Mycobacterium chelonae valve endocarditis resulting from contaminated biological prostheses

Area of Science:

• Infectious Diseases
• Cardiovascular Surgery
• Microbiology

Background:

• Biological prosthetic valve (BPV) endocarditis can be challenging to diagnose, particularly when causative agents are not readily identified through standard blood cultures.
• A potential link between prosthetic manufacturing processes and microbial contamination of BPVs warrants investigation.

Purpose of the Study:

• To describe a series of biological prosthetic valve endocarditis cases in Brazil potentially linked to the prosthetic manufacturing process.
• To identify the causative agent and evaluate diagnostic methods for culture-negative BPV endocarditis.

Main Methods:

• Review of clinical and microbiological data from 39 patients undergoing BPV replacement for suspected endocarditis between 1999 and 2008.
• Histological examination of BPV explants using Ziehl-Neelsen staining for acid-fast bacilli (AFB).
• Molecular identification of AFB using 16S-23S internal transcribed sequence (ITS) analysis on DNA extracted from paraffin-embedded samples.

Main Results:

• 46% (18/39) of BPV explants were positive for AFB, with 13 cases confirmed as endocarditis and 5 as colonization.
• AFB were detected in 5 out of 6 "sterile" non-implanted BPVs from the same manufacturer.
• Molecular analysis identified Mycobacterium chelonae as the causative agent.

Conclusions:

• Rapid-growing mycobacteria, specifically Mycobacterium chelonae, should be suspected in cases of BPV endocarditis, particularly those associated with prosthetic manufacturing.
• The Ziehl-Neelsen stain on histological sections is a critical diagnostic tool for BPV endocarditis, especially when blood cultures are negative.
• Early or late BPV endocarditis may be linked to contaminated prostheses, highlighting the importance of stringent manufacturing and sterilization processes.