The role of pathogenicity factors of hacek bacteria in the development of infectious endocarditis (literature review)

Background. Infective endocarditis caused by gram-negative microorganisms of the HACEK group represents a rare and poorly studied form of the disease. HACEK group bacteria are part of the normal flora of the oral cavity and upper respiratory tract, but under certain conditions can cause severe infectious complications. Understanding the pathogenicity mechanisms of these microorganisms is key to improving the diagnosis and treatment of infective endocarditis.
Objective: to describe the virulence factors of HACEK group bacteria and elucidate their role in the onset and development of infective endocarditis through analysis of current literature.
Materials and methods. A systematic analysis of scientific literature devoted to studying the virulence factors of HACEK group microorganisms (Haemophilus spp., Aggregatibacter spp., Cardiobacterium spp., Eikenella corrodens, Kingella spp.) and their role in the development of infective endocarditis was conducted. Mechanisms of adhesion, invasion, biofilm formation, and toxin production were reviewed.
Results. It was established that the main virulence factors of HACEK group bacteria include: capsule that protects against phagocytosis; type IV pili that ensure adhesion to endocardial cells; ability to form biofilms; production of exotoxins (leukotoxin, cytolethal distending toxin, RtxA); presence of proteases and endotoxins. It was shown that different representatives of the HACEK group have varying abilities to cause infective endocarditis: the highest risk was noted for Aggregatibacter, Cardiobacterium, and Kingella (23-60% of bacteremia cases), lower risk for Haemophilus and Eikenella (6–14%).
Conclusion. Study of virulence factors of HACEK group bacteria contributes to understanding the mechanisms of infective endocarditis development and may help in developing new methods of diagnosis, treatment, and disease prevention. Special attention should be paid to preventive measures in risk group patients, including oral hygiene maintenance and antibiotic prophylaxis during medical procedures.

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