies/mL at week 24, by the FDA snapshot algorithm. Results Of 100 participants 91% maintained viral suppression (95% CI: 83.6–95.8) at week 24 and 89% (81.2–94.4) at week 48. At week 24, there was one virological failure, without emergence of resistance-associated mutation and 10 participants had discontinued, 4 because of adverse events (AEs). Over 48 weeks, 7 AEs of grade 3–4 were reported, one possibly study-drug related (spontaneous abortion). BMI remained stable regardless of previous therapy or baseline BMI category. Over 48 weeks, total cholesterol (p = 0.023) and LDL-cholesterol (p = 0.009) decreased, lifestyle and ease subscale significantly improved (p = 0.04). The quality of life and Patients Reported Outcomes (PROs) also improved at W12 (p = 0.007). Conclusion RAL 1200 mg qd as part of a maintenance triple therapy showed a high efficacy in virologically suppressed HIV-1 infected subjects, with good safety profile and improved lipid profile and patient reported outcomes. Trial registration: Clinical trials.gov NCT03195452 and EudraCT 2016-003702-13.

In Vitro Resistance against DNA Gyrase Inhibitor SPR719 in Mycobacterium avium and Mycobacterium abscessus

Clinical emergence of resistance to new antibiotics affects their utility. Characterization of in vitro resistance is a first step in the profiling of resistance properties of novel drug candidates.

Synergism in Antiplasmodial Activities of Artemether and Lumefantrine in Combination with Securidaca longipedunculata Fresen (Polygalaceae)

Malaria is the most lethal parasitic disease in the world. The frequent emergence of resistance by malaria parasites to any drug is the hallmark of sustained malaria burden. Since the deployment of artemisinin-based combination therapies (ACTs) it is clear that for a sustained fight against malaria, drug combination is one of the strategies toward malaria elimination. In Sub-Saharan Africa where malaria prevalence is the highest, the identification of plants with a novel mechanism of action that is devoid of cross-resistance is a feasible strategy in drug combination therapy. Thus, artemether and lumefantrine were separately combined and tested with extracts of Securidaca longipedunculata, a plant widely used to treat malaria, at fixed extract–drug ratios of 4:1, 3:1, 1:1, 1:2, 1:3, and 1:4. These combinations were tested for antiplasmodial activity against three strains of Plasmodium falciparum (W2, D6, and DD2), and seven field isolates that were characterized for molecular and ex vivo drug resistance profiles. The mean sum of fifty-percent fractional inhibition concentration (FIC50) of each combination and singly was determined. Synergism was observed across all fixed doses when roots extracts were combined with artemether against D6 strain (FIC50 0.403 ± 0.068) and stems extract combined with lumefantrine against DD2 strain (FIC50 0.376 ± 0.096) as well as field isolates (FIC50 0.656 ± 0.067). Similarly, synergism was observed in all ratios when leaves extract were combined with lumefantrine against W2 strain (FIC50 0.456 ± 0.165). Synergism was observed in most combinations indicating the potential use of S. longipedunculata in combination with artemether and lumefantrine in combating resistance.

INSTIs and NNRTIs Potently Inhibit HIV-1 Polypurine Tract Mutants in a Single Round Infection Assay

Integrase strand transfer inhibitors (INSTIs) are a class of antiretroviral compounds that prevent the insertion of a DNA copy of the viral genome into the host genome by targeting the viral enzyme integrase (IN). Dolutegravir (DTG) is a leading INSTI that is given, usually in combination with nucleoside reverse transcriptase inhibitors (NRTIs), to treat HIV-1 infections. The emergence of resistance to DTG and other leading INSTIs is rare. However, there are recent reports suggesting that drug resistance mutations can occur at positions outside the integrase gene either in the HIV-1 polypurine tract (PPT) or in the envelope gene (env). Here, we used single round infectivity assays to measure the antiviral potencies of several FDA-approved INSTIs and non-nucleoside reverse transcriptase inhibitors (NNRTIs) against a panel of HIV-1 PPT mutants. We also tested several of our promising INSTIs and NNRTIs in these assays. No measurable loss in potency was observed for either INSTIs or NNRTIs against the HIV-1 PPT mutants. This suggests that HIV-1 PPT mutants are not able, by themselves, to confer resistance to INSTIs or NNRTIs.

Polyclonal pathogen populations accelerate the evolution of antibiotic resistance in patients

Antibiotic resistance poses a global health threat, but the within-host drivers of resistance remain poorly understood. Pathogen populations are often assumed to be clonal within hosts, and resistance is thought to emerge due to selection for de novo variants. Here we show that pulmonary populations of the opportunistic pathogen P. aeruginosa are often polyclonal. Crucially, resistance evolves rapidly in patients colonized by polyclonal populations through selection for pre-existing resistant strains. In contrast, resistance evolves sporadically in patients colonized by monoclonal populations due to selection for novel resistance mutations. However, strong trade-offs between resistance and fitness occur in polyclonal populations that can drive the loss of resistant strains. In summary, we show that the within-host diversity of pathogen populations plays a key role in shaping the emergence of resistance in response to treatment.One sentence summaryAntibiotic resistance evolves quickly in patients colonized by polyclonal pathogen populations.

