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The effect of zinc on microbial growth and bacterial killing by cefazolin in a Staphylococcus aureus abscess milieu
D M Bamberger1, B L Herndon, P R Suvarna
1Section of Infectious Diseases, School of Medicine, University of Missouri-Kansas City 64108-2792.
Abstract:
Microbial growth and antimicrobial bacterial killing are both diminished in abscesses. It was postulated that zinc depletion in abscesses, perhaps secondary to a neutrophil protein resembling calprotectin, may be partly responsible for these effects. In a rabbit tissue-cage abscess model, pooled abscess supernatant concentration of zinc was < 1.53 microM. The addition of 41.7 microM zinc had no effect on Staphylococcus aureus growth or the bacterial killing effect of cefazolin in serum. In abscess fluid supernatants, bacterial growth without antibiotic and bacterial killing by cefazolin were both enhanced by the addition of zinc. Fractionation of the abscess fluid with ultrafiltration membranes showed that these effects could be reproduced with the fraction between 30 and 50 kDa. These findings suggest that a protein in abscess fluid supernatants that resembles the neutrophil protein calprotectin may, through its zinc binding effects, inhibit microbial growth within an abscess but also inhibit the activity of bactericidal antibiotics.
Insights
Zinc depletion in abscesses may impair bacterial killing. Adding zinc to abscess fluid enhanced bacterial growth and antibiotic effectiveness, suggesting a zinc-binding protein inhibits both.
Area of Science:
- Microbiology
- Immunology
- Pharmacology
Background:
- Abscesses exhibit reduced microbial growth and bacterial killing.
- Neutrophil calprotectin, a zinc-binding protein, may contribute to zinc depletion in abscesses.
- The role of zinc availability in abscess pathophysiology is not fully understood.
Purpose of the Study:
- To investigate the effect of zinc on bacterial growth and antibiotic efficacy in abscess fluid.
- To identify potential zinc-binding factors within abscesses responsible for altered microbial and antibiotic activity.
Main Methods:
- A rabbit tissue-cage abscess model was utilized.
- Abscess supernatants were analyzed for zinc concentration.
- Bacterial growth and cefazolin activity were assessed with and without added zinc.
- Abscess fluid was fractionated using ultrafiltration to isolate active components.
Main Results:
- Abscess fluid zinc concentration was found to be low (< 1.53 microM).
- Zinc supplementation enhanced bacterial growth and cefazolin-mediated bacterial killing in abscess fluid.
- These effects were replicated by a 30-50 kDa fraction of the abscess fluid.
- Zinc addition did not affect bacterial growth or cefazolin efficacy in serum.
Conclusions:
- A protein within abscess fluid, similar to neutrophil calprotectin, binds zinc.
- This zinc-binding protein inhibits microbial growth but also enhances antibiotic activity within the abscess.
- The findings suggest a dual role for this protein in abscess pathogenesis and treatment response.