Volume 23, Number 11—November 2017
Etymologia: Legionella pneumophila
In the summer of 1976, as the United States was celebrating the bicentennial of the Declaration of Independence, a mysterious acute respiratory illness developed in attendees at an American Legion convention in Philadelphia shortly after the attendees returned from the convention. In total, 182 Legionnaires became ill, and 29 died.
Researchers in the Leprosy and Rickettsia Branch at Centers for Disease Control (CDC), headed by Charles C. Shepard, observed that guinea pigs became ill after being inoculated with lung tissues from patients who died. A few gram-negative bacilli were seen in guinea pig tissues, but these were believed to be normal flora or contaminants. The bacteria could not at first be isolated in embryonated eggs because the standard procedure for isolating rickettsiae at the time was to include penicillin and streptomycin to prevent contamination.
Returning to work after Christmas 1976, CDC microbiologist Joseph McDade (Figure 1) was bothered by these unexplained findings. He again attempted to grow the bacteria in embryonated eggs, this time without antibiotics, and successfully isolated a large inoculum of pure culture that could be grown on agar. These bacteria were determined to be the etiologic organism of Legionnaires’ disease and were eventually named Legionella (for the Legionnaires) pneumophila (Greek pneumon [lung] + philos [loving]) (Figure 2).
- McDade JE, Shepard CC, Fraser DW, Tsai TR, Redus MA, Dowdle WR. Legionnaires’ disease: isolation of a bacterium and demonstration of its role in other respiratory disease. N Engl J Med. 1977;297:1197–203.
- Winn WC Jr. Legionnaires disease: historical perspective. Clin Microbiol Rev. 1988;1:60–81.