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Title: Antibacterial activity of excretions/secretions from the medical maggot, Lucilia sericata
Author: Bexfield, A.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2006
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This thesis investigates the antibacterial mechanisms underlying the success of maggot therapy through the examination of excretions/secretions from L. sericata larvae for the presence of antibacterial compounds. Native excretions/secretions (nES) demonstrated potent antibacterial activity against both Gram-positive and Gram-negative bacteria, including MRSA. Native ES also induced bacterial filamentation, i.e. inhibition of cell division, in Gram-positive and Gram-negative bacilli. Investigation into the physiochemical properties of nES revealed heat-stable, protease-resistant antibacterial activity which was not dependent on alkaline conditions. Melanization-related reactive oxygen species and phenol were not determined to be contributing factors to the antibacterial activity. Native ES demonstrated lytic activity against Micrococcus lysodeikticus using the zone of clearance assay. Lysozyme, however, was not detected and lytic activity was attributed to the abundant proteases within ES. Fractionation of nES using ultrafiltration revealed the presence of two low molecular mass antibacterial factors. A 0.5-3 kDa fraction contained a heat-stable, protease-sensitive antibacterial factor, proposed to be an antibacterial peptide, with significant activity against S. aureus. This fraction, however, did not demonstrate activity against MRSA at the concentrations tested in this study. A <500 Da fraction exhibited heat-stable, protease-­resistant, antibacterial activity consistent with that of un-fractionated nES, including significant activity against MRSA. This fraction also induced filamentation in bacilli. HPLC/MS of the <500 Da fraction revealed the presence of a potential antibacterial compound, 3-guanidinopropionic acid (GPA), within HPLC fractions expressing antibacterial activity.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available