Corynebacterium amycolatum is a Gram-positive, rod-shaped, non-spore-forming bacterium within the Corynebacterium genus, which includes human pathogens. It was first identified in 1988 and is capable of fermentation.
Role as a Commensal Organism
Corynebacterium amycolatum commonly inhabits human skin and mucous membranes, making it a part of the body’s normal microbiota. It behaves as a commensal organism, meaning its presence benefits the bacterium without causing harm to its human host. For most healthy individuals, C. amycolatum’s presence is normal and does not lead to health issues.
These bacteria contribute to the diverse microbial communities that naturally colonize various body surfaces from birth. The balance of these microbes is influenced by factors such as diet, overall health, and personal hygiene. Such resident microflora play a role in protecting against more harmful microorganisms and stimulating immune responses.
When It Becomes an Opportunistic Pathogen
While generally harmless, Corynebacterium amycolatum can transition into an opportunistic pathogen under specific circumstances. An opportunistic pathogen is an organism that typically resides as part of the normal microbial flora but can cause disease when an opportunity arises, such as a weakened immune system or a breach in the body’s natural barriers. This shift occurs when the body’s defenses are compromised, allowing the bacterium to proliferate and cause infection.
Several factors increase the risk of C. amycolatum becoming problematic. Individuals with compromised immune systems, due to conditions like cancer, HIV, or the use of immunosuppressive drugs, are more susceptible. The presence of foreign medical devices, such as catheters, prosthetic joints, or pacemakers, provides surfaces for bacterial attachment and biofilm formation. Prolonged hospitalization, significant wounds, or burns also create environments where this bacterium can establish an infection.
Associated Infections and Symptoms
When Corynebacterium amycolatum acts as a pathogen, it can cause a range of infections, often in hospital settings. Bloodstream infections (bacteremia or sepsis) are a common manifestation. Symptoms can include fever, chills, and a general feeling of illness.
The bacterium can also cause heart valve infections, known as endocarditis. This infection typically affects individuals with underlying heart defects or those with prosthetic heart valves. Symptoms of endocarditis may include persistent fever, fatigue, and sometimes new or worsening heart murmurs.
Wound and soft tissue infections are another common presentation, particularly in patients with surgical wounds or burns. These infections can lead to localized redness, swelling, pain, and warmth around the affected area. In more severe cases, bone infections, or osteomyelitis, can occur, especially following orthopedic surgeries or in cases of deep ulcers. Osteomyelitis symptoms can include localized pain, tenderness, swelling, and fever, often requiring targeted medical intervention.
Diagnosis and Treatment Challenges
Diagnosing Corynebacterium amycolatum infections typically involves laboratory culture of samples from the suspected infection site, such as blood, tissue, or fluid. Once cultured, the bacterium can be identified through biochemical tests and molecular techniques. However, differentiating C. amycolatum from other similar Corynebacterium species can be challenging due to their phenotypic similarities.
A challenge in treating C. amycolatum infections is its frequent multidrug resistance. Many commonly used antibiotics, such as beta-lactams, macrolides, and quinolones, may not be effective. Doctors perform antibiotic susceptibility testing on isolated strains to determine which drugs will inhibit bacterial growth. While many isolates show resistance to several drug classes, C. amycolatum strains are generally susceptible to glycopeptide antibiotics like vancomycin and linezolid. The choice of antibiotic treatment relies on these laboratory results to ensure effective patient management.