Entry and intracellular growth of Legionella dumoffii in alveolar epithelial cells

Koji Maruta, Hiroshi Miyamoto, Tetsuo Hamada, Midori Ogawa, Hatsumi Taniguchi, Shin Ichi Yoshida

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)


We have found that Legionella dumoffii strain Tex-KL (ATCC 33343) invades into and proliferates in the human lung alveolar epithelial-cell line A549 in vitro. The organism associated with the A549 cells at a 10-fold greater magnitude than L. pneumophila Philadelphia-1 during in vitro coculture for 1 h. Thereafter, L. dumoffii Tex-KL invaded the cells at a significantly higher rate (100- to 1,000-fold) than did L. pneumophila Philadelphia-1. After internalization, however, both bacteria proliferated at the same rate. This in vitro finding led us to examine the bacterial localization in lungs in a fatal case of L. dumoffii pneumonia. Double immunostaining revealed the bacteria in surfactant apoprotein A-positive cells (i.e., type II alveolar epithelial cells). Next, we infected guinea pigs intratracheally with L. dumoffii Tex-KL. The animals became sick with a fever from 24 h to 48 h after infection with 104 to 109 cfu of L. dumoffii Tex-KL. The lung tissues were examined through electron microscopy at definite intervals. Many bacteria were found not only inside phagocytic cells in the alveolar space, but also in type I and type II alveolar epithelial cells. These findings strongly suggest that L. dumoffii has an ability to invade into and proliferate in human alveolar epithelial cells, which may explain the rapid and fulminant progress of pneumonia caused by L. dumoffii.

Original languageEnglish
Pages (from-to)1967-1974
Number of pages8
JournalAmerican Journal of Respiratory and Critical Care Medicine
Issue number6 PART I
Publication statusPublished - 1998

All Science Journal Classification (ASJC) codes

  • Pulmonary and Respiratory Medicine
  • Critical Care and Intensive Care Medicine


Dive into the research topics of 'Entry and intracellular growth of Legionella dumoffii in alveolar epithelial cells'. Together they form a unique fingerprint.

Cite this