MRSA Infections and Thrombosis

Photo Essay
Focus on Signs and Symptomes 

Methicillin-resistant Staphylococcus aureus (MRSA) infections are increasing in prevalence and severity. Initially recognized as a soft tissue pathogen, MRSA is also responsible for endocarditis, meningitis, ophthalmitis, and osteomyelitis. In addition, novel complications have been appreciated, such as contiguous venous thrombosis and embolization secondary to MRSA infections. Reports of thrombosis consequent to MRSA osteomyelitis in children have predominated.^1-5 Here, we present 2 cases of adults with MRSA infections complicated by left transverse, sagittal cerebral venous thromboses with septic emboli to the lungs and bilateral iliac vein thrombosis, respectively.

CASE 1

An 18-year-old man presented with a 6-day history of fever, neck pain, head-ache with left ear pain, decreased auditory acuity, and double vision. He had been previously healthy.

History. He denied alcohol and drug abuse. He was monogamous and had never been treated for sexually transmitted diseases.

Physical examination. The patient appeared ill. Temperature was 100.9°F; heart rate was 96 beats per minute. Although his pupils were equal and responsive to light, his visual acuity was decreased from 20/20 to 20/75 bilaterally. He had right lateral rectus palsy. Light sensitivity precluded funduscopic examination. The left tympanic membrane was bulging. The remainder of the neurological and physical examinations was normal.

Laboratory results. White blood cell count was 15,300/µL with increased neutrophils. The rest of the complete blood cell count and chemistry results were normal. Blood cultures grew MRSA. Lumbar puncture demonstrated increased pressure (55 mm H₂O); cerebrospinal fluid analysis revealed white cells (3 neutrophils) and increased protein (60 mg/dL). 

Imaging results. An MRI scan of the brain showed thrombosis of the left transverse and sagittal sinuses as well as fluid in the left mastoid air cells (Figure 1). The absence of blood flow within the left sigmoid sinus and left internal jugular vein suggested thrombosis in the left sigmoid sinus. A transthoracic echocardiogram did not implicate endocarditis.

Outcome of this case. Vancomycin was initiated, and continuing ambulatory intravenous therapy with daptomycin was given for a total of 6 weeks. Neurological and ear symptoms and signs resolved.

CASE 2

A previously healthy 34-year-old woman presented to the emergency department with a 4-day history of low back pain radiating to the left abdomen. Initially, she had seen her primary care physician, who prescribed cyclobenzaprine and naproxen. The patient then consulted a chiropractor and underwent manipulation without relief.

History. She had no exposure to alcohol or drugs. She was married and had not been treated for any sexually transmitted diseases.

Physical examination. The patient appeared ill. Temperature was 103.1°F; heart rate was 144 beats per minute; initial blood pressure was 120/63 mm Hg, dropping to 80/60 mm Hg within 90 minutes of arrival. Tenderness was noted in the left upper and lower abdomen without peritoneal signs. She had paraspinal muscle tenderness in the lumbar and lower thoracic region. The rest of the examination was normal.

Laboratory results. White blood cell count was 11,700/µL with increased neutrophils. The rest of the complete blood cell count and chemistry results were normal. Blood cultures grew MRSA.

Imaging results. A transthoracic echocardiogram as well as a transesophageal echocardiogram did not detect vegetations. An initial CT scan of the abdomen and pelvis was normal. An MRI scan of the lumbar spine showed areas of various T-spine abnormalities that were thought to be hemangiomas.

A repeated abdominal/pelvic CT scan 9 days later showed thrombi in the pelvic and iliac veins and inferior vena cava (Figure 2). A chest CT scan showed multiple septic emboli in the lungs (Figure 3).

Outcome of this case. Antibiotic therapy with vancomycin was initiated and then switched to daptomycin and linezolid. The patient received anticoagulation with heparin. After 6 weeks of treatment, she recovered.

DISCUSSION

Community-acquired MRSA (CA-MRSA) infections are epidemic. The literature suggests that MRSA has been associated with cerebral venous sinus thromboses (as in Case 1) as well as thrombotic and embolic events in other venous systems contiguous to primary MRSA infections (Case 2). Although the earliest literature on MRSA-associated thrombophilia addressed pediatric MRSA infections, thrombophilia consequent to MRSA occurs in both children and adults. 

A review by Naesens and colleagues⁶ identified 12 cases of CA-MRSA with central nervous system (CNS) involvement. A report in 2001 of a 30-year-old man with an acute febrile illness and frontal headache implicated MRSA, and a brain MRI scan revealed a cavernous sinus thrombosis.⁷ A report by Sifri and associates⁸ demonstrated septic thrombosis of the superior sagittal sinus after face-lift surgery complicated by a CA-MRSA infection.

The CNS venous system is not the only site at risk for thrombosis. Although secondary venous thrombosis has been considered rare during osteomyelitis in general, CA-MRSA may be associated with venous thrombosis in children with osteomyelitis. The estimated incidence of venous thromboses in children is 0.07 per 10,000; neonates and adolescents are most susceptible.⁹ However, the incidence of secondary venous thrombosis in children with CA-MRSA osteomyelitis has increased since 2001.

Complicating venous thrombosis adjacent to the site of infection occurred in 7 children with CA-MRSA osteomyelitis.¹ Between August 2001 and December 2004, 116 patients at Texas Children’s Hospital experienced CA-MRSA acute hematogenous osteomyelitis and 7 developed venous thrombosis. Femoral and popliteal veins were most commonly affected. Septic emboli were found in 4 children.

Given the increasing incidence of CA-MRSA infections, thrombosis and embolization need to be recognized as a novel and dangerous complication.