Time-to-positivity-based discrimination between Enterobacteriaceae, Pseudomonas aeruginosa and strictly anaerobic Gram-negative bacilli in aerobic and anaerobic blood culture vials

Effects of Blood Culture Aerobic/Anaerobic Bottle Collection Patterns from Both Sides of the Body on Positive Blood Culture Rate and Time-to-Positivity

Background

Although the principles for blood cultures (BCs) guidelines provide a recommendation for collection patterns, the complexity of clinical practice occasionally prompts clinicians to adopt non-standard collection patterns. Here, we investigate the influences of different BC collection patterns on detection of pathogens.

Methods

The BC collection patterns of 96 hospitals were surveyed online. And a retrospective study of BC data from a tertiary hospital was conducted.

Results

The results showed that 53.1% of hospitals adopted the recommended patterns. Among the 1439 episodes of true-positive BCs, 67.4% were found in both the left- and right-sided bottles; 58.2% were found in both aerobic and anaerobic bottles.

Conclusion

The present study suggested that the rate of standard collection patterns of blood culture was low and the non-standard collection patterns were associated with decreased detection of pathogens. Simultaneous collection of blood on the left and right sides was recommended as an effective pattern of BC collection.

Prognostic role of time to positivity of blood culture in children with Pseudomonas aeruginosa bacteremia

BACKGROUND

Pseudomonas aeruginosa (P. aeruginosa) is a major Gram-negative pathogen, which has been reported to result in high mortality. We aim to investigate the prognostic value and optimum cut-off point of time-to-positivity (TTP) of blood culture in children with P. aeruginosa bacteremia.

METHODS

From August 2014 to November 2018, we enrolled the inpatients with P. aeruginosa bacteremia in a 1500-bed tertiary teaching hospital in Chongqing, China retrospectively. Receiver operating characteristic (ROC) analysis was used to determine the optimum cut-off point of TTP, and logistic regression were employed to explore the risk factors for in-hospital mortality and septic shock.

RESULTS

Totally, 52 children with P. aeruginosa bacteremia were enrolled. The standard cut-off point of TTP was18 h. Early TTP (≤18 h) group patients had remarkably higher in-hospital mortality (42.9% vs 9.7%, P = 0.014), higher incidence of septic shock (52.4% vs12.9%, P = 0.06), higher Pitt bacteremia scores [3.00 (1.00-5.00) vs 1.00 (1.00-4.00), P = 0.046] and more intensive care unit admission (61.9% vs 22.6%, P = 0.008) when compared with late TTP (> 18 h) groups. Multivariate analysis indicated TTP ≤18 h, Pitt bacteremia scores ≥4 were the independent risk factors for in-hospital mortality (OR 5.88, 95%CI 1.21-21.96, P = 0.035; OR 4.95, 95%CI 1.26-27.50, P = 0.024; respectively). The independent risk factors for septic shock were as follows: TTP ≤18 h, Pitt bacteremia scores ≥4 and hypoalbuminemia (OR 6.30, 95%CI 1.18-33.77, P = 0.032; OR 8.15, 95%CI 1.15-42.43, P = 0.014; OR 6.46, 95% CI 1.19-33.19 P = 0.031; respectively).

CONCLUSIONS

Early TTP (≤18 hours) appeared to be associated with worse outcomes for P. aeruginosa bacteremia children.

Clinical relevance of Clostridium bacteremia: An 8-year retrospective study

Clostridium spp. are recovered from 25% of the blood culture positive with anaerobes. However, the clinical relevance of Clostridium bacteremia has been controverted in the literature, particularly for C. perfringens. We aimed to evaluate the clinical relevance of Clostridium bacteremia, either due to C. perfringens or other Clostridium species, and to identify the risk factors of mortality in these patients. A retrospective cohort study was conducted from January 2010 to April 2018. All the patients with at least one blood culture positive with any Clostridium species were included. Eighty-one patients with a least one blood culture positive with any Clostridium species were included. Seventy patients (86.4%) fulfilled the criteria for clinically relevant bacteremia. Bacteremia due to C. perfringens tended to be less clinically relevant than other Clostridium species but this was not statistically significant (76% vs 91.2%, P = 0.09). In case of clinically relevant bacteremia, the 30-day mortality rate was 31.4%. In multivariate analysis, adequate empiric antimicrobial therapy was significantly associated with survival (P = 0.03). In conclusion, bacteremia due to C. perfringens or other Clostridium species is usually clinically relevant. This finding was also supported by an improved survival at 30 days when adequate empiric antimicrobial therapy was administered.

Value of Time to Positivity of Blood Culture in Children with Bloodstream Infections

Objective

This study was to investigate the microbiological characteristics and the relationship between the time to positivity (TTP) of blood cultures and different bacterial species and to assess the clinical value of TTP in children with bloodstream infections (BSIs).

Methods

The TTP of all the blood cultures from children with suspected BSIs was retrospectively collected in 2016. The microbiological characteristics and the relationship between the TTP of blood cultures and different bacterial species were also analyzed.

