Pyomyositis Caused by Methicillin-Resistant Staphylococcus aureus
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《新英格兰医药杂志》
To the Editor: Pyomyositis is common in tropical regions but is rarely reported in temperate climates. In the United States, most cases are associated with human immunodeficiency virus infection or other immunosuppressive conditions, including diabetes mellitus, cancer, connective-tissue diseases, and cirrhosis.1 Christin and Sarosi observed that Staphylococcus aureus was the causative organism in 70 percent of cases, and that 31 percent of the patients had bacteremia.2 We describe four patients with community-acquired pyomyositis caused by methicillin-resistant S. aureus who presented to our hospital within a span of six months.
Patient 1 was a 22-year-old Nicaraguan woman without previous medical problems who presented with a boil on the right upper thigh that was treated with incision and drainage. Two weeks later, she presented with increasing thigh pain, swelling, and a temperature of 99.5°F (37.5°C). Magnetic resonance imaging (MRI) showed an abscess of the vastus intermedius muscle (Figure 1). Incision and drainage were performed, and wound cultures grew methicillin-resistant S. aureus.
Figure 1. Coronal, Fat-Suppressed, T1-Weighted MRI Scan of the Thigh of Patient 1, Obtained after the Intravenous Administration of Gadolinium.
The ring-enhancing collection (arrows) is compatible with an abscess.
Patient 2 was a 33-year-old woman with no history of medical problems who presented after three days of pain and swelling in the right thigh and difficulty walking. She had been treated for axillary and gluteal boils with incision and drainage and cephalexin. MRI revealed phlegmon of the piriformis muscle. Blood cultures grew methicillin-resistant S. aureus.
Patient 3 was a 31-year-old woman with AIDS (CD4 cell count, 15 per cubic millimeter) who was not receiving antiretroviral therapy. She had had pain in the right thigh for one week and fever and leg swelling for two days. A computed tomographic (CT) scan showed fluid collection in the right anterior thigh. Blood cultures grew methicillin-resistant S. aureus.
Patient 4 was a 51-year-old man with type 2 diabetes mellitus. He presented with pain and swelling in the left lower extremity and was treated with cephalexin. One week later, he presented with difficulty walking and increased leg swelling. A CT scan showed a 2-cm fluid collection in the anterior thigh. The collection was surgically drained. Wound and blood cultures grew methicillin-resistant S. aureus.
Isolates were tested with an automated system (Vitek, BioMérieux) and were sensitive to tetracycline, vancomycin, gentamicin, and rifampin; all were resistant to azithromycin but sensitive to clindamycin. The isolates showed no inducible resistance to clindamycin with the use of the D-test. Two isolates were further tested against ciprofloxacin and were found to be resistant.
Patients with locally invasive soft-tissue infection should be suspected of having methicillin-resistant S. aureus. These four patients were treated with vancomycin for two to three weeks; two received oral clindamycin to complete their antibiotic course. All four patients had complete resolution of infection. This cluster of cases suggests that community-acquired methicillin-resistant S. aureus is emerging as an important cause of pyomyositis.
Maria E. Ruiz, M.D.
Seife Yohannes, M.D.
Christopher G. Wladyka, M.D.
Washington Hospital Center
Washington, DC 20010
maria.e.ruiz@medstar.net
Patient 1 was a 22-year-old Nicaraguan woman without previous medical problems who presented with a boil on the right upper thigh that was treated with incision and drainage. Two weeks later, she presented with increasing thigh pain, swelling, and a temperature of 99.5°F (37.5°C). Magnetic resonance imaging (MRI) showed an abscess of the vastus intermedius muscle (Figure 1). Incision and drainage were performed, and wound cultures grew methicillin-resistant S. aureus.
Figure 1. Coronal, Fat-Suppressed, T1-Weighted MRI Scan of the Thigh of Patient 1, Obtained after the Intravenous Administration of Gadolinium.
The ring-enhancing collection (arrows) is compatible with an abscess.
Patient 2 was a 33-year-old woman with no history of medical problems who presented after three days of pain and swelling in the right thigh and difficulty walking. She had been treated for axillary and gluteal boils with incision and drainage and cephalexin. MRI revealed phlegmon of the piriformis muscle. Blood cultures grew methicillin-resistant S. aureus.
Patient 3 was a 31-year-old woman with AIDS (CD4 cell count, 15 per cubic millimeter) who was not receiving antiretroviral therapy. She had had pain in the right thigh for one week and fever and leg swelling for two days. A computed tomographic (CT) scan showed fluid collection in the right anterior thigh. Blood cultures grew methicillin-resistant S. aureus.
Patient 4 was a 51-year-old man with type 2 diabetes mellitus. He presented with pain and swelling in the left lower extremity and was treated with cephalexin. One week later, he presented with difficulty walking and increased leg swelling. A CT scan showed a 2-cm fluid collection in the anterior thigh. The collection was surgically drained. Wound and blood cultures grew methicillin-resistant S. aureus.
Isolates were tested with an automated system (Vitek, BioMérieux) and were sensitive to tetracycline, vancomycin, gentamicin, and rifampin; all were resistant to azithromycin but sensitive to clindamycin. The isolates showed no inducible resistance to clindamycin with the use of the D-test. Two isolates were further tested against ciprofloxacin and were found to be resistant.
Patients with locally invasive soft-tissue infection should be suspected of having methicillin-resistant S. aureus. These four patients were treated with vancomycin for two to three weeks; two received oral clindamycin to complete their antibiotic course. All four patients had complete resolution of infection. This cluster of cases suggests that community-acquired methicillin-resistant S. aureus is emerging as an important cause of pyomyositis.
Maria E. Ruiz, M.D.
Seife Yohannes, M.D.
Christopher G. Wladyka, M.D.
Washington Hospital Center
Washington, DC 20010
maria.e.ruiz@medstar.net