Pseudomonas aeruginosa is a type of bacteria that causes a variety of different infections. According to the Centers for Disease Control and Prevention (CDC), multidrug-resistant (MDR) Pseudomonas aeruginosa continues to be classified as a serious antimicrobial resistance threat. Current CDC surveillance data show that approximately 8.2% of tested Pseudomonas aeruginosa isolates were multidrug resistant in 2024, representing 632 resistant isolates among 7,678 tested samples. The CDC continues to estimate approximately 32,600 infections and 2,700 deaths annually associated with multidrug-resistant Pseudomonas aeruginosa in the United States. Although substantial progress has been made through antimicrobial stewardship programs, infection prevention initiatives, and improved prescribing practices, antibiotic resistance remains a significant challenge, particularly among hospitalized and critically ill patients.
Pseudomonas aeruginosa is an aerobic, gram-negative, non-sporing forming rod. It can be found in freshwater and the environment. Anyone can acquire this type of infection, but more commonly, it does affect individuals with weakened immune systems or those in hospital settings. The most common risk factors for patients in the hospital setting are catheters, surgery, and breathing machines. Individuals that are commonly infected are patients with cystic fibrosis, AIDS, neutropenia, burns, cancer, and organ transplantation. Overall, these bacteria can spread through contaminated surfaces, equipment, or by touching contaminated hands.
Common Types of Infections
Pseudomonas aeruginosa can infect nearly any organ system. Common infections include:
- Hospital-acquired pneumonia (HAP)
- Ventilator-associated pneumonia (VAP)
- Urinary tract infections (UTIs)
- Bloodstream infections (bacteremia)
- Surgical site infections
- Burn wound infections
- Skin and soft tissue infections
- Osteomyelitis
- Malignant otitis externa
- Endocarditis
Patients with cystic fibrosis are particularly susceptible to chronic pulmonary colonization and recurrent respiratory infections caused by Pseudomonas aeruginosa.
Antibiotics are used to treat these types of infections. This type of bacteria is affected by antibiotic resistance. Most commonly, patients are started on a broad-spectrum antibiotic. Local antibiograms should be used to determine the correct empiric therapy. If a patient has one or more risk factors for multi-drug resistant organisms, septic shock, respiratory failure with mechanical ventilation, or intensive care unit admissions, they may require double pseudomonal coverage. The drug classes commonly used are carbapenems, cephalosporins, aminoglycosides, fluoroquinolones, and others.
Newer Antipseudomonal Agents
In recent years, several newer therapies have expanded treatment options for resistant infections:
- Ceftolozane-tazobactam (Zerbaxa®)
- Ceftazidime-avibactam (Avycaz®)
- Imipenem-cilastatin-relebactam (Recarbrio®)
- Cefiderocol (Fetroja®)
Current Infectious Diseases Society of America (IDSA) guidance recommends tailoring therapy based on susceptibility results and resistance mechanisms whenever possible.
Recent CDC surveillance highlights the ongoing resistance challenge associated with Pseudomonas aeruginosa. In 2024, approximately 13.0% of tested isolates demonstrated carbapenem resistance, 16.6% demonstrated fluoroquinolone resistance, 16.1% demonstrated extended-spectrum cephalosporin resistance, and 15.3% demonstrated piperacillin-tazobactam resistance.
Resistance mechanisms include:
- Efflux pumps that remove antibiotics from bacterial cells
- Reduced outer membrane permeability
- Production of beta-lactamases
- AmpC enzyme overexpression
- Carbapenemase production
- Biofilm formation
Because of these mechanisms, Pseudomonas aeruginosa may develop multidrug-resistant (MDR), extensively drug-resistant (XDR), or difficult-to-treat resistant (DTR) phenotypes.
Biofilm Formation and Treatment Challenges
One of the reasons Pseudomonas aeruginosa can be difficult to eradicate is its ability to form biofilms. Biofilms are communities of bacteria encased in a protective matrix that adheres to surfaces such as catheters, prosthetic devices, lung tissue, and chronic wounds.
Once a biofilm develops, antibiotics may have difficulty penetrating the protective layer, allowing bacteria to survive despite treatment. Biofilm-associated infections are particularly problematic in patients with cystic fibrosis, chronic wounds, implanted medical devices, and recurrent urinary tract infections.
The specimen is sent off to the laboratory to confirm the exact type of bacteria that is growing. After that, the specific bacteria will be tested against all the antibiotics to determine which antibiotic it is susceptible. Next, narrowing down the antibiotic for the patient will ensure coverage of only that specific bacterium that is growing. Once the results come back, the antibiotic selection will be made based on the susceptibilities, the area where the bacteria are growing, and other patient-specific factors.
For this type of infection, it is important to make sure that the patient not only receives the appropriate antibiotic, but also the appropriate duration and dosage form as well. Oral and IV antibiotics selection is usually dependent on the infection itself and the site of infection. Patients might be required to be on extended courses of antibiotics to ensure that all the bacteria are killed. Sometimes, antibiotics are not the only form of action needed to get rid of the infection. If the infection is deep, patients may be required to take extended intravenous (IV) antibiotics and undergo surgical debridement. This is when interprofessional healthcare teams are important to select the appropriate treatments to make sure that the infection will be gone entirely.
Prevention Strategies
Healthcare facilities continue to focus on preventing Pseudomonas aeruginosa transmission through:
- Proper hand hygiene
- Environmental cleaning and disinfection
- Appropriate catheter management
- Ventilator care bundles
- Water management programs
- Isolation precautions when indicated
- Antimicrobial stewardship initiatives
Patients can also reduce infection risk by following wound-care instructions, practicing good hygiene, and adhering to healthcare provider recommendations regarding medical devices.
Future Directions in Treatment
As antimicrobial resistance continues to evolve, researchers are exploring new approaches to combat Pseudomonas aeruginosa infections.
Current areas of investigation include:
- Novel beta-lactam/beta-lactamase inhibitor combinations
- Bacteriophage therapy
- Anti-biofilm agents
- Monoclonal antibodies
- Rapid molecular diagnostic testing
- Artificial intelligence-assisted antimicrobial stewardship programs
These emerging technologies may improve outcomes and help address the growing challenge of multidrug-resistant infections.
Pseudomonas aeruginosa can cause serious types of infections. It most commonly affects patients in the hospital setting or immunocompromised patients. There are various antibiotics that can be used to treat these types of infections. Due to multidrug resistance seen with these bacteria, it is important to send off the specimen to the laboratory to ensure that physicians or other healthcare professionals can narrow the antibiotic that is susceptible so that it can get to the site of action. Sometimes in certain cases, antibiotics may not be the only form of treatment used for patients to get rid of these infections, which is why interprofessional teams in these situations are very beneficial in considering all specific factors to ensure patients receive the best care possible.
Original Author: Dagmara Zajac
Editorial Update (June 2026): Elizabeth Rodriguez
RxPharmacist Team
References:
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