Pseudomonas aeruginosa is a prominent pathogen in healthcare settings, particularly among immunocompromised patients. It poses a significant threat as it can be transmitted through medical equipment and cross-contamination among patients (Wood et al., 2023). Ventilator-associated pneumonia (VAP) is a serious complication in patients kept on mechanical ventilation for more than 48 h in which P. aeruginosa is responsible for a high proportion of these infections in hospitalized patients. In the context of VAP, P. aeruginosa’s involvement is associated with higher case fatality rates than other bacterial causes. Tracheobronchial colonization is a critical factor in VAP, with Staphylococcus aureus, P. aeruginosa, and Enterobacteriaceae being the primary pathogens. High quantities of P. aeruginosa in ventilated patients’ tracheas correlate with an increased risk of death. The bacterium’s ability to resist conventional antibiotics, often due to complex drug-resistance genes present in plasmids or integrated into the bacterial genome, poses a significant challenge (Pachori et al., 2019). Studies have revealed that Pseudomonas spp. account for about 3–5% of nosocomial pneumonia cases, with P. aeruginosa being a prominent strain in ventilator-associated cases (Leroy et al., 2005). Nosocomial pneumonia secondary to P. aeruginosa has worse clinical outcomes when compared to other typical organisms. The prevalence of MDR P. aeruginosa VAP is reported to be generally high (33%) (Li et al., 2024). The crude mortality rate for P. aeruginosa VAP has been estimated at 42.1–87% even in patients receiving appropriate antimicrobial therapy (Foucrier et al., 2023). In addition to its impact on VAP, P. aeruginosa is among the top microorganisms responsible for healthcare respiratory infections. Infections caused by MDR-P. aeruginosa strains significantly increase the risk of mortality. Risk factors for VAP with P. aeruginosa include prior antibiotic exposure, airway colonization, and mechanical ventilation exceeding five days. On the other hand, P. aeruginosa is capable of chronic colonization, persistence, and infection of lower respiratory tracts in patients with chronic inflammatory airway diseases including asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), and bronchiectasis (Garcia-Clemente et al., 2020). Patients with chronic diseases like obstructive pulmonary disease and other respiratory conditions are also susceptible to the selection of hypermutator P. aeruginosa strains in chronic respiratory tract infections by P. aeruginosa facilitated by the frequent use of antimicrobials in these cases. Additionally, what makes P. aeruginosa particularly challenging is its ability to resist treatment, especially in the context of cystic fibrosis (CF) (Abdulwahab et al., 2017). In this hereditary disease, P. aeruginosa becomes a predominant pathogen in the lungs of affected individuals. Despite efforts to eradicate it, P. aeruginosa often persists, driving disease progression. It’s critical to understand how P. aeruginosa adapts and survives within the hyperinflammatory environment of the CF lung to develop effective treatments. Chronic bronchial infections in persons with CF, bronchiectasis, and COPD have been linked to more severe disease and poor prognosis. Bacterial colonization by P. aeruginosa has also been documented in people with chronic severe long-standing asthma with frequent exacerbations contributing to unfavorable clinical outcomes (Zhang et al., 2012).

P. aeruginosa presents multiple virulent factors and adapts through genotypic and phenotypic alterations to evade antibiotics and the immune system. The chronic infection environment within the CF lung subjects P. aeruginosa to significant stressors, including competition for resources, anaerobic conditions, high antibiotic concentrations, and immune responses like neutrophil attacks (Jurado-Martín et al., 2021). In response, P. aeruginosa undergoes microevolution, acquiring spontaneous mutations that lead to the selection of variants better suited for long-term colonization. These variants exhibit reduced virulence but greater resistance to antibiotics and host immunity. This adaptation includes the downregulation of virulence factors, increased biofilm formation, and upregulation of exopolysaccharides (Sousa and Pereira, 2014). These changes help P. aeruginosa avoid immune recognition, phagocytosis, and proinflammatory responses, promoting its persistence in the host. Moreover, P. aeruginosa forms biofilms within the CF lung, which significantly enhances its resistance to antibiotics and immune effectors. Biofilm communities appear as microcolonies or aggregates closely associated with the airway epithelium. They can evade the complement system, immobilize neutrophils, and resist the actions of neutrophil extracellular traps, further enabling P. aeruginosa to thrive within the CF lung (Maurice et al., 2018).

