Human cadaveric skin allografts are used in the treatment of burns and
can be preserved in glycerol at high concentrations. Previously, glycerol
has been attributed some antimicrobial effect. In an experimental set-up,
we aimed at investigating this effect of prolonged incubation of bacteria
in 85% glycerol. Staphylococcus epidermidis, Staphylococcus
aureus, Pseudomonas aeruginosa, and Bacillus
subtilis were incubated in 85% glycerol. The influence of duration of
incubation and temperature on ultrastructure and viability were
investigated. Unstressed cultures served as controls. Survival was studied
after 24–36 h and 10 days incubation in 85% glycerol at 4°C and
36°C with transmission electron microscopy (TEM) and flow cytometry
using viability stains indicating membrane damage (SYTO9, propidium
iodide) or esterase activity (carboxyfluorescein diacetate). TEM clearly
demonstrated variability in morphological changes of bacteria suggesting
different mechanisms of damage. Viability stains supported these findings
with faster declining viable cell populations in 85% glycerol at 36°C
compared with 4°C. Both methods demonstrated that Gram-negative
species were more susceptible than Gram-positive species. In conclusion,
85% glycerol may have some additional antimicrobial effect. Temperature is
an important factor herein and Gram-negatives are most susceptible. The
latter finding probably reflects the difference in cell wall composition
between Gram-positive and Gram-negative bacteria.