Staphylococcus epidermidis Urinary Tract Infection in an Infant

We describe the case of a previously healthy 7-month-old male infant with urinary tract infection due to Staphylococcus epidermidis grown from two separate urine cultures. Further evaluation showed severe bilateral vesicoureteral reflux. Physicians should not assume that S. epidermidis is always a contaminant in urine cultures. 1. Introduction The majority of urinary tract infections (UTI) in children are caused by gram-negative coliform bacteria [1]. Gram-positive cocci, including enterococci, group B Streptococcus, and Staphylococcus saprophyticus have also been described as urinary pathogens [2–5]. S. saprophyticus infections are more commonly seen in young women and elderly men. Staphylococcus epidermidis urinary tract infection in healthy pediatric patients is rare and only a few cases have been reported in preadolescent children. S. epidermidis when isolated from the urine of previously healthy infants is almost always considered a contaminant. We describe the case of an infant with S. epidermidis isolated on two occasions from the urine during the same episode of illness. Further evaluation revealed severe bilateral vesicoureteral reflux. 2. Case Report A previously healthy 7-month-old infant presented with fever for 2 days. He had runny nose for a week. Nasal wash for respiratory syncitial virus, influenza A, and influenza B antigens was negative. Urinalysis showed <5 white blood cells (WBC) per high power field (hpf). A diagnosis of viral illness was made and he was sent home. Urine culture (catheter specimen) subsequently grew 103–105 colony forming units (CFU)/mL of S. epidermidis. No treatment was given as the organism was considered a contaminant. His fever persisted and he developed intermittent vomiting for 4 days. On admission, his temperature was 40.6°C; he was alert and in no distress. He was noted to be circumcised. Otherwise, physical exam was normal. Laboratory data showed a white blood cell count (WBC) of 15,600/mm3 (70% neutrophils, 2% bands, and 17% lymphocytes). C-reactive protein (CRP) was 238？mg/L (normal <10？mg/L). Urinalysis showed 5–10？WBC/hpf and a catheterized urine sample was sent for culture. His electrolytes and renal function tests were normal. He was started on intravenous ceftriaxone treatment. He continued to spike fevers over the next 48 hours. Cerebrospinal fluid (CSF) showed no evidence of meningitis. Direct fluorescent antibody testing of respiratory secretions was negative for adenovirus and parainfluenza. Urine culture showed pure growth of S. epidermidis, >105？CFU/mL. The organism was sensitive to