Characterizing the biofilm of artificial urinary sphincters (AUS)

There is a paucity of data regarding the bacterial colonization on artificial urinary sphincter (AUS) devices following revision surgery. We aim to evaluate the microbial compositions of explanted AUS devices identified on standard culture at our institution.

Twenty-three AUS devices explanted were included in this study. During revision surgery, aerobic and anaerobic culture swabs are taken from the implant, capsule, fluid surrounding the device, and biofilm, if present. Culture specimens are sent to the hospital laboratory for routine culture evaluation immediately upon case completion. Differences in number of microorganism species detected across samples (richness) against demographic variables were determined through backwards selection of all variables using analysis of variance (ANOVA). We assessed the prevalence (how many times each species occurred) of microbial culture species. Statistical analyses were performed using the statistical package in R (version 4.2.1).

Cultures reported positive results in 20 (87%) cases. Coagulase-negative staphylococci were the most commonly identified bacteria among explanted AUS devices (n=16, 80%). Among two of the four infected/eroded implants, more virulent organisms such as Escherichia coli and fungal species such as Candida albicans were identified. The mean number of species identified amongst culture positive devices was 2.15±0.49. The number of unique bacteria identified per sample was not significantly associated with demographic variables including race, ethnicity, age at revision, smoking history, duration of implantation, etiology for explantation, and concomitant medical comorbidities.

The majority of AUS devices removed for non-infectious reasons harbor organisms on traditional culture at the time of explantation. The most commonly identified bacteria in this setting is coagulase-negative staphylococci, which may be a result of bacterial colonization introduced at the time of implant. Conversely, infected implants may harbor microorganisms with higher virulence including fungal elements. Bacterial colonization or biofilm formation on implants may not necessarily equate to clinically infected devices. Future studies with more sophisticated technology, such as next-generation sequencing or extended cultures, may evaluate microbial compositions of biofilm at a more granular level to understand its role in device infections.