Rapid growing mycobacteria (RGM) are a specific type of bacteria found widely in natural settings like soil and water, and in human-made environments. While many RGM species exist, only a subset can cause infections in people. It is important to understand these organisms because, while some are harmless, others can lead to various illnesses, particularly in individuals with certain predispositions.
Understanding Rapid Growing Mycobacteria
RGM are distinguished from other mycobacteria by their faster growth rate in laboratory cultures, forming visible colonies within seven days. This characteristic helps differentiate them in a clinical setting. These bacteria are widespread in the environment, in soil, dust, and water, including tap water, hot tubs, and even medical devices. This widespread presence means frequent exposure. RGM are largely opportunistic pathogens, meaning they cause infections when an individual’s immune system is weakened or when there is a break in the body’s protective barriers, such as the skin.
Common RGM species causing human infections include Mycobacterium fortuitum, M. chelonae, and M. abscessus. They can persist in both cold and hot water systems, making their presence in various settings, including healthcare facilities, a concern. Their ability to form biofilms (communities of microorganisms that adhere to surfaces) contributes to their persistence in moist environments like plumbing and medical equipment.
Common Infections Caused by RGM
RGM cause various infections in humans, often depending on the route of exposure and the individual’s health status. Skin and soft tissue infections are common, frequently occurring following trauma, surgery, or cosmetic procedures. These can appear as wound infections, cellulitis (a spreading bacterial infection of the skin), or abscesses (pus-filled lumps) often resistant to typical antibiotics. For example, infections have been reported after liposuction, mesotherapy, intramuscular injections, and acupuncture.
Lung infections are also a concern, especially for individuals with pre-existing lung conditions like cystic fibrosis. Symptoms often mimic other respiratory illnesses, such as chronic cough and shortness of breath. While some cases may be asymptomatic, others can lead to severe bronchiectasis (widened and scarred airways), and cavitary lung disease. Certain RGM species, such as Mycobacterium abscessus, are recognized as respiratory pathogens in patients with chronic lung diseases.
In rarer instances, RGM can lead to disseminated infections, where the bacteria spread throughout the body. This is more common in individuals with compromised immune systems. Disseminated infections can affect multiple organs, including lymph nodes, bones, joints, and other soft tissues, presenting with symptoms like fever and rigors. Catheter-related infections are also reported, with RGM like M. fortuitum, M. chelonae, and M. abscessus being common culprits, leading to local or systemic symptoms.
Identifying and Treating RGM Infections
Diagnosing RGM infections is challenging because symptoms are non-specific and routine bacterial cultures may not detect them. The initial step often involves collecting samples from the affected tissue or fluid for laboratory culture. Because RGM grow slowly, specialized acid-fast bacilli (AFB) cultures are often required, needing incubation for up to 14 days for detection.
Identifying the specific RGM species is important due to varying antibiotic susceptibilities. Molecular methods, such as gene sequencing, have improved RGM identification accuracy and speed, providing reliable results faster than traditional biochemical tests.
Treating RGM infections is often challenging due to their natural resistance to many common antibiotics. It typically involves a prolonged course of specific antimicrobial agents, often a combination of two or three drugs, lasting six months to a year or more. For severe or localized infections, surgical intervention (e.g., draining abscesses, removing infected tissue or foreign bodies like catheters) is often necessary for a cure. Treatment regimens are often individualized based on the specific RGM species and infection site, due to a lack of controlled trials.
Reducing Your Risk of RGM Exposure
While RGM are ubiquitous, certain practices can help minimize the risk of infection. Proper wound care after injury or surgery is important to prevent bacteria from entering the body. This includes keeping wounds clean and covered as they heal.
Ensuring clean water sources for medical procedures is also a preventative measure, especially in healthcare settings where outbreaks have been linked to contaminated water. This applies to water used in dialysis, hydrotherapy equipment, and ice machines. General hygiene practices, such as handwashing, also reduce exposure. Although completely avoiding RGM is not feasible due to their widespread presence, these measures can lower the likelihood of infection.