Bacterial biofilm in silver -impregnated contact lens cases

Purpose: This study investigated the efficacy of pre -conditioning lens cases on bacterial biofilm formation and removal. Methods: Silver impregnated (MicroBlock / ProGuardn? &i-Clean) and control storage cases were pre -condi- tioned for 24 h with their respective multipurpose solutions (MPDSs). Cases were then inoculated with 2 ml of 10 6 CFU/mL of ocular isolates of either P. aeruginosa or S. aureus and incubated for 48 h. Cases were subse- quently disinfected (4-6 hours) as per the manufacturer?s recommended disinfecting time (MRDT) followed by the recommended case hygiene procedures - recapping wet (MicroBlock / ProGuardn? cases only) or rinse and air-dry or rinse, tissue -wipe and air dry (mechanical disruption). Surviving bacteria were enumerated using standard techniques. Results: Pre -conditioning the MicroBlock / ProGuardn? cases with MPDS significantly reduced biofilm formation (-1.1 log 10 CFU, p < 0.01 for P. aeruginosa & -1.3 log 10 , p < 0.001, CFU for S. aureus ) compared to the i-Clean lens cases. Maintaining the MicroBlock / ProGuardn? lens cases wet after the MRDT resulted in partial removal of bacterial biofilms (-2.9 log 10 CFU, p < 0.001 for P. aeruginosa and -2.6 log 10 CFU, p < 0.001 for S. aureus ). Air - drying of all three types of lens storage cases after MRDT significantly reduced the bacterial biofilm (-5.4 log 10 CFU, p < 0.001 for P. aeruginosa and -3.5 log 10 CFU, p < 0.001 for S. aureus ). Mechanical disruption produced the greatest reduction in the levels of bacterial biofilm in all 3 types of lens cases tested (-6.8 log 10 CFU, p < 0.001 for P. aeruginosa and -4.5 log 10 CFU, p < 0.001 for S. aureus ). Synergi MPDS was significantly better than AQuify MPDS in removing bacterial biofilm from all 3 lens case types for case hygiene treatments with an air -drying step. Conclusion: Pre -conditioning of silver -impregnated ProGuardn? lens cases inhibited initial bacterial biofilm for- mation. Synergi MPDS was more effective than AQuify MPDS in removing bacterial biofilm in silver impregnated cases and tissue -wiping significantly improved biofilm removal.