Survival of the Slimiest: The Persistent Nature of Biofilms

Sonali D. Advani, MD, MBBS, MPH


March 22, 2018

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The Role of Biofilm in Nosocomial Transmission

Biofilms are sessile microbial communities growing on surfaces, frequently embedded in a matrix of extracellular polymeric substances (also known as slime). Suboptimal environmental cleaning and reprocessing of instruments is a common problem in healthcare facilities, allowing for biofilm formation and risk for nosocomial transmission. Three recent articles[1,2,3] highlight how our understanding of bacterial persistence and recent advances in disinfection modalities may provide a means for control of biofilms and nosocomial infections.

No Wet Surface? No Problem

Bravo and colleagues[1] investigated the ability of Acinetobacter pittii strains to form biofilms after long-term desiccation if they were fed with nutrient media. Five strains of A pittii were inoculated on white laboratory coat fragments, glass, and plastic or into sterile saline and monitored at room temperature for a period of 43 days. Biofilm formation and bacterial viability during the survival analysis were assessed. The culturability of the A pittii strains decreased by 77.3%, 80.9%, 68.1%, and 14.5% for white coat, plastic, glass, and saline, respectively. However, 85.6% of these populations retained their culturability in saline solution. Despite the reduction in culturability over time, all strains that recovered from starvation on solid-surface experiments retained their capacity to form biofilms after rehydration, an addition of nutrients, and changing temperature. These findings are consistent with a tendency of other Acinetobacter species to survive on dry surfaces, form biofilms, and contribute to nosocomial outbreaks.

How Hidden Biofilms Escape Disinfection

Alfa and colleagues[2] looked at the impact of improper positioning of the elevator lever of a duodenoscope on bacterial persistence, biofilm formation, and endoscope contamination. Duodenoscope levers were inoculated with 108 CFU/mL Escherichia coli and Enterococcus faecalis and subsequently sampled after high-level disinfection (HLD). The automated endoscope reprocessor (AER) did not provide the expected 6 Log10 kill with the elevator lever in the incorrect position (not at 45º as instructed by the manufacturer), regardless of whether the AER had a cleaning cycle. These data highlight the persistence of bacteria despite HLD due to the narrow margin of safety with lever positioning in endoscope reprocessing.

'You Missed a Spot'

In the third study, Mustapha and colleagues[3] conducted a small-scale blinded experiment to study the impact of an additive on the efficacy and visibility of disinfectants during the cleaning process. The chemical additive used was Highlight solution (Kinnos Inc; Brooklyn, New York), which temporarily colorizes chlorine-based disinfectants and fades to undetectable within approximately 5 minutes when applied to surfaces. In this study, nine healthcare personnel were randomly assigned to assess surfaces 30 seconds and 3 minutes after bleach application with and without Highlight. For non-black surfaces, people were more likely to correctly identify suboptimal disinfectant application when Highlight was used. The data showed that addition of Highlight to chlorine-based disinfectants increased the ability of personnel to identify high-touch surfaces with suboptimal application of disinfectant.


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