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Septic arthritis in sickle-cell thalassemia. Pathophysiology of impaired response to infection
Abstract:
The knee of a boy with sickle-cell thalassemia became infected with Salmonella enteritidis, sensitive to ampicillin. Doses of ampicillin that achieved anti-bacterial titers of 32 in synovial fluid failed to eradicate the organism. The synovial fluid exhibited severe hypoxia, hypercapnia, and lactic acidosis. Methods were developed to estimate the oxygen saturation of blood in regional venous capillaries, the degree of periarticular sickling, changes in the viscosity of local blood, and the articular ratio of blood flow to oxygen utilization. The results suggest that local vascular insufficiency associated with sickling may affect host response to infection and efficacy of antibiotics. The Salmonella C1 readily transformed to an L form on hypertonic medium, thus acquiring resistance to ampicillin and other cell-wall inhibitors.
Insights
Sickle-cell thalassemia patients may experience reduced antibiotic effectiveness due to local vascular issues and sickling. Salmonella bacteria also developed resistance by transforming into an L-form, hindering treatment.
Area of Science:
- Microbiology
- Hematology
- Infectious Diseases
Background:
- Sickle-cell thalassemia can predispose individuals to infections.
- Salmonella enteritidis is a common cause of bacterial infections.
- Antibiotic resistance is a growing global health concern.
Purpose of the Study:
- To investigate the efficacy of ampicillin in treating Salmonella enteritidis infection in a patient with sickle-cell thalassemia.
- To explore the impact of local physiological conditions on antibiotic treatment outcomes.
- To understand the mechanisms of antibiotic resistance development in Salmonella.
Main Methods:
- Developed methods to assess synovial fluid oxygenation, periarticular sickling, blood viscosity, and local blood flow to oxygen utilization ratio.
- Monitored ampicillin levels and bacterial titers in synovial fluid.
- Observed bacterial transformation to an L-form in response to hypertonic medium.
Main Results:
- Ampicillin failed to eradicate Salmonella enteritidis despite achieving therapeutic titers in synovial fluid.
- Synovial fluid exhibited severe hypoxia, hypercapnia, and lactic acidosis, indicating local vascular insufficiency.
- Salmonella C1 transformed into an ampicillin-resistant L-form on hypertonic medium.
Conclusions:
- Local vascular insufficiency associated with sickle-cell thalassemia may impair host response to infection and antibiotic efficacy.
- Bacterial transformation to L-forms is a significant mechanism for developing resistance to cell-wall inhibitors.
- This case highlights the complex interplay between host condition, pathogen characteristics, and treatment outcomes in sickle-cell disease patients.