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Role of urine Gram stain in young febrile infants with a suspected urinary tract infection: a cohort study
  1. Borja Gomez1,
  2. Ana Mier2,
  3. Alberto Ugedo2,
  4. Amaia Aguirre-Quiñonero3,
  5. Javier Benito1,4,
  6. Santiago Mintegi1,4
  1. 1 Pediatric Emergency Department, Hospital Universitario Cruces, Biobizkaia Health Research Institute, Barakaldo, Spain
  2. 2 Pediatric Emergency Department, Hospital Universitario Cruces, Barakaldo, Spain
  3. 3 Department of Microbiology, Hospital Universitario Cruces, Barakaldo, Spain
  4. 4 Department of Pediatrics, Universidad del Pais Vasco, Bilbao, Spain
  1. Correspondence to Dr Borja Gomez, Pediatric Emergency Department, Cruces University Hospital, Barakaldo, 48903, Spain; borja.gomezcortes{at}osakidetza.eus

Abstract

Objective To analyse the performance of the urine Gram stain for predicting a positive urine culture (UC) in young infants with fever without source (FWS) and pyuria.

Design Observational study; secondary analysis of a prospective registry-based cohort study.

Setting Paediatric emergency department; tertiary teaching hospital.

Patients Infants ≤90 days old with FWS, pyuria and urine Gram stain requested seen between 2010 and 2022.

Main outcome measure Performance of the Gram stain, defined as positive if any bacteria were seen, for predicting urinary tract infection (UTI: UC by urethral catheterisation growing >10 000 CFU/mL of a single bacterial pathogen).

Results Among 367 febrile infants with pyuria, 281 (76.6%) had a positive Gram stain and 306 (83.3%) had a positive UC (277; 90.5% Escherichia coli).

Rates of positive UC in patients with positive and negative Gram stains were 97.2% and 38.4%, respectively (p<0.01), showing a sensitivity of 89.2% (95% CI: 85.2% to 92.2%) and a specificity of 86.9% (95% CI: 76.2% to 93.2%). Sensitivity was lower for diagnosing UTIs caused by bacteria other than E. coli (69.0% vs 91.3% for UTIs caused by E. coli; p<0.01).

Two (2.1%) of the 86 infants with negative Gram stains were diagnosed with bacteraemia unrelated to a UTI (Streptococcus pneumoniae and Staphylococcus aureus).

Conclusions Around a third of infants with pyuria and a negative Gram stain will eventually be diagnosed with a UTI. These patients have a higher rate of UTIs caused by bacteria other than E. coli. Bacterial infections other than UTIs should also be considered in such cases.

  • Emergency Care
  • Infectious Disease Medicine

Data availability statement

Data are available upon reasonable request. Deidentified participant data are available in a specific database. Researchers interested in developing a meta-analysis or a systematic review about the topic presented in this manuscript can contact with the first author to request additional data.

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Data availability statement

Data are available upon reasonable request. Deidentified participant data are available in a specific database. Researchers interested in developing a meta-analysis or a systematic review about the topic presented in this manuscript can contact with the first author to request additional data.

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Footnotes

  • X @MintegiSanti

  • Contributors BG conceptualised and designed the study, coordinated and supervised data collection, carried out the initial analyses, drafted the initial manuscript and critically reviewed and revised the manuscript. AM and AU collected data, carried out the initial analyses and critically reviewed and revised the manuscript. AA-Q and JB critically reviewed and revised the manuscript for important intellectual content. SM conceptualised and designed the study, designed the data collection instruments and critically reviewed and revised the manuscript for important intellectual content. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work. BG is the guarantor of this contributorship statement.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.