Stenotrophomonas - An Overview

Introduction:

Stenotrophomonas occur in the soil, environments, and mainly in plants. It belongs to the Xanthomonadaceae family and comprises more than ten species. They are Stenotrophomonas maltophilia, S.nitritireducens, S. rhizophila, S. acidaminiphila, S. chelatiphaga, S. koreensis, S. terrae, S. humi, S. bentonitica, and S. pavani. These bacteria have a wide range of activities.

What Are the Uses of Stenotrophomonas Species?

Stenotrophomonas bacteria are used in different biotechnological processes in agriculture. For example, some species produce antimicrobial compounds that generate factors to promote plant growth and protect plants. In addition, they can degrade pollutants, as they have intrinsic resistance to heavy metals and pollutants. Some species are used in phytoremediation and bioremediation. Stenotrophomonas species are also used in sulfur and nitrogen cycles.

What Are the Different Species of Stenotrophomonas?

The different species of Stenotrophomonas include the following.

• Stenotrophomonas maltophilia is the most predominant species causing the disease in humans, such as bacteremia, septicemia, and severe lung infections.

• Stenotrophomonas nitritireducens is a yellow-pigmented, aerobic, and mesophilic bacteria commonly found in the soil. It can reduce nitrite and transform unsaturated fatty acids into hydroxy fatty acids.

• Stenotrophomonas rhizophila is commonly associated with plants in tomato leaves. It is isolated from the internal plant tissues. It provides osmoprotective substances and protects plants from pathogens. It accumulates the solutes of trehalose and glucosyl glycerol under salt-stress conditions. This bacteria has genes for plant cell wall degrading enzymes and increases salinity resistance. In addition, it produces dodecanal to inhibit fungal mycelial growth and chitinases.

• Stenotrophomonas acidaminiphila is a Gram-negative, mesophilic, aerobic, non-spore-forming bacterium. It was isolated from the industrial wastewater in Mexico. They can degrade polycyclic aromatic hydrocarbons. The probiotic strain of Stenotrophomonas acidaminiphila BJ1 reduces chlorothalonil and stimulates soil health.

• Stenotrophomonas chelatiphaga is an aerobic Gram-negative bacterium isolated from Russia's sewage sludge. This species can degrade ethylenediaminetetraacetic acid.

• Stenotrophomonas koreensis is a Gram-negative bacterium isolated from compost in South Korea. This species is a biosurfactant producer for reducing heavy metals from the environment.

• Stenotrophomonas terrae and Stenotrophomonas humi are Gram-negative, rod-shaped, and non-spore-forming bacteria. These are nitrate-reducing bacteria from the soil of Belgium.

• Stenotrophomonas bentonitica is a Gram-negative, aerobic, rod-shaped bacterium isolated from bentonite formation in Southern Spain.

• Stenotrophomonas pavani is a Gram-negative, non-spore-forming rod-shaped bacterium. It is a nitrogen-fixing bacterium isolated from the stems of sugarcane in Brazil.

What Is Stenotrophomonas Maltophilia?

Stenotrophomas maltophilia is a multi-drug resistant bacillus that causes nosocomial infections in hospitalized, debilitated, and immunocompromised individuals. It is the only stenotrophomonas species to infect humans.

The bacteria colonize the fluids used in hospital settings. The sources of Stenotrophomonas maltophilia bacteria are disinfectants, nebulizers, sink drains, hospital suction tubing, hand washing soaps, catheters, breathing tubes, and intravenous lines, which are contaminated with Stenotrophomonas maltophilia bacteria and not adequately sterilized.

What Is the Pathophysiology of Stenotrophomonas Maltophilia Infection?

The pathophysiology of Stenotrophomonas maltophilia includes the following influential virulence factors.

• The bacterium can form a biofilm that allows it to adhere firmly to the surfaces of ventilation tubes, circuits, and respiratory epithelial tissues.

• It has two enzymes: the class B zinc-dependent penicillinase and the class A serine cephalosporinase, which resist beta-lactam antibiotics.

