Anaeróbios

Cutibacterium acnes (antigo Propionibacterium acnes)

Anaerobic diphtheroid Gram-positive bacilli

Identification & Growth

Identification

Catalase-positive, indole-positive, aerotolerant anaerobe

Growth Conditions

Anaerobic blood agar, 35 °C, 5–14 days; blood cultures may flag after 7 days

Clinical Significance

Shoulder and hip prosthetic joint infection, prosthetic valve endocarditis, shunt infection
Frequent contaminant when isolated from a single blood culture

Intrinsic Resistance

Intrinsic resistance to metronidazole and aminoglycosides

Bench Alerts

In prosthesis revision surgery, hold cultures for 14 days before reporting as negative
Multiple positive samples from the same site indicate true infection

Clinical Notes

Clinical presentations

Prosthetic-device-associated infection (shoulder prosthesis, valves, ventricular shunts) with indolent presentation, often without classic inflammatory signs.
Etiological role in acne vulgaris pathogenesis, via inflammatory response to follicular colonization.
Delayed-onset postoperative endophthalmitis, presenting as chronic low-grade inflammation months after cataract surgery.

Specimens and collection

Multiple intraoperative tissue samples (≥3–5) are recommended when prosthetic infection is suspected, since a single positive culture may represent contamination.
Prolonged culture for up to 10–14 days under anaerobic conditions, given the organism's slow growth, especially relevant in prosthetic material infection.
Sonication of the removed implant increases detection sensitivity compared with tissue culture alone.

Epidemiology and at-risk populations

Dominant member of normal skin microbiota, especially in sebaceous-gland-rich areas (face, scalp, upper trunk).
Frequent contaminant of blood cultures and surgical specimens due to skin origin, requiring careful clinical correlation before assuming true infection.
Increased risk of true infection in shoulder orthopedic surgery, likely due to higher organism density in follicles of that region.

Resistance and therapeutic implications

Generally susceptible to penicillin G and beta-lactams, which remain the backbone of treatment for confirmed infections.
Increasing resistance to macrolides and clindamycin has been reported, relevant in the management of acne with prolonged topical/systemic therapy.
Prosthetic device infection often requires device removal combined with prolonged antibiotic therapy to eradicate biofilm.

Bench and reporting notes

Anaerobic (aerotolerant), pleomorphic Gram-positive rod with slow growth; definitive identification may require MALDI-TOF.
Interpret isolation in light of the number of positive samples, the site, and time to positivity in culture, as these criteria help distinguish infection from contamination.
The taxonomic reclassification from Propionibacterium acnes to Cutibacterium acnes should be reflected in the report to match current nomenclature.

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 Cutibacterium acnes (antigo Propionibacterium acnes) in the lab?

Cutibacterium acnes (antigo Propionibacterium acnes) is identified through catalase-positive, indole-positive, aerotolerant anaerobe.

What are the intrinsic resistances of Cutibacterium acnes (antigo Propionibacterium acnes)?

This organism is naturally resistant to intrinsic resistance to metronidazole and aminoglycosides. These drugs should not be reported as susceptible.

Where is Cutibacterium acnes (antigo Propionibacterium acnes) commonly found?

It is typically associated with shoulder and hip prosthetic joint infection, prosthetic valve endocarditis, shunt infection, frequent contaminant when isolated from a single blood culture.

Antibiogram InterpreterCheck BrCAST 2026 breakpoints Rugai InterpreterBiochemical identification tools