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In 2002, 495 indole-positive proteae strains were isolated from patients at 60 hospitals in Japan. Nine indole-positive proteae strains had reduced susceptibility to imipenem (MIC > or = 8 microg ml(-1)) and were identified as Providencia rettgeri by BD Phoenix. Eight of the nine Prov. rettgeri isolates were confirmed as metallo-beta-lactamase producers by the double-disc synergy test. All the metallo-beta-lactamases were classified as IMP-1 by PCR and DNA sequence analysis. These bla(IMP-1) genes were encoded in the integron structure on conjugative plasmids. These plasmids could transfer from Prov. rettgeri clinical isolates to Escherichia coli ML4903 at a frequency between 1.5 x 10(-5) and 5.5 x 10(-7). The eight bla(IMP)-positive strains were isolated from two hospitals, and showed two different PFGE patterns, two different integron structures and two different incompatibility groups, which corresponded to the two hospitals. These results strongly suggest the possibility of nosocomial infections by bla(IMP-1)-producing Prov. rettgeri isolates.

Among the main characteristics of Legionella pneumophila pneumonia are acute lung injury and severe hypoxemia. Although high oxygen supplementation is a valuable supportive therapy in these patients, oxygen itself is known to be a risk factor for acute lung injury. The effects of hyperoxia on lung injury of mice with Legionella pneumonia were examined. Hyperoxia treatment reduced survival of the infected mice in an oxygen concentration- and exposure time-dependent manner. The enhanced lethality was associated with an increase in total lung weight and apoptosis markers, but not with bacterial burden in the lungs. Hyperoxia decreased the levels of the antioxidant glutathione (GSH) in infected lungs. Exogenous tumour necrosis factor-alpha (TNF-alpha) improved the survival of infected mice kept under hyperoxia. TNF-alpha effects were associated with restoration of total lung weight and histone DNA and GSH levels on day 2, whereas the lung bacterial burden did not differ significantly. Moreover, upregulation of GSH by TNF-alpha was observed in the lungs of mice without infection. These results demonstrate that hyperoxia exacerbates L. pneumophila pneumonia. The data suggest that TNF-alpha may be a potential therapeutic candidate for these individuals, not only through modulating host antibacterial systems, but also by mediating induction of the antioxidant GSH., (Copyright 2004 SGM)

The study was designed to determine the role of interferon (IFN)-gamma in inflammatory responses against experimentally induced pneumonia caused by Klebsiella pneumoniae. The host immunological responses in IFN-gamma gene knockout (IFN-gamma(-/-)) mice and immunocompetent control mice were compared. K. pneumoniae strain T-113 was inoculated intranasally into anaesthetised mice to induce pneumonia. Infected control mice survived significantly longer than infected IFN-gamma(-/-) mice. Viable bacterial counts in lungs and blood abruptly increased in IFN-gamma(-/-) mice; in contrast, a gradual decrease in the number of bacteria was noted in control mice. During the early stages of infection, the concentrations of interleukin (IL)-1beta and IL-6 in broncho-alveolar lavage fluid and IL-1beta in serum of IFN-gamma(-/-) mice were significantly lower than in control mice. During the late stage of infection, serum IL-6 level in IFN-gamma(-/-) mice was significantly higher than in control mice. These results suggest that the defective immunological host response, including inflammatory cytokine production caused by deficiency of IFN-gamma, is one of the mechanisms that allow the progression of pulmonary infection to systemic septicaemia.