Individual case: Streptococcus agalactiae infective endocarditis

The patient presented with progressive weakness of the extremities that had become so severe he could not walk.


The patient

A 58-year-old man with limited previous medical contact presented with weakness. Over the course of three weeks, he had experienced mild “flu-like” symptoms that had progressed to diffuse myalgias, arthralgias, anorexia, and malaise, without fevers. He had not sought medical care for these symptoms. Over the next several days, he began developing progressive weakness of the extremities that became so severe that he could not walk. He was brought by ambulance to the ED after his family members found him in bed incontinent and unable to stand.

Figure 1 CT of the chest axial view with soft-tissue window A 75 times 91 times 101-cm air-containing mass red arrow is centered over the left sternoclavicular joint with associated osteon
Figure 1. CT of the chest, axial view with soft-tissue window. A 7.5 × 9.1 × 10.1-cm air-containing mass (red arrow) is centered over the left sternoclavicular joint with associated osteonecrosis and extension to the anterior mediastinum and supraclavicular region.
Figure 2 CT of the chest sagittal view A hybrid view window emphasizes soft-tissue gas and fluid and disruption of the osseous cortex of the clavicle red arrow
Figure 2. CT of the chest, sagittal view. A hybrid view window emphasizes soft-tissue gas and fluid and disruption of the osseous cortex of the clavicle (red arrow).

His initial vitals included a temperature of 99 °F, blood pressure of 105/60 mm Hg, heart rate of 134 beats/min, respiratory rate of 16 breaths/min, and an oxygen saturation of 97% on room air. Physical examination was notable for a large 10-cm soft mass at the base of his neck and left sternoclavicular joint. He reported no prior awareness of the lesion. There were no neurological deficits, murmurs, or skin findings. Laboratory investigations were notable for a white blood cell count of 19 × 109 cells/L (reference range, 4.2 to 9.1 × 109 cells/L), a lactate level of 3.4 mmol/L (reference range, ≤1.2 mmol/L), an HbA1c level of 11% (reference range, 4.8% to 5.8%), and a troponin I level of 1.41 ng/mL (reference range, <0.034 ng/mL) without significant abnormalities on electrocardiogram. Urine was positive for leukocyte esterase and pyuria. CT imaging demonstrated a 7.5 × 9.1 × 10.1-cm necrotic mass involving the left sternoclavicular joint, as well as a splenic infarct (Figures 1, 2). A head CT showed a right-sided parieto-occipital infarct. The patient was fluid resuscitated and started on broad-spectrum antibiotics.

Figure 3 Transesophageal echocardiography mid-esophageal aortic valve long-axis view showing a 13-cm broad-based vegetation on the aortic side of the aortic valve red arrow and aortic root thick
Figure 3. Transesophageal echocardiography, mid-esophageal aortic valve long-axis view, showing a 1.3-cm broad-based vegetation on the aortic side of the aortic valve (red arrow) and aortic root thickening suggestive of abscess (blue arrow).

His blood cultures grew Streptococcus agalactiae (2 of 2 bottles), and transesophageal echocardiography revealed a 1.3-cm aortic valve vegetation with a perivalvular abscess (Figure 3). His broad-spectrum antibiotics were narrowed to a six-week course of ceftriaxone, including an initial two weeks of combination therapy with gentamycin. He eventually underwent abscess debridement and partial resection of his first rib, clavicle, and sternum, followed by aortic valve replacement. Cultures from debridement of his chest wall were also positive for Streptococcus agalactiae. His postoperative course was prolonged and complicated by cytomegalovirus colitis, hemorrhagic shock, a sacral wound, and respiratory failure. He died after an eight-month hospitalization.

The diagnosis

The diagnosis in this case was Streptococcus agalactiae endocarditis. Infective endocarditis is not an uncommon disease state, and this patient's subacute presentation with nonspecific signs and symptoms is often encountered. However, endocarditis secondary to Streptococcus agalactiae, also known as Group B streptococcus (GBS), is not as well described. GBS is a major cause of invasive disease in neonates and pregnant women, but incidence in nonpregnant adults has increased in recent years, with rates ranging from 4.1 to 7.2 per 100,000. Although immunocompromised patients (e.g., those with HIV infection, diabetes, cirrhosis, or malignancy) are considered to be at higher risk for invasive GBS infection, GBS endocarditis has been described in nonpregnant immunocompetent adults.

GBS most commonly presents as skin and soft-tissue infections. Endocarditis is a rare manifestation, accounting for 18% of invasive presentations in adults, and 1.3% to 3% of all cases of endocarditis. GBS endocarditis is particularly virulent with rapidly progressive disease, comparable in severity and disease course to infection with Staphylococcus aureus. It is often complicated by large, distinctive, friable vegetations; embolization; heart failure; and severe valve destruction necessitating early surgical intervention. Mortality rates remain high at 41% to 47%. Current European and U.S. treatment guidelines recommend cephalosporin or penicillin for four to six weeks and consideration of combination therapy with an aminoglycoside for the first two weeks given penicillin resistance patterns, as was used in this case. However, given the rarity of the disease, clinical evidence to support combination therapy is lacking outside of in vitro studies.

Pearls

  • Incidence of Streptococcus agalactiae invasive infections is increasing among nonpregnant immunocompromised adults.
  • Streptococcus agalactiae can cause an aggressive form of endocarditis with serious complications and high morbidity and mortality.

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