Fetching details from the dictionary...
microorganisms; saprophyte; saprophytic bacteria
手を洗って雑菌を防ごう。
Let's wash our hands to prevent germs.
まな板を放置したら、雑菌だらけになっていた。
I left the cutting board out, and it became covered in germs.
雑菌の混入を防ぐため、器具を滅菌する。
To prevent contamination by unwanted bacteria, sterilize the equipment.