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The relationship of pathogenicity to the growth of Pasteurella multocida serotype 3,4 isolates in normal turkey
1Department of Medical Microbiology, College of Veterinary Medicine, University of Georgia, Athens 30602.
Abstract:
The percent mortality (M%) caused by various isolates of Pasteurella multocida serotypes 3,4 in turkeys challenged with these organisms was significantly associated with the growth curve when these organisms were grown in normal turkey plasma. The organisms that lysed the most caused the least mortality. In turn, the longer it took for an organism to reach the lowest point on its growth curve, the lower the M%. The highest point on the growth curve and the time that it took to reach that point were analyzed in normal and heat-treated plasma (HTP). The isolates with the maximum growth had the highest M%. The isolates that reached their maximum growth faster also had the greatest M%.
Insights
Turkey mortality from Pasteurella multocida serotypes 3,4 was linked to bacterial growth curves in plasma. Faster growth and higher peaks correlated with increased mortality, while slower growth and lysis reduced turkey deaths.
Area of Science:
- Veterinary Microbiology
- Poultry Pathology
- Bacterial Pathogenesis
Background:
- Pasteurella multocida serotypes 3,4 are significant pathogens in turkeys.
- Understanding the factors influencing virulence is crucial for disease control.
- Bacterial growth dynamics may correlate with disease severity.
Purpose of the Study:
- To investigate the association between Pasteurella multocida growth curves in turkey plasma and mortality rates.
- To determine if bacterial lysis impacts disease outcome.
- To analyze growth parameters in different plasma conditions.
Main Methods:
- Culturing various Pasteurella multocida serotype 3,4 isolates in normal and heat-treated turkey plasma.
- Monitoring bacterial growth curves, including maximum growth and time to reach peak.
- Correlating growth curve characteristics with percent mortality (M%) in challenged turkeys.
- Assessing bacterial lysis as a factor.
Main Results:
- Percent mortality (M%) was significantly associated with bacterial growth curves.
- Isolates exhibiting faster maximum growth and reaching peak growth sooner resulted in higher M%.
- Greater bacterial lysis correlated with lower M%, and longer times to reach the lowest growth point also indicated lower M%.
Conclusions:
- Bacterial growth kinetics in turkey plasma are a key determinant of Pasteurella multocida virulence.
- Rapid growth and high yield of P. multocida serotypes 3,4 are associated with increased turkey mortality.
- Bacterial lysis and slower growth phases may indicate reduced pathogenicity.