The genus Tsukamurella is a group of bacteria that has gained attention in medical settings as an emerging cause of infection, particularly in vulnerable patient populations. These organisms are naturally present in the environment, but they are classified as opportunistic pathogens, meaning they primarily cause disease when a person’s defenses are compromised. Infections caused by Tsukamurella are rare, but their increasing recognition is linked to improvements in laboratory identification techniques.
Characteristics and Environmental Presence
Tsukamurella is an aerobic, Gram-positive, rod-shaped bacterium belonging to the order Actinomycetales, which includes other medically relevant bacteria like Nocardia and Mycobacterium. A defining characteristic is the presence of mycolic acid in its cell wall, causing it to be partially or weakly acid-fast. This composition contributes to its resilience.
This genus is widely distributed as an environmental saprophyte, living on decaying organic matter. Its natural habitats include soil, water, sewage sludge, and the foam in activated sludge plants. This broad environmental presence makes exposure possible in various settings, contributing to hospital-acquired infections.
The bacterium’s ability to adhere to surfaces and form a protective biofilm is a significant factor in its persistence. This biofilm formation allows it to colonize medical equipment and indwelling devices, providing a pathway to enter the human body. It is capable of slow growth within the human body.
Types of Human Infection
Infections caused by Tsukamurella species are rare but increasingly reported as diagnostic methods improve. The most common clinical presentation involves the bloodstream, often manifesting as bacteremia. This is frequently associated with indwelling medical devices, leading to catheter-related bloodstream infections.
Tsukamurella can cause localized and systemic diseases across multiple organ systems. Pulmonary infections, presenting as pneumonia, are a significant concern, particularly in patients with pre-existing chronic lung conditions. These respiratory infections can resemble tuberculosis, sometimes leading to misdiagnosis. The bacteria also cause infections of the skin and soft tissues, often arising after trauma or surgery. Furthermore, it has been implicated in serious infections of the central nervous system, such as meningitis and brain abscesses, and ocular infections like keratitis.
Identifying and Treating Infection
Identifying Tsukamurella in a clinical laboratory presents challenges due to its slow growth and similarity to other bacteria. Colonies may take 24 to 72 hours to become visible on routine culture, delaying diagnosis. Conventional biochemical tests often struggle to differentiate Tsukamurella from related genera like Nocardia, Rhodococcus, and Mycobacterium.
Accurate identification relies on advanced molecular methods, such as 16S ribosomal RNA gene sequencing or matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). These techniques analyze the organism’s genetic material or protein profile, providing definitive species-level identification. Correct identification is important, as misdiagnosis can lead to ineffective treatment.
Treatment is complicated by the bacterium’s intrinsic resistance to several common antimicrobial agents. Tsukamurella isolates are resistant to penicillin, oxacillin, and most cephalosporins. This resistance profile necessitates specific drug choices, guided by laboratory susceptibility testing.
Effective agents frequently include:
- Amikacin
- Ciprofloxacin
- Trimethoprim/sulfamethoxazole
- Linezolid
- Minocycline
Because of the lack of standardized guidelines, treatment often involves a combination of antibiotics, and therapy courses are generally prolonged. For cases involving indwelling devices, the physical removal of the infected foreign body is necessary for a successful outcome.
Patient Risk Factors and Prevention
The patient population most susceptible to Tsukamurella infection includes individuals with compromised immune systems. Immunosuppressive states resulting from conditions like cancer, HIV infection, or the use of immunosuppressive medications significantly increase the risk. Chronic underlying health problems, such as bronchiectasis or renal failure requiring hemodialysis, also act as major risk factors. The presence of indwelling medical devices is a strong predisposing factor because the bacteria can colonize these surfaces.
Prevention strategies focus on limiting exposure and maintaining strict sterile techniques in healthcare environments. Scrupulous attention to the insertion and maintenance of indwelling devices is important. When infection occurs, a swift diagnosis and removal of any infected foreign material, combined with targeted antibiotic therapy, are necessary to manage the disease.