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

Abstract

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.

Keywords: Culture; Mortality; Sepsis; Septic shock; Time to blood culture positivity.

Fig. 1

Flowchart of the study population. Prospective septic shock registry excluded 605 patients (218 for transfer from/to other hospitals, 298 for do-not-resuscitate orders, 89 for refuse to manage), and 176 patients with proven viral and fungal pathogen were also precluded from this analysis

Fig. 2

Frequencies of infection foci (a) and the culture types (b) by the culture results. a Isolated blood stream infection, skin and soft tissue, and central nervous system were categorized as “other”. b Other culture types included pleural, ascites, stool, and pus. Abbreviations: LRT = lower respiratory tract; UT = urinary tract; GI = gastro-intestinal; HBP = hepatobiliary-pancreas

Fig. 3

Comparison of Kaplan–Meier survival curves between patients with culture-negative (CNSS) and culture-positive septic shock (CPSS)

Fig. 4

Distributions and scatter plots of the first detected culture-positive time of the aerobic and anaerobic pathogens. Time-to-positivity in both aerobic (a) and anaerobic (b) pathogens. Scatter plots of aerobic (c) and anaerobic (d) time according to sequential organ failure assessment (SOFA)