Is cefazolin an option for treatment of staphylococcal endogenous endophthalmitis?

We read with great interest the article by Lee et al. on the cefazolin inoculum effect in a murine pneumonia model.1 Endophthalmitis is a severe infection usually associated with low bacterial inocula; thus, the use of cefazolin in this setting merits consideration. We report the case of a 92-year-old woman with calcific aortic stenosis and a pacemaker implanted seven years earlier, admitted for fatigue. She weighed 42 kg, and presented with fever, confusion and a known aortic systolic murmur. Laboratory tests showed an elevated creatinine of 138 µmol/L (eGFR 28 mL/min/1.73 m², CKD-EPI). Blood cultures yielded methicillin-susceptible Staphylococcus aureus. Transthoracic echocardiography identified a vegetation (8 × 6 mm) on the left cusp of the aortic valve. PET scan (positron emission tomography scan) showed no pacemaker involvement or septic emboli. Intravenous cefazolin was started on day 1 as a continuous infusion of 1 g over 8 h. Blood cultures remained positive until day 5, when the patient developed visual impairment in the left eye. Ophthalmologic examination revealed panuveitis, an anterior chamber hypopyon and dense vitritis. Anterior chamber paracentesis was performed; microscopy, culture and metagenomic next-generation sequencing were negative.