Impact of multidrug resistance on experimental empyema by Pseudomonas aeruginosa
Evangelos J Giamarellos-Bourboulis1, Ira Tzepi, Irini Tsovolou
14th Department of Internal Medicine, University of Athens, Medical School, Athens, Greece. giamarel @ ath.forthnet.gr
Background:
Pseudomonas aeruginosa is a cause of infections of the lower respiratory tract among patients with chronic lung disorders. It is questionable whether virulence of this species may be influenced by multidrug resistance (MDR).
Objectives:
To define the impact of MDR in experimental lung infection.
Methods:
Experimental empyema was induced in rabbits by MDR (group A, n = 16) and by susceptible isolates (group B, n = 10). Pleural fluid was sampled for quantitative culture and estimation of cell apoptosis and of tumor necrosis factor-alpha (TNFα) and malondialdehyde (MDA). Survival was recorded. Cytokine production was stimulated in U937 monocytes by samples of pleural fluid. Whole blood of rabbits was incubated with the isolates; induction of apoptosis was assessed.
Results:
Survival of group A was prolonged compared to group B. This was accompanied by lower bacterial counts of the inoculated pathogens in pleural fluid and in the lungs of group A compared with group B. Early apoptosis of neutrophils of pleural fluid of group A was lower compared with group B. Pleural fluid concentrations of TNFα and MDA did not differ between the groups. Cytokine production by U937 monocytes after stimulation with pleural fluid was greater in group B than in group A. The susceptible isolate induced apoptosis of neutrophils in vitro at a greater rate than the MDR isolate.
Conclusions:
Experimental empyema by susceptible P. aeruginosa is accompanied by greater mortality compared with MDR P. aeruginosa. This phenomenon may be attributed to the different growth pattern of the pathogens or to their interaction with the innate immune system.
Insights
Multidrug-resistant Pseudomonas aeruginosa infections in the lungs show lower mortality than susceptible strains. This may be due to pathogen growth patterns or immune system interactions.
Area of Science:
- Infectious Diseases
- Microbiology
- Immunology
Background:
- Pseudomonas aeruginosa is a common cause of lower respiratory tract infections in patients with chronic lung conditions.
- The influence of multidrug resistance (MDR) on the virulence of P. aeruginosa remains unclear.
Purpose of the Study:
- To investigate the impact of multidrug resistance (MDR) on the severity and outcomes of experimental lung infections caused by Pseudomonas aeruginosa.
Main Methods:
- Experimental empyema was induced in rabbits using either MDR or susceptible isolates of P. aeruginosa.
- Pleural fluid was analyzed for bacterial load, neutrophil apoptosis, and levels of TNF-α and MDA.
- Immune responses, including cytokine production and apoptosis induction in immune cells, were assessed.
Main Results:
- Rabbits infected with MDR P. aeruginosa exhibited prolonged survival and lower bacterial counts compared to those infected with susceptible strains.
- Neutrophil apoptosis and cytokine production in response to MDR isolates were reduced.
- Susceptible P. aeruginosa isolates induced higher mortality and greater apoptosis in neutrophils in vitro.
Conclusions:
- Experimental lung infections with susceptible P. aeruginosa are associated with higher mortality than those with MDR strains.
- Differences in pathogen growth or interaction with the host's innate immune system may explain the observed variations in virulence.
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