legionella micdadei legionella micdadei legionella micdadei is a gram-negative bacterium from the genus legionella, which stains acid-fast. it stains weakly, but loses this trait upon being grown in culture. tatlockia micdadei is an alternative term for l. micdadei, the pittsburgh pneumonia agent and tatlock strain. it is named after joseph e. mcdade, who first isolated l. pneumophila. legionella micdadei scientific classification domain: bacteria phylum: pseudomonadota class: gammaproteobacteria order: legionellales family: legionellaceae genus: legionella species: l. micdadei binomial name legionella micdadeihébert et al. 1980 synonyms tatlockia micdadei legionella pittsburghensis