Estimation of missed bloodstream infections without the third blood culture set: a retrospective observational single-centre study

Deficits in blood culture collection in the emergency department if sepsis is suspected: results of a retrospective cohort study

PURPOSE

Blood cultures (BCs) are key for pathogen detection in septic patients. We investigated the extent to which sampling was performed and what factors were associated with the absence of general or inadequate BC sampling.

METHODS

We conducted a retrospective cohort study of hospitalized patients with sepsis admitted to one of three EDs in 2018. Primary outcome was the extent of general BC collection of at least 1 set. Secondary outcome was the extent of adequate BC sampling, defined as ≥ 2 sets before antibiotic therapy (AT). Multivariable logistic regression analysis was performed to identify factors associated with deficits in both outcomes.

RESULTS

1143 patients were analyzed. BCs were collected from 946 patients. Single BCs were taken from 520 patients, ≥ 2 sets from 426 patients. Overall, ≥ 2 BCs were taken from 349 patients before AT. BC sampling before AT occurred significantly more frequently when ≥ 2 BC sets were taken rather than a single one (81.9%, versus 68.4%, p < 0.001) and this also led to the highest pathogen detection rate in our cohort (65.6%). A body temperature of ≥ 38 °C was the a supporting factor for general and adequate BC collection in all three EDs. Retrospective analysis of 533 patients showed that the qSOFA score had no influence on general or adequate BC collection.

CONCLUSION

Data on everyday clinical practice in the pre-analytical phase of microbiological diagnostics shows considerable deficits and indicates the need for more implementation of best practice. The variations identified in BC sampling between EDs should be further investigated.

Retrospective cohort study comparing two versus three blood culture sets in people who inject drugs

BACKGROUND

The current standard of drawing two vs three blood culture sets lacks adequate guidance. Because people who inject drugs are at higher risk for bacteraemia and life-threatening infection, consideration of a third blood culture becomes more important.

AIM

To investigate the risks and benefits of obtaining two versus three blood culture sets.

METHODS

Retrospective cohort study of adults who inject drugs at a multicentre catch-net hospital system from 2017-2022.

FINDINGS

998 people who inject drugs and 2278 blood culture sets were analysed. There were 1618 episodes with two blood culture sets and 660 episodes with three. A potential benefit of adding a third blood culture was seen in 30 (4.5%) episodes. However, only 13 (2.0%) episodes showed pathogen-identifying benefit, as 17 (2.6%) involved known inadequately treated infections or the same pathogen in another culture. The number of blood culture sets needed to achieve diagnostic benefit was 51. There were more contaminants for three blood culture sets (65, 9.8%) than for two (114, 7.0%) (p < 0.00001). By adding a third blood culture, the risk of a contaminant increased by 39.7%; the number of blood culture sets needed to find a contaminant was 36. Of 122 episodes with only contaminants and available for analysis, 111 (91.0%) experienced at least one complication. 33 (27.0%) patients experienced either prolonged admission, readmission, or unnecessary antibiotic administration.

CONCLUSIONS

The benefits of possibly isolating a pathogen from a third blood culture set do not universally outweigh the risks for contaminant growth for people who inject drugs. A third blood culture should be considered in specific clinical scenarios (i.e. inadequately treated endocarditis and osteomyelitis).

The Yield of One vs. Two Blood Cultures in Children: Under-Detection and Over-Testing

We aimed to determine whether obtaining two blood cultures (BCs) instead of one improved the detection of bloodstream infections (BSIs) in children. For this descriptive study, we used surveillance data collected in 2019-2021 from all Israeli hospitals serving children. The sample included 178,702 culturing episodes. One BC was taken in 90.1% of all episodes and 98.2% of episodes in the emergency department. A true pathogen was detected in 1687/160,964 (1.0%) of single-culture episodes and 1567/17,738 (8.9%) of two-culture episodes (p < 0.001). The yield was significantly different even when considering only the first BC in two-culture episodes: 1.0% vs. 7.5%. Among 1576 two-culture episodes that were positive for a true pathogen, the pathogen was detected only in the second culture in 252 (16.0%). We estimated that if a second culture had been taken in all episodes, an additional 343 BSIs by a true pathogen would have been detected. Among 1086 two-culture episodes with commensal bacteria, the second BC was sterile in 530 (48.8%), suggesting contamination. A commensal was isolated in 3094/4781 (64.7%) positive single-culture episodes, which could represent BSI or contamination. The yield of a single BC bottle was low, reflecting both lower sensitivity of a single bottle and the taking of single bottles in patients with a low probability of BSI.

Impact of a strategy based on unique blood culture sampling on contamination rate and detection of bloodstream infections in critically ill patients

BACKGROUND

Unique blood culture (UBC) has been proposed to limit the number of venipuncture and to decrease the risk of BC contaminations (BCC) without affecting their yield. We hypothesized that a multi-faceted program based on UBC in the ICU may reduce the rate of contaminants with a similar performance for bloodstream infections (BSI) identification.

