Corynebacterium kroppenstedtii is a Gram-positive bacterium within the genus Corynebacterium. This particular species was first identified in 1998 from a sputum sample. Unlike many other members of its genus, C. kroppenstedtii is distinct because it lacks specific mycolic acids in its cell envelope. This characteristic influences its growth requirements and plays a role in its preferred environments.
Its Natural Habitat
Corynebacterium kroppenstedtii is primarily associated with the human body, particularly breast tissue. Its unique characteristic of being lipophilic, meaning it requires lipids, explains its prevalence in lipid-rich environments such as the mammary glands. This bacterium can exist as part of the normal human skin microbiome without causing any adverse effects.
While it was initially isolated from sputum, subsequent research has predominantly linked C. kroppenstedtii to breast tissue, where it can reside without causing disease.
Health Conditions It Causes
Corynebacterium kroppenstedtii is strongly linked to granulomatous mastitis (GM), also known as non-lactational mastitis, a condition characterized by inflammation of the breast tissue. This bacterium accounts for over 40% of isolates recovered from patients with this specific breast inflammation. Granulomatous mastitis can lead to the formation of painful breast lumps, redness, and abscesses, which are collections of pus.
The disease can be recurrent and may have a prolonged clinical course, lasting weeks to months. Patients with C. kroppenstedtii-related mastitis often experience a hot, painful breast mass and may develop sinus or fistula formation. While GM is the most prominent condition, C. kroppenstedtii has also been associated with other infections, including skin infections, bloodstream infections, or prosthetic valve infections.
The inflammatory response in granulomatous mastitis is characterized by granulomas, small areas of inflammation. This condition primarily affects women of childbearing age, regardless of whether they have given birth. The link between C. kroppenstedtii and granulomatous mastitis has led to its recognition as an opportunistic human pathogen.
Identifying and Managing Infections
Diagnosing infections caused by Corynebacterium kroppenstedtii involves bacterial culture from affected tissue or fluid samples, such as breast aspirates. Due to its lipophilic nature, specific culture media enriched with lipids, such as Tween 80, are necessary to enhance its growth and detection. Cultures may need extended incubation periods, sometimes up to 72 hours, for sufficient growth of this slow-growing organism.
Challenges in identification arise because Corynebacterium species are frequently found as part of the normal skin microbiota, making it difficult to distinguish between colonization and actual infection. Advanced methods like Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) and 16S rRNA gene sequencing are used for accurate species-level identification. Once identified, treatment involves antibiotics.
Antibiotic susceptibility testing is important to guide treatment, as resistance patterns can vary. Some effective antibiotics include doxycycline, ciprofloxacin, linezolid, vancomycin, and trimethoprim-sulfamethoxazole. Beta-lactam antibiotics may be less effective due to poor penetration into lipid-rich breast tissue and reported resistance. In cases of abscess formation, surgical drainage is necessary for resolution and to reduce recurrence.