A 53-year-old male patient was hospitalized in the respiratory outpatient department of our hospital. He had fever with headache for half a month, slight cough, and sore muscles and joints. The patient did not have diabetes or immunosuppressive diseases, and there was no history of hypertension. Considering that no signs of pneumonia were found by thoracic CT, the patient was given cefixime sustained-release capsules plus clarithromycin sustained-release capsules for 4 days. However, the fever with headache remained, and he was admitted to the neurology department.
The patient was treated with a three-day course of ceftriaxone, with no signs of improvement. Brain magnetic resonance imaging (MRI) showed a high T2WI signal and T2 flair in the left lateral ventricle, and DWI indicated no significant diffusion restriction. The lesion was not enhanced. Brain MRI showed left paraventricular demyelination (Figure 1). A lumbar puncture was performed, and cerebrospinal fluid (CSF) examination demonstrated a nucleated cell count of 2120 cells/microL, neutrophil percentage of 95%, glucose level of 2.29 mmol/L, protein level of 57.3 mg/dL, and adenosine deaminase activity of 1.5 U/L. The ratio between CSF and blood glucose levels was 0.47. The CSF samples were centrifuged, and the sediment was smeared and stained with Gram, ink, fluorescence and anti-acid stains. No acid-fast bacilli, cryptococci or fungi were detected in the CSF smears; the Xpert MTB/RIF assay was also negative. Hepatitis B surface antigen (HbsAg), hepatitis B core antibody (HbcAb) and hepatitis B e-antigen (HbeAb) were positive, and upper-abdomen enhanced CT showed cirrhosis of the liver, multiple small cysts of the liver, gallstones and cholecystitis. The Child-Pugh score of liver cirrhosis was class A.
CSF culture vials were incubated in an automated culture system (Bact/ALERT Virtuo , bioMerieux, France). The bacteria primarily grew under both anaerobic and aerobic conditions. After the CSF culture became positive, 10 microL of fluid was plated on Columbia blood agar, and S. aureus isolate SA17 was cultured. Microbiological identification was performed by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry using a MALDI/TOF Biotyper (Bruker Italia, Milan, Italy). Antimicrobial susceptibility testing was performed using E-test strips in three replicates, revealing that the isolate was methicillin-resistant S. aureus.
After multidisciplinary discussion, the patient received antibiotic treatment with 0.6 g linezolid bid intravenously for 17 days, and the patient's platelet counts decreased to 27x109/L. The time course of linezolid administration and the onset of thrombocytopaenia are illustrated in Figure 2. When linezolid was stopped, his platelet counts gradually increased. The patient recovered well, his symptoms and signs improved significantly, and the results of CSF re-examination were normal.
S. aureus strain SA17 was detected as a result of routine hospital laboratory procedures. This study was performed in accordance with the Declaration of Helsinki and approved by the Ethics Committee of The Affiliated Hospital of Hangzhou Normal University, Hangzhou, China. Written informed consent, which included publication of the case details, was obtained from the patient.