Microbiology and biofilm of corneal sutures.

AIM: To investigate the relationships between corneal suture bacteriology, biofilm and the clinical setting using culture studies and scanning electron microscopy (SEM).

METHODS: This is a prospective, observational study of patients with a history of penetrating keratoplasty presenting to a tertiary cornea clinic for routine or symptoms-related corneal suture removal. We documented for each patient the suture clinical setting (quiescent, exposed and keratitis-related), retention time, antimicrobial therapy, bacterial growth on culture studies, and bacterial presence and biofilm coverage on SEM.

RESULTS: There were significantly different culture positivity rates between the quiescent (8%), exposed (12%) and keratitis-related (60%) suture groups (p=0.039). As expected, keratitis-related sutures had the longest retention time compared with quiescent and exposed ones (p=0.02). The biofilm coverage score was higher for sutures from the keratitis-related and exposed groups, although this trend was not statistically significant (p=0.90). Higher biofilm scores were seen in samples that also yielded a positive culture result (p=0.36) and in samples with bacterial presence on SEM images (p=0.16 and p=0.73). Both of these were important trends but not statistically significant.

CONCLUSIONS: Evidence for active bacterial and biofilm presence on corneal sutures was found. Corneal sutures should be considered for removal sooner, before becoming exposed and/or keratitis-related. Traditional culture studies and SEM imaging are helpful in investigating biofilm and its clinical importance. More studies of the spectrum of bacterial growth on embedded biomedical devices such as corneal sutures are needed.