Culturable microorganisms in preservation fluids of historical anatomical wet collections

Fluid-preserved anatomical specimens are widely used in anatomy education and represent an important part of medical heritage. However, the microbiological stability of preservation fluids and the occurrence of recoverable microorganisms during prolonged preservative exposure remain poorly understood. This study investigated culturable microorganisms in preservation fluids from historical anatomical specimens and screened ethanol/formaldehyde inhibition endpoints.

Forty preservation-fluid samples from historical anatomical specimens (pre-1945) housed at Wrocław Medical University (formerly Breslau) were analyzed, including in situ samples from display containers and archived biobank aliquots. After enrichment culture, culturable microorganisms were identified by MALDI-TOF mass spectrometry. Isolates were tested by broth microdilution against ethanol and formaldehyde at final concentrations of 1%, 5%, and 10% (v/v).

Culturable microorganisms were recovered from 16/40 samples (40.0%). The recovered culturable profile was taxonomically limited and dominated by aerobic Gram-positive cocci and rods; Enterobacteriaceae were not recovered under the applied culture conditions, and only one Gram-negative isolate, Pseudomonas stutzeri, was identified. The most frequent taxa included Bacillus cereus and staphylococci, whereas yeasts were rare and limited to Candida spp. Culture-positive findings were more frequent in specimens with compromised container closure. No visible growth was observed at any tested formaldehyde concentration, whereas ethanol inhibition endpoints were taxon-dependent: several Gram-positive isolates grew at 10% ethanol, while Candida isolates were inhibited at 5%.

Preservation fluids did not yield uniformly negative cultures under the applied conditions. The findings support closure surveillance and targeted culture-based testing of jars with seal defects or macroscopic fluid changes.