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Title: Activity of ortho-phthalaldehyde against biofilm bacteria using an in-vitro model system
Author: Shackelford, Jennifer Claire Neame
ISNI:       0000 0001 3395 0430
Awarding Body: University of Brighton
Current Institution: University of Brighton
Date of Award: 2007
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Biofilm associated infections relating to endoscopic procedures may result in asymptomatic colonisation to potentially death. An appropriate high-level disinfectant and adequate pre-cleaning steps are therefore required to prevent the risk of hospital acquired infections relating to endoscopes. OrtllO-phthalaldehyde (OPA) is an alternative high-level disinfectant to glutaraldehyde (GTA) used for the disinfection of endoscopes. The aims of this thesis were to: i) investigate the efficacy of OPA against planktonic, surface dried bacteria and bacterial biofilm ii) to develop and test a novel in-vitro sodium alginate biofilm method for the testing of OPA iii) to develop a predictive mathematical model for measuring the effect ofOPA against bacterial biofilm and iv) to investigate the effect of ill-situ re-processing steps used to re-process endoscopes colonised with bacterial biofilm. The efficacy of OPA was tested against Pseudomonas aeruginosa, Mycobacterium che/ollae and a GTA-resistant mycobacterial strain (Mycobacterium elle/ollae Epping), using a quantitative suspension test, quantitative carrier test and using bacteria grown as sedimentation biofilms. OPA (0.5 % w/v) was shown to be an effective high-level disinfectant against M.elle/ollae, M.c1le/onae (Epping) and P.aeruginosa in suspension and carrier tests. The efficacy of OPA against the three bacterial strains grown as sedimentation biofilms was however reduced, in comparison to the planktonic and surface dried cells. Bacteria grown using the novel in-vitro alginate biofilm system showed an increased resistance to OPA in comparison to the sedimentation biofilms. The novel biofilm protocol was demonstrated to be highly reproducible, simple and robust, in comparison to the sedimentation biofilm methodology. A comparison between the biofilm and planktonic outer membrane protein (OMP) profiles of P.aerugillosa cells was undertaken using I-Dimensional and 2-Dimensional SDS-PAGE. However it was not clear if the novel sodium alginate biofilms exhibited a biofilm OMP profile, although bacterial resistance to disinfection indicated a biofilm phenotype. A mathematical model was produced using extensive efficacy testing data. The predictive model was shown to be very accurate in predicting the efficacy of variable concentrations of OPA, in the presence of variable concentrations of organic load, against mycobacterial biofilm. Finally, P.aeruginosa, M.elle/onae and M.elle/ollae Epping biofilms were treated with OPA and subsequently re-incubated. Re-growth was observed for all bacterial strains. The pre-cleaning steps used in endosopce reprocessing were shown to reduce surface attached biofilm by an average of 2-3 log reductions. In addition, the adherence of bacteria to surfaces after endoscope reprocessing steps and the surface quality of polypropylene discs was investigated using scanning electron microscopy. Bacteria were observed on all surfaces even after complete reprocessing steps had been undertaken. This study further highlighted the necessity for testing the efficacy of biocides against bacterial biofilms and the value of using an organic load. The production of biofilms using the novel sodium alginate methodology in conjunction with the predictive mathematical model produced in this thesis, was shown to have the potential to represent a faster, less labour intensive method to study the efficacy of biocides, in comparison to the standard methods used currently. The importance of adequate reprocessing steps for endoscopes using appropriate biocides has also been further highlighted.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: B000 Health Professions ; B500 Public Health ; C500 Microbiology