Identification of causative organisms using enrichment cultures for cardiac implantable electronic device infections

Approximately 7% to 29% of cardiac implantable electrical device (CIED) infection patients have unknown causative organisms using normal culture methods. An "enrichment culture" is an effective technique for identifying slow-growing, low-abundance, and fastidious microorganisms.

This study aimed to explore the causative organisms of CIED infections using enrichment cultures and to examine their relationship with the infection onset timing.

A total of 117 patients with CIED infections were analyzed. We categorized the onset timing of the CIED infections as the "early group" (n = 45) within 365 days of the last device procedure and the "late group" (n = 72) thereafter.

Using the enrichment culture method, the causative microorganisms were identified in 97% of cases with CIED infections. The Staphylococcus species accounted for most (63%) infections. However, Cutibacterium acnes was notably high at 18%, surpassing prior findings. Patients who experienced early infections exhibited characteristics of having more pocket infections, fewer male patients, a lower left ventricular ejection fraction, higher brain natriuretic peptide level, and lower renal function. Furthermore, late infections exhibited a significantly higher frequency of Cutibacterium acnes (24% vs 8%; P = .02), and lower frequency of Staphylococcus aureus than early infections (25% vs 43%; P = .04). Enrichment cultures demonstrated a significantly higher detection rate of causative organisms than conventional blood agar cultures, regardless of the bacterial species.

Utilization of enrichment cultures could highlight a disparity in pathogen distribution compared with previous reports. Cutibacterium acnes played a particularly significant role as the causative pathogen in the late onset of CIED infections.