Antimicrobial therapies for pulmonary Klebsiella pneumoniae infection in B6D2F1/J mice immunocompromised by use of sublethal irradiation.

Klebsiella pneumoniae is a common cause of nosocomially acquired pneumonia in immunocompromised patients. Previously, we established a pneumonia model using Klebsiella pneumoniae in B6D2F1/J mice sublethally irradiated with 7-Gy 60Co gamma-radiation and inoculated intratracheally. In the study reported here, we investigated survival of mice following 10 days of antimicrobial therapy with ceftriaxone, gentamicin, gatifloxacin, and a ceftriaxone-gentamicin combination given once daily.

Management of postirradiation infection: lessons learned from animal models.

Ionizing radiation depresses host defenses and enhances susceptibility to local and systemic infection due to endogenous or exogenous microorganisms. Exposure of mice to a lethal dose of ionizing 60Co-gamma radiation induces a dose-related reduction in the number of both aerobic and anaerobic bacteria from 10(10-12) to 10(4-6) per gram of stool within 4 days. The number of anaerobic bacteria stays low, but the number of Enterobacteriaceae per gram of stool increases significantly up to 10(9) by the 12th day after irradiation.

Susceptibility of irradiated B6D2F1/J mice to Klebsiella pneumoniae administered intratracheally: a pulmonary infection model in an immunocompromised host.

Bacteria such as Klebsiella pneumoniae can invade and colonize an immunocompromised host and complicate clinical recovery. In the study reported here, an experimental model of induced pneumonia was developed in 60Co gamma-photon-irradiated mice for the purpose of evaluating efficacy of therapeutic agents. The model was characterized by use of probit analysis of bacterial dose, and microbiologic, and histopathologic results.

Antimicrobial therapy for bacillus anthracis-induced polymicrobial infection in (60)Co gamma-irradiated mice.

Challenge with both nonlethal ionizing radiation and toxigenic Bacillus anthracis spores increases the rate of mortality from a mixed bacterial infection. If biological weapons, such as B. anthracis spores, and nuclear weapons were used together, casualties could be more severe than they would be from the use of either weapon alone.

Nuclear, biological, and chemical combined injuries and countermeasures on the battlefield.

The Armed Forces Radiobiological Research Institute (AFRRI) has developed a research program to determine the major health risks from exposure to ionizing radiation in combination with biological and chemical warfare agents and to assess the extent to which exposure to ionizing radiation compromises the effectiveness of protective drugs, vaccines, and other biological and chemical warfare prophylactic and treatment strategies. AFRRI's Defense Technology Objective MD22 supports the development of treatment modalities and studies to assess the mortality rates for combined injuries from exposure to ionizing radiation and Bacillus anthracis, and research to provide data for casualty prediction models that assess the health consequences of combined exposures. In conjunction with the Defense Threat Reduction Agency, our research data are contributing to the development of casualty prediction models that estimate mortality and incapacitation in an environment of radiation exposure plus other weapons of mass destruction.

Management of postirradiation sepsis.

Ionizing radiation depresses the immune defenses and enhances susceptibility to local and systemic infection due to endogenous or exogenous microorganisms. Exposure to a lethal dose of ionizing cobalt-60 gamma radiation induces a dose-related reduction in the number of both aerobic and anaerobic bacteria from 10(10-12) to 10(4-6) per gram of stool within 4 days. Whereas the number of anaerobic bacteria stays low, the number of Enterobacteriaceae per gram of stool increases significantly--up to 10(9) by the 12th day following irradiation.

Susceptibility of irradiated mice to Bacillus anthracis sterne by the intratracheal route of infection.

The susceptibility of sublethally irradiated mice to pulmonary infection with Bacillus anthracis was investigated in a mouse model. Female B6D2F1/J mice were challenged intratracheally with 4.3 x 10(6), 3.