Epidemiological Insights into HACEK Bacteria: A Seven-year Retrospective Analysis at a Tertiary Care Center in Istanbul

Abstract

Objective: HACEK bacteria (Haemophilus parainfluenzae, Aggregatibacterspp., Cardiobacterium hominis, Eikenella corrodens, and Kingella kingae) represent a group of fastidious organisms implicated in endocarditis and a range of opportunistic infections. Despite their clinical importance, epidemiological data on HACEK infections remain limited, particularly in T & uuml;rkiye. Methods: This retrospective analysis investigated 30 cases of HACEK infections diagnosed at a tertiary care hospital in Istanbul over a sevenyear period (2017-2023). Data were collected from electronic medical records and laboratory databases. Results: Patients ranged in age from 0 to 76 years, with isolates derived from a variety of clinical specimens. Cardiobacterium hominis was notably absent among the identified species. Polymicrobial growth was documented in 20 cases, predominantly involving Gram-positive cocci, particularly Streptococcus spp. Antimicrobial susceptibility testing was performed for four isolates, revealing significant challenges in interpretation due to the absence of standardized guidelines for HACEK pathogens. None of the cases received pathogen-specific therapy; all were managed with empirical antimicrobial regimens. Clinical outcomes were favorable in all but one patient, who succumbed to complications of coronavirus disease-2019. No cases of recurrent HACEK infection or infective endocarditis were observed during follow-up. Conclusions: These findings underscore the diagnostic challenges associated with HACEK infections and the potential underestimation of their prevalence. Prospective, multicenter studies are needed to clarify the epidemiological and clinical significance of these organisms. Moreover, the development of standardized antimicrobial susceptibility testing protocols and evidence-based therapeutic strategies is essential to optimize patient management and improve clinical outcomes.