Other coryneforms and Cutibacterium
- Bacterium
Gram-positive
Thick peptidoglycan wall: stains purple.- Exam priority: medium
Skin and environmental bacteria shaped like clubs; usually harmless, they infect catheters, prosthetic joints and immunocompromised patients.
Also called: Corynebacterium jeikeium, Corynebacterium striatum, Corynebacterium ulcerans, Cutibacterium acnes (formerly Propionibacterium acnes), Rhodococcus equi
Quick facts
- Type
- Bacterium · Gram-positive rods
- Gram / shape
- Gram-positive · Club-shaped or pleomorphic rods in V shapes
- Spread
- C · Rhodococcus
- Causes
- Catheter-related bacteraemia · Acne vulgaris
- Treatment
- C
At a glance
- Gram
- Gram-positive
- Shape
- Club-shaped or pleomorphic rods in V shapes and palisades
- Oxygen
- Corynebacterium and Rhodococcus aerobic or facultative; Cutibacterium anaerobic and slow-growing
- Family
- Corynebacteriaceae, Propionibacteriaceae, Nocardiaceae (Rhodococcus)
- Stain
- Rhodococcus can be weakly acid-fast
Morphology
- Non-spore-forming Gram-positive rods arranged like Chinese letters or palisades
- Rhodococcus equi: coccoid to rod forms with salmon-pink mucoid colonies
- Cutibacterium acnes: slow-growing anaerobic rod that may need up to two weeks of culture
Transmission
- Endogenous skin flora entering through catheters, surgery or prosthetic material
- C. ulcerans: contact with pets (dogs, cats) or farm animals and raw milk
- Rhodococcus: inhalation of soil contaminated with horse or other herbivore manure
Reservoir: Human skin and mucous membranes (C. jeikeium, C. striatum); sebaceous skin of the shoulder, face and back (C. acnes); Dogs, cats and cattle (C. ulcerans); Soil and herbivore manure (Rhodococcus)
Isolation precautions
What the care team adds to standard precautions.
- Standard
Virulence factors
- Biofilm on catheters and prosthetic joints
- C. ulcerans can carry the diphtheria toxin gene
- Rhodococcus survives and multiplies inside macrophages
- C. acnes drives inflammation in blocked sebaceous follicles
Diseases it causes
- Catheter-related bacteraemia in patients with blood cancers and neutropenia (C. jeikeium, C. striatum) Febrile neutropenia →
- Prosthetic valve and device endocarditis Infective endocarditis →
- Indolent prosthetic shoulder and joint infection after surgery (C. acnes) Surgical site infection →
- Acne vulgaris (C. acnes) Acne vulgaris →
- Diphtheria-like illness of throat or skin from toxigenic C. ulcerans Diphtheria →
- Cavitary pneumonia in people with advanced HIV or transplants (Rhodococcus equi) HIV infection and AIDS →
Clinical picture
- Often dismissed as contaminants; repeated positive cultures with signs of infection mean true infection
- Prosthetic shoulder infection: pain and stiffness months or years after surgery, with normal blood markers
- Rhodococcus: subacute upper-lobe cavity that can resemble tuberculosis
Diagnosis
- Two or more positive blood cultures drawn from separate sites support true bacteraemia
- Species identification by MALDI-TOF mass spectrometry and susceptibility testing
- Several periprosthetic tissue samples with anaerobic culture held 10–14 days for C. acnes
- Toxin testing of C. ulcerans at a reference laboratory
- Rhodococcus: weakly acid-fast stain and pink colonies from sputum or blood
Treatment
C. jeikeium and C. striatum are often multidrug-resistant and are treated with vancomycin (linezolid as an alternative) plus catheter removal; C. acnes prosthetic infection needs surgery plus a beta-lactam such as penicillin; toxigenic C. ulcerans is managed like diphtheria (penicillin or erythromycin, antitoxin when indicated); Rhodococcus needs combination therapy (for example vancomycin or a carbapenem with rifampicin, a macrolide or a fluoroquinolone).
Drug class only; doses and regimens are set by the clinician from the current guideline.
In Pharmacology:
Prevention
- Catheter care bundles and skin antisepsis before surgery
- Diphtheria toxoid vaccination also protects against toxin from C. ulcerans
- Antiretroviral therapy prevents Rhodococcus disease in HIV
Vaccine: No vaccine for these organisms; diphtheria toxoid vaccines (in Colombia's PAI schedule) protect against toxin-mediated disease from toxigenic C. ulcerans.
Test yourself
Think of the answer, then tap the question to see it.
Which coryneform is a classic multidrug-resistant cause of catheter bacteraemia in neutropenic patients?
Corynebacterium jeikeium (and C. striatum); vancomycin is the reliable drug.
Why should cultures for prosthetic shoulder infection be kept for up to two weeks?
Cutibacterium acnes grows slowly and anaerobically, so short incubation misses it.
Which coryneform transmitted by pets can produce diphtheria toxin?
Corynebacterium ulcerans.
Which organism causes cavitary pneumonia in advanced HIV and is linked to horse manure?
Rhodococcus equi, a weakly acid-fast rod with pink colonies.
Connections
← Back to the group: Gram-positive rods
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Clinical Characteristics of Corynebacterium Bacteremia Caused by Different Species, Japan, 2014–2020 (Emerging Infectious Diseases (CDC), 2021); Notes from the Field: Toxigenic Corynebacterium ulcerans in Humans and Household Pets — Utah and Colorado, 2022–2023 (MMWR (CDC), 2024); A Literature Review of Cutibacterium Acnes: From Skin Commensal to Pathogen in Shoulder Surgery (Cureus, 2024).
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Representative model, for educational purposes only.