A shorter time to blood culture positivity could be associated with infective endocarditis, but not with mortality or sepsis, suggesting a potential role in identifying adult patients at risk for infective endocarditis in Streptococcus agalactiae bacteremia, according to a population-based study.
In the retrospective observational study, investigators included 463 adult patients who experienced episodes of S agalactiae bacteremia in southern Sweden between 2016 and 2023. The median patient age was 72 years, and 56% of the patients were male. Skin and soft tissue were the most common focus of infection. Infective endocarditis (IE) was diagnosed in 23 cases, and the 30-day mortality rate was 9% (n = 40).
An analysis of time to blood culture positivity (TTP), defined as the interval from blood culture bottle incubation to the detection of growth, included 411 patients. Those who visited hospitals without blood culture incubators were excluded from the analyses. The investigators found that there was no statistically significant difference in TTP measures between patients with 30-day mortality and survivors: 8.6 hours (interquartile range [IQR] = 7.6–10.1) vs 9.1 hours (IQR = 7.8–10.4), respectively. However, the patients with IE had statistically significantly lower levels of TTP compared with patients without IE: 7.5 hours (IQR = 5.9–8.8) vs 9.1 hours (IQR = 7.9–10.5), respectively.
The investigators noted that TTP may reflect a higher bacterial load and more invasive infection, consistent with findings that have been found for Staphylococcus aureus bacteremia.
The investigators identified several limitations of the study, specifically, the retrospective design and absence of data on the interval between blood culture sampling and incubation. This included transport time from hospitals without incubators to the central laboratory and the time from sampling to incubation within the five hospitals with incubators. Because TTP is highly dependent on the exact start of incubation, samples from hospitals without incubators couldn't be reliably assessed and were excluded from the analyses examining associations between TTP and clinical outcomes. Their TTP values are substantially affected by preanalytical delays, and consequently not directly comparable to those from hospitals in which incubation begins immediately.
Hospitals without incubators were also smaller facilities, lacking intensive care units, intermediate care units, general surgery, obstetrics, and night-time emergency coverage, resulting in a patient population that differed from that of larger hospitals and introducing potential selection bias in comparisons of both TTP and clinical outcomes. Additional limitations included the lack of data on blood volume collected in each culture bottle, a known determinant of TTP. These factors limited the ability to assess the impact of preanalytical delays on TTP measurement and on the clinical course of patients with S agalactiae bacteremia.
In addition, the investigators noted that sepsis ascertainment was further limited by the use of only two distinct time intervals, potentially missing patients who developed sepsis more than 48 hours following blood culture collection. Despite these limitations, the investigators said the study's strengths included its large population-based cohort, design, and comprehensive microbiological data, offering insights into the clinical significance of TTP in S agalactiae bacteremia.
"S agalactiae bacteremia primarily affects older adults with comorbidities, most commonly presenting with skin and soft tissue infections and carries a relatively high mortality rate. Shorter TTP was associated with IE, but not with mortality or sepsis in S agalactiae bacteremia," concluded lead study author Torgny Sunnerhagen, of the Division of Infection Medicine in the Department of Clinical Sciences Lund at Lund University in Sweden, and colleagues.
Disclosures: The study was funded by Lund University, the Royal Physiographic Society of Lund, and Swedish governmental clinical research funding. The study authors reported no competing interests.
Source: European Journal of Clinical Microbiology & Infectious Diseases
