Micrococcus / Kocuria spp.
Gram-positive cocci in tetrads and packets
Identification & Growth
Identification
- Catalase-positive, coagulase-negative, modified oxidase-positive (Micrococcus)
- Resistant to bacitracin 0.04 U and susceptible to furazolidone — the opposite pattern to Staphylococcus
Growth Conditions
- Blood agar, 35 °C, 24–48 h; dry, yellow or pink colonies
Clinical Significance
- Normal skin flora; rarely catheter, prosthetic, and dialysis-related peritonitis infections
Intrinsic Resistance
- No disk-diffusion breakpoints in BrCAST/EUCAST — do not interpret as if it were Staphylococcus
Bench Alerts
- Most often a single-bottle blood culture contaminant
- Only regard as significant with multiple positive bottles and a compatible clinical picture
Clinical Notes
Clinical presentations
- Catalase-positive Gram-positive cocci usually regarded as skin contaminants in blood cultures, but can cause bacteremia and endocarditis in immunocompromised or catheter-bearing patients.
- Rare cases of peritoneal dialysis-associated peritonitis and prosthetic joint infection have been reported.
- Meningitis and ventriculoperitoneal shunt infection occur occasionally in case reports.
Specimens and collection
- Repeat blood cultures from distinct sites help distinguish true bacteremia from skin contamination.
- Peritoneal or joint fluid should be collected aseptically for quantitative culture when device infection is suspected.
- Skin should be adequately decontaminated before venipuncture to reduce false-positive rates.
Epidemiology and at-risk populations
- They are part of the normal skin and mucosal microbiota, being frequent culture contaminants.
- Neutropenic patients, central venous catheter carriers and prosthesis recipients are at higher risk of true infection.
- Hospital outbreaks are rare but have been linked to contaminated solutions or equipment.
Resistance and therapeutic implications
- Generally susceptible to beta-lactams, but Kocuria spp. may show variable intrinsic resistance to oxacillin.
- No standardized EUCAST/BrCAST clinical breakpoints exist for the genus, requiring case-by-case interpretation.
- Catheter or device removal is often necessary in addition to antibiotic therapy in confirmed cases.
Bench and reporting notes
- Clinical correlation is essential before reporting the isolate as a significant pathogen, given its common role as a contaminant.
- Differentiation from coagulase-negative Staphylococcus may require catalase testing, cluster morphology and biochemical tests or MALDI-TOF.
- Multiple positive blood cultures with the same profile suggest true clinical significance.
Sources
- CDC — Micrococcus and related organisms
- PubMed — Micrococcus species clinical significance
- EUCAST — Clinical breakpoints
Educational decision-support content. It does not replace laboratory validation, current guidelines or review by the responsible professional.
FAQ: Frequently Asked Questions
How to identify Micrococcus / Kocuria spp. in the lab?
Micrococcus / Kocuria spp. is identified through catalase-positive, coagulase-negative, modified oxidase-positive (micrococcus), resistant to bacitracin 0.04 u and susceptible to furazolidone — the opposite pattern to staphylococcus.
What are the intrinsic resistances of Micrococcus / Kocuria spp.?
This organism is naturally resistant to no disk-diffusion breakpoints in brcast/eucast — do not interpret as if it were staphylococcus. These drugs should not be reported as susceptible.
Where is Micrococcus / Kocuria spp. commonly found?
It is typically associated with normal skin flora; rarely catheter, prosthetic, and dialysis-related peritonitis infections.
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