Adult Empyema Necessitans by Methicillin-Resistant Staphylococcus Aureus Christopher Betts, MS-III1, Pantea Hashemi, MD2

1Ross University School of Medicine – Dominica, West Indies 2Department of Internal Medicine – Harbor Hospital, Baltimore MD Abstract: Empyema necessitans is a complication of refractory empyema that spreads outward from the pleural space, through the parietal pleura and intercostal space, and into the subcutaneous tissue of the thoracic wall. The infection can involve soft and even bone tissue, causing osteonecrosis of the affected rib. The most common pathogens involved in empyema necessitans are either Mycobacterium tuberculosis or Actinomyces species, but in rarer cases, Streptococcus and Staphylococcus species can also be involved. Only up to four recorded cases of empyema necessitans by methicillin-resistant staph aureus (MRSA) have been seen. This report briefly reviews the evolution of an empyema necessitans, and it introduces the fifth most recent case recorded of empyema necessitans caused by MRSA. Case Report: A 40 year old African American female with a history of past cocaine and heroin use was admitted to the emergency department with initial complaints of fever, chills, and sweats for one week. The symptoms were accompanied by productive cough with yellow sputum. She denied any other physical complaints, as well as having any sick contacts at home, recent travel outside her home, or any past respiratory infections. Her past medical history only consisted of a recent uncomplicated urinary tract infection. Medications she took prior to admission were Naprosyn and ciprofloxacin. She had no pertinent family history to any respiratory disease. She was a 10 pack-year active smoker, denied any alcohol use, and admitted to using cocaine and heroin three years ago. Further review of systems was noncontributory.

Her vital signs were stable and most of the physical exam was unremarkable. Her general appearance showed a well-developed African American female who appeared alert, oriented, and in no acute distress. Examination of the skin showed a palpable, non-tender, non-erythematous subcutaneous mass over the right anterior chest wall above the nipple along the midclavicular line. Her lab values showed leukocytosis and the initial AP chest radiograph showed right hilar and perihilar opacification measuring 11 cm by 6 cm (Figure A). CT of the chest showed a 7.5-cm wide intrathoracic mass residing over the anterior segment of the right upper lobe. This was compatible with an abscess with an inflammatory extension into the right pectoralis muscle (Figure B).

Initially, the patient was started on Zosyn 3.375 mg PO. Blood cultures were ordered and demonstrated gram positive cocci in clusters compatible with MRSA. IV vancomycin was added with her regimen of Zosyn. No initial aspiration of the abscess was done and the patient was directly sent to surgery for drainage of the abscess including right anterior thoracotomy. This was followed with debridement and evacuation of pleural empyema with wound VAC placement. The drained fluid was cultured and demonstrated heavy growth of MRSA and did not show fungal or acid-fast bacillus growth. The resected ribs showed to be fractured and necrotic. Following surgery, patient was sent to ICU and continued on only vancomycin. A 2D echo was performed to rule out any valvular vegetative growth, due to bacteremia, but results were

