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Differences in virulence for mice among strains of Mycoplasma pulmonis
M K Davidson1, J R Lindsey, R F Parker
1Department of Comparative Medicine, University of Alabama, Birmingham.
Abstract:
The mouse model of acute murine respiratory mycoplasmosis was used to screen 18 strains of Mycoplasma pulmonis for their ability to establish respiratory infections and produce gross lung lesions in the susceptible C3H/HeN mouse strain. All experiments were designed to minimize host, environmental, and microbial differences to ensure that experimental results would reflect differences in mycoplasmal virulence. There were differences in the 50% infectious dose (range, 3 X 10(2) to greater than 10(7) CFU) and the 50% gross pneumonia dose (range, 10(3) to greater than 10(7) CFU) among the 18 mycoplasmal strains. Only 10 strains (UAB CT, M1, UAB 5782C, UAB 6510, 66, UAB T, UAB 8145D, Nelson C, Peter C, and Negroni) established respiratory infections, and only 2 of the 10 strains (UAB CT and M1) produced gross lung lesions. Strains UAB CT, UAB T, M1, UAB 5782C, and PG34(ASH) were chosen for qualitative and quantitative evaluation of lung lesions in C3H/HeN and C57BL/6N mice. Lesion incidence and severity was dependent on the mycoplasmal strain and the mouse strain. Microscopic lesions varied among mycoplasmal strains and mouse strains in the amount of lymphoid infiltrate, neutrophilic exudate, and consolidation, as well as overall severity. The most virulent strain, UAB CT, produced acute pneumonitis in the 10(7) CFU dosage group and required a threshold dose of 10(3) CFU to consistently produce microscopic lung lesions. These results suggest that M. pulmonis virulence is multifactorial and different strains of mycoplasmas yield disease expressions that differ both qualitatively and quantitatively.
Insights
This study evaluated 18 Mycoplasma pulmonis strains in mice, finding significant differences in their ability to cause respiratory infections and lung lesions. Strain UAB CT was the most virulent, highlighting multifactorial Mycoplasma pulmonis virulence.
Area of Science:
- Veterinary Microbiology
- Infectious Diseases
- Pulmonary Pathology
Background:
- Mycoplasma pulmonis is a common respiratory pathogen in rodents.
- Understanding Mycoplasma pulmonis strain virulence is crucial for disease management and research.
- Murine respiratory mycoplasmosis serves as a model for studying Mycoplasma pulmonis infections.
Purpose of the Study:
- To screen and compare the virulence of 18 Mycoplasma pulmonis strains.
- To evaluate the ability of different strains to establish respiratory infections and cause lung lesions in mice.
- To determine the influence of mycoplasmal and host strain on disease severity.
Main Methods:
- Infection of susceptible C3H/HeN mice with 18 Mycoplasma pulmonis strains.
- Determination of 50% infectious dose (ID50) and 50% gross pneumonia dose (GPD50).
- Qualitative and quantitative evaluation of lung lesions in C3H/HeN and C57BL/6N mice for selected strains.
Main Results:
- Significant variations in ID50 and GPD50 were observed among the 18 strains.
- Only 10 strains established infection, and only 2 (UAB CT and M1) produced gross lung lesions.
- Lesion incidence and severity were dependent on both the Mycoplasma pulmonis strain and the mouse strain, with UAB CT being the most virulent.
Conclusions:
- Mycoplasma pulmonis virulence is multifactorial, influenced by both the microbial strain and the host genetic background.
- Different Mycoplasma pulmonis strains exhibit distinct qualitative and quantitative disease expressions.
- Strain-specific virulence is a critical factor in the pathogenesis of murine respiratory mycoplasmosis.