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Role of bacterial capsule in local and systemic inflammatory responses of mice during pulmonary infection with Klebsiella pneumoniae

2000; Microbiology Society; Volume: 49; Issue: 11 Linguagem: Inglês

10.1099/0022-1317-49-11-1003

1473-5644

Kanako Yoshida, Keizo Yamaguchi, KOU UCHIDA, Shiro Tsujimoto, TETSUYA MATSUMOTO, Kazuhiro Tateda,

Antimicrobial Peptides and Activities

The role of bacterial capsule in inflammatory responses in experimentally induced pneumonia caused by Klebsiella pneumoniae was evaluated by comparing the host immunological responses in mice infected with capsulate strain DT-S and non-capsulate mutant strain DT-X. Anaesthetised ICR mice were infected intranasally with inocula of strain DT-S or DT-X. Mice infected with strain DT-X survived significantly longer than those inoculated with strain DT-S. Viable bacterial counts in lungs and blood increased rapidly in mice infected with strain DT-S, in contrast to the gradual decrease in their density in lungs and intermittent bacteraemia in mice infected with strain DT-X. The number of broncho-alveolar lavage (BAL) cells in mice infected with strain DT-X at 24 h after inoculation was significantly higher than in those infected with strain DT-S. In the early stages of infection, the levels of tumour necrosis factor-α and interleukin-6 in BAL fluid of mice infected with strain DT-X were significantly higher than those of mice infected with strain DT-S. In contrast, in the late stage of infection, the levels of these cytokines in serum of mice infected with strain DT-S were significantly higher than in mice infected with strain DT-X. These results suggest that K. pneumoniae capsule may suppress the host immunological responses, thus allowing the bacteria to grow, causing pneumonia, septicaemia and death.