The Clinical and Prognostic Importance of Positive Blood Cultures in Adults

doi:10.1016/j.amjmed.2010.03.021

The American Journal of Medicine

Volume 123, Issue 9, September 2010, Pages 819-828

https://doi.org/10.1016/j.amjmed.2010.03.021 Get rights and content

Abstract

Background

Bloodstream infections are a major cause of morbidity and mortality in adults. Bloodstream infections should be reassessed periodically because of increased antibiotic resistance, more patients receiving immunomodulatory therapy, improved antiretroviral therapy, and acquisition of infection in health care settings other than hospitals.

Methods

We conducted retrospective assessment by infectious disease physicians of hospitalized adults with positive blood cultures at 3 academic medical centers.

Results

Two thousand two hundred seventy positive blood culture episodes occurred in 1706 patients. Of 2669 isolates, 51% represented true infection, 41% contamination, and 8% unknown clinical significance. Although coagulase-negative staphylococci were most common, only 10% were clinically significant. Among 1225 true bloodstream infections, the most frequent isolates were Staphylococcus aureus, Escherichia coli, Enterococcus spp., Klebsiella pneumoniae, coagulase-negative staphylococci, Pseudomonas aeruginosa, Candida albicans, Enterobacter cloacae, and Serratia marcescens. Intravenous catheters were the most common primary source of bloodstream infection (23% of episodes). Most (81%) bloodstream infections were acquired in the hospital or other health care settings. Crude and attributable in-hospital case-fatality ratios were 20% and 12%, respectively, lower than in previous studies. Increasing age, hypotension, absence of fever, hospital acquisition, extreme white blood cell count values, and the presence of the acquired immunodeficiency syndrome, malignancy, or renal disease were significantly associated with an increased risk of in-hospital attributable death in multivariable analysis.

Conclusions

The proportion of bloodstream infections due to intravenous catheters is continuing to increase. Most episodes were acquired in the hospital or other health care setting. In-hospital case-fatality ratios have decreased compared with previous studies. Several previously identified factors associated with an increased mortality remain statistically significant.

Section snippets

Study Design

A multicenter retrospective study was performed on an open cohort of adults who had at least one positive blood culture at 3 academic hospitals (Robert Wood Johnson University Hospital, Duke University Medical Center, and the Durham Veterans Affairs Medical Center) from January 1 through December 31, 2004. Institutional review board approval was obtained at all 3 institutions.

Study Cohort

Patients who had blood culture isolates obtained from standard bacterial, fungal, or mycobacterial blood culture

Patient Characteristics

A total of 2669 blood culture isolates from 2270 positive blood culture episodes in 1706 patients were reviewed. There were 1225 patients who developed a true bloodstream infection and had a median age of 60 years (interquartile range 50-72 years). Approximately 60% of adult patients with a true bloodstream infection were male, 59% were white, and 80% had at least one predisposing comorbid illness. The patients from the Durham Veterans Affairs Medical Center were older, with a higher proportion

Discussion

Studies over the past 4 decades have documented both recurrent findings and evolving changes in the microbiology, epidemiology, and outcomes of adult bloodstream infections.1, 2, 3, 4, 5, 6, 7, 8, 9 Compared with the 2 similarly designed studies that were performed by members of our group, S. aureus and E. coli remain the most frequently isolated bloodstream pathogens.1, 2, 3 Approximately 40% of all positive blood culture episodes represent contamination, mostly due to coagulase-negative

Acknowledgments

We thank Lauren Lindblad and Shein Chung-Chow of the Duke Clinical Research Institute for their assistance with the multivariable logistic regression model. We appreciate all the efforts of the Duke University Medical Center, Robert Wood Johnson University Hospital, and Durham Veteran's Affairs Medical Center Clinical Microbiology Laboratory staff.

References (25)

