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Title: The resistance of Pseudomonas aeruginosa to preservatives used in industrial formulations
Author: Weiser, Rebecca
ISNI:       0000 0004 5371 0110
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2015
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P. aeruginosa is a versatile microorganism with high levels of antimicrobial resistance and a common contaminant of home and personal care (HPC) products. Relatively little is known about P. aeruginosa in industrial settings and to further investigate this, four areas were considered: (i) culture-dependent and –independent detection of P. aeruginosa; (ii) P. aeruginosa and bacterial diversity in HPC products; (iii) preservative susceptibility and phenotypic characterisation of industrial P. aeruginosa strains, and; (iv) P. aeruginosa adaptation to a preservative combination. A large collection of P. aeruginosa and non-P. aeruginosa industrial isolates was utilised to evaluate five selective agars for the detection of P. aeruginosa. Media using negative selection performed best overall, but media using positive selection had potential as enrichment media. Culture-independent detection of P. aeruginosa and overall bacterial diversity was achieved via direct DNA extraction from contaminated HPC products, species specific PCRs and 16S rRNA gene sequencing analysis. The bacterial diversity in HPC products was low, with less than three contaminating genera in each product. The diversity of P. aeruginosa strains from industrial, clinical and environmental sources was investigated using five genotyping techniques, ranging from PCR-fingerprinting methods to whole genome sequencing, and phenotypic assays examining preservative susceptibility, growth dynamics and motility. P. aeruginosa strain diversity was high and there was no association between genotype, phenotype and isolation source. The development of adaptive resistance of P. aeruginosa to a preservative combination used in HPC products was modelled using planktonic growth and biofilm assays. P. aeruginosa PA14 grew in elevated levels of the preservatives chloromethylisothiazolinone, methylisothiazolinone and dimethylol dimethyl hydantoin but it was unknown whether the increased tolerance was stable. Whilst eradication of P. aeruginosa from the industrial environment is unlikely, improved detection methods and understanding of the species will inform industrial practices and preservative formulations to minimise HPC product contamination.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QH301 Biology