Routine Use of Anaerobic Blood Culture Bottles for Specimens Collected from Adults and Children Enhances Microorganism Recovery and Improves Time to Positivity

A mathematical model to estimate the probability of blood cultures positive for pyogenic streptococci

Aims

The aim of this study was to assess the possible use of time to positivity (TTP) of blood cultures (BCs) collected at the Emergency Department (ED) to estimate the probability of pyogenic streptococci versus other Gram positive cocci in pairs and chains, such as Streptococcus pneumoniae, other viridans group streptococci or enterococci.

Methods

All patients 18 years of age or older evaluated at the ED from whom BCs were collected and were positive for Gram positive cocci in pairs and chains at the microscopic examination, were included in the study. The BCs included were collected by venipuncture, were mono-microbial and were the first bottles that flagged positive in each set. Complete blood count requested simultaneously with BCs along with medical history taken by the ED physician were also evaluated.

Results

In our case series, all BCs positive for Gram positive cocci in pairs or chains at microscopic examination with a TTP ≤6.3 hours were consistent with a pyogenic streptococcus (100% specificity; 95% CI: 92.7-100). Consequently, a TTP ≤6.3 hours has a 100% positive predictive value (95% CI: 30.9-100). Conversely, no pyogenic streptococci were recovered from positive BCs with a TTP >12.6 hours. Therefore, as screening test, it has 100% sensitivity (95% CI: 77-100) and 100% negative predictive value (95% CI: 83.4-100). The binomial logistic regression model showed how as TTP increases, in BCs positive for Gram positive cocci in pairs and chains at the microscopic examination, the probability of a positive result for pyogenic streptococci decreases (odds ratio: 0.548; 95% confidence interval: 0.387-0.775; P=0.001).

Conclusions

The results of this study are an adjunctive tool to clinical aspects and fast microbiology laboratory tests to help assessing the likelihood of a positive blood culture for pyogenic streptococci.

Utility of anaerobic blood cultures in the clinical management of infectious patients

Paired aerobic/anaerobic cultures are routinely performed for the diagnosis of bacteraemia. This study aimed to assess the utility of anaerobic cultures in the management of infectious patients. All positive blood cultures taken from adult patients in a French hospital between November 2018 and March 2020 were evaluated. Clinical and microbiological data were collected for all patients with a positive anaerobic culture. Among the 17,272 positive pairs, 1402 included an anaerobic culture (8 %). In the 487 patients with anaerobic bacteraemia, the most commonly detected microorganisms were Enterobacterales (45 %), Staphylococcus aureus (16 %) and obligate anaerobes (6 %). In the 30 patients with obligate anaerobic bacteraemia, the most commonly detected bacterial species were Bacteroides spp. (30 %). When the bacteraemia-causing microorganism grew in both cultures (76 %), the anaerobic culture became positive prior to the aerobic culture in 54 % of cases-mainly for Enterobacterales and S. aureus. Our findings support the utility of performing anaerobic cultures.

Microbiological diversity among patients with Lemierre syndrome and clinical implications: an individual patient-level analysis

PURPOSE

Lemierre syndrome is a rare condition traditionally defined by bacterial infection of the head/neck region, local thrombophlebitis, and septic embolism. Although in most cases Fusobacterium necrophorum is isolated, it is questionable whether the presence of this microbe is mandatory for diagnosis. In this study, we investigated microorganisms isolated in cases of Lemierre syndrome and their association with demographical and clinical features.

METHODS

We conducted an analysis of individual patient data from 712 patients diagnosed with Lemierre syndrome. Demographics, clinical presentation, treatment strategies, and outcomes according to different pathogens were evaluated.

RESULTS

Among a total of 712 patients, in 574 cases bacterial growth was detected. In 415 patients Fusobacterium spp. was isolated, in 108 either Streptococcus spp. or Staphylococcus spp., and in 51 other bacteria. Patients with different bacteria differed markedly in age, site of preceding infections, clinical presentation, and treatment. Fusobacterium spp. was typically isolated in younger patients (69% of patients aged 16 to 30 years) while Streptococcus spp. and Staphylococcus spp. were more prevalent in older subjects (30% of patients aged over 45 years). Of all cases with Fusobacterium spp., 63% had a thrombosis of the internal jugular vein and 91% septic embolism, compared with 94% and 69%, respectively, in cases with Streptococcus spp. or Staphylococcus spp.

