A Case of Acute Pyogenic Sacroiliitis and Bacteremia Caused by Community-Acquired Methicillin-Resistant Staphylococcus aureus
A 57-year-old woman had severe right sacral-area pain and heating sensation that had begun 2 days before admission. She did not receive any medical treatment for her symptoms; she eventually visited the emergency room because of worsening of pain. The patient had no history of diabetes, hypertension, or pulmonary tuberculosis, but had received a hysterectomy 19 years ago as a treatment for uterine myoma. She had no history of hospital admission, surgery, hemodialysis, or medical prosthesis insertion in the last 10 years. The patient did not drink alcohol or smoke, had not been exposed to any trauma, and had not travelled to a foreign country in the previous 5 years. At the time of admission she was residing at home alone, was unemployed, and had not been in contact with any healthcare professionals or hospitalized patients in her recent past.\nHer vital signs were mostly normal: her blood pressure was 110/60 mmHg, her heart rate was 82 beats per minute, and her respiration rate was 20 breaths per minute. However, the patient was febrile (38.9℃). Physical examination revealed tenderness in the right sacral area and limitation in flexion of the right hip joint due to severe pain. Lung sounds were clear without any wheezing or crackles, and her heartbeat was regular without any murmur. Her abdomen was free of tenderness or rebound tenderness, and hepatosplenomegaly was not detected. Neurological examinations revealed normal lower extremity motor and sensory function. Peripheral blood examination showed a white blood cell (WBC) count of 13,000/mm3 (neutrophils 77.3%, lymphocytes 12.9%, monocytes 9.6%), a hemoglobin level of 12.7 g/dL, a platelet count of 196,000/mm3, an erythrocyte sedimentation rate of 53 mm/hr, and a C-reactive protein level of 18.05 mg/dL. Blood chemistry revealed a total protein level of 7.0 g/dL, an albumin level of 4.1 g/dL, a total bilirubin level of 3.2 mg/dL, an aspartate aminotransferase level of 30 IU/L, an alanine aminotransferase level of 25 IU/L, an alkaline phosphatase level of 125 IU/L, a blood urea nitrogen/creatine level of 11.4/0.4 mg/dL, a sodium/potassium level of 134/3.9 mEq/L, and a calcium/phosphorus level of 9.2/3.8 mg/dL. Urinalysis was normal. Chest and abdomen radiographs were normal, and echocardiography to rule out infective endocarditis was also normal. Hip magnetic resonance imaging (MRI) was performed, and revealed a 1.8 × 3.0 cm abscess anterior to the right sacroiliac joint, accompanied by infective arthritis with adjacent myositis ().\nPeripheral blood and urine cultures were performed before initiating antibiotic therapy under the suspicion of infective myositis and arthritis. Ceftriaxone (2 g every 24 h) was given intravenously. The abscess was surgically removed, and S. aureus was identified in blood and pus cultures 5 days after hospitalization. Vitek2 AST-P601 card (BioMérieux, France) analysis demonstrated susceptibility to ciprofloxacin, fusidic acid, gentamicin, habekacin, linezolid, mupirocin, nitrofurantoin, quinupristin/dalfopristin, rifampin, teicoplanin, telithromycin, tetracycline, tigecycline, TMP-SMX, and vancomycin (MIC 1 g/mL). It was also revealed that the pathogen was resistant to clindamycin, erythromycin, oxacillin, and penicillin. The D-test for inducible clindamycin resistance was positive.\nThe cultured strain was tested for the staphylococcal cassette chromosome mec (SCCmec) gene and the Panton-Valentine leukocidin (PVL) gene. Multilocus sequence typing (MLST) for SCCmec was carried out with multiplex-polymerase chain reaction methodology using a specific primer set, following the method of Oliveira et al. []. The results showed that the strain was SCCmec type IV-A. that was negative for PVL (). MLST analysis, according to the method of Enright et al., was conducted by sequencing analysis of 7 housekeeping genes (arcC, aroE, glpF, gmk, pta, tpi, and yqiL) []. The analysis revealed ST 72. The MLST database () revealed a sequence type of 1-4-1-8-4-4-3 (ST 72). On the sixth day of admission, the antibiotic regimen was changed to vancomycin (1 g every 12 h) plus rifampin (600 mg every 24 h). Rifampin was stopped after 20 days, and thereafter vancomycin was switched to teicoplanin (400 mg every 12 h due to the emergence of neutropenia after 25 days) and combined with intravenous levofloxacin (750 mg every 24 h). The latter antibiotic therapy was continued for an additional 10 days. The patient was discharged after her symptoms had subsided and her blood test results normalized. The patient was prescribed oral levofloxacin (750 mg every 24 h for 1 week) upon discharge. The patient did not show additional symptoms, and levofloxacin was continued for an additional 10 days on an outpatient basis. Treatment was stopped after a total of 8 weeks of antibiotic therapy, and no disease recurrence was reported after 1 year of follow-up.