RECOVERY OF BACTERIAL-SPORES DRIED ON ALUMINUM STRIPS

Bacterial spores dried on aluminium strips are used in microbiological validation of packaging and processing systems. Vortex agitation and sonication in Butterfield's buffer, 70% ethanol or 0.1% Tween 80 were evaluated for ease of recovery of bacillus spores dried on aluminium s trips to compare the concentration of dried spores to dilutions used t o inoculate such strips. The highest recovery for Bacillus subtilis va r. globigii spores was observed with sonication in 70% ethanol with av erage recovery close to the initial inoculum. The highest recovery for B. stearothermophilus spores was with sonication in Butterfield's buf fer, averaging 0.8 log less recovery than the initial inoculum. Bacill us subtilis var. globigii spores were recovered from strips in greater numbers than B. stearothermophilus spores for all treatment medium co mbinations. Scanning electron microscopy revealed unrecovered spores a dhering to strips after treatment. Recovery of B. subtilis var. globig ii spores decreased with time over the 4 week storage period.