Optimizing microbiological controls of corneal organ culture media

To compare the efficiency of an automated method using blood bottles with conventional microbiological tests for controlling sterility in cornea organ culture media. Two complementary studies were conducted. Experimental study: standard organ culture media were contaminated with four different inocula of 14 bacteria and 3 fungi. The bactericidal activity of organ culture media were evaluated after 48 hours of incubation at 31C. Observational study: 357 samples of organ culture media were collected over 1 year in our cornea bank. For both studies, media were inoculated in three blood bottles (aerobic, anaerobic, fungal) placed in an automat with automated detection every 10 minutes, and in three conventional microbiological media as a control. Changes in organ culture medium color and growth on conventional broth were checked daily by visual inspection. All samples were observed experimentally for 14 days. The sensitivity and rapidity of contamination detection were compared across the three methods: blood bottles, conventional method, and visual inspection of medium color. Experimental study: organ culture medium eradicated five bacteria: S. pneumoniae, B. catarrhalis, E. coli, P. acnes and H. influenzae. For the others, (Methicillin-resistant S. aureus, Methicillin-sensitive S. aureus, S. epidermidis, S. haemolyticus, P. aeruginosa, A. baumannii, B. subtilis, K. pneumoniae, E. faecalis, C. albicans, C. kruzei, A. fumigatus) the blood bottle method, the conventional microbiological method, and the visual inspection detected microbiological growth respectively in 100%, 76.5%, and 70% of cases. Mean detection time using blood bottles was 15.1 hours (standard deviation, 13.8; range, 2-52). In cases of detection by the blood-bottle method and the conventional method, the former was always faster: 95.5% versus 65.2% detection within 24 hours (p=0.022). Observational study: the global contamination rate was 8% (29/357 analysis). The gain in sensitivity with blood bottles was 25% compared with the conventional method. Five bacteria (three coag. neg Staphylococcus, one E. faecalis, one P. paucimobilis) were detected only by the blood bottles. In addition, these were always detected more quickly with, respectively, 66.6% versus 26.6% detection with 24 hours (p=0.028). Blood bottles detect contaminations of cornea organ culture media more efficiently and faster than conventional microbiological methods. They make it possible to reduce the quarantine period with an e