Is early time to positivity of blood culture associated with clinical prognosis in patients with Klebsiella pneumoniae bloodstream infection?

Determinants of time to positivity in bloodstream infections: an analysis of a population-based cohort in Queensland, Australia

PURPOSE

Time to Positivity (TTP) measures the interval from incubation to bacterial growth detection in blood cultures. Although shorter TTP is associated with higher mortality, factors associated with TTP remain uncertain.

METHODS

A retrospective cohort study was conducted among Queensland residents with positive blood cultures between 2000-2019. Incident bloodstream infections (BSIs) were identified using Pathology Queensland data, with demographic, clinical, and outcome data linked to state-wide databases.

RESULTS

The study analysed 84,341 patients with monomicrobial BSI with a median patient age of 65.6 years (IQR 45.4-78.1), and most infections being community-associated (77.0%). Age showed a non-linear relationship with TTP, and male sex was linked with slightly higher TTP (Incidence Rate Ratio (IRR) 1.01; 95% Confidence Intervals (CI) 1.00-1.02; p = 0.011), reflecting a small but measurable association. Liver disease and malignancy were associated with lower TTP (IRR 0.93; 95% CI 0.91-0.95; p < 0.0001 and IRR 0.95; 95% CI 0.94-0.97; p < 0.0001 respectively), whilst diabetes showed no significant difference (IRR 1.01; 95% CI 1.00-1.02; p = 0.0840). Hospital onset infections exhibited longer TTPs (IRR 1.09; 95% CI 1.08-1.10; p < 0.0001).

CONCLUSIONS

There are several host characteristics associated with TTP that may in part explain the complex relationship between this variable and mortality. Beyond microbiological factors such as isolate type, TTP is also influenced by clinical variables including patient demographics and infection characteristics highlighting its potential as a prognostic marker. Further evaluation is needed to clarify its role in predicting patient outcomes and guiding tailored treatment strategies.

Modified time-to-positivity as a crucial determinant of short-term mortality among adults with community-onset monomicrobial bloodstream infections

The potential performance of time-to-positivity (TTP) in predicting the prognosis of individuals experiencing Bloodstream infections (BSIs) has achieved little consensus. The retrospective cohort of 1015 treatment-naive adults with community-onset monomicrobial BSIs aimed to assess the performance of TTP and modified TTP (mTTP, TTP plus transportation time) in predicting 30-day mortality after adjusting for prognostic confounders, particularly the time-to-appropriate antibiotic (TtAa). Through Spearman's correlation, a significant linear-by-linear association (ρ = -0.943, P = 0.005) was exhibited between mTTP and 30-day mortality rates, but no significant association (ρ = -0.423, P = 0.26) was disclosed between TTP and 30-day mortality rates in the overall patient population. In the logistic regression model, each additional hour of mTTP or TTP was associated with an average decrease of 5 % (adjusted odds ratio [AOR], 0.95; P = 0.001) or 3 % (AOR, 0.97; P = 0.03) in the 30-day mortality rates, respectively, after adjusting for independent predictors of 30-day mortality. In conclusion, for adults with community-onset monomicrobial BSIs, mTTP revealed a favorable performance over TTP alone in predicting short-term mortality.

Time to positivity as a predictor of catheter-related bacteremia and mortality in adults with Pseudomonas aeruginosa bloodstream infection

BACKGROUND

Time to positivity (TTP) and differential TTP (DTP) emerge as diagnostic and prognostic tools for bloodstream infections (BSI) though specific cut-off values need to be determined for each pathogen. Pseudomonas aeruginosa BSI (PAE-BSI) is of critical concern, particularly in immunocompromised patients, due to high mortality rates. Catheter-related infections are a common cause, necessitating rapid and accurate diagnostic tools for effective management (source-control).

METHODS

Unicentric retrospective observational study analyzing the diagnostic utility and best cut-off values of time to positivity (TTP) and differential time to positivity (DTP) to identify catheter-related PAE-BSI and the association of TTP with 30-day mortality.

RESULTS

1177 PAE-BSI cases TTP were included in the study. TTP was available in all episodes whereas DTP was available in 355 episodes. Breakthrough bacteremia disregarding the TTP, more than one positive blood culture or > 7 days with a catheter in place and both a TTP < 13h and a DTP > 2h were independently associated to catheter-related PAE-BSI. Secondly, lower TTP were significantly associated with higher 30-day mortality rates in both catheter-related and non-catheter-related PAE-BSI. For catheter-related infections, TTP < 14h exacerbated mortality among patients among patients in whom the catheter was not removed within 48h (OR 2.9[1.04-8]); whereas for other sources TTP < 16h increased mortality (OR 1.6[1.1-2.4]) particularly when the empiric antibiotic therapy was not active (OR 3.8[1.5-10]).

CONCLUSION

These findings advocate for the routine use of TTP over DTP as a diagnostic tool to guide timely interventions such as catheter removal, thereby potentially improving patient outcomes in PAE-BSI. Moreover, lower TTP have also prognostic implications in both catheter-related and non-catheter-related infections.