Pseudomonas aeruginosa is a formidable pathogen with increasing clinical significance, particularly concerning skin and soft tissue infections. Its impact becomes far more pronounced in hospitalized patients due to its high resistance to a wide array of commonly available anti-pseudomonal agents (Wang et al., 2019). P. aeruginosa plays a critical role in burn wound infections, accounting for approximately one-third of all burn-related infections. These infections are notorious for their resistance to treatment, despite the availability of newer antibiotics with broad-spectrum activity (Gonzalez et al., 2016). Burned patients are particularly vulnerable, and infections caused by P. aeruginosa can lead to severe morbidity and, in some cases, mortality. The resistant nature of these infections not only prolongs hospital stays but also escalates treatment costs, representing a significant burden on healthcare systems. In skin infections, P. aeruginosa can cause a range of infections, from mild to severe, with unique clinical presentations. These infections typically affect otherwise healthy individuals and may sometimes resolve spontaneously without specific antibacterial therapy. Skin manifestations associated with P. aeruginosa infections may range from less severe localized forms of primary skin infections including Green Nail Syndrome, Interdigital Infections, and hot tub Folliculitis to more severe forms occurring in immunocompromised patients such as Ecthyma Gangrenosum and subcutaneous nodules usually occurring with bloodstream infections and also necrotizing skin and soft tissue infections occurring in diabetic, alcoholic and immunocompromised patients (Spernovasilis et al., 2021). P. aeruginosa plays an important role as a pathogen that extends beyond human infections; it also poses a significant threat to animals, including pets and livestock, with skin infections being a notable concern (Singh et al., 2005). In animals, P. aeruginosa can cause a range of dermatological conditions, including wound infections, hot spots, and otitis infections (de Sousa et al., 2023; Elfadadny et al., 2023b). These infections can lead to discomfort, pain, and, in severe cases, systemic illness. Veterinarians often encounter challenges in treating P. aeruginosa infections due to their ability to develop resistance to antibiotics, mirroring the issues seen in human medicine (Nielsen et al., 2022). The increasing trends of antibiotic resistance observed in this bacterium severely limit the choice of effective antimicrobial agents. Studies have demonstrated rising resistance rates of P. aeruginosa to numerous antibiotics, including those commonly used to combat skin and soft tissue infections.

Pseudomonas aeruginosa can also invade the ears of both humans and animals. In humans, P. aeruginosa ear infections can lead to a painful condition known as swimmer’s ear or otitis externa. This infection often occurs after exposure to contaminated water, such as in swimming pools or hot tubs (Mittal et al., 2016). P. aeruginosa live in these moist environments, causing inflammation, itching, discharge, and sometimes even hearing difficulties or complicated to otitis media and malignant external otitis if left untreated. Treatment typically involves antibiotic ear drops, but the bacterium’s ability to develop resistance can complicate the therapeutic process (Sun et al., 2021). Malignant otitis externa is a serious invasive life-threatening condition that affects the external ear and skull base and can be complicated by mastoiditis and cranial nerve palsy if left untreated. It classically occurs in elderly, immunocompromised, and diabetic patients (Wu et al., 2011). Similarly, in animals, particularly dogs, cats, and other domestic pets, P. aeruginosa ear infections are a concerning issue. These infections can stem from various factors, including allergies, foreign objects in the ear canal, or underlying health conditions. P. aeruginosa’s adaptability and antibiotic resistance underscores the importance of prompt diagnosis and appropriate treatment to prevent further complications in both human and animal ear infections.

