A Case of Rapid Development of Methicillin‑Resistant Staphylococcus aureus Mechanical Aortic Root Abscess Despite Appropriate Antibiotic Use

Abstract

A 74-year-old male with a past medical history of mechanical aortic valve replacement presented with abdominal pain and fever. Blood cultures revealed methicillin-resistant Staphylococcus aureus (MRSA) and the patient was started on target antibiotics. Initial transthoracic echocardiogram and transesophageal echocardiogram (TEE) did not show any vegetations or significant valvular regurgitation. No other sources of infection were identified. Five days after the initial TEE, a repeat TEE revealed new areas of thickening and echolucency seen anterior to the mechanical aortic valve, suggestive of aortic root abscess (AoRA). It also extended down the mitral-aortic intervalvular fibrosa and was associated with mitral valvular vegetation.Due to worsening clinical status and persistent bacteremia on appropriate antibiotics, a high index of suspicion for infective endocarditis (IE) remained after the initial TEE. As such, the repeat TEE was obtained only five days after and demonstrated clear evidence of rapidly growing endocarditis and abscess formation. This case uniquely demonstrates how rapid MRSA endocarditis may progress and emphasizes its high mortality. This case highlights the importance of a low threshold for repeat imaging when the index of suspicion for endocarditis remains high despite negative imaging.

Transesophageal Echocardiography vs. Transthoracic Echocardiography for Methicillin-Sensitive Staphylococcus aureus and Methicillin-Resistant Staphylococcus aureus Endocarditis

“…It is relevant to mention that two patients had histories of aortic valve replacement [ 28 ], pacemaker, and hip prosthetic implantation [ 29 ]. Despite receiving antibiotic treatment, the first patient who had undergone aortic valve replacement seven years prior developed an aortic root abscess.…”

“…Despite receiving antibiotic treatment, the first patient who had undergone aortic valve replacement seven years prior developed an aortic root abscess. The blood cultures revealed that the infection was caused by MRSA, highlighting the aggressiveness of this microbe and its association with aortic root abscess [ 28 ]. The other patient developed IE related to their intracardiac device implantation.…”

“…The other comorbidity cases were attributed to hypertension with five patients [ 21 , 22 , 24 , 26 ] and type 2 diabetes mellitus also with five patients [ 21 , 22 , 24 , 26 , 28 ]. The three patients diagnosed with chronic hepatitis C have also reported a history of intravenous drug use [ 22 , 23 , 30 ].…”

“…The cultures performed in these patients resulted in eight MSSA [ 21 - 27 ], and three MRSA [ 28 - 30 ].…”

“…Five different sites were identified to be the sites of IE: the aortic valve, tricuspid valve, mitral valve, papillary muscles, and an atrial pacer lead. The aortic valve was involved in five of the patients [ 21 , 22 , 26 , 28 ], tricuspid in three [ 25 , 27 , 30 ], and mitral in three [ 23 , 24 , 27 ]. Papillary muscle was affected in one of the patients [ 27 ], and atrial pacer lead was the site of vegetation in one patient [ 29 ].…”