SURVEY of CONDITIONS for SPORE FORMATION of Geobacillus stearothermophilus ATCC 7953

Abstract

Biological indicators are considered the gold standard for sterilization process control, one of the criteria
for evaluating autoclaves, and a measure that directly reflects the effectiveness of sterilization. In Vietnam,
the use of biological indicators to proactively control the effectiveness of the sterilization process has not
received due attention and has not been implemented regularly, especially in local medical facilities.
Research on Geobacillus stearothermophilus bacteria that create biological indicators is still very limited.
This study investigated 16 conditions for the spores formation of G. stearothermophilus ATCC 7953 from 4
culture mediums NA-CaKMgMn, NA-CaMn, YMMn, PCA; 2 pH conditions of 7.0 and 8.5; 2 incubation
temperatures of 55oC and 61oC. The research results showed that at pH 8.5 and incubation temperature of
61oC, the rate and proportion of G. stearothermophilus ATCC 7953 spores formation were superior to those
at pH 7.0 and 55oC. The four spore formation conditions NA-CaKMnMg/ 8.5/ 61oC, NA-CaMn/ 8.5/ 61oC,
YMMn/ 7.0/ 61oC and YMMn/ 8.5/ 61oC had a spore formation rate of over 95% and a spore yield of over
105 cfu/mL. Of which, the condition YMMn/8.5/ 61oC had the fastest rate of G. stearothermophilus ATCC
7953 spores formation, reaching 90% after 4 days. The results of the research could be the premise for
further research to create biological indicators that meet ISO standards.