Abstract
Purpose: Staphylococcus epidermidis in urine cultures from previously healthy children is usually considered to be a contaminant. The goal of this study was to identify cases in which S. epidermidis was an infectious cause of urinary tract infection (UTI) in children.
Methods: A literature search identified 7 cases, 6 of which were previously published and 1 which was unpublished, described herein.
Results: S. epidermidis was identified as the causative organism of UTIs in children with underlying urinary tract abnormalities.
Conclusion: UTIs caused by S. epidermidis in a previously healthy child should not be disregarded as a contaminant and further workup for urinary tract abnormality is indicated.
In healthy children, urinary tract infections (UTIs) are usually caused by Gram-negative organisms (mainly Escherichia coli) and certain Gram-positive organisms such as Staphylococcus saprophyticus and Enterococcus.1 When Staphylococcus epidermidis is isolated in urine culture, it is assumed to be a contaminant.2 As demonstrated in the following case, however, this assumption should not be made in a symptomatic child for whom an alternate source of infection cannot be identified. This case also highlights the importance of suspecting an underlying urinary tract abnormality when S. epidermidis is identified as the causative agent of UTIs in children.
Case Report
A previously healthy 4-year-old circumcised boy presented with fever, abdominal pain and vomiting for 1 day. A clean catch urinalysis showed 4 to 6 white blood cells per high-powered field and moderate bacteria. His symptoms continued to worsen; his white blood cell count was 23,900/mm3 (83.7% neutrophils, 9.2% lymphocytes, 6.5% monocytes) and his C-reactive protein concentration was 5.8 mg/dL. He was admitted for dehydration and systemic inflammatory response syndrome. Imaging was done to rule out appendicitis and pneumonia.
On hospital day 3, C-reactive protein spiked to 20 mg/dL and urine culture grew >100,000 colony-forming units (CFUs) of S. epidermidis/mL. Because of reluctance to ascribe the patient's illness to S. epidermidis, the urine culture was repeated and again grew 100,000 CFUs of S. epidermidis/mL. The patient was treated with intravenous levofloxacin 10 mg/kg twice a day and improved back to his baseline within 12 hours.
The new working diagnosis was sepsis secondary to pyelonephritis, at which point a renal ultrasound was ordered and showed normal kidneys bilaterally; the bladder was incompletely distended but grossly normal.
The patient completed a 3-day course of intravenous levofloxacin and was sent home with oral levofloxacin for 12 days. An outpatient vesicocystourethogram was performed and revealed right grade II reflux and no reflux on the left. The patient was referred to urology for follow-up.
Discussion
S. epidermidis is not generally regarded as the causative agent of UTI in children with no preexisting conditions. This organism has more commonly been associated with UTIs in patients with indwelling urinary catheters and other instrumentation in the urinary tract.3 When grown in culture in a healthy patient, S. epidermidis has traditionally been considered a contaminant. This case and 6 others like it (summarized in Table 1) provide evidence that this assumption should be avoided in symptomatic patients.
A PubMed literature search was done using the following terms: Staphylococcus epidermidis, urinary tract infection, healthy, and pyelonephritis and filtered to ages 0 to 18. Four case reports of S. epidermidis UTI were identified and are detailed in Table 1. All cases identified occurred in previously healthy boys, most of whom were circumcised. Most patients presented with gastrointestinal complaints and were incorrectly diagnosed with viral gastroenteritis after exclusion of appendicitis. Although not all patients displayed frank pyuria on urinalysis, in all cases urine cultures grew >100,000 CFUs/mL. All patients were treated with antibiotics and fully recovered within a few days. Of greatest significance, all the children had underlying urinary tract abnormalities, detailed in Table 1, which were identified via renal ultrasound and vesicocystourethogram.
Conclusion
While S. epidermidis has classically been regarded as a urinary contaminant, caution should be taken before making this assumption. In a symptomatic patient with repeat positive urine cultures, the possibility of an S. epidermidis UTI should be considered as the cause of the patient's symptoms. In addition to treatment with proper antibiotics, further workup for underlying urinary tract abnormalities is essential.
Notes
This article was externally peer reviewed.
Funding: none.
Conflict of interest: none declared.
- Received for publication April 10, 2014.
- Revision received July 21, 2014.
- Accepted for publication July 29, 2014.
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