Judicious utilization of healthcare resources: reducing unindicated pediatric anaerobic blood cultures in a pediatric hospital

Time to positivity of blood cultures in paediatric patients

AIM

Continuous monitoring of blood culture (BC) systems allows rapid detection of microbial growth. We aimed to determine differences in time to positivity (TTP) in BACTEC BC between organisms and whether a 36-h period was sufficient to detect all relevant pathogenic bacteria for children admitted to a tertiary care paediatric hospital.

METHODS

This was a retrospective audit of positive aerobic (AE) and anaerobic (AN) BC from paediatric inpatients with available TTP from 1 August 2016 to 2 January 2019. First positive BC per bacteraemia episode was analysed.

RESULTS

Overall, 649 BC were positive, of which 480 first positive BC were analysed: 246 AE (51.3%) only, 216 paired (45%) (108 AE and 108 AN) and 18 AN (3.8%) only. There were 372 episodes of bacteraemia in 340 patients. Median age was 19 months (interquartile range (IQR): 1.25-60). Median TTP for AE and AN cultures was 13.20 (IQR: 9.84-18.48) and 13.92 h (IQR: 10.32-17.04), respectively. Organisms were GNR 49.7%, GPC 29.6%, contaminants 14.5%, mixed 3.0%, other 2.4% and yeast 0.8%. Streptococcus agalactiae had the fastest median TTP in AE and AN cultures, followed by Escherichia coli (AE 8.88 vs. 10.20 h). For paired AE and AN cultures, TTP was faster for AE versus AN cultures (13.36 vs. 14.52 h, P = 0.001). A 36-h cut-off time captured 97.7% AE BC and 99.1% AN BC with pathogens, and 86.5% AE BC and 91.7% AN BC with contaminants, respectively.

CONCLUSIONS

GNR were the commonest pathogens in paediatric BC and faster growth was detected in AE versus AN cultures. By 36 h, >97.7% of BC were positive for pathogens versus 86.5% for contaminants.

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.

Pediatric Anaerobic Blood Culture Practices in Industrialized Countries

BACKGROUND

Routine anaerobic blood culture collection in febrile children is controversial, as clinicians try to account for the severe but relative infrequency of anaerobic bacteremia. Furthermore, clinical and laboratory practice variation among institutions may lead to potentially inaccurate epidemiological data. Our goal was to assess blood culture practices in pediatric patients throughout an international network of hospitals in industrialized countries.

METHODS

We conducted a survey of current clinical and laboratory practice patterns in a convenience sample of international institutions participating in 6 pediatric emergency research networks in the US, Canada, Europe, Australia, and New Zealand. A lead clinician at each institution queried institutional practices from the emergency department, pediatric intensive care unit, and oncology medical directors. The microbiology director at each institution completed the laboratory survey.

RESULTS

Sixty-five of 160 (41%) invited institutions participated in the survey. Routine anaerobic blood cultures are collected in 30% of emergency departments, 30% of intensive care units, and 48% of oncology wards. Reasons for restricting anaerobic culture collection included concerns regarding blood volume (51%), low pretest probability (22%), and cost-effectiveness (16%). The most common reasons institutions allow for selectively obtaining anaerobic cultures are clinical suspicion (64%) and patients who are immunosuppressed (50%). The microbiology survey showed variation in systems, although most use the BACTEC™ culture system and MALDI-TOF for organism identification.

CONCLUSIONS

There is broad variation in anaerobic blood culture practices among a network of pediatric hospitals in industrialized countries.

Yield of Anaerobic Blood Cultures in Pediatric Emergency Department Patients

BACKGROUND

Anaerobic bacteremia is rare in children and current recommendations advocate against the routine use of anaerobic cultures in children. However, the incidence of anaerobic bacteremia and the utility of anaerobic blood cultures in children have not been assessed in recent years. Our pediatric emergency department (PED) policy still supports the use of both aerobic and anaerobic blood cultures in all cases of suspected bacteremia. This allowed us to re-evaluate the yield of anaerobic cultures in PED settings.

METHODS

Retrospective data of all blood cultures taken in the PED in a single tertiary center from 2002 to 2016 were collected. The incidence and characteristics of children with positive anaerobic blood cultures were assessed. Risk factors for anaerobic bacteremia were defined.

RESULTS

Of the 68,304 blood culture sets taken during the study period, 971 (1.42%) clinically significant positive cultures were found. Pathogenic obligatory anaerobic bacteria were isolated in 33 (0.05%) cultures. The leading risk factors for anaerobic bacteremia were head and neck abscess and intra-abdominal infection. Of all the true positive cultures, 187 (22%) were only detected in the anaerobic culture and would have otherwise been missed.

CONCLUSIONS

True anaerobic bacteremia is extremely rare in children admitted to the PED. Nevertheless, using anaerobic cultures may increase the overall yield of blood cultures.

Diagnosis of Bloodstream Infections in Children

Identification of bloodstream infections is among the most critical tasks performed by the clinical microbiology laboratory. While the criteria for achieving an adequate blood culture specimen in adults have been well described, there is much more ambiguity in pediatric populations. This minireview focuses on the available pediatric literature pertaining to the collection of an optimal blood culture specimen, including timing, volume, and bottle selection, as well as rapid diagnostic approaches and their role in the management of pediatric bloodstream infections.