Pseudomonas aeruginosa has been increasingly implicated in UTIs. These infections represent a significant clinical concern, particularly in healthcare environments where indwelling urinary catheters are prevalent (Newman et al., 2022). Catheter-associated UTIs by P. aeruginosa are of substantial clinical consequence due to their association with pyelonephritis, prolonged morbidity, and mortality. P. aeruginosa contributes to approximately 10% of catheter-associated UTIs (CAUTI) and up to 16% of UTIs in ICU patients, with an alarming increase in nosocomial-acquired infections (Rosenthal et al., 2016; Farzin et al., 2023). The bacterium’s ability to exploit catheters as a tool for host entry underscores its clinical significance in UTIs. The insertion of urinary catheters can disturb mucosal epithelial layers, thereby promoting bacterial colonization and subsequent infection. Consequently, P. aeruginosa emerges as a dominant uropathogen in this clinical context. P. aeruginosa encompasses cell-associated factors such as alginate, lipopolysaccharides (LPS), flagella, and pili, alongside secretory virulence factors like proteases, elastases, toxins, and hemolysins (Mekonnen et al., 2022). Biofilm formation represents a hallmark of P. aeruginosa’s strategy to establish and persist in UTIs. The bacterium’s innate tendency to adhere to catheter surfaces leads to robust biofilm development. These biofilms present exceptional resistance against antimicrobial agents and host immune defenses. The ability of biofilms to promote persistent and recurrent infections is a pressing clinical concern in UTIs which renders P. aeruginosa infections challenging to manage (Mekonnen et al., 2022). Additionally, the ability of P. aeruginosa to invade the bladder epithelium has been recently demonstrated. Extensive evidence exists about the ability of P. aeruginosa to preferentially bind to, invade, and injure wounded epithelium. This ability to invade vulnerable epithelial cells has been recently proven to correlate well with the high prevalence of P. aeruginosa UTI in hospitalized elderly populations (Newman et al., 2022).

Bloodstream infections (BSIs) caused by P. aeruginosa are emerging as a significant concern in clinical settings. P. aeruginosa is responsible for a significant number of bacteremia, ranking third, after Escherichia coli and Klebsiella species, among Gram-negative bacteria isolated during nosocomial bloodstream infections, and seventh among all pathogens (Holmes et al., 2021). Its significance arises from its place in case of fatality among all pathogens. Bacteremia caused by P. aeruginosa carries a poor prognosis, rapidly progressive course, and high mortality rate (Murray et al., 2022). Overall mortality associated with P. aeruginosa BSIs was recently reported at 26.8% (Shi et al., 2019). The incidence of P. aeruginosa-induced BSI is on the rise, contributing to elevated rates of morbidity and mortality among affected individuals. Understanding the sources and risk factors associated with these infections is crucial for effective management and prevention. Various studies have attempted to identify the origins of BSI associated with P. aeruginosa. Among these reports, respiratory tract infections and central venous catheters stand out as the most frequent sources. Several risk factors have been linked to P. aeruginosa BSIs. Patients who are immunocompromised, particularly those in intensive care units (ICUs), face an increased susceptibility to such infections (Bhardwaj et al., 2021). Furthermore, individuals with underlying conditions like lung cancer are at an increased risk. Previous antimicrobial therapy has also been identified as a risk factor, emphasizing the need for judicious and appropriate use of antibiotics. The severity of infection and pathogenesis of bloodstream infections have been linked to producing type III secretion-dependent exo-products and quorum-sensing dependent virulence (van Delden, 2007). During the COVID-19 pandemic, the overall incidence of BSIs including those caused by P. aeruginosa increased. P. aeruginosa BSIs overall increased among COVID-19 patients due to multiple factors including prolonged hospitalization, high-dose systemic corticosteroids treatment for acute respiratory distress in the ICU, and the administration of immune-modulator treatment such as tocilizumab or baricitinib (Bongiovanni and Barda, 2023).

Natural Bioactive Compounds (NBCs) are metabolites originating from plants that possess antioxidant, antitumor, anti-inflammatory, and antimicrobial functions (Youns and Abdel Halim Hegazy, 2017; Pai et al., 2022; Elfadadny et al., 2023a). Researchers worldwide are actively investigating novel antimicrobial agents to combat P. aeruginosa infections. These studies employ advanced molecular techniques and thorough drug screening to explore the potential of NBCs in countering P. aeruginosa. These NBCs have shown promise in inhibiting P. aeruginosa’s quorum sensing system, thereby reducing its virulence factors and preventing biofilm formation, a key protective mechanism of P. aeruginosa.

