Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Little is known about the impact of nutrient conditions on antimicrobial resistance in biofilms
grown under continuous flow conditions. Furthermore, community-level response of biofilms
to antimicrobial substances and different nutrient regimes are poorly described. A better
understanding of the influence of environmental conditions on biofilm behavior and
antimicrobial susceptibility may contribute to the efforts, addressing the problems associated
with increased antimicrobial resistance. Therefore, the aim of this study was to evaluate the
survival and population dynamics in a defined mixed-species biofilm community grown under
different nutrient conditions and when subjected to biocide treatment.
Epi-fluorescence microscopy in conjunction with the LIVE/DEAD® BacLight™ viability kit,
a conventional cultivation technique (plate counts), and culture-independent techniques
(terminal restriction fragment length polymorphism and fluorescent in situ hybridization) were
applied to observe biofilm and planktonic antimicrobial susceptibility, as well as population
dynamics. A defined mixed-species community, consisting of four bacterial strains, was
cultivated and monitored in a flow cell system. Two nutrient types were used: 1) a complex
growth medium [tryptone soy broth (TSB)] and 2) a defined synthetic medium [minimal salts
supplemented with glucose (MSM + Glucose)]. In addition, these two nutrient types were
applied in different concentrations.
Biofilm and planktonic community behavior was influenced by the nutrient type and
concentration. Species evenness in the planktonic community was influenced by the nutrient
conditions, while species richness changed in response to biocide treatment and nutrient
conditions. TSB-grown microbial communities were more susceptible directly after biocide
treatment than those grown in MSM + Glucose, however, biofilm viability in the latter nutrient
condition decreased within 24 h after biocide treatment. Furthermore, a surprising difference
in the recovery rate between biofilm and associated planktonic communities was observed. A
conceptual model was developed that aimed to explain the observed biofilm-planktonic
interactions. This model proposes that the cells found in the outer regions of a biofilm are the
primary source of the associated planktonic cells, and that this phenomenon is independent
from overall biofilm activity. / AFRIKAANSE OPSOMMING: Daar IS tans mm bekend oor die invloed van nutriënte op die antirnikrobiese
weerstandbiedendheid van biofilms onder kontinue vloeitoestande. Verder is daar 'n groot leemte
in die literatuur oor die invloed van nutriënte op die antimikrobiese sensitiwiteit van bakteriese
gemeenskappe in multispesie-biofilms. 'n Beter begrip van die invloed van omgewingsfaktore op
biofilmgedrag en antimikrobiese sensitiwiteit sal bydra om die probleem van verhoogde
antimikrobiese weerstandbiedendheid te beheer. Die doel van hierdie studie was gevolglik om die
oorlewingsvermoë, asook die gemeenskapverskuiwings binne 'n bekende biofilmgemeenskap te
evalueer, nadat dit blootgestel was aan biosiedbehandeling en verskillende nutriëntkondisies.
Epifluoressensie-mikroskopie in kombinasie met 'n lewensvatbaarheidskleurstof (LIVEIDEAD®
BacLight™ viability kit), konventioneie kweektegnieke (spreiplaattegniek) en kweekonafhanklike
identifikasietegnieke (terminale restriksie fragment lengte polimorfisme en
fluoressensie in situ hibridisasie) is gebruik om biofilm- en planktoniese lewensvatbaarheid,
asook gemeenskapverskuiwings te bestudeer. 'n Gedefinieerde biofilmgemeenskap, bestaande uit
vier verskillende bakteriese rasse, is gekweek en gemonitor in 'n vloeiselsisteem. Twee tipes
nutriënte is gebruik: (1) 'n komplekse groeimedium [Tryptone Soy Broth (TSB)] en (2) 'n
chemies-gedefinieerde medium [minimale soutoplossing met glukose (MSM + Glucose)]. Beide
nutriënttipes is in verskillende konsentrasies toegedien.
Die gedrag van biofilm- sowel as planktoniese populasies is beïnvloed deur beide die nutriënttipe
en konsentrasie. Planktoniese populasiegetalle is beïnvloed deur nutriëntkondisies, terwyl die
aantal populasies beïnvloed is deur biosiedbehandeling en nutriënttoestande. Bakteriese
gemeenskappe wat in komplekse medium (TSB) gekweek is, was meer sensitief teenoor die
biosied direk na behandeling as die wat in MSM + Glukose gekweek is. Die lewensvatbaarheid
van die biofilm wat in MSM + Glukose gekweek is, het egter eers 24 uur na biosiedbehandeling
begin daal. Daar was verder 'n opvallende verskil in die tempo van herstel van die
biofilmgemeenskap in vergelyking met die planktoniese gemeenskap. Die planktoniese
gemeenskap het vinniger herstel as die biofilm gemeenskap. 'n Model is ontwikkel om die
biofilm-planktoniese interaksies te verklaar. In die model word voorgestel dat selle wat in die
buitenste lae van 'n biofilm groei, die primêre bron is van planktoniese selle in 'n vloeisisteem, en
dat hierdie verskynselonafhanklik is van die algehele biofilm-aktiwiteit.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/49847 |
| Date | 03 1900 |
| Creators | Garny, Kerstin |
| Contributors | Wolfaardt, G. M., Stellenbosch University. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 132 p. : ill. |
| Rights | Stellenbosch University |
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