What is Stenotrophomonas Maltophilia?

Stenotrophomonas maltophilia is a type of bacteria that was first identified in a human fluid sample in 1943, originally named Bacterium bookeri. Over the years, its classification has changed several times, eventually landing on its current title as Stenotrophomonas in 1991. The name is derived from Greek words that mean “The narrow feeder – that loves malt.” In 2008, the complete genetic package (or genome) of this bacteria was published.

More recently, S. maltophilia is being acknowledged as a ‘newly discovered worrisome pathogen’ and is increasingly being found in medical tests. The World Health Organization (WHO) has recognized it as one of the underestimated yet significant bacteria that can resist multiple drugs that are commonly found in hospitals. British microbiologists have even ranked it as the ninth most important such bacteria. It’s becoming a significant challenge within medical circles because it’s known to cause serious illness and death rates among patients with weakened immune systems.

What Causes Stenotrophomonas Maltophilia?

Stenotrophomonas maltophilia is a type of bacteria that doesn’t feed on sugar and is often found in humans. This bacteria is the third most common of its kind, behind Pseudomonas aeruginosa and Acinetobacter. It’s also similar to Achromobacter xylosoxidans and Burkholderia cepacia. Out of seventeen kinds of Stenotrophomonas bacteria, this is the only one that infects humans.

People with certain conditions are more likely to get infected with this bacteria. These include chronic respiratory diseases such as cystic fibrosis, blood cancer, weak immune systems due to chemotherapy, organ transplant patients, HIV patients, and patients on dialysis. Newborn babies are also at risk.

Being in a hospital environment, especially for a long time or in a high-intensity care unit, can increase the risk of getting this infection. Other risk factors include having a mechanical ventilator, a tracheostomy, a central venous catheter, major burns or injuries, mucositis (inflammation of the digestive tract lining), and various factors damaging the mucosal barrier. Broad-spectrum antibiotics, which are meant to kill a variety of bacteria, also increase the risk of infection.

The risk of this infection increases with each additional antibiotic used and how long it’s used for. It’s worth noting that Stenotrophomonas maltophilia is usually not killed by these broad-spectrum antibiotics, especially the ones called carbapenems, meaning there’s no specific antibiotic that works better than others against it.

Risk Factors and Frequency for Stenotrophomonas Maltophilia

Stenotrophomonas maltophilia is a type of bacteria often found in various environments, including water bodies like rivers, wells, lakes, and even bottled water. It can also be found in other substances like sewage, swine or chicken feces, soil, salads, frozen fish, and raw milk. Interestingly, this bacteria is often found in animals, particularly aquatic ones, and some of these animal strains fall within the same groups as the strains that infect humans. This hints at the possibility that the strains or genes causing human infections could be exchanged with these animals. Certain strains of this bacteria are used for the growth of organic compounds or their breakdown, promoting plant growth against certain fungal pathogens, and cleaning up soil or water.

Importantly, this bacteria is also commonly found in various healthcare environments. It can be found on hospital tap water faucets, sinks, shower outlets, air-cooling systems, ice-making and soda fountain machines, disinfectant solutions, and various medical devices. This bacteria can even be found on the hands of healthcare workers. As such, most infections caused by Stenotrophomonas maltophilia are caught in hospitals, and numerous outbreaks have been reported in hospitals and intensive care units in recent years. Studies have shown that there is a lot of genetic diversity among the strains of this bacteria that cause hospital-acquired infections. This suggests that multiple independent sources in the environment transmit the bacteria, although patient-to-patient transmission has also been reported.

Stenotrophomonas maltophilia is estimated to be the most common bacteria resistant to a certain type of antibiotic (carbapenem) that causes bloodstream infections in US hospitals. It causes about 1% of all hospital-acquired bloodstream infections. The number of infection cases is estimated to be between 5.7 and 37.7 cases per 10,000 hospital discharges. This number has been progressively increasing since the 1970s. This increase in infection rates is believed to be primarily due to an increase in the number of patients with compromised immune systems and the widespread use of broad-spectrum antibiotics.

