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. 2022 Jun 3;11(1):81.
doi: 10.1186/s13756-022-01112-z.

Tolerance of biofilm of a carbapenem-resistant Klebsiella pneumoniae involved in a duodenoscopy-associated outbreak to the disinfectant used in reprocessing

Melanie S Brunke #  1 , Katharina Konrat #  2 , Christoph Schaudinn  3 , Brar Piening  4 , Yvonne Pfeifer  5 , Laura Becker  5   6 , Ingeborg Schwebke  2 , Mardjan Arvand  2   7
Affiliations

Tolerance of biofilm of a carbapenem-resistant Klebsiella pneumoniae involved in a duodenoscopy-associated outbreak to the disinfectant used in reprocessing

Melanie S Brunke et al. Antimicrob Resist Infect Control. .

Abstract

Background: One possible transmission route for nosocomial pathogens is contaminated medical devices. Formation of biofilms can exacerbate the problem. We report on a carbapenemase-producing Klebsiella pneumoniae that had caused an outbreak linked to contaminated duodenoscopes. To determine whether increased tolerance to disinfectants may have contributed to the outbreak, we investigated the susceptibility of the outbreak strain to disinfectants commonly used for duodenoscope reprocessing. Disinfection efficacy was tested on planktonic bacteria and on biofilm.

Methods: Disinfectant efficacy testing was performed for planktonic bacteria according to EN standards 13727 and 14561 and for biofilm using the Bead Assay for Biofilms. Disinfection was defined as ≥ 5log10 reduction in recoverable colony forming units (CFU).

Results: The outbreak strain was an OXA-48 carbapenemase-producing K. pneumoniae of sequence type 101. We found a slightly increased tolerance of the outbreak strain in planktonic form to peracetic acid (PAA), but not to other disinfectants tested. Since PAA was the disinfectant used for duodenoscope reprocessing, we investigated the effect of PAA on biofilm of the outbreak strain. Remarkably, disinfection of biofilm of the outbreak strain could not be achieved by the standard PAA concentration used for duodenoscope reprocessing at the time of outbreak. An increased tolerance to PAA was not observed in a K. pneumoniae type strain tested in parallel.

Conclusions: Biofilm of the K. pneumoniae outbreak strain was tolerant to standard disinfection during duodenoscope reprocessing. This study establishes for the first time a direct link between biofilm formation, increased tolerance to disinfectants, reprocessing failure of duodenoscopes and nosocomial transmission of carbapenem-resistant K. pneumoniae.

Keywords: Antimicrobial resistance; Carbapenemase; Disinfection; Duodenoscope; Gram-negative; OXA-48; Outbreak; Peracetic acid; Reprocessing.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Efficacy of peracetic acid (PAA) using three different disinfectant testing methods. Bars show mean recovered CFUs after 10 min exposure to different concentrations of PAA of the K. pneumoniae outbreak strain and the type strain that were tested as: (a) planktonic cells (suspension test, EN 13727) (b) surface-fixed planktonic cells (carrier test, EN 14561) and (c) biofilm (Bead Assay for Biofilms). Disinfection was defined as ≥ 5log10 reduction in mean recoverable CFUs and is marked by a dashed red line in the respective assays. At comparable PAA concentrations, the outbreak strain shows a higher number of recovered CFUs than the type strain in all three models. Experiments were performed in triplicates
Fig. 2
Fig. 2
Effect of PAA on K. pneumoniae strains as surface-fixed cells (a) and biofilm (b). Scatter Plot with each dot representing recovered CFUs for a replicate after 10 min exposure to PAA. Disinfection was defined as ≥ 5log10 reduction in mean recoverable CFUs (dashed red line). The horizontal lines show the mean value for the respective replicates. In the biofilm model, 0.15% PAA, the concentration used in duodenoscope reprocessing, was not sufficient to achieve disinfection of the outbreak strain
See this image and copyright information in PMC

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