Results

A total of 808 strains were isolated from 15835 blood cultures collected, and 145 (17.9%) were Gram-negative, 636 (78.7%) were Gram-positive, and 27 (3.3%) were fungi. The bacteria were divided into definite pathogens (174), possible pathogens (592), fungi (27), and contaminants (15). The average TTP of all positive blood cultures was 30.97 and ranged from 3.23 h to 92.73 h. The TTP of Gram-negative strains was significantly shorter than that of Gram-positive strains (P < 0.001) and fungi (P = 0.032). The mean TTP for E. coli (15.60 h) was shortest within the group of Gram-negative isolates, and the mean TTP for Streptococcus (17.34 h) within the group of Gram-positive isolates. Significant difference of the TTP was detected in methicillin-resistant vs methicillin-susceptible S. aureus, extended-spectrum beta-lactamases (ESBLs) positive vs negative Enterobacteriaceae, and extensive drug-resistant and non-XDR A. baumannii. The median TTP in patients with BSI was significantly shorter than in those without it (P < 0.001). ROC curve analysis indicated that the TTP cutoff value of CoNS, S. aureus, E. coli, and K. pneumoniae was 22.72 h, 19.6 h, 18.58 h, and 16.43 h, respectively, with most sensitive and specific predictor of BSIs.

Conclusions

Our data acknowledged that TTP is a valuable index for the early prognosis of BSIs. TTP not only provides additional utility as a general predictor of bacteria with smear result but also provides the implication of drug-resistant organisms.

Bloodstream Infections

Bacteremia and sepsis are conditions associated with high mortality and are of great impact to health care operations. Among the top causes of mortality in the United States, these conditions cause over 600 fatalities each day. Empiric, broad-spectrum treatment is a common but often a costly approach that may fail to effectively target the correct microbe, may inadvertently harm patients via antimicrobial toxicity or downstream antimicrobial resistance. To meet the diagnostic challenges of bacteremia and sepsis, laboratories must understand the complexity of diagnosing and treating septic patients, in order to focus on creating algorithms that can help direct a more targeted approach to antimicrobial therapy and synergize with existing clinical practices defined in new Surviving Sepsis Guidelines. Significant advances have been made in improving blood culture media; as yet no molecular or antigen-based method has proven superior for the detection of bacteremia in terms of limit of detection. Several methods for rapid molecular identification of pathogens from blood cultures bottles are available and many more are on the diagnostic horizon. Ultimately, early intervention by molecular detection of bacteria and fungi directly from whole blood could provide the most patient benefit and contribute to tailored antibiotic coverage of the patient early on in the course of the disease. Although blood cultures remain as the best means of diagnosing bacteremia and candidemia, complementary testing with antigen tests, microbiologic investigations from other body sites, and histopathology can often aid in the diagnosis of disseminated disease, and application of emerging nucleic acid test methods and other new technology may greatly impact our ability to bacteremic and septic patients, particularly those who are immunocompromised.

Clinical prognostic factors for time to positivity in cancer patients with bloodstream infections

PURPOSE

Time to positivity (TTP) has been used in recent years as a simple and rapid method for the additional characterization of the degree of bacteremia. However, prognostic factors for TTP in cancer patients with bloodstream infections have rarely been studied. The aim of this study was to investigate the clinical factors for TTP involving various isolated organisms in cancer patients.

METHODS

We analyzed 386 episodes of bloodstream infections (BSIs) in patients with or without cancer during a 19 month period. Information on age, gender, tumor type, ICU stay, organisms, multidrug resistance (MDR), TTP and outcome was collected. Multivariate logistic regression analysis was performed.

RESULTS

The mean TTP of Enterobacteriaceae in patients with hepatocellular carcinoma, gastroenterological cancer, and lung cancer was shorter than in non-cancer patients (9.86 ± 3.22, 10.05 ± 3.47, 8.85 ± 2.78 vs 13.11 ± 5.37 h). The mean TTP of nonfermentative bacilli in patients with lung cancer (12.37 ± 5.96 h) and hematologic diseases (8.72 ± 4.21 h) was also shorter than in non-cancer patients (20.74 ± 2.46 h), and the mean TTP of Staphylococcus isolates was significantly different between non-cancer patients (22.06 ± 3.71 h) and hematologic disease patients (11.93 ± 5.44 h). The presence of a benign tumor was a significant prognostic factor for a long TTP only in the Staphylococci group (OR 0.076, 95 % CI 0.014-0.412), according to multivariate analysis. MDR (OR 2.178, 95 % CI 1.196-4.239) was an independent significant predictor in the Enterobacteriaceae group, with a short TTP, and it was also a significant clinical factor for a long TTP in nonfermentative bacilli and the Staphylococci group (OR 5.037, 95 % CI 1.065-23.82; OR 0.167, 95 % CI 0.059-0.474).