Signs and Symptoms of Stenotrophomonas Maltophilia

Stenotrophomonas maltophilia is a bacterium often responsible for hospital-acquired infections, but it’s also capable of causing infections in the community. One difficulty with this bacterium is its non-specific symptoms, which can be hard to distinguish from other infections. However, the late onset of related illnesses can be a hint. For instance, symptoms for hospital-acquired pneumonia may take up to five days to appear and 19 days for a bloodstream infection.

It’s critical to determine whether the bacterium is merely present in non-sterile samples or genuinely causing an infection that needs treatment. This distinction relies on assessing the symptoms, signs, and the evidence of the infection through laboratory tests and radiography (x-rays).

Commonly, Stenotrophomonas maltophilia causes respiratory infections, accounting for 55% of all infections. These infections often occur in patients with cystic fibrosis, those who have undergone a tracheostomy, or those on mechanical ventilation. Alarmingly, in specific circumstances – especially in people with underlying blood cancers – the bacterium can lead to a lethal, rapid onset lung infection that involves severe bleeding.

Around 33% of Stenotrophomonas maltophilia infections present as bloodstream infections.
These bloodstream infections can often involve multiple types of bacteria, typically Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterococcus faecalis.
The majority of the reported cases have been linked to infections related to the use of a central venous catheter (a tube placed in a patient’s vein to provide medication).
Recurrent infections can occur if the central venous catheter has not been removed or if appropriate antibiotics are delayed.

Less common infections caused by Stenotrophomonas maltophilia include skin and soft tissue infections (7.8% of total infections), such as wound infections, celery stalk infection, and a severe skin infection called ecthyma gangrenosum. Stenotrophomonas maltophilia can also affect various other parts of the body, causing conditions like meningitis, eye infections, gum diseases, sinusitis, heart infections, abdominal infections, urinary tract infections, joint infections, and others.

Testing for Stenotrophomonas Maltophilia

Stenotrophomonas maltophilia is a type of bacteria that can be grown in the lab, either by itself or alongside other bacteria like Pseudomonas aeruginosa. When it’s grown, colonies of this bacteria typically look yellow-green on one kind of lab plate called a nutrient agar. On another type of lab plate known as blood agar, it gives a slight lavender color and smells like ammonia, but doesn’t cause any damage (non-hemolytic). On MacConkey plates, it looks colorless because it doesn’t ferment lactose. Its growth in the lab often looks similar to Pseudomonas because they both have opaque, flat surfaces with irregular edges. Some specific types of culture media, which contain substances like imipenem, vancomycin, amphotericin-B, and mannitol/bromothymol blue, tend to be more successful in growing Stenotrophomonas maltophilia.

In the lab, this bacteria needs oxygen to survive (strict aerobe), and usually does not produce an enzyme known as oxidase (oxidase negative), though sometimes some can produce it. It also tests positive for enzymes known as catalase and DNase, and a biological process described as lysine decarboxylation. However, it tests negative for indole, hydrogen sulfide (HS), and urease. It also produces acid from a sugar called maltose – this characteristic led to the name “maltophilia”. Commercial testing systems are available for identifying this bacteria, but they can sometimes mistake Stenotrophomonas maltophilia for other types of bacteria.

Another difficulty related to this bacteria is testing its susceptibility to antibiotics. This is because determining the standard minimum amount of the antibiotic needed to inhibit its growth (MIC) can be challenging. Nevertheless, in the U.S., the Clinical and Laboratory Standards Institute (CLSI) established the MICs for antibiotics such as trimethoprim-sulfamethoxazole, levofloxacin, and minocycline. Other medications are still under study.

Nucleic-acid amplification testing (NAAT) and techniques centered around the enzyme polymerase chain reaction (PCR) have shown to accurately identify this bacteria nearly 100% of the time. A technique called matrix-assisted laser desorption ionization, time of flight (MALDI-TOF) mass spectrometry, also accurately identifies the bacteria and can potentially recognize strains that produce biofilms. These techniques can be particularly helpful in quickly diagnosing critical patients, enabling doctors to start treatment faster with suitable antibiotics.

