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<p>No Comment</p> / <p>The increase in antibiotic resistance has accelerated the search for novel antibacterial agents. As proteins with toxic properties appear to be less susceptible to common resistance mechanisms, they may serve as potential substitutes for current antibiotics. The present study focuses on a toxic peptide called tGcd derived from the <em>Escherichia coli</em> genome that can cause cell death when it is expressed. To better understand the mechanism of tGcd and to decipher the sequence determinants for its toxic phenotype, sequence analyses of this peptide were conducted. First, we conducted growth analysis for two full-length Gcd constructs to test whether the observed growth suppression was caused by the overexpression of tGcd in <em>E. coli</em> cells. We also generated a series of truncation mutants to determine the minimal sequence required for toxicity. Finally, to test whether tGcd’s toxicity was due to differences in expression levels, Western blot analysis was conducted. This study reveals that full length Gcd does not have an effect on bacterial growth when overexpressed. We also observed that some internal amino acids of tGcd can be truncated without the loss of the toxicity to the <em>E. coli</em> cells. Finally, Western blot analysis showed that the toxicity of this peptide is independent on its expression levels. These findings offer additional insights into properties common to membrane targeting antimicrobial peptides in Gram negative microbes, and contribute to the discovery of small bacterial peptides that may be useful for combating multidrug-resistant bacteria.</p> / Master of Science (MSc)

BACKGROUND: Antibiotics are essential medicines and their effectiveness is under threat due to antimicrobial resistance. Guidelines are one way to conserve antibiotic effectiveness given that they are intended to modify clinician prescribing. Guidelines that provide antibiotic recommendations should make explicit contextual considerations that influence antimicrobial resistance and their downstream effects on resistance emergence. METHODS: We conducted a systematic review of tuberculosis, gonorrhoea, and respiratory tract infection guidelines and recommendations to examine how and to what extent they are considering contextual factors that influence antimicrobial resistance. We also investigated whether there are guidelines and recommendations that can be adopted or adapted to local contexts. RESULTS: We found that within 74 included guidelines, two thirds of recommendations considered antimicrobial resistance. Of which only five guidelines considered all factors required to consider local aspects such as values, resource use, acceptability, feasibility, and equity. As such, these five guidelines can be either adopted or adapted to Canadian and other contexts. We also found that 39% of guidelines met credibility scores of 60% or greater in AGREE II domains: scope and purpose, rigor of development, and editorial independence. CLINCAL IMPLICATIONS: There are very few Infectious disease guidelines for highly prevalent diseases that do not consider all important contextual factors may influence antimicrobial resistance. Our findings can support societies and organizations, public health policy, and health care stakeholders to develop and implement guidelines that are applicable to local contexts efficiently and resourcefully. Our antimicrobial resistance recommendation framework, used in addition to GRADE Evidence to Decision frameworks, is a start to having this come to fruition. / Thesis / Master of Public Health (MPH)

Yes / Concrete structures in sewer systems, marine engineering, underground engineering and other humid environments are easily subjected to microbial attachment, colonization and, eventually, deterioration. With careful selection and treatment, some additives including inorganic and organic antimicrobial agents were found to be able to endow concrete with excellent antimicrobial performance. This paper reviews various types of antimicrobial concrete fabricated with different types of antimicrobial agents. The classification and methods of applying antimicrobial agents into concrete are briefly introduced. The antimicrobial and mechanical properties as well as mass/weight loss of concrete incorporating antimicrobial agents are summarised. Applications reported in this field are presented and future research opportunities and challenges of antimicrobial concrete are also discussed in this review. / National Science Foundation of China (51908103 and 51978127), China Postdoctoral Science Foundation (2019M651116)

Microbial infections are a global problem. Due to the over and misuse of antibiotics, drug-resistant pathogens are becoming more common. It is imperative to explore broad spectrum antimicrobial approaches. In this work, we modified collagen/hyaluronic acid polyelectrolyte multilayers (PEMs) with the natural antimicrobial peptide, LL-37 to study hepatic infections. LL-37 was physisorbed and covalently linked to the surface of the PEMs. Escherichia coli DH10B were cultured in the presence of LL-37modified PEMs in bacterial adhesion and contact killing models. Physisorbed LL-37 PEMs prevented bacterial adhesion and could also kill pathogens in the surrounding environment due to the release of LL-37 from the film. Immobilized LL-37 PEMs resulted in less bacterial adhesion on the surface due to the presence of the peptide. Films were then placed in contact with primary rat hepatocytes as well as in hepatocyte/bacteria co-cultures. LL-37 input concentrations up to of 16μM did not exhibit cytotoxic effects on hepatocytes. The LL-37 modified PEMs exhibited a hepatoprotective effect on albumin and urea secretion functions in co-cultures. The hepatoprotective effects were dependent on the ratio of hepatocytes and bacteria as well as the concentration of LL-37. These findings are encouraging and demonstrate that LL-37 modified PEMs can be used to investigate hepatic infections caused by bacteria. / Master of Science

