Search

BACKGROUND: The effect of live yeast Saccharomyces cerevisiae strain CNCM I‐1077 (SC) on the ruminal degradability of different forages commonly found in dairy diets in South America was evaluated. We also assessed if SC supplementation interacts with forage group to affect ruminal fiber degradability. Four non‐lactating rumen‐cannulated Holstein cows were randomly assigned to two treatment sequences: Control‐SC‐Control or SC‐Control‐SC, in a switchback design, with three 30‐day periods. Cows in the SC treatment were supplied with 1 × 1010 colony‐forming units of yeast daily via rumen cannula. In situ degradability of dry matter (DM) and neutral detergent fiber (aNDF) was measured in 15 forages collected in South America. Forages were assigned to one of three groups: corn silages; tropical grasses (sugarcane silages and tropical grass silages); and temperate grasses and alfalfa (oat silages, ryegrass silages, alfalfa silage, and alfalfa hay). RESULTS: Cows supplemented with SC had higher (P = 0.05) counts of yeasts and lower (P = 0.03) concentration of lactate in rumen fluid. There was no interaction between forage group and yeast supplementation (P > 0.10) on in situ degradability. The SC increased DM (by 4.6%) and aNDF degradation (by 10.3%) at 24 h of incubation (P < 0.05). Metabolomics revealed that a chemical entity (C17H29N6O3, m/z 365.2284 [M + H]+) from the family of lipids and related molecules was suppressed in the rumen fluid of cows supplemented with SC. CONCLUSION: The SC supplementation improved DM and aNDF degradability regardless of the forage group. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Soybean is an important crop in South America, and its production is limited by fungal diseases caused by species from the genus Diaporthe , including seed decay, pod and stem blight, and soybean stem canker (SSC). In this study, we focused on Diaporthe species isolated from soybean plants with SSC lesions in different parts of Uruguay. Diaporthe diversity was determined by sequencing the internal transcribed spacer (ITS) regions of ribosomal RNA and a partial region of the translation elongation factor 1-alpha gene (TEF1α). Phylogenetic analysis showed that the isolates belong to five defined groups of Diaporthe species, Diaporthe caulivora and Diaporthe longicolla being the most predominant species present in stem canker lesions. Due to the importance of D. caulivora as the causal agent of SSC in the region and other parts of the world, we further characterized the interaction of this pathogen with soybean. Based on genetic diversity of D. caulivora isolates evaluated with inter-sequence single repetition (ISSR), three different isolates were selected for pathogenicity assays. Differences in virulence were observed among the selected D. caulivora isolates on susceptible soybean plants. Further inspection of the infection and colonization process showed that D. caulivora hyphae are associated with trichomes in petioles, leaves, and stems, acting probably as physical adhesion sites of the hyphae. D. caulivora colonized the stem rapidly reaching the phloem and the xylem at 72 h post-inoculation (hpi), and after 96 hpi, the stem was heavily colonized. Infected soybean plants induce reinforcement of the cell walls, evidenced by incorporation of phenolic compounds. In addition, several defense genes were induced in D. caulivora –inoculated stems, including those encoding a pathogenesis-related protein-1 (PR-1), a PR-10, a β-1,3-glucanase, two chitinases, two lipoxygenases, a basic peroxidase, a defensin, a phenylalanine-ammonia lyase, and a chalcone synthase. This study provides new insights into the interaction of soybean with D. caulivora , an important pathogen causing SSC, and provides information on the activation of plant defense responses. [ABSTRACT FROM AUTHOR]

Abstract: Inga vera, native to South America, is an important leguminous species used for ecological restoration of riparian forests and its seeds are among the most recalcitrant ones described up to date. In this work, we analysed the metabolic profile, cell ultrastructure as well as cell wall polysaccharides of I. vera seeds in order to better understand its maturation, which allows embryo germination without a quiescent phase. Increased amounts of citric, glutamic, pyroglutamic, and aspartic acids from stages I to II (120 and 129 days after flowering (DAF)) corroborate the hypothesis of high metabolism, shifting from fermentative to aerobic respiration at seed maturity. This phase was characterized by an extensive vacuolization of embryonic cells, which also indicate high metabolic activity. The proportion of arabinose in the cell walls of embryonic axis (approx. 20%) was lower than those found in some orthodox seeds (nearly 40%), suggesting that arabinose-containing polysaccharides, which are thought to provide more flexibility to the cell wall during natural drying, are less abundant in I. vera seeds. Taken together, our results provide evidence that the major changes occurred during early stages of seed maturation of I. vera, indicating that the rapid temporary metabolic shift observed between stages I and II may be related to the lack of desiccation phase, moving directly to germination. [Copyright &y& Elsevier]

