P2463 Antibiotic treatment for invasive listeriosis and patient outcome: a retrospective cohort study Yaakov Dickstein*1, Yonatan Oster2, Orit Shimon3, Lior Nesher4, Dafna Yahav5,3, Yonit Wiener-Well6, Regev Cohen7,8, Ronen Ben-Ami9,3, Miriam Weinberger10,3, Galia Rahav11,3, Yasmin Maor12,3, Michal Chowers13,3, Ran Nir-Paz2, Mical Paul8,14 1 Rambam Healthcare Campus, Haifa, Israel, 2 Hadassah University Hospital - Ein Kerem, Jerusalem, Israel, 3 Tel Aviv University, Sackler Faculty of Medicine, Ramat Aviv, Israel, 4 Soroka Medical Center, Beersheba, Israel, 5 Rabin Medical Center, Petah Tikva, Israel, 6 Shaare Zedek, Jerusalem, Israel, 7 Laniado Hospital, Netanya, Israel, 8 Technion, The Ruth and Bruce Rappaport Faculty of Medicine, Haifa, Israel, 9 Tel Aviv Sourasky Medical Center , Tel Aviv, Israel, 10 Assaf Harofeh Medical Center, Be’er Ya’akov, Israel, 11 Sheba Medical Center, Ramat Gan, Israel, 12 Wolfson Medical Center, Holon, Israel, 13 Meir Medical Center, Kefar Sava, Israel, 14 Infectious Diseases Unit, Rambam Health Care Campus, Haifa, Israel Background: Current recommendations for treatment of invasive listeriosis suggest ampicillin-based therapy with the addition of an aminoglycoside. However, several reports have suggested higher morbidity and mortality with this regimen as compared with beta-lactam monotherapy. We aimed to evaluate the association between penicillin-aminoglycoside combination therapy and mortality in patients with invasive listeriosis while adjusting for timing of treatment onset. Materials/methods: This is a multicenter retrospective observational study of adult patients with invasive listeriosis (primary bacteremia, central nervous system [CNS] disease and pregnancy-associated listeriosis) in 11 hospitals in Israel between the years 2008-2014. We evaluated the effect of penicillin-based monotherapy compared with early combination therapy with gentamicin, defined as treatment started within 48 hours of culture results and continued for a minimum duration of 7 days. Patients who died within 48 hours of the index culture were excluded. The primary outcome was 30-day all-cause mortality. Subgroup analyses were performed by diagnosis. Results: A total of 246 invasive listeriosis patients were identified of whom 243 were included in the analyses. Seventy-two (29.6%) patients were treated with early combination therapy, 117 (48.1%) received monotherapy and 54 (22.2%) received other treatments. Overall 30-day mortality was 16.0% (39/243). Factors associated with mortality included age, functional capacity, no pregnancy, renal function, congestive heart failure, clinical diagnosis, Sequential Organ Failure Assessment (SOFA) score, elevated liver-function tests and therapy. Time from culture-taken-date to initiation of appropriate therapy was not associated with mortality. In multivariable analysis, a non-significant trend was observed between monotherapy and higher 30-day mortality compared with early combination therapy (OR 1.867, 95%CI 0.653-5.334). Results were similar in patients with non-pregnancy- associated listeriosis (OR 2.069, 95%CI 0.694-6.163), CNS disease (OR 3.037, 95%CI 0.574-16.057) and primary bacteremia (OR 2.983, 95%CI 0.575-15.492). Conclusions: In our retrospective cohort there was no statistically-significant difference between monotherapy and combination therapy, but possibly a clinically-significant benefit to combination therapy. Our results were limited by sample size which may have been insufficient to show superiority of one antibiotic regimen to the other. A randomized controlled trial may be necessary to assess optimal treatment. Figure 1: Survival function based on treatment group 29TH ECCMID 13-16 APRIL 2019 AMSTERDAM, NETHERLANDS POWERED BY M-ANAGE.COM .