First report of bacteremia caused by CO 2 -dependent methicillin-resistant Staphylococcus epidermidis in a patient with symptomatic multiple myeloma.
Takeharu Iida, Takahiro Fujita, Akira Iwata et al.
✦ AI-curated · Sources linked
Case in brief
A patient with symptomatic multiple myeloma had blood cultures showing Gram-positive cocci. Molecular testing identified S. epidermidis with mecA/C, but the isolate did not grow in ambient air and formed colonies only under 5% CO₂. An automated system used in ambient air misidentified it as Micrococcus and could not provide interpretable susceptibility results because growth was insufficient. Testing under 5% CO₂ identified methicillin-resistant S. epidermidis (MRSE), consistent with molecular findings; MALDI-TOF confirmed the species. The same CO₂-dependent isolate was recovered from fluid at a posterior spinal fusion surgical site.
What made this case unusual
The isolate’s CO₂ dependence caused both failure to grow in ambient air and an erroneous automated identification, creating a diagnostic and susceptibility-testing pitfall.
Diagnostic / clinical pearl
When S. epidermidis is detected molecularly but fails to grow or is misidentified in ambient air, consider CO₂-dependent growth and repeat culture and susceptibility testing under 5% CO₂.