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Pseudomonas aeruginosa Bacterial Biofilms

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dc.contributor.advisor Weese, J. Scott
dc.contributor.author Pye, Charlotte
dc.date.accessioned 2013-09-05T17:00:24Z
dc.date.available 2013-09-05T17:00:24Z
dc.date.copyright 2013-08
dc.date.created 2013-08-23
dc.date.issued 2013-09-05
dc.identifier.uri http://hdl.handle.net/10214/7459
dc.description.abstract This thesis is an investigation of Pseudomonas aeruginosa bacterial biofilms. The objective of the first study was to evaluate the biofilm-forming capacity of canine otitis isolates of P. aeruginosa and to compare the minimum inhibitory concentrations (MICs) of antimicrobials for planktonic versus biofilm-embedded bacteria. Biofilm forming ability was assessed using a microtitre plate assay. Broth microdilution was used to assess the MICs of neomycin, polymyxin B, enrofloxacin and gentamicin for the planktonic and biofilm-embedded bacteria of eighty-three isolates. Thirty-three (40%) isolates were biofilm producers and MICs for biofilm-embedded bacteria were significantly higher than their planktonic counterparts for all antimicrobials (all P<0.05). The objective of the second study was to evaluate the impact of Tromethamine edetate disodium dihydrate (Triz-EDTA®) in combination with antimicrobials on antimicrobial susceptibility of P. aeruginosa biofilm-embedded bacteria. MICs of the four antimicrobials for the biofilm embedded bacteria and biofilm-embedded bacteria with added Triz-EDTA® were assessed with broth microdilution for thirty-one biofilm-producing isolates. Addition of Triz-EDTA® significantly reduced MICs for neomycin (P < 0.008) and gentamicin (P < 0.04) but not enrofloxacin (P = 0.7), or polymyxin B (P = 0.5). The objective of the third study was to determine the presence of biofilm-associated genes in biofilm forming and non-biofilm forming isolates. Four genes involved with carbohydrate matrix production (pelA), irreversible attachment (sadB) and quorum sensing (lasB, rhlA) were selected. DNA was extracted and polymerase chain reaction (PCR) was performed for all isolates. All isolates possessed lasB and sadB, 74 (90%) possessed pelA and 74 (90%) possessed rhlA. All thirty-two (100%) isolates that were classified as biofilm producers contained all genes. There was an association between the presence of pelA and rhlA and biofilm production (P < 0.017) and between the presence of rhlA and pelA and the quantity of biofilm produced (both P < 0.001). These results highlight that biofilm formation of Pseudomonas aeruginosa otic isolates does occur and can impact antimicrobial therapy. Certain compounds can also influence antimicrobial susceptibility of biofilm-embedded bacteria. Genetics may also play a role in biofilm formation. en_US
dc.language.iso en en_US
dc.subject Pseudomonas aeruginosa en_US
dc.subject bacteria en_US
dc.subject biofilms en_US
dc.subject canine en_US
dc.subject otitis en_US
dc.title Pseudomonas aeruginosa Bacterial Biofilms en_US
dc.type Thesis en_US
dc.degree.programme Veterinary Science en_US
dc.degree.name Doctor of Veterinary Science en_US
dc.degree.department Department of Clinical Studies en_US
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