To the Editors: Elizabethkingia meningoseptica causes life-threatening infections in humans, especially in immunocompromised patients and infants with low birth weights. It is one of the main causes of meningitis in pediatric and immunocompromised patients in the context of nosocomial diseases associated with devices and is also related to low-birth-weight infants and prematurity1 Due to their resistance to many commonly used antibiotics (beta-lactams, carbapenemics, aminoglycosides, etc.), clinicians face treatment challenges.2 There are currently few publications on pediatric cases regarding E. meningoseptica device-associated meningitis with breakthrough resistance to trimethoprim-sulfamethoxazole (TMP/SMX) while treatment with dual intravenous (IV) therapy with TMP/SMX and high-dose ciprofloxacin requiring intraventricular ciprofloxacin for eradication. This letter is written to describe a case that posed a diagnostic challenge in our center. A 1-month-old female patient with hydrocephalus secondary to a history of myelomeningocele that required correction at birth with a ventriculoperitoneal (VP) shunt system presented during her prolonged hospitalization with device-associated meningitis due to E. meningoseptica initially susceptible to TMP/SMX MIC <16 µg/L, follow-up cerebrospinal fluid (CSF) cultures remained positive for the same pathogen with TMP/SMX breakthrough resistance acquired (MIC > 64 µg/L) (Table 1). Different antibiotics were tested in vitro and showed resistance to vancomycin, minocycline, and rifampicin, maintaining only susceptibility to ciprofloxacin without achieving eradication with systemic dual high-dose IV therapy. TABLE 1. - Cerebrospinal Fluid Culture Analyzed in Vitek2 System (Biomérieux) Initial Control Antibiotic Value/Interpretation Value/Interpretation Amikacin ≥64 µg/mL (R) ≥64 µg/mL (R) Aztreonam ≥64 µg/mL (R)) Cefazolin ≥64 µg/mL (R) Cefepime ≥64 µg/mL (R) ≥64 µg/mL (R) Ceftazidime ≥64 µg/mL (R) ≥64 µg/mL (R) Ceftriaxone ≥64 µg/mL (R) Ciprofloxacin ≥1 µg/mL (Susceptible) ≥1 µg/mL (S) Gentamicin ≥16 µg/mL (Resistant) ≥16 µg/mL (R) Meropenem ≥64 µg/mL (Resistant) ≥64 µg/mL (R) Piperacillin/tazobactam 32 µg/mL (Susceptible) ≥128 µg/mL (R) Tigecycline 1 µg/mL (S) ≥8 µg/mL (R) Trimethoprim/sulfamethoxazole (TMP/SMX) 40 µg/mL (S) ≥320 µg/mL (R) Colistin ≥16 µg/mL (R) Doripenem ≥8 µg/mL (R) Imipenem ≥16 µg/mL (R) (R), resistant; (S), susceptible. Intraventricular antimicrobial therapy with ciprofloxacin was proposed based on a case report in the literature: 21 days of systemic treatment combined with Intrathecal therapy, and another 21 days of systemic therapy alone. Negative CSF cultures were obtained after 6 days of dual therapy plus intraventricular ciprofloxacin with clinical improvement in the patient and replacement of the VP shunt. Although recent literature suggests that antibiotics such as fluoroquinolones can achieve good concentrations in the CSF fluid after IV administration and do not suggest their use in intraventricular or intrathecal routes,3 and that the FDA has not approved any antimicrobial agent for intraventricular use,3,4 when therapeutic options are limited due to multidrug-resistant pathogens in central nervous system infections, intraventricular/intrathecal antibiotic therapy with fluoroquinolones appears to be a viable option in the absence of other available treatments. More studies are required, particularly in cases, such as the one presented for antibiotics that theoretically achieve adequate CSF concentrations when only IV route is used.