Mycobacterium chelonae is a type of bacterium that can cause infections in humans, particularly in healthcare settings or among individuals with weakened immune systems. This organism is commonly found in various natural environments. Understanding its characteristics, how infections develop, and management strategies is important.
Understanding Mycobacterium chelonae
Mycobacterium chelonae is classified as a rapidly growing nontuberculous mycobacterium (NTM). This means it reproduces quickly in laboratory settings, typically showing growth within seven days on culture media. It is distinct from the mycobacteria that cause tuberculosis or leprosy.
This bacterium is ubiquitous, meaning it is found widely in the environment, including in soil, water, and even dust. It can also be present in natural and treated water sources, such as tap water and sewage. While M. chelonae is common in these environments, it generally causes infections in humans only under specific circumstances, often involving a breach in the skin barrier or exposure during medical procedures.
How Infections Develop
Infections primarily occur through environmental exposure, especially when the bacteria enter the body through breaks in the skin. This can happen through minor cuts, punctures, or abrasions. However, a more common route of infection involves contaminated medical or cosmetic procedures.
Surgical sites, injections, cosmetic procedures like tattooing or mesotherapy, and the implantation of medical devices can provide entry points for the bacteria. M. chelonae has been identified in contaminated water distribution pipes, faucets, and even medical equipment cleaned with such water. This bacterium is not typically spread from person to person.
Signs and Symptoms of Infection
Mycobacterium chelonae infections most frequently present as skin and soft tissue infections, particularly on the arms and legs. These infections can manifest as persistent redness, swelling, and pain, often progressing to abscesses, non-healing wounds, pustules, or nodules. The lesions may also appear as small raised rashes or inflammatory nodules along lymphatic vessels.
Symptoms can be slow to develop, sometimes taking weeks to months after exposure, and may initially be mistaken for other conditions. While less common, M. chelonae can also cause more severe disseminated infections or affect bones and joints, particularly in individuals with compromised immune systems.
Diagnosis and Treatment
Diagnosing Mycobacterium chelonae infections often begins with culturing tissue samples or pus from the infected site. While M. chelonae grows relatively quickly, growth on culture media may be observed within three to five days, but full identification can take longer, often weeks. Molecular tests are frequently used to accurately identify the bacteria to the species level, which is important for guiding treatment.
Treatment of M. chelonae infections presents challenges due to the bacterium’s inherent drug resistance and the lack of standardized guidelines for therapy. Treatment typically involves prolonged courses of combination antibiotic therapy, as monotherapy can quickly lead to resistance. Macrolides, such as clarithromycin or azithromycin, are frequently used because M. chelonae isolates are usually susceptible to them. Other antibiotics that may be used in combination include aminoglycosides (like tobramycin), linezolid, clofazimine, and sometimes imipenem, fluoroquinolones, and tetracyclines.
Antibiotic susceptibility testing is routinely performed to determine the most effective drug combination for an individual’s infection. For localized skin and soft tissue infections, antibiotic therapy may last for three to twelve months after wound healing to prevent recurrence. In cases where the infection involves abscesses or infected medical devices, surgical debridement or removal of the device is often necessary in conjunction with antibiotics to achieve a cure.
Preventing Infection
Preventing Mycobacterium chelonae infections involves several practical measures, focusing on wound care and procedural safety. Proper care for cuts, scrapes, and other skin abrasions is important to minimize entry points for bacteria. Cleaning wounds thoroughly and keeping them covered helps reduce the risk of environmental contamination.
When undergoing medical or cosmetic procedures, choose reputable clinics that adhere to strict sterile techniques. Ensure all equipment is properly disinfected and sterilized to prevent bacterial introduction during invasive procedures. For individuals with compromised immune systems, avoiding prolonged exposure to potentially contaminated water sources like hot tubs or untreated well water is advisable, especially with open wounds or compromised skin integrity.