Methicillin-resistant Staphylococcus aureus empyema necessitatis in an eight-month-old child.

Abstract: Empyema necessitatis is a rare complication of empyema characterized by a spontaneous extension of pus from the pleural space into adjacent soft tissues. It is uncommon in the pediatric population and is usually caused by Mycobacterium tuberculosis. This report describes the youngest reported case of empyema necessitatis. The clinical examination and CT scan are diagnostic. The causative organism was methicillin-resistant Staphylococcus aureus, which has not been previously reported. Treatment involves drainage of the abscess and appropriate antimicrobial therapy.

Key Words: empyema necessitatis, methicillin-resistant Staphylococcus aureus, pleural effusion, pneumonia, tuberculosis

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Empyema necessitatis (Latin, "need or necessity") is a rare complication of empyema characterized by a spontaneous extension of pus from the pleural space into adjacent soft tissues. Empyema necessitatis is uncommon in the pediatric population and is usually caused by Mycobacterium tuberculosis. It was first described in 1640 by Gullan De Baillon, who reported the rupture of a syphilitic aneurysm. The first review on empyema necessitatis by Sindel (1) in 1940 described 115 cases, 73% of which were caused by tuberculosis. Since the antibiotic era, tuberculosis still accounts for approximately 50% of cases by one report. (2) We present the youngest reported case, to our knowledge, of empyema necessitatis. The causative organism was methicillin-resistant Staphylococcus aureus (MRSA), which has not been previously reported.

Case Report

A previously healthy 8-month-old black male presented on transfer from an outlying hospital with the diagnosis of a right-sided pneumonia with pleural effusion. The patient became ill 1 week before admission with a temperature of 103 [degrees]F (39.4 [degrees]C), cough, nausea, and vomiting. The patient was taken to his primary care physician and was prescribed azithromycin. Two days later, the patient was admitted to an outlying hospital for persistent fever, decreased oral intake, and continued cough. Chest radiography revealed a right lower lobe consolidation and a right pleural effusion. The patient was begun on cefotaxime, and vancomycin was added when the blood culture was reported positive for MRSA resistant to amoxicillin/clavulanate, ampicillin/sulbactam, cefazolin, ciprofloxacin, erythromycin, oxacillin, and penicillin. The MRSA was sensitive to clindamycin, gentamicin, rifampin, trimethoprim/sulfamethoxazole, vancomycin, and tetracycline. The organism was not assayed for Panton-Valentine leukocidin. The patient continued to have fever to 103 [degrees]F (39.4 [degrees]C), and, the next day, his right chest wall was noted to visually increase in size. The patient was then transferred to our facility.

On arrival, vital signs included a temperature of 100.0 [degrees]F (37.7 [degrees]C), heart rate of 177 beats per minute, respiratory rate of 48 breaths per minute, and a blood pressure of 80/55 mm Hg. On examination, the patient appeared nontoxic. There was no murmur or evidence of bone or joint infection. The lung examination was significant for decreased breath sounds on the right and soft tissue swelling extending along the right posterior chest wall. Laboratory studies revealed a white blood cell count of 27,100/[mm.sup.3] (with 18% band forms, 55% neutrophils, 19% lymphocytes, 7% monocytes, 1% eosinophils), hemoglobin of 8.5 g/dL, and platelet count of 727,000/[mm.sup.3]. Serum electrolytes and creatine phosphokinase were within normal limits. A CT scan of the chest demonstrated a moderate right-sided density with a chest wall fluid collection (Figure). These findings were noted to be consistent with empyema necessitatis. The next day, a right thoracostomy and drainage of the empyema were performed. The surgeon noted a chest wall abscess that communicated with the thoracic cavity. Culture of the empyema yielded MRSA. The patient had a chest tube placed and was continued on vancomycin (10 mg/kg for a total of 10 days). The patient improved significantly after surgery and was eventually discharged home on oral trimethoprim/sulfamethoxazole (10 mg/kg per day, based on trimethoprim component) to complete a 21-day course of antibiotics. On follow up 3 weeks after discharge, the patient was afebrile and asymptomatic.

Discussion

In empyema necessitatis, most frequently the inflammatory tissue ruptures through an intercostal space, resulting in a subcutaneous abscess. The most common location of rupture is the anterolateral chest wall. Rupture is commonly associated with bronchopleural fistula formation. Other locations of reported extension include the abdominal wall, paravertebral space, vertebrae, esophagus, bronchus, mediastinum, diaphragm, pericardium, flank, thigh, breast, and retroperitoneum. (2,3) The median age at diagnosis is 44.5 years. (2) Approximately 50 to 70% of cases are associated with tuberculosis, and the second most common cause is actinomycosis. (2) Other reported causes include Streptococcus pneumoniae, methicillin-sensitive S aureus, Streptococcus milleri, Fusobacterium nucleatum, Mycobacterium avium-intracellulare, Burkholderia cepacia, blastomycosis, and lymphoma. (2) To our knowledge, there have been no reported cases of MRSA. The clinical presentation may be subacute, or, in the case of the more indolent organisms such as in tuberculosis and actinomycosis, the cough may persist for years before diagnosis. Physical examination usually reveals fever, a painful fluctuant mass on the chest wall, and localized lung findings. Diagnosis is made with CT. Treatment involves drainage, excision of the abscess, and appropriate antibiotic therapy. Empyema necessitatis has a favorable prognosis if treated with appropriate antimicrobial therapy and the abscess is drained. Since the antibiotic era, mortality rate has been reported as 0%. (2) This case report serves as another example of the emergence of MRSA in significant pediatric infections.

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Conclusions

Our patient is unique because of the young age and the implicated organism. In the face of both rampant antibiotic resistance and immunosuppression, bacterial disease has become more diverse and difficult to treat. Because of recent reports of community-acquired MRSA emerging as a major bacterial pathogen in soft tissue infections, (3) the authors speculate that this pathogen may become more prevalent in association with more complicated diseases. Health care providers should be aware of empyema necessitatis in the treatment of children with complicated pneumonia.

References

1. Sindel EA. Empyema necessitatis. BullSea View Hospital 1940;6:1-49.

2. Freeman AF, Ben-Ami T, Shulman S. Streptococcus pneumoniae empyema necessitatis. Pediatr Infect Dis J 2004;23:177-178.

3. Dietrich DW, Auld DB, Mermel LA. Community-acquired methicillin-resistant Staphylococcus aureus in southern New England children. Pediatrics 2004;113:e347-e352.

James Stallworth, MD, Elizabeth Mack, MD, and Christopher Ozimek, MD

From the Department of Pediatrics, University of South Carolina, Columbia, SC.

Reprint requests to James R. Stallworth, MD, University of South Carolina School of Medicine, Department of Pediatrics, 14 Medical Park, Suite 400, Columbia, SC 29203. Email: [e-mail]

Accepted June 28, 2005.

None of the authors has any commercial or proprietary interest in any drug, device, or equipment mentioned in this manuscript. There was no financial support for this work. The authors have no financial conflicts of interest relevant to this work.

RELATED ARTICLE: Key Points

* Empyema necessitatis is an uncommon complication of pneumonia in which pus extends from the pleural space into adjacent soft tissues, usually the anterolateral chest wall.

* Mycobacterium tuberculosis is the most common cause of empyema necessitatis.

* Empyema necessitatis has a good prognosis after abscess drainage and appropriate antimicrobial agents.

* Clinicians should be aware of uncommon suppurative complications of pneumonia in patients of all ages.