<p>Antimicrobial peptides (AMPs) are part of the innate immune system that is widely distributed in nature, acting as a defense mechanism against invading microorganisms. AMPs have potent antimicrobial activity against a range of microorganisms including fungi, bacteria and viruses. In view of growing multidrug resistance, AMPs are increasingly being viewed as potential therapeutic agents with a novel mechanism of action. Mastoparan is a natural, highly positively charged AMP derived from the venom of wasps. It was originally of interest based on its inherent mast cell degranulation activity. Previously, mastoparan has been shown to exhibit antimicrobial activity in vitro however these studies have been limited in scope. Here we hypothesize that mastoparan possess the capacity to be a potent broad spectrum antibacterial agent including activity against multidrug resistant bacteria. </p><p>We examined the scope of antibacterial activity exhibited by mastoparan using a variety of antimicrobial susceptibility tests and have utilized a bacterial skin infection (S. aureus) model to determine the potential of mastoparan to serve as a therapeutic agent. We tested mastoparan against 4 Gram-positive clinical isolates (e.g., S. aureus, and E. faecium), 9 Gram-negative clinical isolates (e.g., E. coli, P. aeruginosa, and B. cepacia), and 4 multidrug resistant clinical isolates (e.g., MRSA, ESBL E.coli, and ESBL K. pneumonia). These studies reveal that mastoparan exhibits broad spectrum activity against both Gram-negative (MIC: 1.9 - 125 &mug/ml) and Gram-positive (MIC: 15.6 - 125 &mug/ml) bacteria and against multidrug resistant bacteria (MIC: 7.8 - 125 &mug/ml). We also demonstrated that mastoparan disrupts the bacterial membrane, exhibits fast acting antibacterial activity and is highly effective against both multiplying and non-multiplying bacteria. Furthermore, we have shown that mastoparan demonstrates efficacy as a topical antimicrobial agent reducing lesion size by up to 79% and the amount of bacteria recovered from skin lesions by up to a 98% reduction. Based on these results we conclude that mastoparan is a highly effective antibacterial agent and is therefore a potential alternative to currently antibiotics. Mastoparan offers a promising new therapeutic option for treating bacterial infections.</p> / Dissertation

Cyanobacterial secondary metabolites, often identified as toxins such as microcystin, have also demonstrated biological functions including inhibition of bacterial and viral growth. In this study, 10 cyanobacterial strains were isolated from field sites around Adelaide and laboratory cultures and assessed for bioactivity against bacterial, viral and fungal pathogens. A comprehensive literature search identified a number of screening assays employed by research groups to identify cyanobacterial strains with biological activity. Within the review, methods to optimise extraction of the compounds were also noted. Combinations of extraction methods, solvents and assay procedures were investigated to optimise the success of this phase of the study. Bioactivity was confirmed by development of agar disc diffusion and microtitre plate assays to analyse cyanobacterial biomass extracts. Result of the assays indicated a methanolic extract of one species, Microcystis flos-aquae (Wittr Elenkin), inhibited growth of bacterial cells and viral infectivity and was selected for further analysis. The bioactive compound was isolated by HPLC and mass spectrometric analysis. Separation of the bioactive extract into component peaks indicated only one that was likely to represent the metabolite of interest, at a retention time of approximately 18 min. A second profile was constructed of a methanolic extract of the same species in a later growth stage that did not inhibit growth of either the bacterial or viral test organisms. Comparison of the profiles exposed the absence of the peak at 18 min retention time in the second profile. Accumulation of the fraction was conducted using a semi-preparative HPLC column for analysis by mass spectrometry. A sample of the isolated peptide was submitted to Proteomics International, a subsidiary of Murdoch University, WA, for identification and structural characterisation. Proteomics International analysed the data by electronspray ionisation time of flight mass spectrometry (LC/MS/TOF) followed by LC. De novo sequence analysis of the data was carried out using Analyst QS software; however, PI was unable to provide a readily interpretable, continuous amino acid sequence, despite their admission that some gaps in the fragmentation ladder corresponded to known amino acids. Interpretation of the data generated by Proteomics International by a research chemist within the University of Adelaide proposed the following amino acid sequence and subsequent structure for the compound: [Figures omitted] Proposed (a) amino acid sequence and (b) structure for the bioactive compound isolated from non-toxic M. flos-aquae. Comparison of the proposed sequence with those contained in peptide databases was unable to classify the compound (B Neilan, personal communication, April 2008), suggesting the bioactive metabolite is perhaps previously undetected and therefore may be considered a novel compound, or has undergone a modification and is thus a variant of a known compound. Taxonomic classification of the strain used during this study was completed by PCR amplification of 16S ribosomal RNA, using primers from alternative cyanobacterial sources. The sequence was classified in the following taxonomic hierarchy (with 100% assignment detail, for a confidence threshold of 95%): Domain: Bacteria Phylum Cyanobacteria Class Cyanobacteria Family Family 1.1 Genus Microcystis This classification confirms that the species investigated during this research is of the genus Microcystis. Synthesis of cyanobacterial metabolites is generally accepted to be a result of nonribosomal synthetic pathways. The presence of non-ribosomal peptide synthetase and polyketide synthetase genes in Microcystis flos-aquae was confirmed by PCR amplification using degenerate primers from other cyanobacterial sources. Analysis of sequence data identified the presence of an NRPS gene demonstrating significant similarity (98%) to the NRPS cyanopeptolin gene of Microcystis sp. However, the PKS (polyketide) gene identified verified only a 63% similarity to a known sequence, that of the PKS (mcyG) gene of M. aeruginosa PCC 7806 (Koch). Results of the molecular investigation imply this compound may belong within the cyanopeptolin family. Researchers have speculated that the majority of cyanobacteria possess genes for production of toxins, though in many instances the gene cluster may be incomplete or one or more genes may be absent or mutated. The presence of microcystin genes was confirmed by PCR amplification using primers from previously characterised cyanobacterial genes. Analysis of the sequence data identified the presence of several mcy genes generally found in toxic strains of cyanobacteria noted for synthesis of the toxin microcystin. The DNA sequences show significant similarity to the mcyA, mcyC, mcyD and mcyE genes described for Microcystis sp. and Microcystis aeruginosa PCC 7806. However, analysis of the sequence data for the mcyB gene revealed that this gene was not present. Further PCR amplification of the region between mcyA and mcyC using the reverse complements of the original primers indicated that a sequence was present that may have been a truncated variant of mcyB or another gene entirely. Time constraints prohibited submission of this region for sequence analysis. The primary objective of this research project was to screen a field strain of cyanobacteria for synthesis of biologically active secondary metabolites, and to isolate those compounds using a combination of analytical chemistry and molecular biotechnology. This study forms part of a collaborative project between the University of Adelaide, South Australian Research and Development Institute (Aquatic Sciences) and the Environmental Biotechnology Cooperative Research Centre, entitled “P6: Commercial scale integrated biosystems for organic waste and wastewater treatment for the livestock and food processing industries”. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1352988 / Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering, 2009