CONCLUSION

In contrast to the available literature, our study suggests that Lemierre syndrome may be caused by multiple bacterial species, and that the clinical presentation and course may vary according to the specific bacterial species involved.

Rapid molecular assays versus blood culture for bloodstream infections: a systematic review and meta-analysis

Background

Timely management of sepsis with early targeted antimicrobial therapy improves patient outcomes. Rapid molecular assays (RMAs) have emerged, enabling the detection of bloodstream infection (BSI) with a shorter turnaround time than blood cultures (BCs). The accuracy of several RMAs has not been comprehensively reviewed. We aimed to identify commercial RMAs reported in the literature and evaluate their diagnostic performance compared to BC.

Methods

A systematic review and meta-analysis was conducted, covering MEDLINE, Cochrane Library, Embase, and Web of Science from inception to September 23, 2024. Eligible studies included patients with suspected or documented BSI, tested with both an RMA (turnaround time of ≤12 h, targeting ≥20 pathogens) and BC. Non-original research articles and animal studies were excluded. The primary outcomes were pooled sensitivity and specificity of RMAs for pathogen detection compared to BC. Bivariate analysis was used to produce summary receiver operating characteristic plots and diagnostic metric measures stratified by different units of analysis (sample versus patient), RMA types, and patient populations. Risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) and Quality Assessment of Diagnostic Accuracy Studies-Comparative (QUADAS-C) tools. The study was registered with PROSPERO, CRD42022377280.

Findings

A total of 63,916 articles were identified, of which 104 were included in the qualitative synthesis and 75 in the quantitative synthesis, covering 17,952 samples and 11,393 patients analyzed separately. Eleven RMAs were identified, with four included in the RMA-based subgroup analysis (LightCycler SeptiFast Test MGRADE®, IRIDICA BAC BSI assay, SepsiTest, MagicPlex Sepsis Test) and five additional ones in the pooled analysis (UMD-SelectNA, VYOO®, MicrobScan assay, MicrobScan-Kairos24/7, REBA Sepsis-ID test). Two RMAs were included in the qualitative synthesis only (InfectID-BSI, Pilot Gene Technology droplet digital polymerase chain reaction). Pooled specificity of RMAs was higher (0.858, 95% confidence interval (CI) 0.830-0.883) than sensitivity (0.659, 95% CI 0.594-0.719) by patient. Sensitivities varied by RMA type from 0.492 (95% CI 0.390-0.594, MagicPlex Sepsis Test) to 0.783 (95% CI 0.662-0.870, IRIDICA BAC BSI assay) by patient. Specificities varied more by patient population, ranging from 0.811 (95% CI 0.716-0.879) in the intensive care population to 0.892 (95% CI 0.838-0.930) in the emergency department population, by patient. Similar metrics were observed when the analysis was done by sample. Risk of bias was judged to be high in all included articles.

Interpretation

Despite their shorter turnaround time, low sensitivity means RMAs cannot replace BCs. However, our data indicate that RMAs may have value as an add-on test by increasing pathogen detection rates. Higher-sensitivity RMAs are needed which could possibly be achieved by expanding pathogen coverage and increasing blood sample volumes. High-quality implementation studies and standardized reporting are required to assess the clinical advantages of RMAs.

Funding

Centre for Translational Medicine, Semmelweis University.

Every Crisis Is an Opportunity: Advancing Blood Culture Stewardship During a Blood Culture Bottle Shortage

The current manufacturing disruption of BACTEC blood culture bottles has drawn attention to diagnostic stewardship around blood culture utilization. In this perspective, we offer strategies for implementing blood culture stewardship using a graded approach based on a hospital's blood culture bottle supply. These strategies should inform plans to mitigate the impact of the shortage on patient care and reinforce fundamental principles of blood culture stewardship.

Microbiological performance and adherence in blood culture protocols: The role of a second anaerobic bottle

Background

Bacteremia represents high rates of morbidity and mortality, especially in developing countries, highlighting the need for a diagnostic method that allows prompt and appropriate patient treatment. This study compared microbiological performance and adherence of two blood culture protocols for the diagnosis of bacteremia.