unremarkable. After 5 days, blood culture showed no growth and a second chest radiograph revealed a decreased size of the abscess (Figure C). Postoperatively, the patient was discharged on Linozelid, which led to significant improvement and resolution of the empyema. The final impression from this case: Empyema necessitans of the right anterior chest wall and bacteremia associated with methicillin-resistant Staphylococcus aureus. Discussion: Empyema necessitans (EN) is a rare complication of empyema in the pleural space where inflammation and bacterial invasion spread outward into the soft tissues of the thoracic wall. It was first depicted in medical literature in 1640 by Gullan De Baillon and first demonstrated in clinical cases by Sindel in 1940. Since the dawn of antibiotic therapy, the incidence of EN has diminished and is now rare in clinical practice. An empyema initiates as a parapneumonic effusion, or a pleural effusion secondary to pneumonia. The evolution of a parapneumonic effusion into an empyema consists of three subsequent steps: an exudative phase, a fibropurulent phase, and an organized phase. In this process the effusion can become infected with bacteria and become a collection of pus in the pleural space, forming a pyelothorax. A parapneumonic effusion in its exudative phase is self-limited, requiring no drainage if immediately treated with antimicrobial therapy. During this phase, the inflammatory process causes release of cytokines that cause increased capillary permeability and transudation of plasma into the pleural space1. In the fibropurulent phase, the effusion is invaded of bacteria and requires antibiotics and tube drainage. There can also be early formation of intrapleural loculations and pleural peels made of woven collagen deposits by fibroblasts. In the organized phase, cytokines like transforming growth factor cause proliferation of fibroblast cells along the surface of the pleural space and increased deposition of collagen along this surface1. The phase is thus characterized by established fibrotic peels, viscous pleural pus, and loculations. These pleural peels can encase the lung, trap it, and prevent it from expanding. In rare cases, the empyema can continue through the parietal pleural and cause inflammation of the intercostal muscles, dissecting into the intercostal space forming a subcutaneous abscess along the chest wall. This is known as empyema necessitans. In the US, the most common pathogens involved in cases of empyema necessitans are Mycobacterium tuberculosis and Actinomyces species2. To a lesser degree, other causative bacterial pathogens are Streptococcus species, Fusobacterium nucleatum, Mycobacterium avium-intracellulare, Staphylococcus species, notably S. aureus, and Burkholderia cepacia3. Most cases of empyema necessitans by S. aureus involve methicillin-sensitive species, but up to four cases in the US have been from MRSA. This may be due to the rising prevalence of MRSA in the US over the past decades. Stallworth et al3 and Moore et al4 described the first two cases in pediatric patients, in 2005 and 2006 respectively. Mizell et al5 reported the third case in 2008, which was the first adult case. Contreras et al6 reported the fourth case on a pediatric patient in 2009. To our knowledge, this patient presented as the fifth case of MRSA empyema necessitans in the US and the second adult case of its kind. Acknowledgments:

Strong thanks to both Dr. P. Hashemi and Dr. J. Fernandez for their permission to review this case, as well as their thoughtful collaboration in setting up this case report. Also, a strong thanks you to Justin Clark (Third year medical student, Saba University) in his personal collaboration with this case report. No conflicts of interest were present and no financial support was given. References: 1. Llamas-Velasco, M., Dominguez, I., et al. Empyema necessitatis revisited. Eur J

Dermatol 20(1): 115-119. 2. Freeman, A.F., Ben-Ami, T., Shulman, S.T. 2004. Streptococcus pneumoniae

Empyema Necessitatis. Pediatr. Infect. Dis. J. 23:177-179. 3. Stallworth, S., Mack, E., Ozimek, C. 2005. Methicillin-resistant Staphylococcus

arueaus empyema necessitatis in an eight-month-old child. South. Med. J. 98: 1130-1131.

4. Moore, F.O., Berne, J.D., et al. 2006. Empyema necessitatis in an infant: a rare surgical disease. J. Pediatr. Surg. 41:E5-E7.

5. Mizell, K.N., Patterson, K.V., Carter, J.E. 2008. Empyema Necessitatis Due to Methicillin-Resistant Staphylococcus aureus: Case Report and Review of Literature. J. Clin. Micro. 46:3534-3536

6. Contreras, G.A., Perez, N., et al. 2009. Empyema necessitans and acute osteomyelitis associated with community acquired methicillin resistant Staphylococcus aureus in an infant. Biomed. 29:506-512.

Images:

Figure A: An initial AP chest radiograph showing a right hilar and perihilar opacification that measured 11 cm by 6 cm.

Figure B: An initial CT of the chest showing a 7.5 cm intrathoracic mass compatible with an abscess residing over the anterior segment of the right upper lobe, including inflammatory extension through the chest wall and into the right pectoralis muscle. .

Figure C: A follow-up AP chest radiograph revealing a decreased size of rounded infiltrate within the middle right lung and persistent infiltrate in right lower lung