Flavonoids, a group of compounds found in plants, play a dual role in this context. They act as antioxidants for the host system, contributing to overall health without toxicity. However, they also act as pro-oxidants when encountered by pathogenic microbes, inducing the formation of reactive oxygen species (ROS) that cause oxidative stress within the bacteria. Researchers have developed an inhibitor called meta-bromo-thiolactone (mBTL) targeting LasR and RhlR, key components of the QS system in P. aeruginosa (Eltayb et al., 2022). This inhibitor has demonstrated efficacy both in laboratory settings and in vivo. Furthermore, flavonoids have been explored for their inhibitory effects on P. aeruginosa biofilm formation, hinting at their potential to disrupt the QS system (Paczkowski et al., 2017). Certain flavonoids with specific structural features, such as dihydroxyl groups in the A ring of flavones, have been identified as inhibitors of LasR and RhlR. Examples include baicalein, naringenin, and quercetin. These flavonoids act allosterically, reducing the binding affinity of LasR and RhlR to regulatory promoters.

Naringenin, a unique QS inhibitor derived from a natural source, is found in plant flavonoids. Its mechanism of action involves reducing the production of QS-regulated virulence factors in P. aeruginosa by directly binding to LasR, thereby competing with N-(3-oxo-dodecanoyl)-l-homoserine lactone (HSL), which activates LasR (Hernando-Amado et al., 2020). Consequently, this QS inhibitor can effectively disrupt QS responses only when administered during the early exponential growth phase, allowing naringenin to compete with unbound HSL for binding to LasR. It’s worth mentioning that naringenin is most suitable for targeting P. aeruginosa populations at low cellular densities. This scenario may not always align with the clinical infection situation, where bacterial densities tend to be higher. To fully harness the potential of QS inhibition, there is a need for the development of inhibitors capable of targeting P. aeruginosa QS signaling irrespective of bacterial density or QS status (Hernando-Amado et al., 2020).

Phenols, specifically 2,4-Di-tert-butylphenol (2,4-DBP), sourced from Daldinia eschscholtzii, an endophytic fungus, exhibit significant potential in combating P. aeruginosa infections. This compound plays a crucial role in reducing the secretion of pyocyanin and chitinase. Additionally, 2,4-DBP effectively suppresses the expression of genes associated with QS in P. aeruginosa, such as lasI, lasR, rhII, and rhIR (Mishra et al., 2020).

Ginkgolic acid is an NBC found in medicinal plants, which are rich sources of various bioactive compounds known for their antimicrobial, antiviral, antitumor, and other beneficial properties. In a study conducted by Tahrioui et al. (2020), the antivirulent properties of ginkgolic acid were investigated concerning its impact on P. aeruginosa in infected C. elegans models and found that ginkgolic acid inhibits pyocyanin formation in P. aeruginosa. Moreover, ginkgolic acid also influences the mechanical properties of P. aeruginosa’s cell membrane by modulating SigX, an extracytoplasmic function σ-factor. SigX plays a role in responding to cell wall stress, contributing to the maintenance of the cell envelope’s integrity, and interacting with specific envelope-related compounds, including ginkgolic acid and hydroginkgolic acid. Exposure of P. aeruginosa to ginkgolic acid leads to a significant reduction in the expression of SigX and its associated genes, such as accA, accB, and fabY, which are involved in fatty acid biosynthesis (Tahrioui et al., 2020).

Various other NBCs, like itaconimides, operate on signaling pathways and exhibit the ability to suppress the expression of QS-related genes, thereby mitigating the pathogenicity of P. aeruginosa. Additionally, compounds like N-acyl cyclopentamine, the lactone SsoPox enzyme, and N-acyl homoserine lactonase have emerged as potent inhibitors of QS (Chan et al., 2015). Substances such as curcumin and coumarin possess dual capabilities, acting against virulence factors and biofilm formation, while naringenin, gliptin, and taxifolin demonstrate the potential to reduce the expression of QS-related genes (Khayat et al., 2022; Sadaqat et al., 2022). These findings highlight the rich potential of natural compounds in combatting P. aeruginosa infections through multifaceted mechanisms.

