Characteristics and clinical outcomes of culture-negative and culture-positive septic shock: a single-center retrospective cohort study

BACKGROUND: We evaluated the characteristics and outcomes of culture-negative versus culture-positive septic shock. METHODS: We performed a retrospective observational study of data from a prospective registry from 2014 to 2018. A total of 2,499 adult patients with septic shock were enrolled. The primary outcome was 90-day mortality, and the secondary outcomes were the length of hospital stay, a requirement for mechanical ventilation or renal replacement therapy, and in-hospital mortality. RESULTS: Of 1,718 patients with septic shock, 1,012 (58.9%) patients were culture-positive (blood 803, urine 302, sputum 102, others 204) and the median pathogen detection time was 9.5 h (aerobic 10.2 h and anaerobic 9.0 h). The most common site of culture-positive infection was the hepatobiliary tract (39.5%), while for the culture-negative it was the lower respiratory tract (38.2%). The culture-negative group had a lower mean body temperature (37.3 vs 37.7 ℃), lactate (2.5 vs. 3.2 mmol/L), C-reactive protein (11.1 vs 11.9 mg/dL), and sequential organ failure assessment score (7.0 vs. 8.0) than that of the culture-positive group. However, 90-day mortality between the groups was not significantly different (32.7 vs 32.2%, p = 0.83), and the other clinical outcomes also did not differ significantly. Moreover, a shorter culture detection time was correlated with a higher sequential organ failure assessment score but not with mortality. CONCLUSION: Patients with septic shock are frequently culture-negative, especially in cases where the infection focus is in the lower respiratory tract. Although culture-negative was associated with a degree of organ dysfunction, it was not an independent predictor of death.