Neisseria mucosa Urinary Tract Infection in a Neonate With Posterior Urethral Valves: A Case Report.

Neisseria mucosa is a Gram-negative diplococcus that usually colonizes the upper respiratory tract and is generally regarded as a commensal organism. It has, nevertheless, been implicated as an opportunistic pathogen in bacteremia, endocarditis, septic arthritis, meningitis, and peritoneal dialysis-associated peritonitis; urinary tract infection (UTI) remains exceptionally rare. We report a UTI caused by N. mucosa in a 24-day-old male neonate with posterior urethral valves (PUVs), who presented with frank pyuria for 10 days. Direct Gram staining of urine revealed Gram-negative diplococci with a coffee-bean morphology, and the organism was recovered in pure culture. Species identification was achieved by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Antimicrobial susceptibility testing by ETEST® showed susceptibility to ceftriaxone and resistance to benzylpenicillin and ciprofloxacin. Treatment with ceftriaxone was associated with a favorable clinical and biological outcome. This case illustrates the opportunistic potential of N. mucosa in neonates with structural urinary tract abnormalities and emphasizes the value of accurate microbiological identification when UTIs occur in an unusual clinical setting.