Phages, which are viruses capable of causing bacterial lysis, were initially identified in 1915 by British bacteriologist Frederick Twort. Independently, two years later, Félix d’Herelle in Paris made a similar discovery and introduced the concept of phage therapy. Phage therapy boasts numerous advantages, including its ability to replicate at the infection site, highly specific targeting of bacteria without affecting beneficial flora, minimal side effects compared to other treatments, effectiveness against antibiotic-resistant strains, and ease of administration (Summers, 2012). As an alternative to antibiotics, the use of phages to combat P. aeruginosa infections has been extensively researched. Currently, there are 137 distinct phages characterized to target the Pseudomonas genus (Pires et al., 2015). Numerous in vitro and in vivo studies have explored the efficacy of phages against chronic P. aeruginosa infections. Phage therapy offers a notable advantage over antibiotic treatment due to its effectiveness against P. aeruginosa biofilms. A recent study demonstrated that phage PELP20 effectively eradicated P. aeruginosa strain LESB65, isolated from CF patients, within an artificial sputum medium biofilm model in vitro. It also significantly enhanced bacterial clearance in a mouse model of chronic lung infection caused by P. aeruginosa (Waters et al., 2017). Significantly, pretreating hydrogel-coated catheters with phage M4 substantially reduced the formation of P. aeruginosa biofilms. Another advantage of phage therapy lies in the potential to genetically engineer phages as delivery vehicles for antimicrobial agents, thereby enhancing treatment efficacy (Fu et al., 2010). Over the past decade, researchers have tested genetically engineered P. aeruginosa phages. For instance, the P. aeruginosa phage Pf3 was genetically modified into a nonlytic, nonreplicating phage, Pf3R, by replacing an export protein gene with a BglII restriction endonuclease gene. Pf3R efficiently killed P. aeruginosa PAO1 in vitro, similarly to the lytic phage Pf3, while significantly reducing endotoxin release. Moreover, Pf3R-treated mice displayed an increased survival rate compared to those treated with Pf3, likely due to reduced endotoxin levels and fewer host inflammatory responses (Hagens et al., 2004). An alternative strategy in phage therapy involves using phages to influence the evolution of antibiotic resistance, favoring the development of phage resistance while simultaneously restoring antibiotic susceptibility. As an example, the lytic Myoviridae bacteriophage, OMKO1, employs the bacterial multidrug efflux systems MexAB and MexXY, specifically OprM, as its receptor-binding site. Selecting for resistance to OMKO1 phage attack triggers an evolutionary trade-off in MDR P. aeruginosa. This trade-off results in a modification of the efflux pump mechanism, which in turn increases the sensitivity of the bacteria to various antibiotics, including ciprofloxacin, tetracycline, ceftazidime, and erythromycin—four drugs representing different antibiotic classes (Chan et al., 2016). Phage steering becomes achievable when the binding receptor for the bacteriophage is implicated in both antibiotic resistance and phage resistance. This approach offers the advantage of employing two distinct and opposing mechanisms to combat bacterial infections (Gurney et al., 2020).

Despite the proven effectiveness of phages against bacterial infections in vitro and animal models, the number of clinical trials for phage therapy remains limited. This is primarily attributed to concerns about phage clearance after treatment, impurities in phage preparations, poor stability of phage preparations, and a lack of detailed knowledge about phage mechanisms of action and the potential for bacterial resistance to phages (Jaglan et al., 2022). Clinical trials examining the use of phages against P. aeruginosa infections in patients with venous leg ulcers, burn wounds, and otitis have reported no adverse effects.

