Characterisation of the microbiome of tracheostomy tube biofilms

Infection, including ventilator-associated pneumonia are a major risk for patients with tracheostomies since the tracheostomy tubes are prone to microbial colonisation through the formation of polymicrobial biofilms that adhere to the tube surface. The microbiota of tracheostomy tube biofilms within the United Kingdom (UK) has not previously been described and the interaction of the full spectrum of bacterial and fungal species within tracheostomy tube biofilms, particularly the role of less pathogenic commensal species including Corynebacterium, is incompletely understood; although Candida species, namely Candida albicans are known to play a role.

Culture-dependent and culture-independent microorganism identification methodologies, microscopy, in vitro biofilm modelling, and infection modelling in Galleria mellonella were utilised to describe the tracheostomy tube microbiota in the UK and to characterise the distinct relationship between two biofilm-residing organisms for the first time.

As expected, common biofilm-forming pathogens including Pseudomonas aeruginosa, Staphylococcus aureus, and Enterobacterales species were frequently identified by both culture-dependent and -independent methods. Corynebacterium and Candida species were also frequently identified by both methodologies. This finding formed the foundation for further experiments to characterise the relationship between these genera, which yielded an antagonistic growth relationship in vitro between C. albicans and Corynebacterium striatum.

Together, these data support the established role of C. albicans and also propose a role for C .striatum as a keystone species in biofilm formation, virulence and likelihood for developing infection that was not previously identified. These findings shine further light on the role of commensals within biofilms and suggest a use for localised, prophylactic, topical antifungals to reduce the risk of biofilm-associated infections in patients with tracheostomy tubes. Further work is required to fully characterise the complex polymicrobial, inter-Domain relationships in tracheostomy tube biofilms, which will assist in developing further targeted prevention strategies to reduce the likelihood of tracheostomy-associated infection.