Thesis (PhD.(Pharmacology)--Faculty of Health Sciences)-University of Pretoria, 2005. / Summary in English and Afrikaans. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1971. / Typescript. Vita. Description based on print version record. Includes bibliographical references.

Thesis (Ph.D.) - University of St Andrews, April 2008. / Restricted until 11th April 2010.

Thesis (M.S.) -- University of Tennessee, Knoxville, 2006. / Title from title page screen (viewed on May 31, 2006). Thesis advisor: John R. Buchanan. Vita. Includes bibliographical references.

Thesis (M.D.S.)--University of Hong Kong, 2005.

Dissertation submitted in partial compliance with the requirements for the Master's Degree in Technology: Homoeopathy, Durban Institute of Technology, 2002. / The aim of this in vitro microbial study was to evaluate the efficacy of Calendula officinalis tincture 60% (v/v) ethanol as an antibacterial on in vitro Pseudomonas aeruginosa. The standardised disc - diffusion method was employed. Seven pairs of Mueller - Hinton agar plates were used. / M

Nowdays, an emphasis is plased on an antibacterial properties of various products, including floor and coating materials. This work is about an testing of effectivity of the chosen antibacterial agents in the water born and solvent free floor systems which are epoxide or polyurethane based. As first step, the most suitable representative of each floor system was chosen, the silver based agents (respectively silver anion Ag+ based) which should have an antibacterial effect when incorporated into the floor system was chosen. The selected ones are Ag/SiO2, Ag/TiO2, Ag/Al2O3, Ag/ZnO, Ag/BaO, Ag/zeolite, AgI. The necessary was a creating of the test method which has to offer exact and reproducable outputs. At the begining, the method came out from the norms ČSN EN ISO 20645 Squared textiles – Determination of antibacterial activity – Test of diffusion throught the agar plate, ČSN 79 3880 Testing of antimicrobial properties of material and product of boot industry, Antifugal and antibacterial properties. Testing by this way did not bring repriducable outputs. Only the bacterial strains Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus was used according to the norms. The method of recultivation was used for testing. The process is: an application of the coating on the bottom of the Petri´s dish, curing, appplication of the bacterial solution, cultivation for 24 hours at 37 °C, inoculation onto the agar in the Petri´s dish, cultivation for 24 hours at 37 °C, interpretation of the grow/inhibition of the bacteries. The results offer the overview about the advantages and disadvantages of each antibacterial agent in the chosen systems.

Four strains of Listeria monocytogenes (LCDC 81-861, ATCC 19115, M1 and M2) examined in pure culture behaved similarly when exposed to a concentration of 0.5% CharSol C-10 liquid smoke by reducing Listeria numbers to an undetectable level within 4 hours post treatment. However, at the lower concentration of 0.25% liquid smoke, differences in resistance to the antimicrobial properties of smoke components become evident among these strains indicating that a level of 0.5% liquid smoke is more effective in controlling this organism. CharSol C-10 liquid smoke was used as a full strength dip treatment for beef franks surface inoculated with six strains of L. monocytogenes (LCDC 81-861, ATCC 19115, M1, M2, M5, and C6) then vacuum packaged and stored at 4 ± 1°C for 72 hours. Beef franks dipped in CharSol C-10 liquid smoke exhibited a significant (P < 0.001) reduction in L. monocytogenes numbers after 72 hours of storage at both inoculum levels of 1 x 10³ cells/ml and 1 x 10⁵ cells/ml.