• The target site modification genes mediate Trimethoprim-Sulfamethoxazole resistance.

• The bacterium has exoenzymes such as mucinase, elastase, DNase, RNase, hyaluronidase, lipases, and proteases, which help them with tissue invasion.

What Are the Risk Factors Associated With Stenotrophomonas Maltophilia Infections?

The following are the risk factors associated with infections caused by Stenotrophomonas maltophilia bacteria.

• Older age.

• Long hospitalization.

• Septic shock.

• Immunosuppressive therapy.

• Underlying diseases.

• Patients who have undergone more invasive operations.

• Increased mechanical ventilation duration.

• Neutropenia.

• HIV or AIDS.

• Malignancy.

• Cystic fibrosis.

What Are the Infections Caused by Stenotrophomonas Maltophilia?

The following are the infections caused by the Stenotrophomonas maltophilia bacteria.

• Bacteremia.

• Endocarditis.

• Respiratory tract infections with symptoms such as dyspnea and cough.

• Meningitis.

• Urinary tract infections due to catheterization.

• Biliary sepsis.

• Cellulitis.

• Wound infections.

• Central venous catheter-related infections.

• Ocular infections such as conjunctivitis, keratitis, and orbital necrotizing fascitis.

• Pacemaker infections.

• Intra-abdominal infections such as enteritis, peritonitis, and cholangitis.

• Gingivitis and periodontitis.

How to Evaluate Stenotrophomonas Maltophilia?

The following methods and techniques are used to evaluate Stenotrophomonas maltophilia and help in treatment.

• Culture media - This bacterium produces yellow-green colonies on nutrient agar, faint lavender-colored colonies with an ammonia odor on blood agar, and appears colorless on McConkey plates, as it is a non-lactose fermenting bacteria.

• Nucleic-acid amplification testing (NAAT), species-specific 23S rRNA-directed polymerase chain reaction (PCR) techniques identify the bacterial species.

• Matrix-assisted laser desorption ionization and time of flight(MALDI-TOF) mass spectrometry recognize the strains that produce biofilms.

How to Treat Stenotrophomonas Maltophilia Infection?

The therapeutic options for the treatment of Stenotrophomonas maltophilia infection include the following.

1. The first line of treatment is Trimethoprim-Sulfamethoxazole (TMP-SMX) for Stenotrophomonas infections. An increased dose of TMP-SMX is recommended for critically ill patients with S. maltophilia infections.

2. Fluoroquinolones such as Levofloxacin and Moxifloxacin are used in cases of TMP-SMX resistances.

3. Monotherapy includes Tetracyclines such as Minocycline and Tigecycline and cephalosporines such as Ceftazidime to treat S. maltophilia infections.

4. Combination therapies include TMP-SMX and Ticarcillin-Clavulanate, TMP-SMX and Ceftazidime, TMP-SMX, and Tigecycline, and aerosolized Colistin and Doxycycline.

5. Colistin and Rifampicin or Colistin and TMP-SMX are used for multi-drug resistance species.

6. The future and targeted therapies include inhibitors of efflux pumps and beta-lactamases, cationic compounds, bacteriophages, nanoemulsions, plant oils, and constituents of green tea.

How to Prevent Stenotrophomonas Maltophilia Infections?

Technologies that kill bacteria rather than suppress them are vital. For example, an advanced copper-silver ionization system can stop bacteria. In this process, positively charged silver and copper ions are injected into the pipes, which form a bond with the negatively charged cell walls of the microorganisms resulting in the death of the pathogens. The copper-silver ionization technique can be used in the plumbing systems in the healthcare sector to prevent S. maltophilia infections from contaminated hospital settings.

Conclusion:

The clinicians, nurses, pharmacists, and infection prevention team should know the treatment plan and prevention strategies for Stenotrophomonas maltophilia infections. In addition, the healthcare team should follow prevention measures such as hand hygiene, proper disposal of contaminated solutions, and using disinfectants like 3 percent hydrogen peroxide and 10 percent peracetic acid.