Non-HACEK gram-negative bacilli infective endocarditis: data from a retrospective German cohort study

Infective endocarditis caused by non-HACEK gram-negative bacilli (GNB-IE) is rare but associated with significant morbidity and case fatality. Evidence on optimal treatment and management is limited. We aimed to describe the characteristics and management of GNB-IE patients, investigating factors associated with disease acquisition and unfavorable outcomes.

We conducted a retrospective descriptive single-center study (tertiary care and referral hospital) between 2015 and 2021, including adult patients with definite GNB-IE. We reviewed demographic, clinical and microbiological data, focusing on predisposing factors, clinical outcomes and 1-year mortality.

Of 1093 patients with probable or definite IE, 19 patients (median age 69 years) had definite GNB-IE, with an increasing incidence throughout the study period. Median age-adjusted Charlson Comorbidity Index score was 4 points. Prosthetic valve IE (PVIE) was present in 7/19 (37%) patients. Nosocomial acquisition occurred in 8/19 (42%) patients. Escherichia coli and Klebsiella pneumoniae were the most common pathogens. Beta-lactam (BL) based combination therapy was applied in 12/19 (63%) patients (58% BL + fluoroquinolone, 42% BL + aminoglycoside). Cardiac surgery was required in 8/19 (42%) patients (PVIE 71%, native valve IE 25%), primarily for embolism prevention and heart failure. Complications occurred in 14/19 (74%) patients. The in-hospital mortality rate was 21% (4/19); the one-year mortality rate was 44% (7/16). One-year mortality did not significantly differ between patients who underwent cardiac surgery and patients managed with anti-infective treatment alone (p = 0.633).

GNB-IE affects elderly patients with high comorbidity levels and recent health-care exposure. GNB-IE was associated with high complication rates and high mortality.