Summary auto-generated
This study evaluated desferrioxamine, an iron-chelating agent, as a rapid diagnostic test for identifying Staphylococcus epidermidis among coagulase-negative staphylococci (CNS). Researchers tested 95 clinical CNS isolates, 10 S. aureus strains, and reference cultures using both agar dilution and disk-diffusion methods with desferrioxamine-impregnated disks on brain heart infusion agar. All S. epidermidis and S. hominis strains showed susceptibility to desferrioxamine, while all other CNS species, S. aureus, and Micrococcus species were resistant. Using a 1000-μg desferrioxamine disk alone achieved 96.4% efficiency in identifying S. epidermidis. When combined with alkaline phosphatase production and trehalose fermentation tests to differentiate S. epidermidis from S. hominis, identification efficiency reached 100%. The desferrioxamine disks were simple to prepare, inexpensive, stable at both room temperature and 4°C for at least five weeks, and easy to interpret. The test works because S. epidermidis cannot utilize iron in the ferrioxamine complex, while other staphylococci can. The authors conclude this test offers a practical, cost-effective alternative to conventional identification methods for clinical microbiology laboratories.
Key findings
- All S. epidermidis and S. hominis strains were susceptible to 1000-μg desferrioxamine disks on brain heart infusion agar, while all other CNS, S. aureus, and Micrococcus species were resistant
- Desferrioxamine susceptibility alone identified S. epidermidis with 96.4% efficiency (sensitivity 100%, specificity 92.5%, positive predictive value 93.1%)
- Combined with alkaline phosphatase and trehalose fermentation tests, identification efficiency reached 100%, with trehalose fermentation being most reliable for differentiating S. epidermidis from S. hominis
- Desferrioxamine disks were simple to prepare, inexpensive, and remained stable with no significant variation in zone sizes over a 5-week storage period at room temperature or 5°C
- The test requires blood-free media because S. epidermidis cannot utilize iron in the ferrioxamine complex, whereas supplemented media with blood allows growth due to available iron from hemoglobin
This summary was generated automatically from the article PDF and is not part of the original publication. Refer to the PDF for the authoritative text.
Abstract
The ability to identify Staphylococcus epidermidis quickly and accurately has become increasingly important in clinical microbiology. Susceptibility to desferrioxamine, an iron-chelating agent, was investigated as a new test for the identification of S. epidermidis. All strains of S. epidermidis and S. hominis tested were susceptible to a 1000-micrograms disk of desferrioxamine when grown on brain heart infusion agar. All other strains of coagulase-negative staphylococci, S. aureus and micrococci were resistant. As a single test, susceptibility to desferrioxamine was 96.4% efficient in identifying S. epidermidis; when combined with additional tests such as alkaline phosphatase production and fermentation of trehalose, the efficiency improved to 100%. Desferrioxamine disks were easy to prepare, stable and inexpensive. The test was simple to perform and interpret and should readily find application in clinical microbiology laboratories.