Among the recent alternative antibacterial agents being studied now are phage lytic antimicrobial peptides (AMPs). These are bacterial peptidoglycan-degrading enzymes produced by bacteriophages and cause instantaneous cell death (Briers, 2019). Endolysins are lytic enzymes produced during the late phase of the lytic bacteriophage replication cycle to target the bacterial cell walls for progeny release. The use of endolysins as antimicrobial agents against P. aeruginosa presents a promising avenue for combatting this resilient bacterium (Furusawa et al., 2016). However, deploying endolysin therapy against P. aeruginosa is not straightforward, primarily due to the protective outer membrane that shields the bacterial cell from lysin attack. The outer membrane of Gram-negative bacteria, including P. aeruginosa, consists of phospholipids and lipopolysaccharides. LPS molecules are held together by phosphate bonds, making them challenging to breach. To enable endolysins to access the peptidoglycan cell wall and effectively target P. aeruginosa, researchers have employed creative strategies. One such method involves the use of ethylenediaminetetraacetic acid (EDTA) to permeabilize the Gram-negative cell membrane (Murray et al., 2021). EDTA is a chelating agent that removes divalent cations, essential for stabilizing the outer membrane, from their binding sites. This disrupts the membrane’s integrity, rendering it vulnerable to endolysin attack. Permeabilizing the outer membrane can also be achieved through mechanical means, such as high hydrostatic pressure (HPP). HPP has been employed to sensitize Gram-negative bacteria, including P. aeruginosa, to molecules like bacteriocins and antimicrobial peptides by optimizing pressure and time parameters (Prudêncio et al., 2015). Another approach involves fusing endolysins with components such as antimicrobial peptides that facilitate penetration of the peptidoglycan layer. This fusion strategy enhances the endolysin’s ability to reach its target within the bacterial cell. In the case of P. aeruginosa, a bacterium renowned for its antibiotic resistance, endolysin therapy has shown promise. Researchers isolated a phage-derived endolysin called LysPA26 in 2017, which exhibited potent lytic activity against MDR strains of P. aeruginosa. Remarkably, this endolysin achieved a reduction in bacterial numbers of up to four log units in just 30 min. Furthermore, LysPA26 demonstrated stability under varying pH and temperature conditions (Guo et al., 2017). Notably, this endolysin exhibited a broad spectrum of activity, effectively targeting other Gram-negative bacteria such as Klebsiella pneumoniae, Acinetobacter baumannii, and Escherichia coli. The success of LysPA26 underscores the potential of endolysin therapy in addressing MDR P. aeruginosa infections. Its selective targeting of Gram-negative bacteria without the use of antibiotics holds promise as a primary therapeutic option for the future. Currently, not enough data is available regarding the safety profile of endolysins. Also, there is a lack of information about the pharmacokinetics and pharmacodynamics of endolysins as possible medications. Cellular toxicity and cell-penetrating properties of phage-derived endolysins should be studied before being administered as human therapeutic medications (Nandi et al., 2022). In vivo studies are limited to topical models with some concerns about systemic administration related to their short half-life, immunogenicity, and release of proinflammatory components during bacteriolysis which should addressed before further development (Lai et al., 2020).

