Biology subjects

Mantovani, H. C.

Publications and source records attributed to Mantovani, H. C..

3 recordsLinked to original sources

bioRxiv2025

Characterization of the Gastrointestinal Tract Holstein x Angus Cross Cattle Microbiome During Harvest after Feed Withdrawal

Stress during the beef pre-harvest period can induce an inflammatory response and acidotic conditions in the gastrointestinal tract (GIT), which affects the gastrointestinal tract microbiome. The objective of this study was to characterize the status of the GIT microbiome at harvest in beef cattle entering a small USDA processing facility. Nine beef cattle were shipped from a producer in Columbia County, WI to the USDA processing facility at University of Wisconsin-Madison and were harvested across four dates. Digesta samples were collected from eight GIT locations: rumen solids, rumen liquids, abomasum, duodenum, jejunum, ileum, cecum, and large intestines. After DNA extraction with the DNeasy Blood & Tissue Kit, the V4 region of the 16S rRNA gene was amplified and sequenced on the Illumina MiSeq platform. Sequences were analyzed for alpha and beta diversity metrics (ANOVA and ADONOS), core microbiome, ANCOM, and co-occurrence network analyses. Harvest date and GIT location had a significant impact on microbial diversity and community composition (P<0.05), and there was an interaction between GIT location and harvest date (P<0.05). Taxonomic composition shifted throughout the GIT, though Prevotella and Treponema were core members in several different GIT locations. The co-occurrence analysis revealed microorganisms potentially associated with clinical infections, such as Moryella in the rumen and Acinetobacter in the hindgut, were considered keystone species. These results suggest that the pre-harvest period may negatively impact the beef cattle GIT microbiome. Modulating the GIT microbiome during the pre-harvest period may offer an opportunity to improve food safety.

molecular biology↗

bioRxiv2019

In silico identification of novel peptides with antibacterial activity against multidrug resistant Staphylococcus aureus

Herein we report the identification and characterisation of two linear antimicrobial peptides (AMPs), HG2 and HG4, with activity against a wide range of multidrug resistant (MDR) bacteria, especially methicillin resistant Staphylococcus aureus (MRSA) strains, a highly problematic group of Gram-positive bacteria in the hospital and community environment. To identify the novel AMPs presented here, we employed the classifier model design, a feature extraction method using molecular descriptors for amino acids for the analysis, visualization, and interpretation of AMP activities from a rumen metagenomic dataset. This allowed for the in silico discrimination of active and inactive peptides in order to define a small number of promising novel lead AMP test candidates for chemical synthesis and experimental evaluation. In vitro data suggest that the chosen AMPs are fast acting, show strong biofilm inhibition and dispersal activity and are efficacious in an in vivo model of MRSA USA300 infection, whilst showing little toxicity to human erythrocytes and human primary cell lines ex vivo. Observations from biophysical AMP-lipid-interactions and electron microscopy suggest that the newly identified peptides interact with the cell membrane and may be involved in the inhibition of other cellular processes. Amphiphilic conformations associated with membrane disruption are also observed in 3D molecular modelling of the peptides. HG2 and HG4 both preferentially bind to MRSA total lipids rather than with human cell lipids indicating that HG4 may form superior templates for safer therapeutic candidates for MDR bacterial infections.\n\nAuthor SummaryWe are losing our ability to treat multidrug resistant (MDR) bacteria, otherwise known as superbugs. This poses a serious global threat to human health as bacteria are increasingly acquiring resistance to antibiotics. There is therefore urgent need to intensify our efforts to develop new safer alternative drug candidates. We emphasise the usefulness of complementing wet-lab and in silico techniques for the rapid identification of new drug candidates from environmental samples, especially antimicrobial peptides (AMPs). HG2 and HG4, the AMPs identified in our study show promise as effective therapies for the treatment of methicillin resistant Staphylococcus aureus infections both in vitro and in vivo whilst having little cytotoxicity against human primary cells, a step forward in the fight against MDR infections.

microbiology↗

bioRxiv2018

Nisin penetrates Staphylococcus aureus biofilms but shows differences in killing effects against sessile and planktonic cells.

Biofilms may restrict antimicrobial penetration and contribute to the recalcitrance of bacterial infections. In this work, we investigated the penetration of nisin into S. aureus biofilms and compared the susceptibility of S. aureus planktonic and sessile cells to this lantibiotic. Biofilms were grown under continuous flow in CDC reactors and calcein fluorescence was used to monitor the effect of nisin on the cytoplasmic membrane of S. aureus cells. Confocal scanning laser microscopy (CLSM) showed that calcein was lost within approximately 20 min in CDC biofilms, demonstrating that nisin penetrated to the bottom of the biofilm and caused membrane permeabilization. Viability analysis using PI staining showed that nisin was bactericidal against S. aureus sessile cells. Time-kill assays were performed against S. aureus in the following conditions: homogenized exponential planktonic (HEP), homogenized stationary planktonic (HSP), homogenized CDC biofilm (HB) and intact CDC biofilm (IB). The mean viability reduction of HEP and HSP were 6.71 and 1.64 log CFU.ml-1, respectively, confirming that stationary S. aureus cells were much less susceptible than exponential cells. The HB and IB treatments showed mean viability reductions of 1.25 and 0.50 log CFU.ml-1, respectively. Nisin activity against S. aureus was not limited by its ability to penetrate the bacterial biofilm, but the killing efficacy of the antimicrobial peptide was reduced by the physiological status of the biofilm-grown cells.\n\nImportanceBiofilms represent a major problem to control microorganisms in industrial environments and medical devices. We developed a direct real-time microscopic visualization technique to demonstrate experimentally that the antimicrobial peptide nisin is able to penetrate S. aureus biofilms. Our results confirmed that nisin caused membrane permeabilization of sessile bacteria and revealed qualitative agreement between viability loss and membrane integrity loss. This approach could improve the evaluation of antibacterial susceptibility breakpoints when testing the efficacy of standard and novel antimicrobials.

microbiology↗