Transmission of dry surface biofilm (DSB) by and through cotton bed sheets.

Dr Durdana Chowdhury1, Dr Shamaila  Tahir, Mr Mark  Legge, Dr. Honghua  Hu, Mr. Khalid  Aljohani, Dr Tania  Prvan, Dr Karen  Vickery

1Macquarie University, North Ryde, Australia


Patients shed pathogens into the environment and high touch items, including the bed, become heavily contaminated. As dry surface biofilms (DSB) are highly tolerant to cleaning/disinfectants, DSB on mattresses may be a source of pathogens, despite being covered with bedsheets. We aimed to determine if DSB could be transmitted through cotton sheets and if sheets could become vehicles of transmission.


Staphylococcus aureus DSB was grown in vitro on coupons. A piece of sheet was placed over a coupon, and the coupon lifted to a height of 30cm by griping with the forefinger and thumb (n=18/test parameter). For transmission through the sheet the forefinger and thumb were then touched horse blood agar plates (HBA). To determine transfer by the sheet, the sheet was then touched to HBA 20 sequential times. To stimulate cleaning, the DSB was treated with 5% neutral detergents for 5 seconds.


Less bacteria were transferred through thicker bedsheets with 250 thread/inch2 sheets transmitting ≤10 cfu while the 1/3rd of 150 thread/inch2 transmitted >100cfu. Wetting the biofilm increased transmission through the sheet.

 The cotton sheets were able to act as vehicles transferring between 100 and 1000 bacteria colonies for up to 20 touches. Surprisingly, thicker sheets transferred less bacteria than thin sheets with less than 100 colonies transferred/touch. Wetting the DSB increased the number of colonies transmitted to ≥1000 bacteria/touch.


As biofilm bacteria can be transferred through cotton sheets, this study highlights the importance of cleaning bed mattresses to prevent transmission of pathogens.


Durdana Chowdhury is a medical doctor graduated from Bachelor of Medicine and Bachelor of Surgery (MBBS) with honours in 2002 and worked as medical officer in Bangladesh for long five years. She did her specialisation on Medical Microbiology and Immunology in 2012 with a research work on methicillin resistant Staphylococcus aureus (MRSA). She is now pursuing her PhD focusing on hospital environmental dry surface biofilm, its transmission and eradication. She received Macquarie University research excellence (MQRES) scholarship in 2015. Durdana is currently working on developing novel chemistries for removing environmental surface biofilms to reduce hospital acquired infections.

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