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Title: Molecular basis of biocide resistance and susceptibility in bacteria
Author: Yezli, Saber
ISNI:       0000 0004 2750 6482
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2007
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The molecular basis of biocide resistance and susceptibility in Serratia and mycobacteria was investigated using transposon mutagenesis approach. The killing and growth inhibitory effects of four biocides (triclosan, cetylpyridinium chloride, chlorhexidine diacetate and alkaline orf/io-phthalaldehyde) on Serratia marcescens Dbll, Mycobacterium smegmatis mc2155, M. chelonae type strain NCTC 946, M. abscessus type strain ATCC 19977, and Escherichia coli NCTC 1048 were studied using minimal inhibitory concentration determination, biocide killing, and potassium leakage tests. Transposon mutagenesis using a mariner system did not produce any M. smegmatis mc2155 mutants with altered biocide sensitivity. In contrast mutagenesis of S. marcescens Dbll using the mini-Tn5Km2 transposon system led to the isolation of 26 biocide mutants. Increased resistance, susceptibility and mixed biocide phenotypes were observed in the mutants. Alteration in antibiotic susceptibility was also noted. The locations of transposon insertion in all but two of the mutants were determined, and 14 putative genes coding for putative proteins with diverse functions were found to be disrupted. These functions included anabolism and catabolism, gene regulation, cell envelope biosynthesis, porin, energy production, and virulence. Two mutants, one deficient in the outer membrane protein A (OmpA), and another deficient in the nucleoid-associated protein (NdpA), were complemented. Complementation of the ndpA mutant which showed increased resistance to cetylpyridinium chloride and chlorhexidine diacetate, but was sensitive to triclosan, lead to restoration of the wild type phenotype. Complementation of the ompA mutant, which showed multiple sensitivity to chlorhexidine diacetate, triclosan, and or/Zio-phthalaldehyde however, did not restore the wild type phenotype. The cloned ompA gene was shown to be transcribed but not translated in the complemented mutant. In summary, the genetic basis for biocide resistance in S. marcescens Dbll is multi-factorial and encoded by several novel loci worthy of further study.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available