Effects of Different Times of Glutaraldehyde 2% on Bacillus subtilis Spores (In Vitro)

Background: Due to the importance of disinfectant and sterilization of dental instruments, in total, 14%–28% of dentists, 13% of assistants, and 17% of healthcare workers (HCWs) have been subjected to the hepatitis B virus (HBV), and more than 200 healthcare providers (HCPs) pass away annually in the United States from HBV infection catched from their work place. Objective: This study examined the effects of glutaraldehyde 2% on Bacillus subtilis spores in the Surgery and Microbiology Department of the Dental Branch of Islamic Azad University. Methods: This experimental research evaluated a total of 58 samples, one called first evidence (pure glutaraldehyde not exposed to spore suspension), one called second evidence (spore suspension not exposed to glutaraldehyde), and 40 samples including a suspension with a normal turbidity of 1×108 CFU/mL according to 0.5 McFarland with exposure to glutaraldehyde 2%. Experiments were done in time intervals of 10, 15, 20, 25, 30, 40, and 60 minutes with 8 repeats. In all times, a B. subtilis spore suspension was used as evidence and also as a case. Results: This research was done on 58 samples. The results showed that in the 10th minute there were 102 colonies, 18.6 ± 3.4 in the 15th minute, 6.2 ± 1.4 in the 20th minute, 2.1 ± 0.8 in the 25th minute, and no colonies after 30 minutes. In an overall observation, it was seen that there were more colonies in the first 10 minutes, and from 15 to 20 minutes, this amount significantly decreased; after 30 minutes in each 8 repeats, the growth of colonies had stopped completely, while in the evidence samples, B. subtilis spores grew. Conclusion: It seems that the density of 2% glutaraldehyde in 30 minutes time was enough to destroy the spores of B. subtilis.