Invasion and diversity in Pseudomonas aeruginosa urinary tract infections

Urinary tract infections and catheter-associated urinary tract infections caused by Pseudomonas aeruginosa

SUMMARYUrinary tract infection (UTI) is one of the most common infections in otherwise healthy individuals. UTI is also common in healthcare settings where patients often require urinary catheters to alleviate urinary retention. The placement of a urinary catheter often leads to catheter-associated urinary tract infection (CAUTI) caused by a broad range of opportunistic pathogens, commonly referred to as ESKAPE (Enterococcus, Staphylococcus, Klebsiella, Acinetobacter, Pseudomonas, and Enterobacter) pathogens. Our understanding of CAUTI is complicated by the differences in pathogens, in initial microbial load, changes that occur due to the duration of catheterization, and the relationship between infection (colonization) and disease symptoms. To advance our understanding of CAUTI, we reviewed UTI and CAUTI caused by Pseudomonas aeruginosa which is unique in that it is not commonly found associated with human microbiomes. For this reason, the ability of P. aeruginosa to cause UTI and CAUTI requires the introduction of the bacteria to the bladder from catheterization. Once in the host, the virulence factors used by P. aeruginosa in these infections remain an area of ongoing research. In this review, we will discuss studies that focus on P. aeruginosa UTI and CAUTI to better understand the infection dynamics and outcome in clinical settings, virulence factors associated with P. aeruginosa isolated from the urinary tract, and animal studies to test which bacterial factors are required for this infection. Understanding how P. aeruginosa can cause UTI and CAUTI can provide an understanding of how these infections initiate and progress and may provide possible strategies to limit these infections.

The histidine kinase NahK regulates denitrification and nitric oxide accumulation through RsmA in Pseudomonas aeruginosa

Pseudomonas aeruginosa have a versatile metabolism; they can adapt to many stressors, including limited oxygen and nutrient availability. This versatility is especially important within a biofilm where multiple microenvironments are present. As a facultative anaerobe, P. aeruginosa can survive under anaerobic conditions utilizing denitrification. This process produces nitric oxide (NO) which has been shown to result in cell elongation. However, the molecular mechanism underlying this phenotype is poorly understood. Our laboratory has previously shown that NosP is a NO-sensitive hemoprotein that works with the histidine kinase NahK to regulate biofilm formation in P. aeruginosa. In this study, we identify NahK as a novel regulator of denitrification under anaerobic conditions. Under anaerobic conditions, deletion of nahK leads to a reduction of growth coupled with reduced transcriptional expression and activity of the denitrification reductases. Furthermore, during stationary phase under anaerobic conditions, ΔnahK does not exhibit cell elongation, which is characteristic of P. aeruginosa. We determine the loss of cell elongation is due to changes in NO accumulation in ΔnahK. We further provide evidence that NahK may regulate denitrification through modification of RsmA levels.

IMPORTANCE

Pseudomonas aeruginosa is an opportunistic multi-drug resistance pathogen that is associated with hospital-acquired infections. P. aeruginosa is highly virulent, in part due to its versatile metabolism and ability to form biofilms. Therefore, better understanding of the molecular mechanisms that regulate these processes should lead to new therapeutics to treat P. aeruginosa infections. The histidine kinase NahK has been previously shown to be involved in both nitric oxide (NO) signaling and quorum sensing through RsmA. The data presented here demonstrate that NahK is responsive to NO produced during denitrification to regulate cell morphology. Understanding the role of NahK in metabolism under anaerobic conditions has larger implications in determining its role in a heterogeneous metabolic environment such as a biofilm.

Recent developments of topoisomerase inhibitors: Clinical trials, emerging indications, novel molecules and global sales

The nucleic acid topoisomerases (TOP) are an evolutionary conserved mechanism to solve topological problems within DNA and RNA that have been historically well-established as a chemotherapeutic target. During investigation of trends within clinical trials, we have identified a very high number of clinical trials involving TOP inhibitors, prompting us to further evaluate the current status of this class of therapeutic agents. In total, we have identified 233 unique molecules with TOP-inhibiting activity. In this review, we provide an overview of the clinical drug development highlighting advances in current clinical uses and discussing novel drugs and indications under development. A wide range of bacterial infections, along with solid and hematologic neoplasms, represent the bulk of clinically approved indications. Negative ADR profile and drug resistance among the antibacterial TOP inhibitors and anthracycline-mediated cardiotoxicity in the antineoplastic TOP inhibitors are major points of concern, subject to continuous research efforts. Ongoing development continues to focus on bacterial infections and cancer; however, there is a degree of diversification in terms of novel drug classes and previously uncovered indications, such as glioblastoma multiforme or Clostridium difficile infections. Preclinical studies show potential in viral, protozoal, parasitic and fungal infections as well and suggest the emergence of a novel target, TOP IIIβ. We predict further growth and diversification of the field thanks to the large number of experimental TOP inhibitors emerging.

