Background and Aims Cirrhotic patients presenting with spontaneous bacterial peritonitis (SBP) have elevated risk of shortterm mortality. While high Model for End-Stage Liver Disease-Sodium score (MELD-Na) and ascites culture yielding multidrug resistance (MDR) bacteria are well established risk factors for further aggravating mortality, the impact of individual, causative microorganisms and their respective pathogenesis have not been previously investigated. Methods This is a retrospective study of 267 cirrhotic patients at two tertiary care hospitals undergoing paracentesis from January 2015 to January 2021 who presented with ascitic PMN count > 250 cells / mm 3 . The primary outcome was SBP progression defined as death or liver transplantation within 1-month of paracentesis stratified by microorganism type. Results Of 267 patients with SBP, the ascitic culture yielded causative microorganism in 88 cases [median age 57 years (IQR 52-64)]; 68% male; median MELD-Na 29 . The microbes isolated were E. coli (33%), Streptococcus (15%), Klebsiella (13%), Enterococcus (13%), Staphylococcus (9%) and others (18%); 41% were MDR. Cumulative incidence of SBP progression within 1-month was 91% (95% CI 67-100) for Klebsiella, 59% (95% CI 42-76) for E. coli, and 16% (95% CI 4-51) for Streptococcus. After adjusting for MELD-Na and MDR, risk of SBP progression remained elevated for Klebsiella (HR 2.07; 95% CI 0.98-4.24; p-value = 0.06) and decreased for Streptococcus (HR 0.28; 95% CI 0.06-1.21; p-value = 0.09) compared to all other bacteria. Conclusion Our study found Klebsiella-associated SBP had worse clinical outcomes while Streptococcus-associated SBP had the most favorable outcomes after accounting for MDR and MELD-Na. Thus, identification of the causative microorganism is crucial not only for optimizing the treatment but for prognostication.

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Background & Aims: Absolute PMN count (PMN-C) ≥250cells/mm3 in ascites is the diagnostic hallmark of spontaneous bacterial peritonitis (SBP) and is associated with high morbidity and mortality. However, the clinical significance of ascitic PMN percentage (PMN-%) as well as PMN-C in the absence of SBP as additional biomarkers for mortality and future incidence of SBP has not been determined. Methods: This retrospective cohort included adults with cirrhosis undergoing first-recorded paracentesis with initial PMN-C<250cells/mm3 at two tertiary medical centers between 2015-2020. Patients with prior SBP were excluded. Outcomes were death and SBP development. Cox regression estimated hazard ratios(HR) for risk of death and SBP development and Akaike information criterion(AIC) to compare model fit. Results: 384 adults (73% male, median age 58, 67% with alcohol-associated cirrhosis, median PMN-C 14cells/mm3[IQR 5-34], and median PMN-% 10%[IQR 4-20]) were included in this study. Univariate risk of death increased 10% per 25-unit increase in PMN-C (95%CI 1.01-1.21, p=0.03) and 19% per 10-unit increase in PMN-% (95%CI 1.06-1.33, p=0.003) with PMN-% demonstrating better model fit in assessing mortality risk (AIC:1044 vs. 1048, respectively). In models adjusted for age, HCV, and MELD-Na, PMN-% was associated with risk of death (PMN-% 10-29% HR 1.17, p=0.50; PMN-% ≥30% group HR 1.94, p=0.03; vs. PMN-% <10%) and SBP development (PMN-% 10-29% HR 1.68, p=0.07; PMN-% ≥30% HR 3.48, p<0.001; vs. PMN-% <10%). Conclusion: Our results suggest PMN-% at first paracentesis represents a better biomarker compared to PMN-C for assessing risk of death and future SBP development in patients with PMN-C<250cells/mm3.