bacterium
/ˌbækˈtɪriəm/
noun
A member of a large group of unicellular microorganisms which have cell walls but lack organelles and an organized nucleus, including some that can cause disease.
A urine test can also be used to confirm that the bacteria are the Legionella bacteria.
illness,ailment,infection,disease,disorder,sickness,affliction,malady,complaint,upset,condition,infirmity,indisposition,malaise