METHODS

In a before and after design, we compared the proportion of BSI and BCC. A first 3-year period with multi-sampling (MS) strategy followed by a 4-month washout period, where staff received education and training for using UBC, and a 32-month period, where UBC was routinely used, while education and feedback were maintained. During the UBC period, a large volume of blood (40 mL) was sampled through a unique venipuncture with additional BC collections discouraged for 48 h.

RESULTS

Of the 4,491 patients included (35% female patients, mean age 62 years) 17,466 BC were collected. The mean volume of blood per bottle collected increased from 2.8 ± 1.8 mL to 8.2 ± 3.9 mL between the MS and UBC periods, P < 0.01. A 59.6% reduction (95% CI 56.7-62.3; P < 0.001) of BC bottles collected per week was observed between the MS and UBC periods. The rate of BCC per patient decreased between the two periods from 11.2% to 3.8% (73.4% reduction; P < 0.001) for the MS and UBC periods, P < 0.001. Meanwhile, the rate of BSI per patient remained stable at 13.2% and 13.2% for the MS and UBC periods, P = 0.98.

CONCLUSIONS

In ICU patients, a strategy based on UBC reduces the contamination rate of cultures without affecting their yield.

Faster infection diagnostics for intensive care unit (ICU) patients

INTRODUCTION

: The patient admitted to intensive care units (ICU) is critically ill, to some extent immunosuppressed, with a high risk of infection, sometimes by multidrug-resistant microorganisms. In this context, the intensivist expects from the microbiology service quick and understandable information so that appropriate antimicrobial treatment for that particular patient and infection can be initiated.

AREAS COVERED

: In this review of recent literature (2015-2021), we identified diagnostic methods for the most prevalent infections in these patients through a search of the databases Pubmed, evidence-based medicine online, York University reviewers group, Cochrane, MBE-Trip, and Sumsearch using the terms: adult, clinical laboratory techniques, critical care, early diagnosis, microbiology, molecular diagnostic techniques, spectrometry and metagenomics.

EXPERT OPINION

: There has been an exponential surge in diagnostic systems used directly on blood and other samples to expedite microbial identification and antimicrobial susceptibility testing of pathogens. Few studies have thus far assessed their clinical impact; final outcomes will also depend on preanalytical and post-analytical factors. Besides, many of the resistance mechanisms cannot yet be detected with molecular techniques, which impairs the prediction of the actual resistance phenotype.

Nonetheless, this is an exciting field with much yet to explore.

Single-site sampling versus multi-site sampling for blood cultures; A retrospective clinical study

Objectives The performance of blood cultures (BC) relies on optimal sampling. Sepsis guidelines do not specify which sampling protocol to use, but recommend two sets of BC bottles, each set containing one aerobic and one anaerobic bottle. For the single-site sampling (SSS) protocol, only one venipuncture is performed for all four bottles. The predominating multi-site sampling (MSS) protocol implies that BC bottles are collected from two separate venipuncture sites. The aim of this study was to compare SSS and MSS. Primary outcomes were number of BC sets collected, sample volume and diagnostic performance. Methods This was a retrospective clinical study comparing BC results in an emergency department before and after changing the sampling protocol to SSS from MSS. All BC samples were incubated in the BacT/ALERT BC system. Results The analysis included 5,248 patients before and 5,364 patients after the implementation of SSS. There was a significantly higher proportion of positive BCs sampled with SSS compared to MSS, 1,049/5,364 (19.56%) and 932/5,248 (17.76%) respectively (P=0.018). This difference was due to a higher proportion of solitary BC sets (two BC bottles) in MSS. Analyzing only patients with the recommended four BC bottles, there was no difference in positivity. SSS had a higher proportion of BC bottles with the recommended sample volumes of 8-12 ml than MSS (P<0.001). Conclusions Changing the sampling protocol to SSS from MSS resulted in higher positivity rates, higher sample volume and fewer solitary BC sets. These advantages of SSS should be considered in future sepsis guidelines.

Impact of 24/7 loading of blood culture bottles in a new automated incubator on the diagnosis of bloodstream infections

Blood culturing (BC) remains the gold standard for bloodstream diagnosis but its workflow is slow. We aimed reducing this time by implementing a new automated incubator with a 24/7 BC workflow. With this new strategy, time to incubation was shorter (1.52 h vs 6.82 h), positivity rates were higher (10.6% vs 8.9%, p<0.05), and the number of BSI diagnostics increased (16.1% vs 13.8% patients and 2.3 vs 1.9 density episode per 1000 hospital days). Our results show that implementing automatic loading of BC bottles with a 24/7 strategy not only shortened time to diagnosis but significantly increased the BSI diagnosis rate.

Coinfections among hospitalized patients with covid-19 in the first pandemic wave

BACKGROUND

COVID19 is the novel respiratory illness caused by SARS-CoV-2. The presence of other potentially pathogenic microorganisms could worsen the prognosis of these patients.

AIM

The study aims to describe coinfections in COVID-19 patients and contrast it between standard ward and critical care patients at Hospital Central de la Defensa Gómez Ulla (HCDGU).