For patients exhibiting symptoms of pneumonia, a chest x-ray can be useful. The x-ray may show areas of infection in one or multiple lobes of the lungs, with or without fluid in the lungs (pleural effusions) or cavities on rare occasions.

Treatment Options for Stenotrophomonas Maltophilia

When a person becomes seriously ill due to an infection caused by the Stenotrophomonas maltophilia bacteria, or when there’s solid evidence of the infection, antibiotic treatment is required. While recommendations for suitable treatments primarily come from laboratory studies, case studies, non-randomized clinical trials, and expert opinions, the preferred treatment is typically trimethoprim-sulfamethoxazole. This is an antibiotic that has been used for many years to treat infections caused by this type of bacteria.

The dosage of this antibiotic is usually quite high, due to laboratory studies suggesting it’s effective against Stenotrophomonas maltophilia when used in this way. However, resistance to this treatment has been increasing, and we’ve seen an increase of resistant cases in various studies conducted in the 21st century.

Another study conducted in Mexico showed a high resistance rate to trimethoprim/sulfamethoxazole, meaning the bacteria had developed ways to survive even in the presence of this antibiotic. It’s also worth noting that this antibiotic can have side effects such as hypersensitivity (allergic reactions), increased potassium levels in the blood, decline in kidney function, and suppression of bone marrow. So, if the patient has a known contraindication (a specific situation in which a drug should not be used), intolerance, or experiences adverse reactions to it, other treatment options have to be considered.

Alternatives to trimethoprim-sulfamethoxazole include a group of antibiotics known as fluoroquinolones. These have been effective in about 80-90% of cases, which may be due to their specific action against biofilm properties of bacteria and their high concentration levels in the lungs. Some of these fluoroquinolones include levofloxacin, moxifloxacin, and newer types.

Second-line treatments, or those used when the primary treatment is not effective, include minocycline, tigecycline, ticarcillin-clavulanic acid, ceftazidime, colistin, and chloramphenicol. These have shown variable effectiveness against the bacteria, but their use is considered in case the primary treatment doesn’t work.

However, it’s important to note that there is an increasing trend of resistance to these antibiotics too, and in some cases, the bacteria have developed resistance to multiple antibiotics. This has led to the exploration of new types of antibiotics and combinations of medications.

For example, the combination of trimethoprim with sulfametrole, a new injectable antibiotic called cefiderocol, and eravacycline, omadacycline, and delafloxacin have shown good activity against the resistant bacteria in laboratory studies.

On the other hand, several new combinations of antibiotics have been found not to be effective against Stenotrophomonas maltophilia.

New treatment methods are also being explored, including aerosols (like colistin and levofloxacin), bacteriophage therapy, efflux pump inhibitors, quorum sensing interference, antimicrobial peptides, nanoparticles, cationic compounds, plant oils, and using Bdellovibrio (a type of bacteria) as a bacterial predator.

The duration of the antibiotic treatment for Stenotrophomonas maltophilia pneumonia is usually 7 days, which can be extended to 10-14 days in patients who have a weakened immune system. In the case of bacteremia (bacteria in the blood), the treatment is typically for 14 days.

It’s also crucial to consider source control in some cases for successful treatment; this includes the removal of central venous catheter, retrieving infected metal hardware, debridement (medical removal) of wounds, conjunctival autografting (transplanting conjunctival tissue), and draining collections (build-ups of body fluids).

Usually, species of Stenotrophomonas apart from maltophilia don’t cause infections in people. However, similar infections can be caused or co-exist with other gram-negative non-fermenting bacteria such as Pseudomonas aeruginosa, Acinetobacter baumannii, Achromobacter xylosoxidans, and Burkholderia cepacia-complex. These can get mistaken for Stenotrophomonas maltophilia.

It’s also important to note that there are other common microbes that can cause infections. Which organism is responsible really depends on the specifics of each individual’s medical conditions and symptoms.

