Related Experiment Videos
Role of granulocytes and monocytes in experimental Staphylococcus epidermidis endocarditis
Abstract:
The role of granulocytes and monocytes during the induction and course of Staphylococcus epidermidis endocarditis was investigated by the selective depletion of monocytes with the drug VP16-213 and of both granulocytes and monocytes with nitrogen mustard. The induction of endocarditis was influenced only by the depletion of monocytes: the 50% infective dose differed significantly, being 3.4 X 10(5) CFU in control rabbits and 3.4 X 10(4) CFU in the monocyte-depleted rabbits, whereas no significant differences were found between the latter and those depleted of both granulocytes and monocytes. Also, control rabbits injected with 10(6) or 10(7) CFU had a significantly higher incidence of sterile vegetations than did rabbits selectively depleted of granulocytes or monocytes. Compared with baseline values, mean monocyte numbers at the time of bacterial inoculation were significantly increased in control rabbits whose vegetations remained sterile, whereas this effect was not seen in rabbits whose vegetations became infected. The course of the endocarditis appeared to be significantly influenced by both granulocytes and monocytes. Comparison showed that a decrease of the same numbers of these cells per microliter of blood was accompanied for the monocytes by an approximately fourfold higher increase of the number of staphylococci in the vegetations. The correlation between the number of granulocytes and of monocytes on the one hand and the number of staphylococci in the vegetations on the other was not substantially influenced by the duration of the disease or the number of staphylococci injected to induce the endocarditis. The number injected proved to be significantly correlated with the number of staphylococci in the vegetations. In rabbits with numbers of CFU per gram of vegetation exceeding 10(7), blood cultures were usually positive. This finding applied rarely to control rabbits, but generally to drug-treated rabbits. In the latter animals a significant correlation between the number of staphylococci in the vegetations and in the circulation was found. We conclude that only monocytes have a measurable effect on the induction of Staphylococcus epidermidis endocarditis but during its course both granulocytes and monocytes keep the endocardial infection in check.
Insights
Monocytes are crucial for Staphylococcus epidermidis endocarditis induction, while both monocytes and granulocytes help control infection during its course. Depleting monocytes significantly increased infection susceptibility.
Area of Science:
- Immunology
- Infectious Diseases
- Microbiology
Background:
- Staphylococcus epidermidis is a common cause of infective endocarditis, a serious cardiac infection.
- The roles of specific immune cells, like granulocytes and monocytes, in endocarditis pathogenesis are not fully elucidated.
Purpose of the Study:
- To investigate the distinct roles of granulocytes and monocytes in the induction and progression of Staphylococcus epidermidis endocarditis.
- To determine the impact of selective immune cell depletion on infection susceptibility and severity.
Main Methods:
- Selective depletion of monocytes using VP16-213 and depletion of both granulocytes and monocytes using nitrogen mustard in a rabbit model.
- Assessment of 50% infective dose (ID50) and incidence of sterile vegetations post-bacterial challenge.
- Quantification of bacterial load in vegetations and blood cultures to correlate with immune cell counts.
Main Results:
- Monocyte depletion significantly reduced the ID50, increasing susceptibility to endocarditis induction.
- Both granulocytes and monocytes were essential in controlling the infection during the course of endocarditis.
- Lower monocyte counts correlated with higher bacterial loads in vegetations, indicating a critical role in infection control.
Conclusions:
- Monocytes play a pivotal role in the initial induction phase of Staphylococcus epidermidis endocarditis.
- Both granulocytes and monocytes are vital for controlling the established endocardial infection.
- Understanding these cellular roles can inform therapeutic strategies for infective endocarditis.