First Reported Case of Brain Abscess in an Infant Caused by Staphylococcus argenteus

To the Editors: Staphylococcus argenteus is a newly classified staphylococcus species that is phenotypically like Staphylococcus aureus. It was first described in 20151 and to date has been implicated in cases of bacteremia, otitis externa and ventriculoperitoneal shunt infections. We report, to our knowledge, the first case of cerebral abscesses in a neonate caused by S. argenteus. A 70-day-old preterm baby born at 28 weeks with a routine neonatal intensive care unit course was found to have increasing head circumference from 28 cm (z-score –3.3) to 32 cm (z-score –0.64). There were no other untoward signs pointing toward pathology. A repeat ultrasound 2 weeks later showed 2 hypo-echoic lesions of 27- and 20-mm diameter. Magnetic resonance imaging done on week 10 of life showed intra-axial lesions in the left thalamo-capsular region measuring 28 × 20 × 25 (mm and left frontal periventricular area measuring 23 × 27 × 21 mm crossing the midline and compressing the third ventricle with associated mass effect. The lesions were associated with central significant diffusion restriction and a peripheral thick capsule with associated perilesional edema (Fig 1.) A diagnosis of brain abscess was suspected and cefotaxime/metronidazole started.FIGURE 1.: T1 axial with left thalamo-capsular and left periventricular abscess.Ultrasound-guided needle aspiration of the lesions yielded 15 and 21 mL of thick turbid cerebrospinal fluid. Gram stain showed Gram-positive cocci, and the cerebrospinal fluid analysis showed 2100 × 106 white blood cells/L with high protein (more than 2 g/L) and normal glucose (4.3 mmol/L- 63% of serum glucose). The culture grew Gram-positive cocci that were identified by matrix-assisted laser desorption ionization. as Staphylococcus argenteus. Whole genome sequencing confirmed the identity as Staphylococcus argenteus sequence type 2250. No resistance genes (MecA or other) were identified. Susceptibility testing revealed sensitivity to oxacillin, clindamycin and erythromycin. Antibiotics were changed to cloxacillin. The patient subsequently required a second drainage on day 11 of therapy due to the persistence of the abscesses. Cloxacillin was continued for a total of 50 days and repeat imaging showed complete resolution of the abscesses. The infant was screened for immunodeficiencies: neutrophil function was normal, lymphocyte subsets were largely in the normal range for age, and IgG levels were low (2.03 grams/liter) consistent with prematurity. The indolent presentation of the cerebral abscesses in this case necessitates that clinicians have a high index of suspicion in neonates. The infant in this case only had an increase in head circumference as a sign of cerebral abscesses. C-reactive protein and other blood investigations were normal. We feel that sharing this interesting case adds to the growing literature about Staphylococcus argenteus and its virulent potential in susceptible hosts.