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Replication rate of Pseudomonas aeruginosa in the murine lung
Abstract:
Using a method recently developed at our laboratory, we determined the initial rate of Pseudomonas aeruginosa replication in the lung under different experimental conditions. Mice were exposed to aerosols containing mixtures of a temperature-sensitive (ts) mutant of P. aeruginosa and its parental wild type (wt). The changes in the ratio of ts:wt were determined by quantitatively culturing homogenates of lungs from animals sacrificed over different time periods. The doubling time (DT) was calculated as the reciprocal of the slope of the linear portion of the curve generated by plotting n = (log [r0/rt])/log 2 against time where r is the ratio of ts:wt at a given time. The DTs measured in both outbred ICR mice and F1 hybrids (DBA/2J X B10.D2/nSnJ) were 32 and 30 min, respectively. These DTs were higher than that determined in the peritoneal cavities of ICR mice (20 min). The DT in the lungs of ICR mice rendered granulocytopenic by treatment with cyclophosphamide was 16 min. Experiments performed with inocula of different sizes showed that DTs tended to be higher in animals aerosolized with low doses of the ts-wt mixture.
Insights
Pseudomonas aeruginosa replicates rapidly in mouse lungs, with a doubling time around 30 minutes. Lung infection dynamics were influenced by mouse strain, route of infection, and immune status.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacterial Pathogenesis
Background:
- Pseudomonas aeruginosa is an opportunistic pathogen causing severe lung infections.
- Understanding bacterial replication rates is crucial for developing effective treatments.
Purpose of the Study:
- To determine the initial replication rate of Pseudomonas aeruginosa in the mouse lung.
- To investigate factors influencing bacterial doubling time in vivo.
Main Methods:
- A novel laboratory method was employed to assess bacterial replication.
- Mice were exposed to aerosols containing a temperature-sensitive (ts) mutant and wild-type (wt) P. aeruginosa.
- Bacterial ratios were quantified over time to calculate doubling times (DT).
Main Results:
- The doubling time of P. aeruginosa in mouse lungs was approximately 30-32 minutes.
- Replication was slower in the lungs compared to the peritoneal cavity (20 min).
- Granulocytopenic mice exhibited faster replication (16 min DT), and lower bacterial doses resulted in longer DTs.
Conclusions:
- Lung environment influences P. aeruginosa replication rate.
- Host immune status significantly impacts bacterial proliferation.
- The developed method allows for precise measurement of bacterial replication dynamics.