Developing effective vaccines against P. aeruginosa infections is a crucial strategy to mitigate their consequences and reduce the excessive use of antibiotics, which can lead to antibiotic resistance. Various types of vaccines are under development to enhance the immune response against different elements involved in the infection process. These vaccines often target components of the bacterial surface, such as Opr, and various polysaccharides, including LPS, mucoid exopolysaccharide, and O-polysaccharides (Sharma et al., 2011). Additionally, they focus on structures critical for P. aeruginosa ‘s adhesion and movement, such as flagella and pili, as well as several virulence factors like TTSS, exotoxin A, or proteases. Developing effective vaccines for P. aeruginosa is challenging due to the substantial variability among Pseudomonas species, the complexity of the infection process, and the intricate interaction between the pathogen and the host immune response (Killough et al., 2022). During phases I, II, and III studies, certain vaccine candidates have proven insufficient in providing broad coverage against different P. aeruginosa strains or have exhibited low immunogenicity or safety concerns. Currently, research is ongoing to develop novel P. aeruginosa vaccines. For example, a novel P. aeruginosa vaccine called PcrV28-294-OprI25-83-Hcp11-162 (POH) has been evaluated for its protective efficacy. This vaccine contains components like PcrV, OprI, and a vital part of the type VI secretion system, Hcp1 (Yang et al., 2017). Studies showed that POH vaccination significantly triggered T-cell responses, proliferation, and protected mice against clinical P. aeruginosa strains. The development of multivalent vaccines is also being explored as a potential means of protecting against P. aeruginosa infections in the future. Furthermore, efforts have been directed toward vaccines that target notorious virulence factors responsible for evading the host immune response. Different formulations of LPS extracts have been experimented in clinical trials since 1970 including Pseudogen^® and although showing some success in reducing mortality and sepsis in burn patients, it did not show clinical efficacy and did not show any reduction in colonization in CF patients (Langford and Hiller, 1984). Aerugen^® was another successful candidate consisting of a component of LPS, the O-polysaccharide from eight P. aeruginosa serotypes and exotoxin A and showed favorable outcomes in CF patients (Lang et al., 2004). One promising approach involves using LPS and Oligopolysaccharides (OPS) antigens conjugated with Poly Lactic-co-Glycolic Acid (PLGA) nanoparticles as nano-vaccines. These nano-vaccines have shown the potential to stimulate both cellular and humoral immune responses against P. aeruginosa infections (Wusiman et al., 2022). Additionally, nano-vaccines containing antigens from bacterial lysates of P. aeruginosa and membrane antigens from double-layered membrane vesicles have demonstrated efficiency in preventing infections by drug-resistant P. aeruginosa strains. Alginate, a significant contributor to P. aeruginosa pathogenesis, is also being explored as a target for therapeutic vaccines. Mannuronic acid tetra saccharide, an antigen epitope, has been used to induce immunity against P. aeruginosa in mice. Hybrid proteins composed of the full-length V-antigen (PcrV) and the C-terminal domain of exoenzyme S (ExoS) from P. aeruginosa, along with adjuvants like alum and monophosphoryl Lipid A, have been considered as vaccine candidates to protect against urinary tract infections caused by P. aeruginosa (Asadi Karam et al., 2022). Whole-cell vaccines inactivated by X-ray irradiation, containing nucleic acids and 8-hydroxyguanosine, have demonstrated humoral and innate immune responses, leading to reduced infection levels in mouse models (Ma et al., 2021). Moreover, the concept of multi-target antigens has been explored. Triple-target antigens have been designed to stimulate protective and neutralizing antibodies against multiple pathogens, including P. aeruginosa (Inoue et al., 2023). These antigens combine epitopes from different bacterial species and have the potential to provide broad-spectrum protection. Vaccines represent a promising strategy for preventing P. aeruginosa infections and reducing their impact. They can induce protective responses through active or passive immunization and, in some cases, may even cross-react to protect against related pathogens. Although no effective vaccine is currently available for clinical use despite studies being performed over the last 50 years, the development of glycoconjugate vaccines, protein engineering techniques, and innovative carrier proteins has opened new avenues for creating effective vaccines against P. aeruginosa. Progress has been achieved in pre-clinical studies including antigen discovery, adjuvant use, and novel delivery systems, however, the wealth of virulence factors, its large genome size and great adaptability, and its changing phenotypes across acute and chronic infections all form challenges for vaccine development (Killough et al., 2022).

Monoclonal antibodies (mAbs) have emerged as a valuable strategy in combatting P. aeruginosa infections, particularly for high-risk individuals who may not benefit from vaccines or traditional antibiotics (Kang et al., 2023). These mAbs provide an alternative treatment avenue by directly targeting P. aeruginosa and offering immediate protection. They can be especially effective when used alongside prophylactic vaccines. One notable application of mAbs is their ability to tackle antimicrobial resistance within biofilms, where bacteria reside. These antibodies have been developed to disrupt protective biofilms, making P. aeruginosa and its co-pathogens vulnerable to subsequent antibiotic treatment. Additionally, mAbs targeting specific epitopes like DNABII proteins or type IV pilus have shown promise in impairing biofilms formed by P. aeruginosa and related pathogens (Sanya et al., 2023). Chicken egg yolk immunoglobulins, known as IgY antibodies, have garnered special attention for passive immunization due to their unique properties. IgY antibodies do not cross-react with mammalian IgG or activate the complement system. They offer high antigen-specific production yields without causing disease resistance and can be easily administered to humans. For example, IgY antibodies raised against the T3SS translocating protein PcrV from P. aeruginosa have demonstrated enhanced bacterial killing and reduced invasion in murine models of acute pneumonia and burn wounds (Ranjbar et al., 2019). Moreover, a synergistic effect has been observed when combining anti-P. aeruginosa IgY with beta-lactam antibiotics, suggesting a potential combination therapy for MDR P. aeruginosa infections. In severe cases of P. aeruginosa pneumonia, mAbs can be coupled with antibiotics to enhance therapeutic efficacy (Sanches et al., 2022). DNA-delivered monoclonal antibodies (DMAbs) produced in vivo have been effective in protecting mice from lethal pneumonia caused by aggressive P. aeruginosa strains (Patel et al., 2017). These antibodies not only reduced bacterial colonization but also acted synergistically with commonly used antibiotics, such as meropenem. Importantly, they exhibited stability and hold promise for treating high-risk patients, including those with chronic diseases and infections refractory to broad-spectrum antibiotics. However, it’s crucial to acknowledge that therapeutic monoclonal antibodies have their limitations. For instance, some mAbs, like MEDI3902, have not proven effective in mitigating P. aeruginosa nosocomial pneumonia in clinical trials (Chastre et al., 2022). Additionally, immunogenicity and protective efficacy can vary based on the antibody type and dosing. For example, IgY antibodies may protect certain infection models but not others, depending on the dose and specific target. Current research efforts are focused on using mAbs to prevent infections in high-risk patients and modulate virulence rather than solely aiming for bacterial clearance. Several mAbs are in various stages of development and clinical trials, targeting different aspects of P. aeruginosa infections, such as protein secretion systems and exopolysaccharides. These mAbs hold promise as adjunctive strategies in managing P. aeruginosa infections, particularly in critical care settings.