Analysis of the utility of a rapid vesicle isolation method for clinical strains of Pseudomonas aeruginosa

Pseudomonas aeruginosa, a pathogen capable of causing diseases ranging from mild to life-threatening, has a large arsenal of virulence factors. Notably, extracellular vesicles have emerged as significant players in the pathogenesis of this organism. However, the full range of their functions is still being studied, and difficulties related to vesicle purification (long protocols, low yields, and specialized instruments) have become a major obstacle for their characterization. In this context, the utility of rapid new methods of vesicle isolation from clinical strains is still unknown. Here, we analyze the utility of the ExoBacteria OMV isolation kit for a collection of clinical strains of P. aeruginosa. We first phenotypically characterized 15 P. aeruginosa strains to ensure that our samples were heterogeneous. We then determined the best conditions for purifying vesicles from P. aeruginosa PAO1 reference strain by the rapid method and used them to isolate vesicles from clinical strains. Our results indicated that M9 minimal medium is the best for obtaining high purity with the rapid isolation kit. Although we were able to isolate vesicles from at least four strains, the low yield and the large number of strains with unpurifiable vesicles showed that the kit was not practical or convenient for clinical strains. Our findings suggest that although fast procedures for vesicle purification can be of great utility for Escherichia coli, the more complex phenotypes of clinical isolates of P. aeruginosa are a challenge for these protocols and new alternatives/optimizations need to be developed.IMPORTANCEPseudomonas aeruginosa is recognized as an opportunistic pathogen in humans and animals. It can effectively colonize various environments thanks to a large set of virulence factors that include extracellular vesicles. Different methods were recently developed to reduce the time and effort associated with vesicle purification. However, the utility of rapid vesicle isolation methods for clinical strains of P. aeruginosa (which are recognized as being highly diverse) is not yet known. In this context, we analyzed the utility of the ExoBacteria OMV Isolation kit for vesicle purification in P. aeruginosa clinical strains. Our findings showed that the kit does not seem to be convenient for research on clinical strains due to low vesicle recovery. Our results underscore the importance of developing new rapid vesicle purification protocols/techniques for specific clinical phenotypes.

Molecular Properties of Virulence and Antibiotic Resistance of Pseudomonas aeruginosa Causing Clinically Critical Infections

The increase in the number of hospital strains of hypervirulent and multidrug resistant (MDR) Pseudomonas aeruginosa is a major health problem that reduces medical treatment options and increases mortality. The molecular profiles of virulence and multidrug resistance of P. aeruginosa-associated hospital and community infections in Mexico have been poorly studied. In this study, we analyzed the different molecular profiles associated with the virulence genotypes related to multidrug resistance and the genotypes of multidrug efflux pumps (mex) in P. aeruginosa causing clinically critical infections isolated from Mexican patients with community- and hospital-acquired infections. Susceptibility to 12 antibiotics was determined using the Kirby-Bauer method. The identification of P. aeruginosa and the detection of virulence and efflux pump system genes were performed using conventional PCR. All strains isolated from patients with hospital-acquired (n = 67) and community-acquired infections (n = 57) were multidrug resistant, mainly to beta-lactams (ampicillin [96.7%], carbenicillin [98.3%], cefalotin [97.5%], and cefotaxime [87%]), quinolones (norfloxacin [78.2%]), phenicols (chloramphenicol [91.9%]), nitrofurans (nitrofurantoin [70.9%]), aminoglycosides (gentamicin [75%]), and sulfonamide/trimethoprim (96.7%). Most strains (95.5%) isolated from patients with hospital- and community-acquired infections carried the adhesion (pilA) and biofilm formation (ndvB) genes. Outer membrane proteins (oprI and oprL) were present in 100% of cases, elastases (lasA and lasB) in 100% and 98.3%, respectively, alkaline protease (apr) and alginate (algD) in 99.1% and 97.5%, respectively, and chaperone (groEL) and epoxide hydrolase (cif) in 100% and 97.5%, respectively. Overall, 99.1% of the strains isolated from patients with hospital- and community-acquired infections carried the efflux pump system genes mexB and mexY, while 98.3% of the strains carried mexF and mexZ. These findings show a wide distribution of the virulome related to the genotypic and phenotypic profiles of antibiotic resistance and the origin of the strains isolated from patients with hospital- and community-acquired infections, demonstrating that these molecular mechanisms may play an important role in high-pathogenicity infections caused by P. aeruginosa.