R.L. Lark et al.
Four year prospective evaluation of nosocomial bacteremia: epidemiology, microbiology, and patient outcome
Diagn Microbiol Infect Dis
(2000)
R.L. Lark et al.
Four-year prospective evaluation of community-acquired bacteremia: epidemiology, microbiology, and patient outcome
Diagn Microbiol Infect Dis
(2001)
S.J. Crane et al.
Bloodstream infections in a geriatric cohort: a population-based study
Am J Med
(2007)
M.E. Charlson et al.
A new method of classifying prognostic comorbidity in longitudinal studies: development and validation
J Chronic Dis
(1987)
M.P. Weinstein et al.
The clinical significance of positive blood cultures: a comprehensive analysis of 500 episodes of bacteremia and fungemia in adults. I. Laboratory and epidemiologic observations
Rev Infect Dis
(1983)
M.P. Weinstein et al.
The clinical significance of positive blood cultures: a comprehensive analysis of 500 episodes of bacteremia and fungemia in adultsII. Clinical observations, with special reference to factors influencing prognosis
Rev Infect Dis
(1983)
M.P. Weinstein et al.
The clinical significance of positive blood cultures in the 1990s: a prospective comprehensive evaluation of the microbiology, epidemiology, and outcome of bacteremia and fungemia in adults
Clin Infect Dis
(1997)
D.J. Diekema et al.
Epidemiology and outcome of nosocomial and community-onset bloodstream infection
J Clin Microbiol
(2003)
H. Wisplinghoff et al.
Nosocomial bloodstream infections in US hospitals: analysis of 24,179 cases from a prospective nationwide surveillance study
Clin Infect Dis
(2004)
M.B. Edmond et al.
Nosocomial bloodstream infections in United States hospitals: a three-year analysis
Clin Infect Dis
(1999)

F.R. Cockerill et al.

Optimal testing parameters for blood cultures

Clin Infect Dis

(2004)

N.D. Friedman et al.

Health care-associated bloodstream infections in adults: a reason to change the accepted definition of community-acquired infections

Ann Intern Med

(2002)

Cited by (202)

Epidemiology and clinical significance of persistent bacteremia in severely burned patients
2024, Burns
The utility of follow-up blood cultures (FUBC) for gram-negative bloodstream infections (BSIs) are controversial due to low rates of positivity. However, recent studies suggest higher rates of positivity in critically ill patients. The utility of FUBC in gram-negative BSI in patients with severe burn injuries is unknown.
Patients ≥ 18 years old admitted to the US Army Institute of Surgical Research Burn Center for combat-related thermal burns from 1/2003–6/2014 with a monomicrobial BSI were included. FUBC were defined as repeat cultures 1–5 days from index BSI. Persistent BSI (pBSI) was defined as isolation of the same organism from initial and FUBC. The primary endpoint was all-cause in-hospital mortality in patients with gram-negative pBSI.
Of 126 patients meeting inclusion criteria with BSI, 53 (42%) had pBSI. Compared to patients without persistence, patients with pBSI had more severe burns with median total body surface area (TBSA) burns of 47% ([IQR 34–63] vs. 35.3% [IQR 23.3–56.6], p = 0.02), increased mortality (38 vs. 11%, p = 0.001) compared to those with non-persistent BSI. On multivariate analysis, pBSI was associated with an odds ratio for mortality of 5.3 [95% CI 1.8–15.8, p = 0.003). Amongst gram-negative pathogens, persistence rates were high and associated with increased mortality (41% vs. 11%, p = 0.001) compared to patients without pBSI.
In this cohort of military patients with combat-related severe burns, pBSI was more common than in other hospitalized populations and associated with increased mortality. Given this high frequency of persistence in patients with burn injuries and associated mortality, FUBC are an important diagnostic and prognostic study in this population.
Contamination rate of rare bacterial species detected by MALDI-TOFMS: a retrospective cohort study
2024, Diagnostic Microbiology and Infectious Disease
When rare bacterial species are identified in blood cultures, determining the clinical significance is sometimes difficult. This study aimed to analyze the clinical significance of rare bacterial species detected in blood cultures using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOFMS) by comparing their contamination rates with those of common species. We retrospectively analyzed medical records of adult patients with positive blood cultures at Kyoto City Hospital from 2014 to 2022. Rare species were defined by low detection rates and few PubMed reports. Of 4880 microorganisms identified from 3441 individuals, 1150 (23.6%) were classified as contamination. Meanwhile, 24 rare microorganisms were identified, of which 14 (58.3%) were classified as contamination, which was significantly higher than common species (odds ratio 4.56, 95% confidence Interval 1.88–11.50, P < 0.001). These findings may help in determining the clinical significance of rare bacterial species in blood cultures with few reported cases.
Assessment of the impact of centralized bioMérieux BACT/ALERT® VIRTUO® blood culture system (VIRTUO) implementation on outcomes in patients with gram-negative bacteremia
2023, Diagnostic Microbiology and Infectious Disease
We evaluated pre- and postimplementation of Virtuo on outcome in patients with gram-negative bacteremia using a quasiexperimental time-in-motion design.
Becton Dickinson BACTEC™ 9000 series (Bactec) (2018) and Virtuo system (2020) were utilized in a decentralized and centralized process, respectively. Data collected in August-December in 2018 and 2020 were analyzed with SPSS (ver 28).
For 185 patients in each time period, patient age, gender, length of hospitalization were not different. However, blood culture (BC) volume was significantly lower in 2020 (7.1 ± 2.6 mL) compared to 2018 (8.9 ± 1.9 mL). Time from BC draw and time from pathogen identification (ID) to treatment change were both significantly faster in 2020 (52.9 ± 38.3 hours; 15.1 ± 27.4 hours), compared to 2018 (65.0 ± 46.3 hours; 23.8 ± 33.8), respectively.
Replacement of decentralized Bactec with centralized Virtuo, resulted in significant improvement in management of patients gram-negative bacteremia.
Clinical outcomes and epidemiological characteristics of bacteremia in the older Japanese population
2023, Journal of Infection and Chemotherapy
The characteristics and clinical consequences of bacteremia in older people, who are highly susceptible to infections, need to be clarified. This study aimed to determine the epidemiological characteristics, prognosis, and predictors of 7-day mortality in patients with community-acquired (CA), healthcare-associated (HCA), and hospital-onset (HO) bacteremia in older adults aged ≥65 years.
Patients aged ≥65 years with positive blood cultures between April 1, 2015, and March 31, 2018, were divided into three groups: pre-old (65–74 years), old (75–89 years), and super-old (≥90 years). Characteristics based on medical exposure, including CA, HCA, and HO, were also compared and factors related to mortality were identified.
Overall, 1716 episodes of bacteremia were identified in 1415 patients. Of the 1211 episodes without contamination, 32.8%, 54.3%, and 12.9% occurred in pre-old, old, and super-old patients. Central line-associated bloodstream infections were more common in pre-old patients and urinary tract infections in the old and super-old. The 7-day mortality rates in the pre-old, old, and super-old groups were 7.4%, 5.8%, and 14.2% (P = 0.002), respectively. Multivariable logistic regression showed that super-old age (adjusted odds ratio, aOR: 2.09 [1.13–3.88], P = 0.019) and HO bacteremia (aOR: 1.97 [1.18–3.28], P = 0.010) were independent risk factors for 7-day mortality. Infectious disease consultation had a protective effect on 7-day mortality (aOR: 0.59 [0.35–0.99], P = 0.047).
The epidemiology of bacteremia differs among older people; thus, they should not be treated as a single entity. A careful approach is needed for the optimal management of bacteremia in these vulnerable patients.
Clinical outcomes associated with blood-culture contamination are not affected by utilization of a rapid blood-culture identification system
2023, Infection Control and Hospital Epidemiology
Development of a duplex droplet digital PCR assay for the detection of Burkholderia cepacia complex and Stenotrophomonas maltophilia in bloodstream infections
2024, Microbiology Spectrum

