Deep Sternal Wound Infection Caused by Rhizopus Species After Coronary Artery Bypass Graft

Abstract

Deep sternal wound infection is a rare complication of cardiac surgery that is typically caused by skin resident flora, such as species of Staphylococcus and Streptococcus. Infections caused by fungi are less common and are generally caused by Candida species. Regardless of etiology, these infections are associated with significant morbidity and mortality. We present a case of postoperative mediastinitis that occurred following a 5-vessel coronary artery bypass graft and was caused by a filamentous fungus of the Rhizopus genus. The patient was treated with serial debridement, liposomal amphotericin B, and isavuconazonium and was discharged from the hospital in stable condition. Fungal mediastinitis is a rare entity, and clinicians must maintain a high level of suspicion to make the diagnosis. A fungal cause of postoperative mediastinitis should be considered in patients with negative bacterial cultures, uncontrolled diabetes, or current immunosuppression or those who present weeks after surgery with a subacute onset of symptoms.

Keywords: Mucorales; Rhizopus; cardiac surgery; deep sternal wound infection; mediastinitis.

Figure 1.

Gross appearance of the patient’s sternal wound prior to first surgical debridement shows devitalized tissue, most prominent at the left costal cartilage.

Figure 2.

A, A tape preparation of a Rhizopus culture stained with lactophenol cotton blue. The morphology shows broad pauciseptate hyphae with rhizoids directly opposite sporangiophores. B, Hematoxylin and eosin staining of sternal bone from the patient's initial debridement at our hospital shows fragments of necrotic soft tissue, cartilage, and bone with acute inflammation. Present are scattered fungal organisms with broad ribbon-like hyphae, morphologically consistent with mucormycosis.