What to expect with Stenotrophomonas Maltophilia

There’s been some debate about the death rate associated with a bacterium called Stenotrophomonas maltophilia. Rough estimates suggest that this bacterium causes death in 14% to 69% of cases.

According to a scientific review, the death rate directly due to infections from Stenotrophomonas maltophilia was as high as 37.5%. In cases where this bacterium caused lung infection (pneumonia), the death rate was at least 20%. In cases of bacteremia, which means the bacterium being present in the blood, the death rate was 27%. This range matches the death rate seen in other cases of bacteremia acquired within healthcare settings (referred to as nosocomial bacteremia).

Research has also shown that patients undergoing a particular kind of bone marrow transplant (known as an allogeneic hematopoietic stem cell transplant) and who were colonized with Stenotrophomonas maltophilia, experienced a significantly higher death rate. The cause of these deaths was mainly severe infections.

Possible Complications When Diagnosed with Stenotrophomonas Maltophilia

Stenotrophomonas maltophilia can cause outbreaks in hospitals and critical care units. This bacteria is particularly challenging to address because it forms biofilms, which are sticky communities of bacteria, which allow it to cling on to surfaces found in hospitals such as medical equipment.

Those with cystic fibrosis may find their lung functions deteriorate if they also become infected with Stenotrophomonas maltophilia. Additionally, individuals with blood cancer might suffer from sudden severe lung infections.

For certain patients, a bacteremia infection, which occurs when bacteria enter the bloodstream, can become worse and lead to further complications like disseminated intravascular coagulopathy (DIC, a condition that affects the blood’s ability to clot) or purpura fulminans (a disorder causing sudden, widespread bleeding underneath the skin). Recurring bacteremia infections might happen if central venous catheters (a type of medical equipment inserted into a large vein) aren’t removed or if inappropriate antibiotics are used.

Complications that could happen:

Worsening lung functions in cystic fibrosis patients
Severe lung infections in people with blood cancers
Complications due to bacteremia infections such as DIC and purpura fulminans
Recurring bacteremia infections if proper medical procedures aren’t followed or wrong antibiotics are used

These complications, along with the financial costs associated with them, emphasize the importance of preventing such infections whenever possible.

Preventing Stenotrophomonas Maltophilia

Stenotrophomonas maltophilia is a type of bacteria that is typically resistant to many drugs and usually infects people with weakened immune systems. It’s often hard to treat because there are limited types of antibiotics that can effectively fight against it. Since information about this infection isn’t easily accessible to the general public, it’s really important to talk to your doctor if you have any questions or concerns about it. If you’re allergic to the antibiotic co-trimoxazole, you should let your healthcare provider know. This antibiotic is commonly used in the treatment of this infection.

Frequently asked questions

The prognosis for Stenotrophomonas maltophilia can vary depending on the specific infection and the individual's immune system. However, rough estimates suggest that this bacterium causes death in 14% to 69% of cases. The death rate directly due to infections from Stenotrophomonas maltophilia has been reported as high as 37.5%, with higher death rates seen in cases of lung infection (pneumonia) and bacteremia. Patients undergoing a particular kind of bone marrow transplant and who are colonized with Stenotrophomonas maltophilia have also experienced a significantly higher death rate.

People can get Stenotrophomonas maltophilia through various ways, including being in a hospital environment for a long time or in a high-intensity care unit, having certain conditions such as chronic respiratory diseases, blood cancer, weak immune systems, or being a newborn baby. Other risk factors include having a mechanical ventilator, a tracheostomy, a central venous catheter, major burns or injuries, mucositis, and various factors damaging the mucosal barrier. The use of broad-spectrum antibiotics also increases the risk of infection. Additionally, Stenotrophomonas maltophilia can be found in various environments such as water bodies, sewage, feces, soil, salads, frozen fish, raw milk, and healthcare environments.

