From one biofilm to another: when bacteria from dry-surface biofilms settle in invasive medical devices

Following the recent observation of bacterial deposits on dry surfaces referred to as dry-surface biofilms (DSBs), a number of studies were conducted in vitro on bacterial culturability, sensitivity to cleaning and disinfection protocols, and bacterial transfer via gloves or wipes to culture media or inert surfaces. Our study aimed to reproduce in vitro the cross-transmission of bacteria from dry surfaces to invasive medical devices via healthcare professional's gloves.

Monobacterial DSBs were produced using an automated model with five different bacterial isolates involved in healthcare-associated infections. Bacteria from dried or rehydrated DSBs were first transferred to sterile gloves, then to central venous catheters, urinary catheters or endotracheal tubes. The presence of culturable bacteria and the formation of traditional hydrated biofilms inside the devices were investigated.

Methicillin-resistant Staphylococcus aureus was the only species to be transferred from both dry and rehydrated DSBs to each invasive device, while the other isolates were only transferred from rehydrated DSBs on mainly central catheters and endotracheal tubes. Despite the non-culturability of Pseudomonas aeruginosa in all the DSBs produced, rehydration enabled its transfer to endotracheal tubes and urinary catheters, suggesting residual viability as evidenced by Live/Dead staining.

A possible link appears to be emerging between DSB rehydration, bacterial culturability and transferability. Rehydration may promote bacterial adhesion to gloved fingers and/or the 'resuscitation' of non-culturable bacteria. This viable but non-culturable state of bacteria in DSBs needs to be studied in depth and considered in infection prevention strategies.