Microbiology - Journal Articles

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    A bioengineered nisin derivative to control Streptococcus uberis biofilms
    (American Society for Microbiology, 2021-07-27T00:00:00Z) Pérez-Ibarreche, Mariana; Field, Des; Ross, R. Paul; Hill, Colin; Horizon 2020; Science Foundation Ireland
    Antimicrobial peptides are evolving as novel therapeutic options against the increasing problem of multidrug-resistant microorganisms, and nisin is one such avenue. However, some bacteria possess a specific nisin resistance system (NSR), which cleaves the peptide reducing its bactericidal efficacy. NSR-based resistance was identified in strains of Streptococcus uberis, a ubiquitous pathogen that causes mastitis in dairy cattle. Previous studies have demonstrated that a nisin A derivative termed nisin PV, featuring S29P and I30V, exhibits enhanced resistance to proteolytic cleavage by NSR. Our objective was to investigate the ability of this nisin derivative to eradicate and inhibit biofilms of S. uberis DPC 5344 and ATCC 700407 () using crystal violet (biomass), 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) (viability) assays, and confocal microscopy (viability and architecture). When preestablished biofilms were assessed, both peptides reduced biofilm biomass by over 60% compared to that of the untreated controls. However, a 42% higher reduction in viability was observed following treatment with nisin PV compared to that of nisin A. Accordingly, confocal microscopy analysis revealed significantly more dead cells on the biofilm upper surface and a reduced thickness following treatment with nisin PV. When biofilm inhibition was assessed, nisin PV inhibited biofilm formation and decreased viability up to 56% and 85% more than nisin A, respectively. Confocal microscopy analysis revealed a lack of biofilm for ATCC 700407 and only dead cells for DPC 5344. These results suggest that nisin PV is a promising alternative to effectively reduce the biofilm formation of strains carrying NSR. One of the four most prevalent species of bovine mastitis-causing pathogens is Its ability to form biofilms confers on the bacteria greater resistance to antibiotics, requiring higher doses to be more effective. In a bid to limit antibiotic resistance development, the need for alternative antimicrobials is paramount. Bacteriocins such as nisin represent one such alternative that could alleviate the impact of mastitis caused by However, many strains of have been shown to possess nisin resistance determinants, such as the nisin resistance protein (NSR). In this study, we demonstrate the ability of nisin and a nisin derivative termed PV that is insensitive to NSR to prevent and remove biofilms of NSR-producing strains. These findings will add new information to the antimicrobial bacteriocins and control of research fields specifically in relation to biofilms and mastitis-associated strains.
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    Characterization of an endolysin targeting Clostridioides difficile that affects spore outgrowth.
    (MDPI, 2021-05-26T00:00:00Z) Mondal, Shakhinur Islam; Akter, Arzuba; Draper, Lorraine A.; Ross, R. Paul; Hill, Colin; Horizon 2020
    Clostridioides difficile is a spore-forming enteric pathogen causing life-threatening diarrhoea and colitis. Microbial disruption caused by antibiotics has been linked with susceptibility to, and transmission and relapse of, C. difficile infection. Therefore, there is an urgent need for novel therapeutics that are effective in preventing C. difficile growth, spore germination, and outgrowth. In recent years bacteriophage-derived endolysins and their derivatives show promise as a novel class of antibacterial agents. In this study, we recombinantly expressed and characterized a cell wall hydrolase (CWH) lysin from C. difficile phage, phiMMP01. The full-length CWH displayed lytic activity against selected C. difficile strains. However, removing the N-terminal cell wall binding domain, creating CWH351—656, resulted in increased and/or an expanded lytic spectrum of activity. C. difficile specificity was retained versus commensal clostridia and other bacterial species. As expected, the putative cell wall binding domain, CWH1—350, was completely inactive. We also observe the effect of CWH351—656 on preventing C. difficile spore outgrowth. Our results suggest that CWH351—656 has therapeutic potential as an antimicrobial agent against C. difficile infection.
