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.
METHODS: Observational study; secondary analysis of a prospective registry-based cohort study.
METHODS: Paediatric emergency department; tertiary teaching hospital.
METHODS: Infants ≤90 days old with FWS, pyuria and urine Gram stain requested seen between 2010 and 2022.
METHODS: 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.
METHODS: Observational study; secondary analysis of a prospective registry-based cohort study.
METHODS: Paediatric emergency department; tertiary teaching hospital.
METHODS: Infants ≤90 days old with FWS, pyuria and urine Gram stain requested seen between 2010 and 2022.
METHODS: 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.
摘要：
目的：分析尿液革兰氏染色在预测无来源发热（FWS）和脓尿的低龄婴儿尿液培养（UC）阳性中的表现。
方法：观察性研究；基于前瞻性登记的队列研究的二次分析。
方法：三级教学医院儿科急诊科。
方法：FWS≤90天的婴儿，2010年至2022年期间要求出现脓尿和尿液革兰氏染色。
方法：革兰氏染色的性能，定义为阳性，如果看到任何细菌，用于预测尿路感染（UTI：通过尿道插管生长>10000CFU/mL的单一细菌病原体的UC）。
结果：在367例发热性脓尿婴儿中，281(76.6%)革兰氏染色阳性,306(83.3%)UC阳性(277;90.5%大肠杆菌)。革兰氏染色阳性和阴性的UC患者的阳性率分别为97.2％和38.4％，分别为(p<0.01)，敏感性为89.2%(95%CI:85.2%~92.2%),特异性为86.9%(95%CI:76.2%~93.2%)。诊断由大肠杆菌以外的细菌引起的UTI的敏感性较低(69.0%对由大肠杆菌引起的UTI的91.3%;p<0.01)。86例革兰氏染色阴性的婴儿中有2例（2.1％）被诊断为与UTI（肺炎链球菌和金黄色葡萄球菌）无关的菌血症。
结论：大约三分之一的脓尿和革兰氏染色阴性的婴儿最终会被诊断为UTI。这些患者由大肠杆菌以外的细菌引起的UTI的比率更高。在这种情况下，也应考虑UTI以外的细菌感染。
方法：观察性研究；基于前瞻性登记的队列研究的二次分析。
方法：三级教学医院儿科急诊科。
方法：FWS≤90天的婴儿，2010年至2022年期间要求出现脓尿和尿液革兰氏染色。
方法：革兰氏染色的性能，定义为阳性，如果看到任何细菌，用于预测尿路感染（UTI：通过尿道插管生长>10000CFU/mL的单一细菌病原体的UC）。
结果：在367例发热性脓尿婴儿中，281(76.6%)革兰氏染色阳性,306(83.3%)UC阳性(277;90.5%大肠杆菌)。革兰氏染色阳性和阴性的UC患者的阳性率分别为97.2％和38.4％，分别为(p<0.01)，敏感性为89.2%(95%CI:85.2%~92.2%),特异性为86.9%(95%CI:76.2%~93.2%)。诊断由大肠杆菌以外的细菌引起的UTI的敏感性较低(69.0%对由大肠杆菌引起的UTI的91.3%;p<0.01)。86例革兰氏染色阴性的婴儿中有2例（2.1％）被诊断为与UTI（肺炎链球菌和金黄色葡萄球菌）无关的菌血症。
结论：大约三分之一的脓尿和革兰氏染色阴性的婴儿最终会被诊断为UTI。这些患者由大肠杆菌以外的细菌引起的UTI的比率更高。在这种情况下，也应考虑UTI以外的细菌感染。