CONCLUSION

Time to positivity provides useful diagnostic and prognostic information for the differentiation of frequently isolated organisms. This information may help clinicians to use the correct antibiotics in a timely manner to treat cancer patients with BSIs based on clinical factor analysis.

Time-to-positivity of blood culture: An independent prognostic factor of monomicrobial Pseudomonas aeruginosa bacteremia

BACKGROUND/PURPOSE

Pseudomonas aeruginosa bacteremia is an important cause of nosocomial infections with high morbidity and mortality. Time-to-positivity (TTP) of blood cultures is considered to be a predictor of the clinical outcome for bacteremia. The aim of the study is to investigate the relationship between TTP and clinical outcomes in patients with monomicrobial P. aeruginosa bacteremia.

METHODS

From January 2013 to June 2014, a retrospective cohort study was conducted in a 1200-bed tertiary care hospital. The cases of monomicrobial P. aeruginosa bacteremia were studied. TTP and clinical parameters were determined and analyzed.

RESULTS

In 139 cases of P. aeruginosa bacteremia, TTP ≤ 13 hours was associated with higher Pitt bacteremia scores (5.3 ± 4.2 vs. 2.3 ± 2.8, p < 0.001), severe sepsis (66.1% vs. 35.0%, p < 0.001), higher 30-day mortality rate (54.2% vs. 15.0%, p < 0.001), longer hospitalization in the survivors (25.6 ± 48.5 days vs. 16.3 ± 15.3 days, p = 0.16), and more admission to intensive care unit (27.2% vs. 16.3%, p = 0.14). Risk factors for 30-day mortality in the univariate analysis included corticosteroid exposure, primary bacteremia, concurrent pneumonia, a high Pitt bacteremia score, severe sepsis, and TTP ≤ 13 hours. In the multivariate analysis, primary bacteremia, a pulmonary origin of bacteremia, severe sepsis, and TTP ≤ 13 hours were independent risk factors for 30-day mortality.

CONCLUSION

In cases of monomicrobial P. aeruginosa bacteremia, a short TTP (≤ 13 hours) provides prognostic information, in addition to clinical parameters.

Direct RNA-based detection of CTX-M β-lactamases in human blood samples

Bloodstream infections with ESBL-producers are associated with increased mortality, which is due to delayed appropriate treatment resulting in clinical failure. Current routine diagnostics for detection of bloodstream infections consists of blood culture followed by species identification and susceptibility testing. In attempts to improve and accelerate diagnostic procedures, PCR-based methods have been developed. These methods focus on species identification covering only a limited number of ESBL coding genes. Therefore, they fail to cover the steadily further evolving genetic diversity of clinically relevant β-lactamases. We have recently designed a fast and novel RNA targeting method to detect and specify CTX-M alleles from bacterial cultures, based on an amplification-pyrosequencing approach. We further developed this assay towards a diagnostic tool for clinical use and evaluated its sensitivity and specificity when applied directly to human blood samples. An optimized protocol for mRNA isolation allows detection of specific CTX-M groups from as little as 100 CFU/mL blood via reverse transcription, amplification, and pyrosequencing directly from human EDTA blood samples as well as from pre-incubated human blood cultures with a turnaround time for test results of <7 h.

Time to positivity and detection of growth in anaerobic blood culture vials predict the presence of Candida glabrata in candidemia: a two-center European cohort study

This study shows the accuracy of exclusive or earlier growth in anaerobic vials to predict Candida glabrata in a large series of candidemic patients from two European hospitals using the Bactec 9240 system. Alternatively, C. glabrata can be predicted by a time to positivity cutoff value, which should be determined for each setting.

Time to positivity as prognostic tool in patients with Pseudomonas aeruginosa bloodstream infection

OBJECTIVES

The time to positivity (TTP), measured as the time span between the start of incubation and the alert signal from the blood culture device, has been described as useful tool of prognosis in patients suffering from blood stream infection with Staphylococcus aureus, Escherichia coli and Klebsiella pneumonia. The present study investigates the relationship between TTP and in-hospital mortality in patients with monomicrobial Pseudomonas aeruginosa blood stream infection (PA-BSI).

METHODS

From 2006 until 2012 a retrospective cohort study was undertaken in 3 hospitals in the region surrounding Tübingen, Germany. Seventy-four patients with monomicrobial PA-BSI were studied. TTP and clinical parameters were determined and analyzed by receiver operating characteristic (ROC) analysis and Cox regression.

RESULTS

The in-hospital mortality of our clinical cohort was 33.78%. In multivariate Cox regression, a TTP ≤ 18 h proved to be independently associated with mortality (HR 3.83, P = 0.012) along with SAPS II score (HR 1.04, P = 0.006), cardiac disease (HR 0.33, P = 0.008) and appropriate definitive antimicrobial treatment (HR 0.21, P = 0.013).

CONCLUSIONS

TTP is an easy-to-measure laboratory tool for prognosis in patients with monomicrobial PA-BSI, providing useful information in addition to clinical parameters.