Is Culture-positive Urinary Tract Infection in Febrile Children Accurately Identified by Urine Dipstick or Microanalysis?

Current management of occult bacteremia in infants

OBJECTIVES

To summarize the main clinical entities associated with fever without source (FWS) in infants, as well as the clinical management of children with occult bacteremia, emphasizing laboratory tests and empirical antibiotics.

SOURCES

A non-systematic review was conducted in the following databases--PubMed, EMBASE, and SciELO, between 2006 and 2015.

SUMMARY OF THE FINDINGS

The prevalence of occult bacteremia has been decreasing dramatically in the past few years, due to conjugated vaccination against Streptococcus pneumoniae and Neisseria meningitidis. Additionally, fewer requests for complete blood count and blood cultures have been made for children older than 3 months presenting with FWS. Urinary tract infection is the most prevalent bacterial infection in children with FWS. Some known algorithms, such as Boston and Rochester, can guide the initial risk stratification for occult bacteremia in febrile infants younger than 3 months.

CONCLUSIONS

There is no single algorithm to estimate the risk of occult bacteremia in febrile infants, but pediatricians should strongly consider outpatient management in fully vaccinated infants older than 3 months with FWS and good general status. Updated data about the incidence of occult bacteremia in this environment after conjugated vaccination are needed.

Diagnostic accuracy of urine heparin binding protein for pediatric acute pyelonephritis

Timely antibiotic initiation for acute pyelonephritis (APN) can prevent renal complications. We investigated whether urine heparin binding protein (UHBP), a cytokine released from activated neutrophils, was a useful diagnostic tool for APN. Febrile children with presumed APN were prospectively enrolled between January and September 2013, and divided into two groups based on urine cultures. UHBP levels were measured at enrollment in all children and 1 month after antibiotic treatment in children with APN. UHBP levels in children with APN at baseline and 1 month versus controls were 47.0 ± 8.4 and 16.6 ± 3.8 vs. 15.0 ± 2.9 ng/mL, respectively (p < 0.001). Test performance characteristics were calculated against a gold standard of positive urine cultures and compared with leukocyte esterase (LE) and nitrite measured by dipsticks and pyuria by microscopy. The sensitivity and specificity for UHBP levels ≥34 ng/mL were 100 and 100 %. Spearman's rank coefficient was used to assess the associations between routine laboratory tests and UHBP levels. Significant positive correlations were found with pyuria grade (Spearman's rho = 0.62; p < 0.001), neutrophil count (rho = 0.38; p = 0.03), and platelet count (rho = 0.39; p = 0.03).

CONCLUSIONS

UHBP is a valid adjunctive diagnostic tool for aiding clinicians in making rapid treatment decisions for APN.

Using a urine dipstick to identify a positive urine culture in young febrile infants is as effective as in older patients

AIM

There is limited evidence about the diagnostic value of urine dipsticks in young febrile infants. The aim of this study was to determine whether urine dipsticks would identify positive urine cultures in febrile infants of less than 90 days of age.

METHODS

This study was a subanalysis of a prospective multicentre study developed in 19 Spanish paediatric emergency departments belonging to the Spanish Paediatric Emergency Research Network. It focused on febrile infants of less than 90 days of age admitted between October 2011 and September 2013. A positive urine culture was defined as the growth of ≥ 50,000 cfu/mL of a single pathogen collected by a sterile method.

RESULTS

We included 3401 patients, and 176 (12.8%) female patients and 473 (23.3%) males had a positive urine culture. The leucocyte esterase test showed a mean sensitivity of 82.1% and a mean specificity of 92.4%, with a greater mean negative predictive value for females than males (97.8 versus 94.1%) and a greater mean positive predictive value for males than females (79.4% versus 58%).

CONCLUSION

The leucocyte esterase test showed the same accuracy in young febrile infants as previously reported findings for older children. It predicted positive urine cultures and also revealed important gender differences.

Diafiltration MALDI-TOF mass spectrometry method for culture-independent detection and identification of pathogens directly from urine specimens

OBJECTIVES

With the aim of rapid, culture-independent identification of microorganisms directly from urine specimens, we developed a diafiltration matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method.

METHODS

In this procedure, urine specimens are desalted, fractionated, and concentrated prior to MS analysis. The analytic performance characteristics of the diafiltration method were assessed in a prospective trial whereby 100 fresh urine specimens were processed using diafiltration MALDI-TOF MS. Concomitant with this, conventional culture was performed with results blinded to the MS operator.

RESULTS

The diafiltration method correctly identified urine specimens positive for uropathogens (Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis) and correctly classified all specimens negative for clinically relevant bacteriuria, including a subset of contaminated urine specimens and a subset with growth of clinically insignificant flora. The sensitivity and specificity of the assay were 67% and 100%, respectively. The detection limit of this method was 10(5) to 10(6) colony-forming units/mL.

CONCLUSIONS

Using the diafiltration method, we were able to improve the turnaround time for microorganism identification from 24 to 48 hours (for conventional culture) to 2 to 3 hours. Although methodological refinements are under way to further improve the clinical sensitivity and turnaround time, the 100% positive predictive value of this method suggests that it could be used to guide the selection of antimicrobial agents.