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    Bacteriophage endolysins as a potential weapon to combat Clostridioides difficile infection
    (Taylor & Francis Group, 2020-09-28) Mondal, Shakhinur Islam; Draper, Lorraine A.; Ross, R. Paul; Hill, Colin; Horizon 2020
    Clostridioides difficile is the leading cause of health-care-associated infection throughout the developed world and contributes significantly to patient morbidity and mortality. Typically, antibiotics are used for the primary treatment of C. difficile infections (CDIs), but they are not universally effective for all ribotypes and can result in antibiotic resistance and recurrent infection, while also disrupting the microbiota. Novel targeted therapeutics are urgently needed to combat CDI. Bacteriophage-derived endolysins are required to disrupt the bacterial cell wall of their target bacteria and are possible alternatives to antibiotics. These lytic proteins could potentially replace or augment antibiotics in CDI treatment. We discuss candidate therapeutic lysins derived from phages/prophages of C. difficile and their potential as antimicrobials against CDI. Additionally, we review the antibacterial potential of some recently identified homologues of C. difficile endolysins. Finally, the challenges of endolysins are considered with respect to the development of novel lysin-based therapies.
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    Comparison of the carotenoid profiles of commonly consumed smear-ripened cheeses
    (Elsevier B.V., 2020-09-29) Jonnala, Bhagya R. Yeluri; McSweeney, Paul L. H.; Cotter, Paul D.; Zhong, Siqiong; Sheehan, Jeremiah J.; Kopec, Rachel E.; Teagasc; National Institutes of Health; Ohio State University; Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute
    The objective of this study was to identify the carotenoids imparting the orange colour to the rind, and pale yellow color to the core, of selected smear-ripened cheeses. The cheeses investigated were Charloe, Ashbrook, Taleggio, and Limburger, and were sourced from artisanal markets. Samples of the rind and core were extracted using non-polar solvents, followed by saponification to hydrolyze triglycerides to remove fatty acids, and to release carotenoid esters. Extracts were tested using ultra-high pressure liquid chromatograph-diode array detector-high resolution mass spectrometry (UHPLC-DAD-MS and -MS/MS), and identities of α- and β-carotene, lycopene, and β-cryptoxanthin confirmed with authentic standards. β-Carotene was the predominant species in both the rind and core, absorbing ~80% of the signal at 450 nm in all cheese extracts tested, as well as minor quantities of β-cryptoxanthin and α-carotene. Carotenoids unique to the rind included lycopene as well as the rare bacterial carotenoids previously identified in bacterial isolates of cheeses (i.e. decaprenoxanthin, sarcinaxanthin, and echinenone). This is the first detailed characterisation of carotenoids extracted directly from smear-ripened cheeses, and reveals that smear-ripened cheese can contribute both provitamin A carotenoids as well as C50 carotenoids to the human diet.
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    The infant gut microbiome as a microbial organ influencing host well-being
    (Springer Nature, 2020-02) Turroni, Francesca; Milani, Christian; Duranti, Sabrina; Lugli, Gabriele A.; Bernasconi, Sergio; Margolles, Abelardo; Di Pierro, Francesco; van Sinderen, Douwe; Ventura, Marco; Horizon 2020 Framework Programme; Science Foundation Ireland; Fondazione Cariparma
    Initial establishment of the human gut microbiota is generally believed to occur immediately following birth, involving key gut commensals such as bifidobacteria that are acquired from the mother. The subsequent development of this early gut microbiota is driven and modulated by specific dietary compounds present in human milk that support selective colonization. This represents a very intriguing example of host-microbe co-evolution, where both partners are believed to benefit. In recent years, various publications have focused on dissecting microbial infant gut communities and their interaction with their human host, being a determining factor in host physiology and metabolic activities. Such studies have highlighted a reduction of microbial diversity and/or an aberrant microbiota composition, sometimes referred to as dysbiosis, which may manifest itself during the early stage of life, i.e., in infants, or later stages of life. There are growing experimental data that may explain how the early human gut microbiota affects risk factors related to adult health conditions. This concept has fueled the development of various nutritional strategies, many of which are based on probiotics and/or prebiotics, to shape the infant microbiota. In this review, we will present the current state of the art regarding the infant gut microbiota and the role of key commensal microorganisms like bifidobacteria in the establishment of the first microbial communities in the human gut.