Recurrent Pseudomonas aeruginosa Meningitis in an Extremely Low Birth Weight Infant: A Case Report on the Use of Intrathecal Colistin

We report a case of Pseudomonas aeruginosa meningitis in an extremely low birth weight (ELBW) infant with a complex course. This case highlights the feasibility and safety of intrathecal antibiotic therapy as a potential rescue treatment for severe neonatal central nervous infections.

A male infant was born with good postnatal adaptation after a C-section at 25 5/7 weeks’ gestation due to suspected amniotic infection syndrome (AIS) after a full course of antenatal corticosteroids; the birth weight was 895 g (P60), the birth length was 38 cm (P90) and the head circumference was 24 cm (P50). He received less invasive surfactant administration and was supported with CPAP/NIV, without the need for invasive ventilation within the first 14 days. Due to the suspected infection from AIS, he was given amoxicillin and amikacin for 5 days. Interleukin-6 (IL-6; 137 pg/L) and leucocytes were slightly elevated. Blood cultures were negative. Placental histology showed severe chorioamnionitis with negative amnion swab cultures. The first 14 days were otherwise uneventful with good feeding tolerance and normal cranial ultrasounds.

On day of life (DOL) 15, he experienced increased desaturations and bradycardias, initially attributed to evolving bronchopulmonary dysplasia (BPD). On DOL 20, yellow eye secretions prompted swabbing. By DOL 21, he deteriorated with apneas and lethargy ([Fig. 1]). Cefuroxim and amikacin were initiated for late-onset sepsis and he was intubated and ventilated. Concerns of possible meningitis led to switching of antibiotics to amoxicillin/clavulanic acid and amikacin. His inflammatory markers increased (IL-6: 945 pg/L, CRP: 218 mg/L, leucocytosis, and a proportion of immature leukocytes of 76%). On DOL 23, blood cultures identified pansensitive wildtype P. aeruginosa. Antibiotics were changed to cefepime. A lumbar puncture on DOL 23 revealed low glucose, high protein, and 522 cells/µL with predominance of mononuclear cells. Cerebrospinal fluid (CSF) culture confirmed P. aeruginosa meningitis. Ciprofloxacin was added due to illness severity, later paused and again resumed for CRP elevation. Eye swabs (DOL 25) also grew P. aeruginosa, treated with moxifloxacin for 10 days. A repeat lumbar puncture on DOL 26 showed negative cultures, although cell counts were not performed due to the low CSF volume.

Fig. 1 Timeline in days of life.

In the context of meningitis, an ultrasound revealed cranial venous sinus thrombosis (CVST) and left-sided grade 3 intraventricular hemorrhage (IVH), later progressing to hydrocephalus. Seizures were treated with phenobarbital, levetiracetam and midazolam. MRI confirmed hydrocephalus and showed no abscess ([Fig. 2]).

Fig. 2 MRI (day 33): left: hydrocephalus and bilateral bleeding (T2) and right: CVST in sinus sagittalis superior, sinus transversus bilateral, and sinus rectus (Angio, venous flow). CVST, cranial venous sinus thrombosis; MRI, magnetic resonance imaging.

On DOL 37, decompression surgery for hydrocephalus was performed. After gram staining, the CSF obtained from the ventricles revealed no bacteria, and a Rickham reservoir was implanted. CSF cultures also came back negative. Hydrocephalus was managed with reservoir punctures thrice weekly. He was extubated on DOL 41, and antibiotics were discontinued on DOL 49 after 28 days when the CRP normalized (3 mg/L).

On DOL 56, he deteriorated with apneas. Suspecting recurrent P. aeruginosa meningitis, cefepime and vancomycin were initiated. The CSF obtained via Rickham reservoir puncture confirmed an elevated cell count of 8,600 M/L, undetectable glucose and elevated protein levels. CSF cultures grew P. aeruginosa again showing the same resistance pattern as before. Antibiotics were switched to meropenem and ciprofloxacin.

Due to the severity of the infection, an intrathecal colistin dosing regimen was established additionally after interdisciplinary consultation and critical appraisal of the available evidence, which is limited to a single neonatal case series suggesting both safety and efficacy (Ambreen G et al., Arch Dis Child 2020; 105: 830–836). Consequently, colistin was administered intrathecally once daily via reservoir puncture at a dosage of 0.16–0.24 mg/kg/d (5,000–7,500 IU/kg/d).” This regimen achieved cerebrospinal fluid (CSF) colistin concentrations exceeding 2 mg/L (2.5 mg/L—max. and 10 mg/L)—the level considered necessary for effective eradication of Gram-negative bacteria.

