Resumo

A biological indicator (BI) is a test system containing viable microorganisms that provide a defined resistance to a specified sterilization process. Due to their high resistance to certain sterilization agents, the most recognized application of B. atrophaeus spores is as a biological indicator for sterilization to monitor ethylene oxide (EtO), dry heat sterilization and microwave disinfection. To present a true challenge, these BIs must meet specific standard requirements as set out by international standards or regulatory agencies. Dry-heat sterilization has proven effective in both medical and nonmedical applications, including medical prosthesis, implants, dry chemicals, oils, glycerin and even spacecrafts. The process involves exposing the product to hot air circulated in a closed chamber (batch sterilizers) or in tunnels (continuous sterilizers). EtO sterilization is a gaseous chemical process that is commonly utilized to sterilize medical and pharmaceutical products that cannot support the conventional high temperatures. Two types of B. atrophaeus BIs were formulated by solid-state fermentation from inexpensive alternative substrate (soybean molasses and glycerol) absorbed on sand as dry support. The performances of them were assessed by determining its resistance characteristics to dry-heat and EtO sterilization. The BI resistance was demonstrated by the D-value (time taken, in a specified set of conditions, for the spore population to decrease by 90% or 1 log of its initial value). For dry-heat sterilization it was determined by fraction negative analysis and by a survivor curve based on direct enumeration of the spores. The conditions were as follows: 160°C for 4 up to 48 min in a tabletop air oven. EtO sterilization was performed using 650 mg/L at 55°C and 55% humidity, with a partial cycle time of 15 min up to a total cycle time of 180 min. All BIs studied showed D(160°C) - value ˃ 3,0 min and D(EtO)-value ˃ 2,5 min (regulatory recommendations) demonstrating that soybean-based and glycerol-based BIS met international standards and regulations and could replace the commercial BI for dry-heat and ethylene oxide sterilization.