Methods

Quasi-experimental study conducted between June 2022 and February 2023. Two blood culture protocols were evaluated. Protocol 1 included two aerobic bottles and one anaerobic bottle. Protocol 2 included two aerobic and two anaerobic bottles. Protocols were analyzed in three phases: evaluation of protocol 1 (Phase 1); evaluation of protocol 1 plus educational activities for healthcare staff (Phase 2) and evaluation of protocol 2 (Phase 3).

Results

342 patients and 1155 blood culture bottles (732 aerobic and 423 anaerobic) were included. Positivity was 17.6 %, 22.8 % and 19.4 % in phases 1, 2 and 3, respectively. Among patients with bacteremia, 84.5 % had positive anaerobic bottles, with 9.9 % showing growth only in this bottle. The contamination rates were 1.9 %, 0.3 %, and 0.8 % for each phase, mainly in aerobic bottles. Median positivity time was 11 h for both bottes aerobic and anaerobic. Overall nursing adherence increased from 13.1 % in Phase 1, 25.9 % in Phase 2, and 28.1 % in Phase 3 (p = 0.009).

Conclusions

The findings indicate that adding a second anaerobic bottle does not enhance blood culture positivity. Rather than increasing bottle quantity, staff training might be a more effective approach to optimize results.

Utility of Anaerobic Blood Cultures in Neonatal Sepsis Evaluation

BACKGROUND

Clinicians variably obtain anaerobic blood cultures as part of sepsis evaluations in the neonatal intensive care unit (NICU). Our objective was to determine if anaerobic blood culture bottles yielded clinically relevant information by either recovering pathogens exclusively or more rapidly than the concurrently obtained aerobic culture bottle in the NICU.

METHODS

A retrospective cohort study of blood cultures obtained from infants admitted to the NICU from August 01, 2015 to August 31, 2023. Standard practice was to inoculate 2 mL of blood divided equally between an aerobic and an anaerobic culture bottle. We analyzed positive blood cultures where both aerobic and anaerobic bottles were obtained and compared pathogen recovery and time to positivity between the bottles.

RESULTS

During the study period, 4599 blood cultures were obtained from 3665 infants, and 265 (5.8%) were positive. Of these, 182 cultures were sent as aerobic-anaerobic pairs and recovered pathogenic organisms. Organisms were recovered exclusively from the anaerobic bottle in 32 (17.6%) cultures. Three organisms were obligate anaerobes; the rest were facultative anaerobes including Coagulase-negative staphylococci (40.6%), Escherichia coli (15.6%), and Staphylococcus aureus (15.6%). Cultures with exclusive recovery in the anaerobic bottle were more frequently obtained ≤3 days after birth, compared to other cultures (31.3% vs 15.3%, P = .03). When both bottles recovered the pathogen (n = 113), the anaerobic bottle had a shorter time to positivity in 76 (67.3%) cultures.

CONCLUSIONS

Including anaerobic culture bottles could lead to the identification of pathogens not recovered in the aerobic bottle, as well as earlier identification of pathogens.

A case of bacteremia caused by Dialister micraerophilus with Enterocloster clostridioformis and Eggerthella lenta in a patient with pyometra

BACKGROUND

Infection by Dialister micraerophilus, an obligate anaerobic gram-negative bacillus, has rarely been described, and its clinical characteristics remain unclear.

CASE PRESENTATION

We report a case of bacteremia caused by D. micraerophilus, Enterocloster clostridioformis, and Eggerthella lenta in a 47-year-old woman, associated with pyometra. D. micraerophilus was identified using 16S rRNA gene sequencing and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. D. micraerophilus was detected by polymerase chain reaction using D. micraerophilus-specific primers and E. clostridioformis and E. lenta was isolated from the drainage pus sample obtained from the pyometra uterus. The patient achieved a cure after abscess drainage and 2-week antibiotic treatment.

CONCLUSIONS

To the best of our knowledge, this is the first report of D. micraerophilus bacteremia. D. micraerophilus may be associated with gynecological infections. Clinicians should consider both oral and gynecological sites when searching to identify the focus of D. micraerophilus infection.