View all citing articles on Scopus

: Funding: None.

: Conflict of Interest: None.

: Authorship: All authors had access to the data and a role in writing the manuscript.

: This research was supported in part by a grant from the Department of Veteran Affairs Special Fellowship Program in Health Services Research.

View full text

Clinical research studyThe Clinical and Prognostic Importance of Positive Blood Cultures in Adults

Abstract

Background

Methods

Results

Conclusions

Section snippets

Study Design

Study Cohort

Patient Characteristics

Discussion

Acknowledgments

Diagn Microbiol Infect Dis

Diagn Microbiol Infect Dis

Am J Med

J Chronic Dis

The clinical significance of positive blood cultures: a comprehensive analysis of 500 episodes of bacteremia and fungemia in adults. I. Laboratory and epidemiologic observations

Rev Infect Dis

The clinical significance of positive blood cultures: a comprehensive analysis of 500 episodes of bacteremia and fungemia in adultsII. Clinical observations, with special reference to factors influencing prognosis

Rev Infect Dis

The clinical significance of positive blood cultures in the 1990s: a prospective comprehensive evaluation of the microbiology, epidemiology, and outcome of bacteremia and fungemia in adults

Clin Infect Dis

Epidemiology and outcome of nosocomial and community-onset bloodstream infection

J Clin Microbiol

Nosocomial bloodstream infections in US hospitals: analysis of 24,179 cases from a prospective nationwide surveillance study

Clin Infect Dis

Nosocomial bloodstream infections in United States hospitals: a three-year analysis

Clin Infect Dis

Optimal testing parameters for blood cultures

Clin Infect Dis

Health care-associated bloodstream infections in adults: a reason to change the accepted definition of community-acquired infections

Ann Intern Med

Clinical research study
The Clinical and Prognostic Importance of Positive Blood Cultures in Adults