Hygiene of phacoemulsification and vitrectomy systems. Contamination and relevance

Background. Contamination of automated surgical equipment is widely disrega rded as a potential source of perioperative infection. We investigated the possibility of contamination of the aspiration fluid by the Vacuum control manifold (VCM). The normal, unsterile internal VCM was compared with a modi fied external VCM that was regularly disinfected. Materials and methods. We investigated 37 aspiration fluid specimens from r outine cataract and vitrectomy operations performed with automated evacuati on systems. There were 25 specimens from three automated evacuation systems equipped with an internal VCM (experimental groups) and 12 specimens from one system equipped with a modified external VCM (control group). No hygien e procedures were used with the hidden internal VCM, hut the modified exter nal VCM was regularly rinsed and filled with 70% isopropanol overnight. Spe cimens were collected under sterile conditions,centrifuged, cultured for ba cterial growth on blood agar and MacConkey agar for 24-48 h at 37 degreesC, and analyzed microbiologically. Results. Aspiration fluids of irrigation/aspiration systems used for intrao cular surgery were found to be severely contaminated with bacteria originat ing from the VCM. in all aspiration fluid specimens from internal VCM syste ms,2(+)-4(+) bacterial growth was found. Stenotrophomonas maltophilia (17), Comamonas acidovorans (8), and Agrobacterium radiobacter(13) were found mo st frequently All specimens from the modified external VCM system remained sterile. There was a significant difference with regard to the frequency of contamination of the aspiration fluid between experimental and control gro ups (P = 0.0001, chi (2)). Conclusions. We found that the aspiration fluid of common phaco- and vitrec tomy systems was strongly contaminated by bacteria originating from the int ernal VCM. The technical modification of an external VCM allows easy disinf ection and prevents contamination of the aspiration fluid.