Empyema Necessitans: A Rare Presentation of Methicillin-Sensitive Staphylococcus aureus Bacteremia

AUTHORS:
Xin Yee Tan, MD • Ibrahim Hammada, MD • Addi Feinstein, MD

AFFILIATION:
NYC Health + Hospitals/Lincoln, Bronx, New York

CITATION:
Tan XY, Hammada I, Feinstein A. Empyema necessitans: a rare presentation of methicillin-sensitive Staphylococcus aureus bacteremia. Consultant. 2020;60(4):31-32. doi:10.25270/con.2020.03.00022

Received July 4, 2019. Accepted February 20, 2020.

DISCLOSURES:
The authors report no relevant financial relationships.

CORRESPONDENCE:
Xin Yee Tan, MD, Department of Internal Medicine, NYC Health + Hospitals/Lincoln, 234 East 149 St, Bronx, NY 10451 (tanx@nychhc.org)

A 41-year-old man with a history of treated hepatitis C virus infection, methadone dependence, and intravenous drug use presented with a 1-day history of left suprascapular pain. He reported intravenous heroin injection 2 weeks prior to presentation. He denied any associated trauma, decreased range of motion of the shoulder, or changes in the overlying skin.

During the initial assessment, the patient was noted to have a low-grade fever (temperature, 38.2°C) but was otherwise hemodynamically stable. Results of initial laboratory workup showed leukocytosis (11,000 white blood cells/mm³). Chest radiographs at presentation showed no acute abnormalities. Bedside echocardiography showed no vegetations. Blood cultures were obtained, and antibiotics were initially held, given no clear evidence of bacterial infection. The patient was observed for 1 day on the medicine floor with improvement of symptoms with analgesics and no recurrent fever, and he was discharged the day after.

A few hours after discharge, the patient was recalled when his blood culture results returned positive for gram-positive cocci in clusters. On the second presentation, the patient had a high-grade fever and was tachycardic. Radiographs now showed a left upper lobe lesion concerning for abscess. Computed tomography (CT) scans of the chest confirmed a 6.2-cm abscess in the anterior upper lobe with extension into the left pectoralis major and with a small pleural effusion (Figure 1). He was started on vancomycin, ceftriaxone, and azithromycin.

Figure 1. Chest CT on presentation showing a left upper lobe abscess with extension to the pectoralis.

The patient subsequently underwent a CT-guided placement of a drainage catheter in the left anterior pleural abscess. Approximately 15 mL of purulent fluid was aspirated when the drain was placed. Subsequent transesophageal echocardiography showed no endocarditis.

Final blood cultures grew methicillin-sensitive Staphylococcus aureus (MSSA), and vancomycin was deescalated to nafcillin tailored to sensitivity, and was switched to cefazolin for ease of administration. The patient was treated with 14 days of antibiotics in total.

Repeated chest CT 3 days later showed marked shrinkage of abscess (Figure 2). The drain was removed 12 days after placement, and the patient improved clinically, with subsequent serial blood cultures showing no further growth.

Figure 2. Repeated chest CT, performed after starting treatment and placement of percutaneous drainage, showing clear reduction in the abscess size.

DISCUSSION

Empyema necessitans (EN), also called empyema necessitatis, is an intrathoracic empyema that extends through the parietal pleura and invades the chest wall, forming a collection of pus in the extrathoracic soft tissues—in our patient’s case, the pectoralis major.

Mycobacterium tuberculosis is the most common cause of EN (accounting for 70% of cases), and Actinomyces species is the second most common cause.¹ Other reported causative organisms include Blastomyces, Aspergillus, Nocardia, mucormycetes, and Fusobacterium.¹ S aureus has been reported as the causative organism in very few cases; these were mainly cases of methicillin-resistant S aureus.² Our literature review revealed only one other reported case of MSSA causing EN,³ in which a patient who was an injection drug user had MSSA bacteremia and infective endocarditis causing septic emboli to the lung complicated by EN. Similarly, our patient was an injection drug user who developed MSSA bacteremia but without clinical or echocardiographic evidence of endocarditis. Presumably, injection drug use led to MSSA bacteremia, which in turn led to a lung abscess that rapidly extended to involve the pectoral muscle.

In contrast to the usual chronic progression of EN,⁴ the progression in our case was rapid. Chest radiographs at presentation were negative for abnormalities, and the patient was not septic. When the patient was recalled 2 days later after positive blood culture results, he had become septic. Repeated chest radiographs showed a left upper lobe abscess, and invasion of the pectoral muscle became evident on CT scan. Interestingly, the left-sided pleural effusion was small in size, which is not typical for EN that typically occurs in longstanding parapneumonic effusions.⁴

After rapid progression of the infection, the patient’s recovery was also rapid, under the standard treatment including abscess drainage and intravenous antibiotics. A complete course of 14 days of antibiotics was given for treatment of bacteremia, with no extended course indicated, since the patient was found to have no evidence of infective endocarditis or osteomyelitis.

CONCLUSION

EN is rarely caused by MSSA and, to our knowledge, our case is only the second report of EN in MSSA bacteremia. In contrast to the typical chronic progression of EN secondary to parapneumonic effusions, S aureus-related EN tends to be more acute and does not necessarily occur in association with large pleural effusions. Appropriate antibiotic coverage and timely drainage are essential for full recovery.

REFERENCES:

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