Systemic Infection Caused by Mycobacterium fortuitum Following Aortic Valve Transplantation-Employing Combined Molecular Techniques for Accurate Species Identification.

Mycobacterium fortuitum, a nontuberculous mycobacterium (NTM), is known for causing opportunistic infections, particularly in immunocompromised individuals. Identification of NTM species requires precise diagnostic techniques. Here, we present a study of a systemic infection by M. fortuitum in an elderly patient, identified through MALDI-TOF MS and confirmed by gene sequencing. An 88-year-old Italian man developed an abscess at his pacemaker site, leading to acute infectious endocarditis caused by Staphylococcus capitis. During hospitalization, he experienced multiple complications, including jugular vein thrombosis, pulmonary thromboembolism, and gastrointestinal bleeding. Despite treatment with vancomycin, he developed bacteremia, allowing the isolation of M. fortuitum from blood culture. The strain was identified using MALDI-TOF MS and confirmed by Sanger sequencing of the 16S rRNA and hsp65 genes. Phylogenetic analysis supported the identification. The patient, after treatment with carbapenems and aminoglycosides, returned to Italy without further clinical complications. This case underscores the necessity of precise diagnostic tools for managing NTM infections. The combined application of MALDI-TOF MS and gene sequencing enabled accurate species identification, which is essential for guiding effective treatment of systemic M. fortuitum infections, especially in complex clinical scenarios involving immunosuppression.