The signs and symptoms of Stenotrophomonas maltophilia can vary depending on the type of infection and the affected body part. However, some common signs and symptoms include: - Non-specific symptoms that can be hard to distinguish from other infections. - Late onset of related illnesses, which can be a hint for hospital-acquired infections. - Respiratory infections, accounting for 55% of all infections, especially in patients with cystic fibrosis, those who have undergone a tracheostomy, or those on mechanical ventilation. - Lethal, rapid onset lung infection involving severe bleeding, particularly in people with underlying blood cancers. - Bloodstream infections, which occur in around 33% of Stenotrophomonas maltophilia infections. - Bloodstream infections often involve multiple types of bacteria, such as Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterococcus faecalis. - Infections related to the use of a central venous catheter, which is a tube placed in a patient's vein to provide medication. - Recurrent infections if the central venous catheter has not been removed or if appropriate antibiotics are delayed. - Less common infections include skin and soft tissue infections (7.8% of total infections), such as wound infections, celery stalk infection, and ecthyma gangrenosum. - Stenotrophomonas maltophilia can also affect various other parts of the body, causing conditions like meningitis, eye infections, gum diseases, sinusitis, heart infections, abdominal infections, urinary tract infections, joint infections, and others. It's important to note that the symptoms and signs of Stenotrophomonas maltophilia infections can overlap with other infections, making it crucial to assess the evidence of the infection through laboratory tests and radiography (x-rays) to determine if treatment is necessary.

The types of tests that are needed for Stenotrophomonas maltophilia include: 1. Culture tests: Stenotrophomonas maltophilia can be grown in the lab using specific culture media, such as imipenem, vancomycin, amphotericin-B, and mannitol/bromothymol blue. These tests help in identifying and growing the bacteria. 2. Enzyme tests: Stenotrophomonas maltophilia tests positive for enzymes like catalase and DNase, and a biological process called lysine decarboxylation. It tests negative for indole, hydrogen sulfide (HS), and urease. 3. Nucleic-acid amplification testing (NAAT) and polymerase chain reaction (PCR): These techniques accurately identify Stenotrophomonas maltophilia nearly 100% of the time. 4. Matrix-assisted laser desorption ionization, time of flight (MALDI-TOF) mass spectrometry: This technique accurately identifies the bacteria and can potentially recognize strains that produce biofilms. 5. Chest x-ray: For patients exhibiting symptoms of pneumonia, a chest x-ray can be useful in identifying areas of infection in the lungs. These tests help in diagnosing Stenotrophomonas maltophilia and determining suitable antibiotic treatments.

Pseudomonas aeruginosa, Acinetobacter baumannii, Achromobacter xylosoxidans, and Burkholderia cepacia-complex

When treating Stenotrophomonas maltophilia, the antibiotic trimethoprim-sulfamethoxazole, which is the preferred treatment, can have the following side effects: - Hypersensitivity (allergic reactions) - Increased potassium levels in the blood - Decline in kidney function - Suppression of bone marrow It's important to note that if a patient has a known contraindication, intolerance, or experiences adverse reactions to trimethoprim-sulfamethoxazole, other treatment options should be considered.

Infectious disease specialist.

Stenotrophomonas maltophilia is the third most common type of bacteria of its kind.

Stenotrophomonas maltophilia is typically treated with the antibiotic trimethoprim-sulfamethoxazole. This antibiotic is the preferred treatment and has been used for many years to treat infections caused by this type of bacteria. However, resistance to this treatment has been increasing, so alternative antibiotics such as fluoroquinolones may be used. Second-line treatments, such as minocycline, tigecycline, and ceftazidime, are considered if the primary treatment is not effective. New types of antibiotics and combinations of medications are also being explored. Additionally, source control measures may be necessary in some cases for successful treatment. The duration of antibiotic treatment for Stenotrophomonas maltophilia pneumonia is typically 7 days, but it may be extended to 10-14 days in patients with a weakened immune system.

Stenotrophomonas maltophilia is a type of bacteria that is recognized as a newly discovered worrisome pathogen. It is known to cause serious illness and death rates among patients with weakened immune systems.