Actinotignum-associated prosthetic aortic valve endocarditis complicated by postoperative circulatory collapse and dialysis-requiring acute kidney injury: a case report

Abstract Background Actinotignum species are fastidious genitourinary organisms increasingly recognized in urinary tract and bloodstream infections, but infective endocarditis remains exceptionally uncommon and may be overlooked when a plausible extracardiac infectious focus is present. Case presentation A 71-year-old man with recurrent urinary retention requiring clean intermittent self-catheterization presented 7 months after bioprosthetic aortic valve replacement with fever, severe back pain, and dialysis-requiring acute kidney injury. Magnetic resonance imaging showed T12/L1 spondylodiscitis, providing a plausible extracardiac infectious focus. Echocardiography subsequently revealed a large, highly mobile prosthetic-valve vegetation with outflow obstruction. Urgent surgery was undertaken before definitive microbiological identification because of progressive organ dysfunction and concern that further deterioration would reduce operability. Dense periprosthetic induration made redo valve replacement prohibitively hazardous, and extensive debridement with prosthesis retention was used as a nonstandard, survival-prioritizing fallback. The anaerobic bottle from each of two blood culture sets became positive after 92 h, and Actinotignum spp. were also recovered from urine. Together with the patient’s urologic risk factors, these findings supported a probable urogenital source. A. sanguinis was the highest-ranking matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) match for the blood and urinary isolates, but species identity and strain relatedness were not confirmed by molecular or genomic analysis. Empirical ceftriaxone and linezolid were narrowed to intravenous ampicillin after identification and susceptibility review. Later broad-spectrum therapy treated a secondary Pseudomonas aeruginosa respiratory infection, and intravenous antibacterial therapy was completed on Day 40. Postoperatively, the pre-existing acute kidney injury progressed to anuria, with recurrent renal replacement therapy circuit clotting and circulatory collapse characterized by predominant low-output physiology. After staged multiorgan support, the patient achieved partial renal recovery with sustained dialysis independence and independent ambulation. Conclusions A plausible extracardiac infectious focus should not preclude evaluation for prosthetic valve endocarditis, and urgent source control may need to precede definitive microbiological characterization. Redo valve replacement remains standard; prosthesis-preserving debridement should be regarded only as an individualized, nonstandard fallback when standard surgery becomes prohibitively hazardous. Species-level interpretation of Actinotignum identified by MALDI-TOF MS requires caution without confirmatory molecular or genomic analysis.