Assessment of Bacterial Colonization of Intracranial Pressure Transducers: A Prospective Study

Abstract

Objectives: Cerebral infections related to the presence of an intraparenchymal intracranial pressure transducer (ICPT) are rare. We assessed the incidence of ICPT-related infections and colonization using culture, molecular biology, and electron microscopy.

Methods: All consecutive patients in a neurosurgical intensive care unit who had an ICPT inserted between March 2017 and February 2018 were prospectively included. Presence of colonization on the ICPTs was assessed after removal using culture, scanning electron microscopy (SEM), and next-generation sequencing (NGS).

Results: Fifty-three ICPTs (53 patients), indwelling for a median of 4 (range 3-7) days, were studied. Median patient follow-up was 3 months. SEM, microbial culture, and NGS were performed for 91%, 79%, and 72% of ICPTs, respectively; 28 ICPTs (53%) were assessed using all three techniques. No patient developed ICPT-related infection. Microbial cultures were positive for two of the ICPTs (5%); colonization was identified on all ICPTs using NGS and SEM. Mature biofilm was observed on 35/48 (73%) of ICPTs. A median of 10 (8-12) operational taxonomic units were identified for each ICPT, most being of environmental origin. There was no association between biofilm maturity and antimicrobial treatment or duration of ICPT insertion. Antimicrobial treatment was associated with decreased alpha and beta-diversity (p = 0.01).

Conclusions: We observed no ICPT-related cerebral infections although colonization was identified on all ICPTs using NGS and SEM. Mature biofilm was the main bacterial lifestyle on the ICPTs.

Keywords: Biofilm; Colonization; DNA sequencing; Device-related infection; Intracranial pressure monitoring.

Fig. 1

Intraparenchymal intracranial pressure transducer (ICPT) processing. After removal, the intracerebral portion of the ICPT was immediately cut into three sections of 0.5 cm (labeled 1–3). Section 1 was used for bacterial culture; section 2 was assessed by scanning electron microscopy; and section 3 was assessed using next-generation sequencing

Fig. 2

Categorization of the bacterial lifestyle observed on intraparenchymal intracranial pressure transducers (ICPTs) using scanning electron microscopy. a Control ICPT. b Isolated bacteria. c, d Adhesion bacteria with some extracellular matrix. e Mature biofilm: bacteria are encapsulated in a thick matrix. f Presence of isolated bacteria (on the left) and mature biofilm (on the right) on the same SEM picture

Fig. 3

Heatmap of genus/OTU and their relative abundance in clone libraries from each of 38 intraparenchymal intracranial pressure transducers (ICPTs). The genus subset was assessed according to Callahan et al. [33], and normalization was conducted by sample (grayscale: The OTU count was centered to the mean and the scale to unit variance). Numbers 1–38 represent the individual ICPTs

Fig. 4

Relative frequencies of each genus/OTU in the entire cohort of removed ICPTs. Genus/OTUs are ranked according to the abundance of their clone library relative to the number of total clones. Subsets were created according to Callahan et al. [33], and the category “Others” represents genus clusters with a relative abundance ≤ 1%