Bacterial biofilms in healthcare: transmission and control
thesisposted on 28.03.2022, 15:55 by Shamaila Tahir
It is estimated that more than 99% of bacteria form biofilm where they survive safely in the slime taking refuge from antimicrobials, host immune responses and environmental stress conditions. Scientific literature demonstrates that more than 85% of chronic infections are currently attributed to biofilm development in human tissues (chronic otitis media, non-healing skin ulcers, persistent perionditis, chronic osteoarthritis) on prosthetic medical devices (contact lenses, implants etc.) and on medical equipment (endoscopes, urinary catheters etc.) Transmission and control of bacterial biofilm to reduce these infections has been quite a challenge for clinicians and scientists worldwide, especially owing to the tough resistive life style of bacteria inside biofilms. This study investigated if bacteria residing in environmental biofilms are a potential source for healthcare associated infections by determining:1) The transferral rate of bacteria from dry-surface biofilms via gloved and un-glovedhands ; 2) Determining the killing efficacy of commonly used disinfectants and sterilisation protocols against dry-surface and traditional hydrated biofilms ; 3) Investigating the killing efficacy of combining a physical stress (topical negative pressure and positive pressure ≤10 atmospheres) with a chemical stress (disinfectants/antiseptics) on dry and hydrated biofilms. To study, in-vitro bacterial biofilm was cultured in PC2 laboratory on coupons using Communicable Disease Control and Prevention biofilm reactor and then tested for transmission and various treatments. We found that dry-surface biofilm bacteria are highly transmissible. Although gloved hands transferred up to six folds fewer bacteria than bare hands, total bacterial numbers transferred was more than the dose required to cause infection. Heat treatment as per the prevailing infection control guidelines, successfully eradicated bacteria in hydrated biofilm, but failed to eradicate dry-surface biofilm when autoclaved at 121°C for up to 30 minutes. Similarly, commonly used disinfectants failed to kill dry surfacebiofilm. However, enhanced killing of biofilm bacteria was achieved when compression pressure treatment was combined with biocides. The current thesis establishes high transmissibility of bacteria from dry surface biofilm affirming it to be a potential source of hospital acquired infections whilst demonstrating that current practised methods of decontamination/sterilization are insufficient to eradicate biofilms forming on dry surfaces. However, promising results were achieved after biofilm treatment with combined pressure and biocides therapy encouraging further evaluation of combination disinfection.