There is disclosed a biological indicator (BI) test utilizing oxygen sensing within a microenvironment as a means for determining the presence of viable microorganisms capable of growth, a method for biological indicator (BI) testing for determining the completeness of a sterilization cycle utilizing oxygen sensing as the means for determining the presence of viable microorganism survival, a device for determining oxygen content in a biological indicator (BI) assay vessel containing an optical oxygen sensor, and a method and device for determining antimicrobial drug resistance or sensitivity to a contaminated sample.