Extracts from medicinal mushrooms were prepared and tested for anti-microbial activity against food pathogens and food spoilage microorganisms. The inhibitory activity was measured using a disk diffusion assay and with optical density (OD). For OD, 7 fractions were collected using HPLC for 4 (A. blazei Murrill, G. lucidum, G. frondosa, I. obiquus) medicinal mushrooms and 6 fractions from L. edodes and 8 fractions from P. linteus. The results from disk diffusion assay showed that most mushrooms displayed significant inhibition compared to the ethanol. The exceptions were: A. blazei Murrill, I. obliquus, and L. edodes against E. coli O157:H7; I. obliquus against L. monocytogenes V7; I. obliquus against S. cerevisiae Y99; L. edodes against Z. bailii Y03; and I. obliquus against Z. bailii/bisporus Y108. Inhibition was more effective in yeasts than bacteria. The result from Bioscreen C showed that against L. monocytogenes V7, fraction 7 in A. blazei Murrill; fraction 1, 4 and 5 in G. lucidum; fraction 4 in G. frondosa; and fraction 4 and 5 in I. obliquus significantly inhibited the growth compared to ethanol. Against Z. bailii Y03, fraction 7 in A. blazei Murrill; all fractions from G. lucidum, G. frondosa, and P. linteus; fraction 1, 2, 3, and 6 from I. obliquus; and fraction 4 and 6 from L. edodes significantly inhibited growth compare to ethanol. The results indicated that there is significant antimicrobial activity against food pathogens and spoilage organisms in the medicinal mushrooms studied. / Ph. D.

The purpose of this research is to support the California Department of Food & Agriculture (CDFA) with education and outreach about recent changes regarding antimicrobial use in livestock, and to enhance their emergency communications network. This was done by characterizing a population of small-scale livestock owners underserved with regards to educational outreach about animal health issues, such as antimicrobial use rules. The project also seeks to enhance public understanding of the importance of responsible antimicrobial use in animal and human health. To accomplish this, the study used a survey administered in person at local farm supply stores and online to investigate the level of understanding of antimicrobial rules among livestock owners in San Luis Obispo county. The survey gathered information about the livestock owners’ practices, connection to livestock groups, and access to information pertaining to animal health among other things. The results of the survey showed that respondents were largely unaware of new rules pertaining to use of antimicrobials in livestock. Familiarity with California rules of this kind was used as an indicator of access to information about animal health and was found to correlate positively with knowledge about antimicrobial resistance and familiarity with federal rules concerning antimicrobial use in livestock. As predicted, respondents with a connection to 4-H and FFA had greater familiarity with both federal and state rules concerning antimicrobial use in livestock.

Master of Science / Department of Diagnostic Medicine/Pathobiology / Sanjeev K. Narayanan / The use of antimicrobials in animal feed has come under increasing scrutiny from the public and regulatory agencies. Direct-fed microbials (DFM) are considered valuable alternatives to antimicrobials in food animal nutrition. DFM are products containing live (viable microorganisms). Studies in Europe have reported antimicrobial resistance (AMR) in organisms used in DFM. This is of serious concern because of the potential for transferring resistance to pathogenic bacteria in the gut. The aim of the present study is to characterize phenotypic and genotypic AMR profiles for 20 different antimicrobials in bacterial strains isolated from 10 commercially available DFM used in. Two antimicrobial susceptibility testing methods, disc diffusion and broth micro-dilution based assay were performed. Enterococcus faecium isolates showed resistance towards metronidazole (n=9/9) with a MIC of > 32 µg/mL, erythromycin (n=5/9) with a MIC of ≥ 8 µg/mL, ciprofloxacin (n=2/9) with a MIC ≥ 4 μg/mL, ceftriaxone (n=6/9) with a MIC ≥ 0.25 μg/mL, rifampin (n=8/9) with a MIC of > 4 µg/mL, trimethoprim/sulfamethoxazole (n=4/9) with a MIC ≥ 1 μg/mL and clindamycin (n=5/9) with a MIC of > 0.5 µg/mL. A Propionibacterium freudenreichii isolate showed resistance towards kanamycin with a MIC of > 64 µg/mL. The same strain also had a MIC of 16 µg/mL for levofloxacin. Two Lactobacillus acidophilus were resistant to vancomycin (n=2/6) with a MIC ≥ 32 μg/mL. All the Lactobacillus species including L. acidophilus (n=6), L. casei (n=4) and L. plantarum (n=2) were resistant to metronidazole, MIC > 32 µg/mL. Two strains of Bacillus subtilis showed resistance to clindamycin, with an MIC of 4 µg/mL and erythromycin with an MIC of > 8 µg/mL, and one strain had no zone of inhibition for metronidazole (MIC > 32 µg/mL). Microarray analysis revealed resistance genes in E. faecium strains of 3 different DFM, including aminoglycoside resistance genes, ant(4’)-Ia, erythromycin resistance genes, ere(A2) and ermB, tetracycline resistance genes, tet39, tet31, tetK and tetC, and beta-lactam resistance gene, pbp5. Conjugation with filter mating showed erythromycin resistance gene transfer, msrC gene, from donor strains to a recipient strain (E. faecium 45-24). These studies show that AMR is prevalent among bacterial strains used as DFM in the cattle industry in the U.S., justifying further characterization, detection and observation of transferable antibiotic resistance between the same genus.