METHODS

A retrospective study was carried out of patients with COVID-19 confirmed with RTPCR admitted to the HCDGU from March 5, 2020 to May 7 of 2020.

FINDINGS

Of a total of 703 patients with COVID-19, 75(10.7%) had other microbiologically confirmed infections: 9% (58/648) in standard ward patients and 31.5%(17/54) in critical care patients. In total 86 samples of the 75 patients presented some microorganism; clinically relevant bacteraemias, 50%, respiratory cultures, 32.6% and pneumococcal positive antigens, 17.4%.

CONCLUSIONS

We found a low frequency of microorganism coinfection in COVID-19 patients, however in critical care these coinfections increased considerably.

Collection, transport and storage procedures for blood culture specimens in adult patients: recommendations from a board of Italian experts

Bloodstream infections (BSIs) remain a potentially life-threatening condition. The gold standard for the diagnosis of BSI is still blood cultures (BCs), and the diagnostic yield depends on clinical and technical factors that have an impact on collection and transportation. Hence, monitoring of the entire pre-analytical process from blood collection to transportation to the microbiology laboratory is critical. To optimize the clinical impact of the diagnostic and therapeutic procedures, a multidisciplinary approach and univocal protocols are mandatory. A board of specialists discussed the available evidence on the pre-analytical process and produced the present document to guide physicians and nurses on the ideal execution of BC: (1) timing and preparation for blood collection; (2) skin antisepsis; (3) blood volume; (4) sampling method and safety; (5) medium to be used; (6) time to BC transportation; and (7) quality assurance and quality management.

Strategies for increasing diagnostic yield of community-onset bacteraemia within the emergency department: A retrospective study

Bloodstream infections (BSI) are associated with high mortality. Therefore, reliable methods of detection are of paramount importance. Efficient strategies to improve diagnostic yield of bacteraemia within the emergency department (ED) are needed. We conducted a retrospective analysis of all ED encounters in a high-volume, city-centre university hospital within Germany during a five-year study period from October 2013 to September 2018. A time-series analysis was conducted for all ED encounters in which blood cultures (BCs) were collected. BC detection rates and diagnostic yield of community-onset bacteraemia were compared during the study period (which included 45 months prior to the start of a new diagnostic Antibiotic Stewardship (ABS) bundle and 15 months following its implementation). BCs were obtained from 5,191 out of 66,879 ED admissions (7.8%). Bacteraemia was detected in 1,013 encounters (19.5% of encounters where BCs were obtained). The overall yield of true bacteraemia (defined as yielding clinically relevant pathogens) was 14.4%. The new ABS-related diagnostic protocol resulted in an increased number of hospitalised patients with BCs collected in the ED (18% compared to 12.3%) and a significant increase in patients with two or more BC sets taken (59% compared to 25.4%), which resulted in an improved detection rate of true bacteraemia (2.5% versus 1.8% of hospital admissions) without any decrease in diagnostic yield. This simultaneous increase in BC rates without degradation of yield was a valuable finding that indicated success of this strategy. Thus, implementation of the new diagnostic ABS bundle within the ED, which included the presence of a skilled infectious disease (ID) team focused on obtaining BCs, appeared to be a valuable tool for the accurate and timely detection of community-onset bacteraemia.

Best Practices of Blood Cultures in Low- and Middle-Income Countries

Bloodstream infections (BSI) have a substantial impact on morbidity and mortality worldwide. Despite scarcity of data from many low- and middle-income countries (LMICs), there is increasing awareness of the importance of BSI in these countries. For example, it is estimated that the global mortality of non-typhoidal Salmonella bloodstream infection in children under 5 already exceeds that of malaria. Reliable and accurate diagnosis of these infections is therefore of utmost importance. Blood cultures are the reference method for diagnosis of BSI. LMICs face many challenges when implementing blood cultures, due to financial, logistical, and infrastructure-related constraints. This review aims to provide an overview of the state-of-the-art of sampling and processing of blood cultures, with emphasis on its use in LMICs. Laboratory processing of blood cultures is relatively straightforward and can be done without the need for expensive and complicated equipment. Automates for incubation and growth monitoring have become the standard in high-income countries (HICs), but they are still too expensive and not sufficiently robust for imminent implementation in most LMICs. Therefore, this review focuses on "manual" methods of blood culture, not involving automated equipment. In manual blood cultures, a bottle consisting of a broth medium supporting bacterial growth is incubated in a normal incubator and inspected daily for signs of growth. The collection of blood for blood culture is a crucial step in the process, as the sensitivity of blood cultures depends on the volume sampled; furthermore, contamination of the blood culture (accidental inoculation of environmental and skin bacteria) can be avoided by appropriate antisepsis. In this review, we give recommendations regarding appropriate blood culture sampling and processing in LMICs. We present feasible methods to detect and speed up growth and discuss some challenges in implementing blood cultures in LMICs, such as the biosafety aspects, supply chain and waste management.