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Bacterial virulence and host selection: bacteria "select" patients to infect
C G Ward1, J J Bullen, P B Spalding
1University of Miami School of Medicine, Department of Surgery, FL 33101.
Abstract:
A clinically lethal strain of Pseudomonas aeruginosa was tested and its growth patterns in normal plasma and in normal whole blood clotted with thrombin were compared. Two stock cultures were used; one was maintained in liquid nitrogen and one was passed from plate to plate 24 times on blood agar plates at room temperature. The results showed that plasma alone and whole blood controlled the growth of a clinically pathogenic strain of P. aeruginosa consistently and uniquely for each donor, dependent on size of inoculum, length of incubation, and means by which the culture was maintained. The changing virulence of an organism and its unique growth patterns in different individuals' plasma and whole blood may explain why patients exposed to the same organisms within the same environment vary in susceptibility to clinical infection.
Insights
Pseudomonas aeruginosa growth varied in human plasma and whole blood, controlled uniquely by each donor. This individual variation in controlling bacterial growth may explain differing patient susceptibility to infection.
Area of Science:
- Microbiology and Immunology
- Infectious Diseases
Background:
- Clinically lethal strains of Pseudomonas aeruginosa pose significant infectious disease threats.
- Understanding host-pathogen interactions is crucial for explaining variations in clinical infection susceptibility.
Purpose of the Study:
- To compare the in vitro growth patterns of a pathogenic Pseudomonas aeruginosa strain in normal human plasma and whole blood.
- To investigate the influence of donor variability and culture maintenance on bacterial growth control.
Main Methods:
- A clinically lethal Pseudomonas aeruginosa strain was cultured.
- Bacterial growth was assessed in normal plasma and thrombin-clotted whole blood from different donors.
- Two distinct culture maintenance methods (liquid nitrogen vs. serial plate passage) were employed.
Main Results:
- Both normal plasma and whole blood demonstrated consistent and unique control over Pseudomonas aeruginosa growth for each donor.
- Growth inhibition was dependent on inoculum size, incubation duration, and the method used to maintain the bacterial culture.
- Significant inter-individual variability in the ability to control bacterial proliferation was observed.
Conclusions:
- Human plasma and whole blood possess intrinsic, donor-specific mechanisms to control pathogenic Pseudomonas aeruginosa growth.
- The observed variability in bacterial growth control highlights the potential role of individual host factors in infection susceptibility.
- These findings may elucidate why patients exposed to identical pathogens exhibit differential responses to infection.