Common and Uncommon Pathogens Causing Infective Endocarditis

The most common pathogens in infective endocarditis (IE) are those that colonize the skin, mouth, and gastrointestinal tract, as these are the sites from which microorganisms can gain access to the bloodstream at various times. The most common pathogens causing IE are staphylococci, streptococci, and enterococci. Staphylococcus aureus is identified as the most common cause of IE, overtaking viridans group streptococci, which were predominant until a couple of decades ago. Coagulase-negative staphylococci are common commensal microorganisms that colonize skin. Enterococcus faecalis and E. faecium, and rarely other enterococci, are important causes of IE. Less common pathogens that cause IE include beta hemolytic streptococci, Candida, HACEK group microorganisms, Bartonella, Cutibacterium acnes, and Coxiella. Uncommon pathogens include Abiotrophia, Granulicatella, Gemella, Rothia, Stomatococcus, Pseudomonas aeruginosa, Mycobacterium chimaera, Aerococcus, Gram-positive bacilli, Histoplasma capsulatum, bacteria from the order Enterobacterales, Parvimonas micra, and Aspergillus.