Community-acquired methicillin-resistant Staphylococcus epidermidis pyelonephritis in a child: a case report

INTRODUCTION: Staphylococcus epidermidis is currently the most frequent pathogen of opportunistic and nosocomial infections worldwide. Most cases of Staphylococcus epidermidis infections are associated with indwelling medical devices and/or immunocompromised conditions. Community-acquired urinary tract infections are rare, particularly among pediatric populations, and clinicians often do not consider Staphylococcus epidermidis as a uropathogen. CASE PRESENTATION: A previously healthy Japanese boy developed pyelonephritis caused by Enterococcus faecalis at 10 months of age. Subsequently, he was diagnosed with severe bilateral vesicoureteral reflux (right side grade V, left side grade III), and was administered trimethoprim/sulfamethoxazole as the prophylaxis. At 18 months of age, he presented with fever. Gram staining of urine obtained through catheterization revealed gram-positive cocci. We suspected pyelonephritis caused by enterococci, and administered oral fluoroquinolone empirically. The fever promptly resolved, and eventually, methicillin-resistant Staphylococcus epidermidis was detected at significant levels in the urine. Thus, our final diagnosis was pyelonephritis caused by community-acquired methicillin-resistant Staphylococcus epidermidis. CONCLUSIONS: Our case indicated that even immunocompetent children without a urinary catheter can develop Staphylococcus epidermidis pyelonephritis. Staphylococcus epidermidis can be underdiagnosed or misdiagnosed as sample contamination in community-acquired urinary tract infections. Therefore, when Gram staining of appropriately obtained urine samples reveals gram-positive cocci, clinicians should take into consideration not only the possibility of enterococci but also staphylococci, including Staphylococcus epidermidis, particularly in children with urinary abnormalities and/or those receiving continuous antibiotic prophylaxis.