Endocarditis associated with contamination of cardiovascular bioprostheses with Mycobacterium chelonae: a collaborative microbiological study.

Background: Mycobacterium chelonae is a rare cause of infective endocarditis that is difficult to diagnose and treat. After we found M chelonae in a series of patients, we aimed to investigate its role in cardiovascular prosthesis dysfunction and contamination of bioprostheses as a possible cause of infection.

Methods: In this collaborative microbiological study, we report on nine patients treated in three cardiovascular surgical departments in Germany, who were found to have M chelonae infection after receiving BioIntegral bioprostheses. We performed fluorescence in-situ hybridisation (FISH) combined with broad-range 16S rRNA gene amplification and sequencing (FISHseq) on samples of native cardiovascular tissue and explanted bioprosthetic material, as well as on 12 unused BioIntegral prostheses. We confirmed FISHseq findings with histological examination by staining for acid-fast bacilli, and M chelonae was differentiated from M abscessus by molecular techniques.

Findings: Between Dec 1, 2020, and Feb 28, 2022, we identified M chelonae in BioIntegral bioprostheses from three initial patients treated in Berlin that were explanted following dysfunction or suspected endocarditis, visualising morphologically intact FISH-positive mycobacteria. Despite negative mycobacterial culture, we also detected M chelonae in all 12 unused BioIntegral prostheses. The competent authorities in the EU prompted an alert, leading to the identification of six additional patients between March 1, 2022, and July 31, 2023. To find other cases of M chelonae endocarditis, we reviewed the FISHseq results of 1237 cardiovascular samples that were analysed between Jan 1, 2015, and Aug 31, 2022, including 295 samples from 228 bioprostheses supplied by other manufacturers. M chelonae was only detected in six of 41 patients who had received BioIntegral products.

Interpretation: Bioprostheses manufactured by BioIntegral Surgical might be colonised by M chelonae, which can lead to implant dysfunction. These infections are likely to be missed by conventional routine diagnostics and should be considered in patients with BioIntegral implants and suspected infection or dysfunction. Cases should be reported to public health and regulatory authorities. Routine safety testing of bioprostheses during manufacture should be reconsidered.

Funding: German Federal Ministry of Education and Research.