Efficacy and Synergy of Small Molecule Inhibitors Targeting FLT3-ITD+ Acute Myeloid Leukemia

Constitutive activation of FLT3 by ITD mutations is one of the most common genetic aberrations in AML, present in ~1/3 of cases. Patients harboring FLT3-ITD display worse clinical outcomes. The integration and advancement of FLT3 TKI in AML treatment provided significant therapeutic improvement. However, due to the emergence of resistance mechanisms, FLT3-ITD+ AML remains a clinical challenge. We performed an unbiased drug screen to identify 18 compounds as particularly efficacious against FLT3-ITD+ AML. Among these, we characterized two investigational compounds, WS6 and ispinesib, and two approved drugs, ponatinib and cabozantinib, in depth. We found that WS6, although not yet investigated in oncology, shows a similar mechanism and potency as ponatinib and cabozantinib. Interestingly, ispinesib and cabozantinib prevent activation of AXL, a key driver and mechanism of drug resistance in FLT3-ITD+ AML patients. We further investigated synergies between the selected compounds and found that combination treatment with ispinesib and cabozantinib or ponatinib shows high synergy in FLT3-ITD+ AML cell lines and patient samples. Together, we suggest WS6, ispinesib, ponatinib and cabozantinib as novel options for targeting FLT3-ITD+ AML. Whether combinatorial tyrosine kinase and kinesin spindle blockade is effective in eradicating neoplastic (stem) cells in FLT3-ITD+ AML remains to be determined in clinical trials.

New Delhi metallo-beta-lactamase facilitates the emergence of cefiderocol resistance in Enterobacter cloacae .

Cefiderocol is a promising novel siderophore cephalosporin for the treatment of multi-drug resistant Gram-negative bacilli and with stability against degradation by metallo-β-lactamases. Nonetheless, the emergence of cefiderocol in metallo-β-lactamase-producing Enterobacterales during therapy has been reported on more than one occasion. To understand the underlying mechanisms and factors facilitating the resistance development, we conducted an in vitro evolution experiment using clinical E. cloacae isolates via serial passaging under cefiderocol pressure. In this study, we show that the presence of the New-Delhi metallo-β-lactamase (NDM) facilitates the emergence of resistance via non-synonymous mutations of the CirA catecholate siderophore receptor. Inhibition of metallo-β-lactamase activity using dipicolinic acid prevented the emergence of cefiderocol-resistant mutants successfully. This finding implies that caution should be taken, when using cefiderocol for the treatment of infections caused by metallo-β-lactamase- producing bacteria.

Mutational switch-backs can accelerate evolution of Francisella to a combination of ciprofloxacin and doxycycline

Combination antimicrobial therapy has been considered a promising strategy to combat the evolution of antimicrobial resistance. Francisella tularensis is the causative agent of tularemia and in addition to being found in the nature, is recognized as a threat agent that requires vigilance. We investigated the evolutionary outcome of adapting the Live Vaccine Strain (LVS) of Francisella to two non-interacting drugs, ciprofloxacin and doxycycline, individually, sequentially, and in combination. Despite their individual efficacies and independence of mechanisms, evolution to the combination appeared to progress faster than evolution to the two drugs sequentially. We conducted a longitudinal mutational analysis of the populations evolving to the drug combination, genetically reconstructed the identified evolutionary pathway, and carried out biochemical validation. We discovered that, after the appearance of an initial weak generalist mutation (FupA/B), each successive mutation alternated between adaptation to one drug or the other. In combination, these mutations allowed the population to more efficiently ascend the fitness peak through a series of evolutionary switch-backs. Clonal interference, weak pleiotropy, and positive epistasis also contributed to combinatorial evolution. This finding suggests that, under some selection conditions, the use of non-interacting drug pairs as a treatment strategy may result in a more rapid ascent to multi-drug resistance and serves as a cautionary tale.Author summaryThe antimicrobial resistance crisis requires the use of novel treatment strategies to prevent or delay the emergence of resistance. Combinations of drugs offer one strategy to delay resistance, but the efficacy of such drug combinations depends on the evolutionary response of the organism. Using experimental evolution, we show that under some conditions, a potential drug combination does not delay the onset of resistance in bacteria responsible for causing tularemia, Francisella. In fact, they evolve resistance to the combination faster than when the two drugs are applied sequentially. This result is surprising and concerning: using this drug combination in a hospital setting could lead to simultaneous emergence of resistance to two antibiotics. Employing whole genome sequencing, we identified the molecular mechanism leading to evolution of resistance to the combination. The mechanism is similar to the switch-back route used by hikers while scaling steep mountains i.e., instead of simultaneously acquiring mutations conferring resistance to both drugs, the bacteria acquire mutations to each drug in alternating manner. Rather than scaling the steep mountain directly, the bacteria ascend the mountain by a series of evolutionary switch-backs to gain elevation and in doing so, they get to the top more efficiently.