Related Experiment Videos
Low-inoculum model of surgical wound infection
A B Kaiser1, D S Kernodle, R A Parker
1Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2358.
Abstract:
A model of surgical wound infection that uses low inocula of bacteria and closely simulates clinical infection involved inoculating suspensions of Staphylococcus aureus and dextran microbeads into intermuscular sites on the dorsum of guinea pigs, harvesting lesions at 72-96 h, identifying as a positive end point lesions yielding staphylococci on subculture, and using logistic regression for data analysis. Prophylaxis was placebo, ampicillin, or cefazolin, and three representative strains of S. aureus were used. A highly significant correlation (P less than .001) was observed between inoculum sizes and infection rates. Without antimicrobial prophylaxis, ID50 for each strain was less than 10 organisms; with antimicrobials, ID50 was significantly higher. Differences in the virulence of strains and in the efficacy of the antimicrobial regimens also were observed. The model should prove useful for understanding mechanisms of virulence among pathogenic bacteria and for elucidating subtle but important differences in efficacy among antibiotics used in prophylaxis.
Insights
This study developed a surgical wound infection model in guinea pigs, demonstrating that lower bacterial inocula increase infection risk. Antimicrobials significantly raised the infectious dose, highlighting their prophylactic value.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Surgical wound infections pose a significant clinical challenge.
- Developing reliable models to study bacterial virulence and antibiotic efficacy is crucial.
Purpose of the Study:
- To establish and validate a guinea pig model for surgical wound infection using Staphylococcus aureus.
- To assess the impact of bacterial inoculum size on infection rates.
- To evaluate the prophylactic efficacy of ampicillin and cefazolin.
Main Methods:
- Inoculation of guinea pig intermuscular sites with Staphylococcus aureus and microbeads.
- Harvesting lesions at 72-96 hours post-inoculation.
- Utilizing logistic regression for data analysis and determining the 50% infectious dose (ID50).
Main Results:
- A strong correlation was found between inoculum size and infection rates (P < .001).
- Without prophylaxis, the ID50 for Staphylococcus aureus was less than 10 organisms.
- Antimicrobial prophylaxis (ampicillin, cefazolin) significantly increased the ID50, indicating reduced infection susceptibility.
Conclusions:
- The developed model accurately simulates clinical surgical wound infections.
- The model effectively differentiates bacterial virulence and antibiotic prophylactic efficacy.
- This model is valuable for studying pathogenic bacteria mechanisms and comparing antibiotic effectiveness.