Macquarie University
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Dry surface biofilm a persistent source of pathogens in hospital: decontamination and infection control

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posted on 2022-03-28, 15:44 authored by Durdana Chowdhury
Environmental surface cleaning and disinfection is crucial for preventing HAI and maintaining patient safety. However, biofilms incorporating multiple bacterial species form on dry hospital surfaces. These biofilms are tolerant to biocides making their eradication difficult. Persistence of pathogens on surfaces increases the risk of transmission and development of HAI. Aims:1) To determine if bacteria can be transmitted from dry surface biofilm (DSB) to healthcare workers' hands and through cotton sheets. 2) To develop and test new removal chemistries against dry surface biofilm utilising laboratory models. 3) To develop a mixed species biofilm model analogous to the hospital surface DSB to determine its composition, the effect of multiple species on biofilm's susceptibility to detergents and disinfectants and analyse proteomics and transcriptomics technique. 4) To investigate protein regulatory changes in DSB compared with traditional hydrated biofilm and confirmation with RT PCR. This study revealed that: 1) DSB is highly transmissible. The total bacterial number transferred are sufficient to cause disease. 2) Soil inactivates the commonly used disinfectants. Peracetic acid reduces 64% of the biofilm mass and >6 Log10 viability in single species DSB, 48% of the biofilm mass in mixed DSB in the presence of soil. 3) This study developed a mixed species DSB model with reproducible cell number within and between repeated experiments. This mixed biofilm model was employed to assess the effectiveness of disinfectants. 4) These findings clearly imply that S. aureus biofilms represent a unique growth condition in terms of overall numbers of differentially expressed distinct proteins and genes. This study establishes the transmissibility of bacteria from DSB affirming it to be a potential source of HAI and determined that currently surface disinfectants and methods are insufficient to completely eradicate DSB. This study also established different changes in protein and genetic expression in biofilm, this might act as target group to invent new effective disinfectant for complete eradication of DSB.


Table of Contents

Introduction -- Chapter One. Review of literature -- Chapter Two. Material and methods -- Chapter Three. Biofilm : transmission and inactivation by heat -- Chapter Four. Developing novel chemistries for removing environmental surface biofilms to reduce hospital acquired infections -- Chapter Five. Development of multispecies dry surface biofilm model -- Chapter Six. Comparative proteomic profile : new insight of Staphylococcus aureus dry surface biofilm -- Chapter Seven. General discussion and conclusion -- References -- Appendix.


Bibliography: pages 286-315 Empirical thesis.

Awarding Institution

Macquarie University

Degree Type

Thesis PhD


PhD, Macquarie University, Faculty of Medicine and Health Sciences, Department of Biomedical Sciences

Department, Centre or School

Department of Biomedical Sciences

Year of Award


Principal Supervisor

Karen Vickery

Additional Supervisor 1

Anand Deva

Additional Supervisor 2

Honghua Hu


Copyright Durdana Chowdhury 2018. Copyright disclaimer:




1 online resource (xviii, 318 pages) illustrations (some colour)

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