Evaluation of biofilm formation on nylon sutures removed from clinically noninfected eyes after cataract surgery

Abstract

Reply: We appreciate the comment raised by Liu and coauthors. The main emphasis of our study was the utilization of scanning electron microscopy (SEM) to detect the presence of biofilm. Transmission electron microscopy (TEM) was used to analyze some specimens to confirm the nature of the coccoidal structures seen on some nylon sutures. The fixative and buffers used in the study were physiological solutions. Kämper and coauthors describe the detection of extracellular polymers in biofilm using TEM and not SEM.1 The method described by Taniguchi and coauthors was for loose cells; agarose was used to hold the cells together so they would not diminish further with the various washing and dehydration steps.2 This condition did not apply to our sample type as the bacterial cells were closely associated with the suture and not floating free in fluid. In addition, the use of agarose described by Mansy will mask the morphology of the sample as it will form a coating over the sample during critical-point drying and thus decrease the resolution of the sample.3 Scanning electron microscopy does not require extensive manipulation in the sample preparation required in the TEM processing step. The chance of dislodging the biofilm is minimal. Although the point regarding false negativity cannot be completely dismissed, it is a good point to keep in mind. The method described in our paper was used in the analysis of other samples that demonstrated biofilm formation.4 We can use immunogold labeling to complement traditional SEM for identification of the types of bacteria. James C.H. Pan MRCS Mary M.L. Ng PhD