Background Exebacase (CF-301) is a novel, recombinantly-produced, bacteriophage-derived lysin (cell wall hydrolase) which is the first lysin to report Phase 2 (Ph2) results which demonstrated 42.8% higher clinical responder rates with a single dose of exebacase used in addition to standard of care antibiotics (SOC) vs. SOC alone for the treatment of methicillin-resistant S. aureus (MRSA) bacteremia including endocarditis. We examined exebacase activity by broth microdilution (BMD) against baseline methicillin-sensitive S. aureus (MSSA) and MRSA isolates from each of the 116 participants in the recently complete exebacase"first in-patient' Ph2 study (NCT03163446). Methods Patients with complicated bacteremia or endocarditis caused by S. aureus were enrolled into Study CF-301-102 at study centers in the United States, EU, Latin America, Israel, and Russia from 2017 and 2018. Baseline isolates from blood cultures were collected prior to administration of exebacase. Exebacase MICs against 117 isolates of MSSA (n = 74) and MRSA (n = 43) were determined at a central laboratory using a modified BMD approved by the CLSI for exebacase AST. Results The exebacase MICs of baseline patient isolates from the Ph2 study ranged from 0.125 – 2 µg/mL and the MIC50/90 values for all MSSA and MRSA isolates were 0.5/1 µg/mL. Exebacase MICs reported in a recent surveillance study were similar, with MIC50/90 values of 0.5/1 µg/mL. Of the 6 total subjects with EXE MICs of 2, 3 were clinical responders, 2 were indeterminate (not available for assessment), and 1 was a clinical nonresponder at Day 14. Conclusion Exebacase was highly active against all baseline S. aureus isolates from blood cultures obtained from bacteremic patients enrolled in the Ph2 study. Based on data from previously presented exposure target attainment animal studies, PK/PD modeling and preliminary nonclinical breakpoint assessments, we expected that strains with MIC values of ≤2 µg/mL will have been susceptible to the Ph2 clinical exebacase dose determined based on target attainment studies under study in Ph2. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]

Background Vancomycin (VAN) is a first-line therapeutic option for severe MRSA infections, especially in Latin America where other options are limited. However, reduced susceptibility to VAN may lead to therapeutic failures. The molecular mechanisms leading the development of VAN-intermediate S. aureus (VISA) and heterogeneous-VISA (hVISA) phenotypes are still unclear. We explored genetic signatures associated with hVISA phenotype in MRSA isolates recovered from bacteremic patients in 9 Latin American countries (2011–2014) in order to develop a genomic platform to identify these isolates. Methods From 538 VAN-susceptible MRSA (MIC90 = 1 µg/mL) we identified 30 hVISA isolates using GRD and macromethod E -tests; from these, 3 were confirmed by PAP-AUC. Whole-genome sequencing was performed in all 30 isolates using Illumina platform. Based on previous studies, we selected 46 genes involved in hVISA development. Multiple Blast alignments were performed using genomes of ATCC29213 and N315 (VAN-susceptible), Mu3 (hVISA) and Mu50 (VISA) as references. Results A total of 130 changes in 46 predicted proteins belonging to 8 functional categories were determined: 48 changes related to cell wall biogenesis, 22 to DNA/RNA processing, 17 to regulatory systems, 12 to cofactors and enzymes, 11 to membrane biosynthesis, 9 to virulence, 6 to amino acid metabolism, and 5 to transport of nitrogen and putrescine/spermidine. The most common changes identified in all the hVISA were: Y38H in Atl, N16S in PBP4, S160A in RpoB, L14I in WalK and E156G in YvqF, compared with VSSA strains. The proteins with the highest number of changes detected in the isolates confirmed by PAP-AUC were: CapP, DltA, Pbp4, TcaA, LytM (Cell wall biogenesis); MutL, RpoB (DNA/RNA processing); GraS (Regulatory systems); and PgsA (Membrane biosynthesis). Conclusion Changes in genes associated with cell wall biogenesis, DNA/RNA processing, regulatory systems, and membrane biosynthesis were the most prevalent in Latin American hVISA strains. Genetic signatures in genes encoding GraR (N197S), RpoB (H481Y, H481N), VraS (I5N), WalK (L14F, R222K) and MrsR (E146K) are potentially associated with this phenotype. These changes could be used to develop a platform for possible identification of hVISA isolates. Disclosures All Authors: No reported Disclosures. [ABSTRACT FROM AUTHOR]