The reservoir was removed (DOL 73) due to biofilm concerns but sonication revealed no biofilm. A new reservoir was placed 5 days later and intrathecal colistin was resumed thrice weekly for 14 days. Antibiotics ceased on DOL 98 after a 6-week second course ([Table 1]). A ventriculoperitoneal shunt was placed on DOL 117.

Table 1 Summary of the use of antibiotics.

Antibiotics	Indication	Route	Dosage (per dose)	Frequency	Start date	End date
Amoxicillin	Suspected EOS (empiric)	iv	50 mg/kg	q12h	09.09.23	13.09.23
Amikacin	Suspected EOS (empiric)	iv	15 mg/kg	q48h	09.09.23	13.09.23
Cefuroxim	LOS (empiric)	iv	50 mg/kg	q8h	29.09.23	30.09.23
Amikacin	LOS/meningitis (empiric)	iv	15 mg/kg	q24h	29.09.23	29.09.23
Amoxicillin/Clavulanat	LOS/meningitis (empiric)	iv	50 mg/kg (Amoxi)	q6h	30.09.23	01.10.23
Cefepime a	Meningitis (P. aeruginosa)	iv	50 mg/kg	q8h	01.10.23	27.10.23
Ciprofloxacin	Persistent pos. CSF	iv	10 mg/kg	q8h	03.10.23	06.10.23
Moxifloxacin	Conjunctivitis/colonisation	ocular			04.10.23	15.10.23
Fluconazol	Fungal prophylaxis	iv	3 mg/kg	q72h	10.10.23	20.10.23
Ciprofloxacin	Increasing CRP under treatment/better intracellular coverage	iv	10 mg/kg	q8h	12.10.23	27.10.23
Cefepime	LOS, probable recurrence of meningitis	iv	50 mg/kg	q8h	03.11.23	04.11.23
Vancomycin	LOS, susp. cathetersepsis (empiric)	iv	15 mg/kg	q12h	03.11.23	05.11.23
Meropenem b	Recurrence of meningitis (P. aeruginosa)	iv	40 mg/kg	q8h	04.11.23	15.12.23
Ciprofloxacin b	Better coverage and combination	iv	10 mg/kg	q8h	04.11.23	15.12.23
Colistin b	Recurrence of meningitis (P. aeruginosa)	it	0.24 mg/kg	q24h	05.11.23	20.11.23
Colistin	Meningitis (P.aeruginosa) after Rickhamrevision	it	0.24 mg/kg	q48h (thrice weekly)	30.11.23	14.12.23
Fluconazol	Fungal prophylaxis	iv	3 mg/kg	q72h	06.11.23	22.12.23
Cefuroxim	Peroperativ prophylaxis (VP Shunt)	iv	50 mg/kg	q8h	04.01.24	06.01.24

Abbreviations: CRP, C-reactive protein; CSP, cerebrospinal fluid; it, intrathecally; iv, intravenously.

^aLevel of cefepime (plasma) measured on 03.10., 06.10. and 16.10.23 in an adequate range.

^bLevels of meropenem/ciprofloxacin (plasma) and colistin (CSF) measured on 10.11.23 and 16.11.23 in an adequate range.

Seizures resolved after DOL 58 and antiepileptic medications were discontinued 20 days after the last episode. CVST was managed with subcutaneous enoxaparin for 6.5 weeks, followed by oral rivaroxaban for 7 weeks, until follow-up MRI demonstrated near-complete resolution of the thrombosis. MRI also revealed bilateral periventricular and left intraventricular cyst formation.

Due to persistent postnatal leucocytosis and severity of the infection, diagnostic testing for leucocyte adhesion deficit and chronic granulomatous disease was performed, but yielded negative results.

He was discharged on DOL 120 with moderate BPD, full oral feeds, and appropriate weight gain. Neurological assessment noted muscular hypotonia, left-side rotation preference, and poor repertoire of general movements. Ophthalmologic exams prior to discharge was normal.

Further neurological assessment at 9 months of corrected age showed a mild right-sided hemiparesis. Developmental testing (Griffiths) at 9 months corrected age revealed a normal quotient of 93, with minor motor deficits. An electroencephalogram was normal and audiological tests showed no hearing loss. Ophthalmologic exams show a strabism and a high-grade left-sided amblyopia for which treatment was initiated.

Publication History

Received: 26 May 2025

Accepted after revision: 08 December 2025

Article published online:
15 January 2026