Nocardia Brain Abscess in an Immunocompetent Patient
A 71-year-old male was admitted due to headache, dizziness, and nausea for three days. He was healthy, except that he had been diagnosed with hypertension two years before. His past medical history was unremarkable. His social history included intermittent alcohol consumption without smoking. The initial vital signs revealed blood pressure of 120/80 mmHg, heart rate of 76 beats per minute, respiration rate of 18 breaths per minute and body temperature of 36.9℃. He was alert upon admission. Physical examination revealed clear lung sound without rale or wheezing. The heart beat was regular without any murmur. There was no tenderness or rebound tenderness in the abdomen. Findings from other physical and neurological examinations were normal. There were no other symptoms such as fever, neck stiffness, photophobia, papilledema or other abnormalities. The initial peripheral blood count showed a white blood cell count of 11,200/mm3 (neutrophils 64.6%, lymphocytes 24.5%, monocytes 6.8%), hemoglobin level of 13.0 g/dL, platelet count of 211,000/mm3, erythrocyte sedimentation rate of 38 mm/hr, and C-reactive protein level of 1.11 mg/dL. Blood chemistry showed a total protein level of 7.6 g/dL, albumin level of 4.3 g/dL, total bilirubin level of 0.9 mg/dL, aspartate aminotransferase/alanine aminotransferase 27/16 IU/L, alkaline phosphatase 77 IU/L, BUN/Cr 9.2/0.8 mg/dL, Na/K 136/3.8 mEq/L, and Ca/P 9.0/4.7 mg/dL. Result of urinalysis was normal. Human immunodeficiency virus (HIV) antibody, hepatitis B surface antigen and hepatitis C antibody were all negative. Chest and abdomen radiographs were normal. Brain CT scan and magnetic resonance (MR) imaging showed multiple rim enhancing lesions with surrounding edema, which was presumed to be a brain abscess ().\nAfter admission, the patient underwent a craniotomy with stereotactic aspiration of the abscess. During the operation, yellowish and turbid pus was aspirated and a cerebral abscess was diagnosed. Empirical parenteral antibiotics were started with ceftriaxone 2 g bid and metronidazole 500 mg tid. Gram stain of the pus showed beaded branching gram-positive bacilli. Urease test, esculin hydrolysis test, citrate test, and modified acid-fast stain using 1% acid alcohol were all positive and the bacteria grew at 42℃. Nocardia species were suggested by colonial morphology, Gram-stain, and modified acid fast bacillus (AFB) stain (). By manual, culture was identified as Nocardia species. For the accurate identification of Nocardia species, 16S ribosomal RNA (rRNA) gene-based polymerase chain reaction (PCR) and sequencing was carried out. Primers of 27F (5'-AGA GTT TGA TCM TGG CTC AG-3') and 1492R (5'-TAC GGY TAC CTT GTT ACG ACT T-3') were used for 16S rRNA gene amplification. Size of 1466 bp 16S rRNA gene amplification sequencing was carried out by Solgent (Solgent Co, Daejeon, Korea) company which uses Big Dye Terminator Cycle Sequencing Kit and ABI PRISM 3730 DNA analyzer (PE Applied Biosystem, Foster, CA, USA). It showed 100% concordance to N. farcinica (GenBank accession number: KC478309) by BLAST Similarity Searching in GenBank. The organism was susceptible to amikacin, imipenem, trimethoprim-sulfamethoxazole (TMP-SMX), ciprofloxacin, and resistant to erythromycin, kanamycin, ampicillin, gentamicin. After identifying the result of pus culture, the antibiotic regimen was changed to TMP-SMX (15 mg/kg of the TMP component per day) and imipenem 500 mg qid. Due to the persistence of the patient's symptoms, re-imaging was performed two weeks later. On day 24 of admission, the patient underwent a repeated craniotomy with stereotactic aspiration of the abscess because the abscess and surrounding edema have increased than before. Ciprofloxacin (400 mg every 12 h, intravenous) was added to the TMP-SMX treatment and changed from imipenem to meropenem. After performance of repeated surgery and administration of additional antibiotics, we observed improvement of the patient's symptoms. Contrast-enhanced brain CT scan performed three weeks after reoperation, showed substantial resolution of the brain lesion. Meropenem and ciprofloxacin were continued for six weeks. On hospital day 67, he was discharged to go home to complete four months of oral TMP-SMX therapy. On three-month follow-up brain CT after discharge, resolution of the brain abscess was confirmed.