• Secondary bacterial infections occur in COVID-19 patients treated with corticosteroid. • Rebound phenomenon is observed after the cessation of steroid treatment. • Non-typhoidal Salmonella bacteremia is associated with immunosuppressive conditions. • Blood cultures distinguish between secondary infections and rebound phenomena.

Objective: To evaluate the impact of implementation of a conditional reflex urine culturing strategy on urine culture rates, antimicrobial use, and clinical outcomes in hospitalized adults. Design: Pre-post quasi-experimental study. Setting: Emergency departments and inpatient units within a large, integrated healthcare system in Northeast Ohio, comprising 10 medical centers. Patients: Adult patients with a urine culture ordered from June 1, 2018, to May 31, 2023. Methods: A system-wide intervention was implemented on June 1, 2020, requiring urinalysis (UA) with pyuria findings to trigger a urine culture order. We compared urine culture rates, antimicrobial use (measured by days of therapy [DOT] and days of antimicrobial spectrum coverage [DASC]), and clinical outcomes between pre-and post-intervention periods. Results: The intervention resulted in an 85.4% reduction in urine culture rates (0.54 vs 3.71 per 100 patient days). Antimicrobial use decreased, with DOT per 100 patient days dropping by 11.5% and DASC/DOT by 16.1%. No significant differences were observed in Clostridioides difficile infection rate, subsequent bloodstream infections with urinary pathogens, or mortality between pre- and post-intervention groups. Conclusions: A conditional reflex urine culturing strategy implemented as part of a diagnostic stewardship framework reduced urine culture and antimicrobial use without adverse clinical outcomes. This highlights the potential of diagnostic stewardship to optimize antimicrobial use in hospitalized adults.

Staphylococcus lugdunensis is a common skin commensal. However, S. lugdunensis found in multiple blood culture sets is concerning for life-threatening bacteremia. When a single set is positive, the National Healthcare Safety Network classifies S. lugdunensis as a common commensal (contaminant), while multiple publications found bacteremia and suggested an Infectious Diseases (ID) consultation. Here, a retrospective review spanning 9 years at a large health system evaluated the clinical significance of a single-positive S. lugdunensis blood culture when multiple cultures were collected. S. lugdunensis was found in blood cultures from 137 patients, who were stratified into single ( n = 91) and multiple ( n = 46) set-positive groups. The single-positive group was more likely to be deemed contaminants by clinicians, less likely to have a diagnosis of endocarditis or catheter-related bloodstream infection, and less likely to have an intravascular device ( P < 0.01). Treatment occurrence and duration were also statistically different ( P < 0.01). Single-positive cultures were statistically more likely to be polymicrobial ( P = 0.04). Additionally, each case was reclassified as significant bacteremia, indeterminate bacteremia, or contamination using the Souvenir criteria. In single-positive cultures, significant bacteremia occurred less often (12.1% vs. 43.5%, P < 0.01), while contamination was more common (81.3% vs. 32.6%, P < 0.01). Of note, nearly all significant bacteremia cases involved an intravascular device (96.8%). Taken together, these findings suggest single-positive S. lugdunensis blood cultures are often contaminants, but certain clinical features, including intravascular devices, strongly predict bacteremia. IMPORTANCE: A single-positive blood culture set with Staphylococcus lugdunensis can be difficult to distinguish between contamination and bacteremia. Conflicting clinical guidance has added to the confusion and emphasizes the need for additional studies. Our results suggest a single-positive S. lugdunensis blood culture set often reflects contamination and polymicrobial cultures, whereas multiple-positive sets strongly predict significant bacteremia. We also identified predictors of significant bacteremia, such as the presence of an intravascular device, emphasizing the need to incorporate additional metrics into clinical decision-making algorithms. Our findings underscore the role of clinical judgment when S. lugdunensis is recovered from a blood culture. Taken together, the proposed practice for the microbiology laboratory is to include a contamination comment on the report of a single-positive S. lugdunensis blood culture set and to recommend an infectious disease consultation for clinical adjudication.

Background: There have been few reports on secondary bacteremia in patients hospitalized with COVID-19. We aimed to analyze the onset time of secondary bacteremia after the onset of illness and hospital admission and determine the proportion of secondary bacteremia on blood cultures drawn from patients with COVID-19. Methods: We conducted a retrospective cohort study of all hospitalized patients with COVID-19 who took blood culture tests between January 1, 2020 and September 30, 2021 at Kyoto City Hospital, Japan. Results: Of 507 patients hospitalized with COVID-19, blood culture tests were performed in 169. Eleven of them had secondary bacteremia, and 158 had a negative blood culture test. The onset time with the highest proportion of secondary bacteremia in blood cultures drawn from the day of symptom onset and hospitalization was from 11^th-15^th day (12.8%) and 6^th-10^th day (18.2%), respectively. The median time in which patients were diagnosed with secondary bacteremia from the onset of COVID-19 symptoms and hospital admission was 12.5 [interquartile range (IQR) 12-19.5] days and 6 (IQR 5-9) days, respectively. Conclusions: The timing from symptom onset and hospital admission may be a valuable indicator for making a clinical decision of taking blood cultures in patients hospitalized with COVID-19.