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Microbiological and scanning electron microscopic evaluation of epidural catheters
  1. Ganapathy van Samkar1,
  2. Payal P S Balraadjsing2,
  3. Henning Hermanns1,
  4. Irene V Hoogendijk2,
  5. Markus W Hollmann1,
  6. Sebastian A J Zaat2 and
  7. Markus F Stevens1
  1. 1Department of Anesthesiology, AMC, Amsterdam, The Netherlands
  2. 2Department of Medical Microbiology, AMC, Amsterdam, The Netherlands
  1. Correspondence to Dr Henning Hermanns, Department of Anesthesiology, AMC, 1105 AZ Amsterdam, The Netherlands; h.hermanns{at}


Background Epidural catheters are frequently colonized by gram-positive bacteria. Although the incidence of associated epidural infections is low, their consequences can be devastating. We investigated bacterial growth on epidural catheters by quantitative bacterial culture and scanning electron microscopy (SEM) in order to explore the patterns of epidural catheter colonization.

Methods 28 patients undergoing major abdominal surgery with thoracic epidurals (treatment ≥72 hours) were studied. Before the removal of the catheter, the skin surrounding the insertion site was swabbed. The entire catheter was divided into extracorporeal, subcutaneous, and tip segments. Skin swabs and catheter segments were quantitatively cultured, bacterial species were identified, and SEM was performed on four selected catheters.

Results 27 of 28 catheters were included. The percentages of positive cultures were: skin swab 29.6%, extracorporeal segments 11.1%, subcutaneous segments 14.8%, and tip segments 33.3%. One patient was diagnosed with a catheter-associated infection. Staphylococcus epidermidis was cultured from the skin and the catheter extracorporeal, subcutaneous, and tip segments. SEM of this catheter showed bacteria-like and intraluminal host cell-like structures. SEM of two other catheters showed intraluminal fibrin networks in their tip segments.

Conclusions We present the first SEM pictures of an epidural catheter with a bacterial infection. Bacterial growth developed from the skin to the tip of this catheter, indicating the skin as a primary source of infection. By SEM, catheters with low levels of bacterial growth demonstrated an intraluminal fibrous network which possibly plays a role in catheter obstruction.

  • neuraxial blocks: epidural
  • regional anesthesia
  • neuraxial blocks: continuous techniques

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  • GvS and PPSB are joint first authors.

  • SAJZ and MFS are joint last authors.

  • Contributors HH, MWH, SAJZ, MFS: design of the study. PPSB, HH, IVH, MFS: acquisition of data. GvS, PPSB, HH, IVH, SAJZ, MFS: analysis and interpretation of data. GvS, PPSB, HH, MWH, SAJZ, MFS: drafting and critical revising of the manuscript. All authors gave final approval of the submitted version and agreed to be accountable for all aspects of the work.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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