Bloodstream infections S247 P942 Time to positivity of blood cultures in patients Escherichia coli bacteraemia G. Peralta, B. Ceballos, L. Garc´ ıa-Mauri˜ no, M.P. Roiz, J.C. Garrido, I. De Benito, L. Ansorena, M.B. Sanchez (Torrelavega, ES) Objectives: Bacterial blood concentration is associated with prognosis of patients with bacteraemia caused by some microorganisms. However quantitative blood cultures are not performed in clinical practice. Time from the starting of incubation to a positive reading of blood cultures has been considered a surrogate marker of bacterial blood concentration and can be associated with prognosis. We analyze time to positivity (ttp) relationships with clinical parameters in patients with E. coli bacteraemia. Methods: charts of all patients with monomicrobial E. coli bacteraemia attended at our hospital between January 1997 and December 2004 were identified by using the Microbiology laboratory database and reviewed. BacT/ALERT (bioM´ erieux) microbial detection system, was used for blood cultures and TTP detection. When multiple cultures were positive only the shortest TTP was selected for the analysis. Mann-Whiney U test was used for the comparison of median values, chi square test and Fisher‘s exact test for the comparison of categorical data. Results: during the study period we identified 567 cases of E. coli monomicrobial bacteraemia, with a mortality of 4.9%. Median (in- terquartile range) TTP was: 11.3 h (10.2 h–11.8 h). Significant correlation among TTP and the number of positive blood cultures was found (Spearman‘s coefficient = -0.5, p < 0.0001). No differences in TTP were detected depending on the comorbidities, or nosocomial or postsurgical acquisition. However TTP was longer in patients treated with antibiotics when blood cultures were performed (21.2 h±27.4 h vs 14.01 h±12.06 h, p = 0.01), and shorter in patients with a non urinary origin of the bacteraemia (12.5±10.1 h vs 16±16.8 h, p < 0.0001), severe sepsis or shock (9.7±3.3 h vs 15.2±1.3 h, p < 0.0001), or patients who died (10.7±5.4 h vs 14.9±15 h, p = 0.006). ROC analysis revealed that a time to positivity of 10.4 h was associated with the best sensitivity and specificity for predicting dead (70% and 59%, respectively). Conclusions: in patients with E. coli bacteraemia TTP is influenced by antibiotic treatment and has relationship with relevant clinical parameters as the origin of the bacteraemia, the presence of severe sepsis or shock and with the outcome. Its usefulness as a prognostic marker should be explored. P943 Time to positivity of BACTEC blood culture bottles S. Baka, I. Logginidis, V. Efstratiou, E. Panagiotopoulou, G. Kaparos, K. Gerolymatos, E. Kouskouni (Athens, GR) Objective: The aim of this study was to detect how long it takes for blood cultures to become positive when using the BACTEC system bottles. Methods: Using a continuously monitoring blood culture system (BACTEC 9050, Becton Dickinson, USA) we determined the time to positivity of blood cultures obtained from the patients of our hospital. We processed a total of 2125 blood culture sets and detected 420 (19.7%) positive blood cultures. Results: Out of the 420 positive blood cultures we recovered 1 pathogen from 392 (93.3%) and 2 pathogens from 28 (6.7%) of them. Four hundred and forty-eight clinically significant pathogens were identified in the following order: 185 (41.3%) Gram-negative rods, 153 (34.1%) staphylococci [131 (29.2%) coagulase-negative staphylococci and 22 (4.9%) Staphylococcus aureus], 51 (11.4%) streptococci, 49 (10.9%) yeasts, 8 (1.8%) anaerobes and 2 (0.5%) Gram- positive rods. Two hundred and twenty-eight (54.3%) blood cultures were obtained from ICU patients, 183 (43.6%) from surgical patients, 7 (1.7%) from OB-GYN patients and only 2 (0.4%) from neonates. In respect to the time to detection or to positivity 274 (65.2%) blood cultures turned positive during the first 24 h of incubation, 119 (28.3%) up to 48 h, 21 (5.0%) in 72h, while 4 (1.0%) and 2 (0.5%) were positive after 4 and 5 days of incubation, respectively. Conclusions: The time to positivity for 65.2% of our positive blood cultures was up to 24h, while in the first 2 days of incubation a total of 93.5% of the positive cultures were detected. Although we maintain the recommended period (7 days for aerobic and anaerobic bottles and 14 days for mycosis bottles), we could consider reducing the incubation time to 5 days (at least for the aerobic and anaerobic bottles) since all our blood cultures turned positive during the first 5 days. P944 Bacteraemia caused by high-level gentamicin-resistant Enterococcus: risk factors, clinical features and outcomes H.C. Jang, W. Park, C-I. Kang, S. Kim, C. Lee, S-W. Park, E. Kim, H-B. Kim, N-J. Kim, E-C. Kim, M-D. Oh, K-W. Choe (Seoul, Jeonju, Cheonan, Kyongju, KR) Objectives: High-level gentamicin resistance (HLGR) was increased in enterococci since 1980, but there were few studies about the impact of HLGR on clinical features and outcomes. So, we performed this study to determine the risk factors, clinical features and outcomes of bacteraemia due to enterococcus with HLGR. Methods: All patients with blood cultures positive for E. faecalis and E. faecium during the period of January 1999 – August 2003 (inclusive) were identified from a retrospective review of the Clinical Laboratory Records at Seoul National University Hospital in Korea. HLGR was determined by using disk diffusion method with 120 ug gentamicin disc (Oxoid), following the recommendation of the NCCLS. Patients who had bacteraemia due to enterococcus without HLGR (Group 1) were compared with patients who had bacteraemia due to enterococcus with HLGR (Group 2). Statistical analysis of the data was performed using SPSS for Windows, version 11.0 (SPSS). Logistic regression analysis was done for multivariate analysis. Clinical features of 215 patients with enterococcal bacteraemia HLGR+ (N = 79) HLGR- (N = 136) n % n % P value Demographic data Male gender 52 66 92 68 NS Age 58.1(±14.2) 56.2(±16.8) NS Underlying disease Haematologic disease 4 5 27 20 0.002 Neutropenia 4 5 39 29 <0.001 Cancer 42 53 70 51 NS Kidney disease 2 3 8 6 NS Urologic disease 5 6 7 5 NS Biliary disease 9 11 9 7 NS GI disease 5 6 6 4 N Infection site Vascular catheter 2 3 12 9 NS Infective endocarditis 6 8 3 2 NS Urinary tract 12 15 20 15 NS GI (except biliary tract) 13 16 35 26 NS Biliary tract 35 44 33 24 0.004 Other status B. faecium infection 45 57 105 77 0.003 Nosocomial infection 51 65 115 85 0.001 Polymicrobial infection 30 38 22 16 <0.001 ICU stay at culture 7 9 36 26 0.002 Appropriate treatment 42 53 54 40 NS APACHE II scores 14.4(±7.3) 20.7(±8.3) <0.001 Outcome 14-day mortality 12 15 50 37 0.001 30-day mortality 17 22 66 49 0.002