Stenotrophomonas maltophilia has increasingly drawn attention in medical settings due to its presence in infections, prompting concerns about its potential harm. This bacterium has become a subject of discussion regarding its severity and impact on human health. Understanding its characteristics and the circumstances under which it causes illness is important for assessing its danger.
Understanding Stenotrophomonas maltophilia
Stenotrophomonas maltophilia is an aerobic, non-fermenting, gram-negative bacterium commonly found in various natural environments. It thrives in water, soil, and on plants. It is also frequently encountered in healthcare environments, where it can colonize hospital water systems, medical equipment, and patient secretions such as respiratory fluids or urine.
This bacterium is classified as an opportunistic pathogen, meaning it typically causes infection when a person’s defenses are weakened. Although it has low virulence, it can establish itself in bodily fluids and on medical devices without immediately causing disease.
Severity and Vulnerable Populations
For healthy individuals, Stenotrophomonas maltophilia generally poses little threat and is not considered life-threatening. Its potential for severe outcomes is primarily observed in specific vulnerable populations with compromised health conditions. These include individuals who are immunocompromised, such as cancer patients, organ transplant recipients, and those with HIV/AIDS. Patients with chronic lung diseases like cystic fibrosis or chronic obstructive pulmonary disease (COPD) are also at increased risk, as are those in intensive care units (ICU).
The presence of indwelling medical devices, such as central venous catheters, urinary catheters, or mechanical ventilators, significantly elevates the risk for infection and more severe outcomes. Mortality rates associated with S. maltophilia infections can vary widely, ranging from 12% to 69%, with some studies reporting averages around 40.5% in patients with bloodstream infections. These higher rates are often linked to the patient’s underlying health status and the severity of their existing conditions. Factors like septic shock, neutropenia, and hematological malignancies are also associated with increased mortality.
How Infections Develop and Present
Infections with Stenotrophomonas maltophilia are typically acquired in healthcare settings, often through exposure to contaminated sources. This can occur via medical equipment, hospital water systems like tap water or dialysis machines, or contaminated irrigation solutions. The bacterium often colonizes body fluids and medical devices, and can then cause an infection if it bypasses the body’s normal defenses.
S. maltophilia can cause a range of infections. Respiratory tract infections, particularly pneumonia (especially ventilator-associated pneumonia), are common. Bloodstream infections, also known as bacteremia, are another frequent manifestation that can lead to systemic illness. Other infections include wound infections, urinary tract infections, and less commonly, infections of the heart, bones, or central nervous system.
The symptoms of these infections are generally non-specific and depend on the site of infection, often resembling those caused by other bacterial pathogens. For example, lung infections may present with fever, cough, and shortness of breath, while bloodstream infections can cause fever, rapid heart rate, and low blood pressure.
Treatment and Overcoming Resistance
Diagnosing Stenotrophomonas maltophilia infections usually involves culturing samples from the suspected infection site to identify the bacterium. Treatment presents a significant challenge because S. maltophilia is intrinsically resistant to many commonly used antibiotics, including most beta-lactams, aminoglycosides, and carbapenems.
The limited effective antibiotic options make susceptibility testing important for guiding treatment decisions. Trimethoprim-sulfamethoxazole (TMP-SMX) is often considered the drug of choice, with susceptibility rates typically ranging from 79% to 96%. However, resistance to TMP-SMX is increasing in some regions.
Other antibiotics that may be used, depending on susceptibility test results, include minocycline, levofloxacin, and more recently, cefiderocol. For severe or multidrug-resistant cases, combination therapy, such as aztreonam with ceftazidime-avibactam, may be considered, though optimal dosing strategies are still being established. Alongside antibiotic treatment, strict infection control measures in healthcare environments are important to prevent the spread of this resistant bacterium.