Diagnostic and prognostic value of time to positivity in blood cultures. An opinion paper

Time to positivity (TTP) refers to the duration required for a microbiological culture test to indicate a positive result, marking the onset of detectable bacterial or fungal growth in the sample. Numerous variables, including patient characteristics, infection source, former antimicrobial therapy, blood sample volume, and sample transportation time can influence the value of TTP. Several studies have been conducted on bloodstream infections, whereas studies on the clinical significance of yeast TTP are quite limited in the literature. Furthermore, many studies are retrospective and have a small sample size. In this opinion paper, we have formulated some questions and attempted to provide answers based on the available literature and our perspective. The objective of this opinion paper is to summarise current knowledge based on the literature, aiming to offer a critical perspective, particularly on aspects with weaker evidence, which could guide future studies in this area. We believe that TTP of blood cultures appears to exhibit considerable potential and may prove to be a valuable tool in clinical practice for estimating patient mortality risk and guiding antimicrobial therapy choices. Topics discussed include the diagnostic and prognostic role of TTP in Gram-positive and Gram-negative bacteremias and in candidemias, and the significance of differential time to positivity (DTTP). In summary, our opinion is that, based on the available literature, it is not possible to determine whether TTP provides prognostic information, particularly concerning candidemia. Therefore, clinical decisions cannot be systematically based on this parameter.

Klebsiella pneumoniae species complex bloodstream infection in adult patients: changing epidemiology and determinants of poor outcomes

PURPOSE

Klebsiella pneumoniae is a common cause of hospital- and community-acquired infection and can readily acquire multiple antimicrobial resistance determinants leading to poor health outcomes. We define the contemporary burden of disease, risk factors for antimicrobial resistance, and poor health outcomes for patients with K. pneumoniae bloodstream infection (Kp-BSI).

METHODS

All blood cultures with growth of K. pneumoniae species complex among residents of Queensland, Australia (population ≈ 5 million) who received care through a public hospital were identified over a 20-year period. Clinical, microbiological and outcome information was obtained from state-wide databases.

RESULTS

A total of 6, 988 patients (7, 496 episodes) with incident Kp-BSI were identified. Incidence rate more than doubled from 5.8 cases to 12.2 cases per 100,000 population over the study period (4.5% rise per year). 258 (3.4%) episodes involved isolates resistant to third-generation cephalosporins (3GC-R). 3GC-R Kp-BSI crude incidence rate increased almost 10% each year. The proportion of hospital-onset episodes reduced from 49.1 to 35.0%. Of all Kp-BSI episodes, 864 (11.5%) died within 30-days. A lower respiratory tract source was associated with a high risk of death (aHR 1.68, 95% CI 1.30-2.16) while a urinary tract source a lower risk (aHR 0.48, 95% CI 0.35-0.66). 3GC-R Kp-BSI was not related to death (aHR 1.08, 95% CI 0.76-1.50).

CONCLUSION

A rising burden of both Kp-BSI and 3GC-R blood isolates in a previous low-prevalence setting is concerning. A significant rise in community-onset Kp-BSI over the 20-year period was noteworthy and requires further evaluation. 3GC-R status was not associated with mortality.

Time to positivity is a risk factor for death among patients with bloodstream infections: a population-based cohort

OBJECTIVES

Studies examining time to positivity (TTP) of blood cultures as a risk factor for death have shown conflicting results. The study objective was to examine the effect of TTP on all-cause-30-day case-fatality among a population-based cohort of patients with bloodstream infections (BSI).

METHODS

A retrospective cohort study including all residents of Queensland, Australia with incident monomicrobial BSI managed in the publicly funded healthcare system from 2000 to 2019 was performed. Clinical, TTP and all-cause 30-day case-fatality information was obtained from state-wide sources.

RESULTS

A cohort of 88 314 patients was assembled. The median TTP was 14 hours, with 5th, 25th, 75th, and 95th percentiles of 4, 10, 20, and 53 hours, respectively. The TTP varied significantly by BSI aetiology. The 30-day all-cause case-fatality rate was 2606/17 879 (14.6%), 2834/24 272 (11.7%), 2378/20 359 (11.7%), and 2752/22 431 (12.3%) within the first, second, third, and fourth TTP quartiles, respectively (p < 0.0001). After adjustment for age, sex, onset, comorbidity, and focus of infection, TTP within 10 hours (first quartile) was associated with a significantly increased risk for death (odds ratio 1.43; 95% CI, 1.35-1.50; p < 0.001). After adjustment for confounding variables (odds ratio; 95% CI), TTP within the first quartile for Staphylococcus aureus (1.56; 1.41-1.73), Streptococcus pneumoniae (1.91; 1.49-2.46), β-hemolytic streptococci (1.23; 1.00-1.50), Pseudomonas species (2.23; 1.85-2.69), Escherichia coli (1.37; 1.23-1.53), Enterobacterales (1.38; 1.16-1.63), other Gram-negatives (1.68; 1.36-2.06), and anaerobes (1.58; 1.28-1.94) increased the risk for case-fatality.

DISCUSSION

This population-based analysis provides evidence that TTP is an important determinant of mortality among patients with BSI.