Abstract
Purpose:
To investigate the pathogens and biofilms responsible for clinically significant infection of silicone stents implanted within the lacrimal system.
Methods:
Retrospective review of culture results for silicone lacrimal stents removed early for clinically significant infection over a thirty year period. As a control, routinely removed, clinically non-infected stents were prospectively sent for culture over a six month period. Four clinically infected stents and six clinically non-infected stents showing mucus within the lumen at removal were sent for scanning electron microscopy to grade the presence of organisms, matrix deposits, organisms within a matrix, and a significant biofilm by a masked electron micrographer.
Results:
Nineteen stents were included in the study; 100% of clinically non-infected stents (n=9) and of those removed for infection (n=10) were culture positive. None of the non-infected stents were culture positive for mycobacteria compared with 90% of infected specimens (p < 0.001). Of non-infected stents, 89% grew gram-positive organisms compared with 50% of infected stents (p=0.07). Sixty-seven percent of non-infected stents had gram-negative organisms versus 50% of infected stents (p=0.46). Electron microscopy of the four infected stents revealed organisms consistent with mycobacteria (size, shape) encased within a matrix. Of the six non-infected stents examined, organisms were identified within the lumens that were consistent with culture results but were without clear biofilm formation. A masked electron micrographer was able to identify and grade the presence of organisms, matrix deposits, organisms within a matrix, and a significant biofilm all with statistical significance.
Conclusions:
In our study population, atypical mycobacteria comprise the primary pathogen responsible for clinically significant infection of silicone stents in the lacrimal system. Robust biofilm production by this organism likely plays a role in pathogenesis. Development of biofilm resistant implant material, targeted liposomal antibiotic delivery, and physical or chemical disruption strategies are potential methods towards reducing rates of infection.