Community-Acquired Necrotizing Pneumonia Caused by ST72-SCCmec Type IV-Methicillin-Resistant Staphylococcus aureus in Korea
A 66-year-old man was referred to the Samsung Medical Center, Seoul, Korea, following a diagnosis of CAP with cytopenia which was made at another hospital. Three weeks prior to admission, he had ingested water of boiled wild mushroom. While he developed nausea and headache, which spontaneously resolved without medication, he did not experience any respiratory symptoms. Two week later, he developed dyspnea on exertion. He visited his regional hospital presenting with fever and dyspnea and was diagnosed with CAP. However, he was referred to our hospital for leukopenia (leukocyte count, 300/µL; absolute neutrophil count, 0/µL) and thrombocytopenia (platelet count, 3,000/µL) found on initial laboratory tests at the regional hospital. On admission to our hospital, his condition deteriorated rapidly and he was placed on mechanical ventilation for severe hypoxemia. Chest computed tomography (CT) showed consolidation and ground-glass opacity with cavitation in the left lower lobe which was compatible with necrotizing pneumonia (). The patient was diagnosed with severe necrotizing pneumonia in a neutropenic patient and was administered vancomycin, piperacillin-tazobactam and levofloxacin. Aplastic anemia associated with wild mushroom toxin was diagnosed with bone marrow biopsy which showed hypocellular marrow with suppressed trilineage hematopoiesis. While the Gram stain of respiratory specimens showed gram-positive cocci in pairs, chains and clusters, the urinary antigen test for Streptococcus pneumoniae was negative. The culture from sputum grew MRSA and while the strain was susceptible to gentamicin, rifampicin, ciprofloxacin and trimethoprim/sulfamethoxazole, it was resistant to erythromycin and clindamycin. The patient recovered completely following a 2 week treatment course with vancomycin. In order to genotype the bacterial isolate, multilocus sequence typing (MLST) was performed using polymerase chain reaction (PCR) amplification and sequencing of seven housekeeping genes (arcC, aroE, glpF, gmk, pta, tpi, and yqiL) as previously described. SCCmec type was determined by the multiplex PCR method. The isolate was screened for the genes (lukF-PV and lukS-PV) encoding the components of the PVL toxin by PCR amplification. Typing of the MRSA isolate from the patient revealed that the isolate belonged to MLST ST72, carried SCCmec type IV and was negative for PVL.