Nanoparticles have emerged as a promising frontier in the battle against P. aeruginosa. These minuscule materials, typically measuring less than 100 nanometers, have attracted significant attention for their potential in treating P. aeruginosa infections. Their diminutive size and high surface area-to-mass ratio make them ideal candidates for a wide range of chemical, biological, and biomedical applications (Al Saqr et al., 2021; Varma et al., 2023). One key advantage of nanoparticles is their ability to penetrate the protective barriers of bacterial cells. P. aeruginosa possesses an outer membrane rich in LPS, creating a formidable defense. However, researchers have developed methods to breach this barrier, allowing nanoparticles to access the bacterial cell wall. One technique involves using EDTA, a chelating agent that removes divalent cations stabilizing the outer membrane. This disruption leaves the membrane vulnerable to nanoparticle attack, allowing them to effectively target and combat P. aeruginosa. Another approach involves engineering nanoparticles to carry antimicrobial agents directly to their target. Porous silicon nanoparticles, for instance, have been designed to transport novel antimicrobial peptides fused with synthetic bacterial toxins. These engineered nanoparticles have demonstrated the ability to enhance survival rates and bacterial clearance in mouse models of P. aeruginosa lung infections (Patel and Hunt, 2023). Moreover, nanoparticles can serve as carriers for antibiotics, significantly augmenting their efficacy. Silver nanoparticles, when coupled with antibiotics like ampicillin, exhibit enhanced killing rates of ampicillin-resistant P. aeruginosa isolates in vitro. Silver nanoparticles, in particular, have shown remarkable promise as antimicrobial agents against P. aeruginosa. They release silver ions, which disrupt crucial bacterial enzymatic systems, including DNA synthesis, leading to bacterial cell death (Palau et al., 2023). Notably, these silver nanoparticles have demonstrated significant antimicrobial effects on clinical strains of P. aeruginosa, effectively eradicating the bacterium and inhibiting its growth in laboratory settings. Furthermore, they exhibit low cytotoxicity toward mammalian cells, a crucial consideration for potential clinical applications. Additionally, nanoparticles have been used as antigen delivery systems as a cost-effective approach to vaccine development. However, it’s important to recognize that the use of nanoparticles is not without challenges. Their reactivity, stemming from their high surface area, can lead to unintended reactions within the human body. Nanoparticles can also migrate to distant organs, potentially causing systemic toxicity. Inhalation of nanoparticles has been associated with pulmonary inflammation and potential cardiovascular effects, making their use in treating bacterial pulmonary infections a matter of careful consideration (Missaoui et al., 2018). To advance the field, future research should focus on material selection, nanoparticle size, and administered doses to optimize their therapeutic efficacy while minimizing potential risks in the clinical aspect.