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Cocos Gram-positivos

Staphylococcus hominis

Gram-positive cocci in clusters

Identification & Growth

Identification

  • Catalase-positive, coagulase-negative, novobiocin-susceptible
  • Small colonies, slower growth than S. epidermidis

Growth Conditions

  • Blood agar, 35–37 °C, 24–48 h

Clinical Significance

  • Skin flora; frequent blood culture contaminant
  • True bacteremia in neutropenic patients and catheter carriers

Intrinsic Resistance

  • No activity of aztreonam, colistin or nalidixic acid

Bench Alerts

  • Only regard as significant with two or more positive bottles and compatible clinical picture

Clinical Notes

Clinical presentations

  • Catheter-associated bacteremia, mainly in neonatology and haemato-oncology.
  • Implantable-device infection and, less often, prosthetic valve endocarditis.
  • It is also one of the most frequent blood-culture contaminants, demanding strict interpretation criteria.

Specimens and collection

  • Collect at least two blood-culture sets from different sites, respecting the minimum volume per bottle.
  • Clinical significance is supported by growth in two or more sets with the same susceptibility profile.
  • Record whether collection was through a catheter or by peripheral venipuncture: this changes interpretation.

Epidemiology and at-risk populations

  • A usual component of skin microbiota, predominating in areas rich in apocrine glands.
  • The novobiosepticus subspecies concentrates multidrug-resistant isolates of genuine clinical significance.
  • Preterm infants and patients with long-dwelling central catheters are the most affected population.

Resistance and therapeutic implications

  • High prevalence of mecA-mediated oxacillin resistance in hospital isolates.
  • Vancomycin is the mainstay for proven invasive infection, with MIC always verified.
  • Do not treat a single isolate without a clinical picture: unnecessary treatment selects for resistance.

Bench and reporting notes

  • Catalase-positive, coagulase-negative, novobiocin-susceptible (distinguishing it from S. saprophyticus).
  • Identify to species level by MALDI-TOF when the isolate comes from a sterile site or a device.
  • In the report, explicitly flag possible contamination when only one bottle is positive.

Sources

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 Staphylococcus hominis in the lab?

Staphylococcus hominis is identified through catalase-positive, coagulase-negative, novobiocin-susceptible, small colonies, slower growth than s. epidermidis.

What are the intrinsic resistances of Staphylococcus hominis?

This organism is naturally resistant to no activity of aztreonam, colistin or nalidixic acid. These drugs should not be reported as susceptible.

Where is Staphylococcus hominis commonly found?

It is typically associated with skin flora; frequent blood culture contaminant, true bacteremia in neutropenic patients and catheter carriers.

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