Automated surgical equipment requires routine disinfection of vacuum control manifold to prevent postoperative endophthalmitis

Purpose: Contamination of automated surgical equipment is a potential sourc e of postoperative endophthalmitis. The effect of disinfecting the unsteril e vacuum control manifold (VCM) on contamination of the aspiration fluid wa s studied. Design: Comparative prospective microbiologic contamination study. Specimens and Controls: The 37 aspiration fluid specimens studied or examin ed consisted of 25 from three automated evacuation systems equipped with an internal VCM (experimental groups) and 12 from one system equipped with a modified external VCM (control group). in addition, the tubings of two inte rnal VCMs were investigated. Methods: We investigated aspiration fluid specimens from routine cataract a nd vitrectomy operations performed with automated evacuation systems. After tracing the source of contamination to the internal VCM, the system was mo dified, creating an external VCM with the possibility for disinfection, and the study was continued. Whereas no sterilizing rinsing procedures were ap plied to the hidden internal VCM, the modified external VCM was regularly r insed and filled overnight with 70% isopropanol. All samples were collected under sterile conditions, centrifuged, and cultured for bacterial growth o n blood agar and MacConkey agar for 24 to 48 hours at 37 degrees C. The sam ples of the two internal VCMs were cultured for fungi as well. Main Outcome Measures: Bacterial growth was quantified, and bacteria and fu ngi were isolated and identified according to standard microbiologic proced ures, Results: In all aspiration fluid specimens from internal VCM-systems, 2+ to 4+ bacterial growth was found. Pseudomonas-related genera (Stenotrophomona s maltophilia, 17x; Comamonas acidovorans, 8x; Chryseomonas spp., 3x), Agro bacterium radiobacter (13x), Flavobacterium spp. (3x), and Micrococcus lute us (7x) were found most frequently. The tubing of the two VCMs contained bi ofilms exhibiting several of these bacteria and fungi. Ail specimens from t he modified external VCM-system remained sterile, There was a significant d ifference with regard to the frequency of contamination of the aspiration f luid between the experimental and control groups (chi-square: P = 0.0001). Conclusions: The technical modification described herein allows facile hygi enic measures, by which contamination of aspiration fluid by the VCM can be eliminated, which otherwise can be a significant source of contamination. (C) 2000 by the American Academy of Ophthalmology.