Sensitive and Enzyme-Free Pseudomonas aeruginosa Detection and Isolation via DNAzyme Cascade Triggered DNA Tweezer

Effective isolation and sensitive detection of Pseudomonas aeruginosa (P. aeruginosa) is crucial for the early diagnosis and prognosis of various diseases, such as urinary tract infections. However, efficient isolation and simultaneous detection of P. aeruginosa remains a huge challenge. Herein, we depict a novel fluorescence assay for sensitive, enzyme-free detection of P. aeruginosa by integrating DNAzyme cascade-induced DNA tweezers and magnetic nanoparticles (MNPs)-based separation. The capture probe@MNPs is capable of accurately identifying target bacteria and transporting the bacteria signal to nucleic acid signals. Based on the DNAzyme cascade-induced DNA tweezers, the nucleic acid signals are extensively amplified, endowing the method with a high sensitivity and a low detection limit of 1 cfu/mL. In addition, the method also exhibits a wide detection of six orders of magnitudes. The proposed method could be extended to other bacteria detection by simply changing the aptamer sequence. Taking the merit of the high sensitivity, greatly minimized detection time (less than 1.5 h), enzyme-free characteristics, and stability, the proposed method could be potentially applied to diagnosing and preventing diseases caused by pathogenic bacteria.

Nur77 protects the bladder urothelium from intracellular bacterial infection

Intracellular infections by Gram-negative bacteria are a significant global health threat. The nuclear receptor Nur77 (also called TR3, NGFI-B, or NR4A1) was recently shown to sense cytosolic bacterial lipopolysaccharide (LPS). However, the potential role for Nur77 in controlling intracellular bacterial infection has not been examined. Here we show that Nur77 protects against intracellular infection in the bladder by uropathogenic Escherichia coli (UPEC), the leading cause of urinary tract infections (UTI). Nur77 deficiency in mice promotes the formation of UPEC intracellular bacterial communities (IBCs) in the cells lining the bladder lumen, leading to persistent infection in bladder tissue. Conversely, treatment with a small-molecule Nur77 agonist, cytosporone B, inhibits invasion and enhances the expulsion of UPEC from human urothelial cells in vitro, and significantly reduces UPEC IBC formation and bladder infection in mice. Our findings reveal a new role for Nur77 in control of bacterial infection and suggest that pharmacologic agonism of Nur77 function may represent a promising antibiotic-sparing therapeutic approach for UTI.

Current state and novel outlook on prevention and treatment of rising antibiotic resistance in urinary tract infections

Antibiotic-resistant bacteria are currently an important public health concern posing a serious threat due to their resistance to the current arsenal of antibiotics. Uropathogens Escherichia coli (UPEC), Proteus mirabilis, Klebsiella pneumoniae and Enterococcus faecalis, antibiotic-resistant gram-negative bacteria, cause serious cases of prolonged UTIs, increasing healthcare costs and potentially even leading to the death of an affected patient. This review discusses current knowledge about the increasing resistance to currently recommended antibiotics for UTI therapy, as well as novel therapeutic options. Traditional antibiotics are still a part of the therapy guidelines for UTIs, although they are often not effective and have serious side effects. Hence, novel drugs are being developed, such as combinations of β-lactam antibiotics with cephalosporins and carbapenems. Siderophoric cephalosporins, such as cefiderocol, have shown potential in the treatment of individuals with significant gram-negative bacterial infections, as well as aminoglycosides, fluoroquinolones and tetracyclines that are also undergoing clinical trials. The use of cranberry and probiotics is another potential curative and preventive method that has shown antimicrobial and anti-inflammatory effects. However, further studies are needed to assess the efficacy and safety of probiotics containing cranberry extract for UTI prevention and treatment. An emerging novel approach for UTI treatment is the use of immuno-prophylactic vaccines, as well as different nanotechnology solutions such as nanoparticles (NP). NP have the potential to be used as delivery systems for drugs to specific targets. Furthermore, nanotechnology could enable the development of nano antibiotics with improved features by the application of different NPs in their structure, such as gold and copper NPs. However, further high-quality research is required for the synthesis and testing of these novel molecules, such as safety evaluation and pharmacovigilance.

Evidence for intracellular Pseudomonas aeruginosa

Pseudomonas aeruginosa is a significant cause of global morbidity and mortality. Although it is often regarded as an extracellular pathogen toward human cells, numerous investigations report its ability to survive and replicate within host cells, and additional studies demonstrate specific mechanisms enabling it to adopt an intracellular lifestyle. This ability of P. aeruginosa remains less well-investigated than that of other intracellular bacteria, although it is currently gaining attention. If intracellular bacteria are not killed after entering host cells, they may instead receive protection from immune recognition and experience reduced exposure to antibiotic therapy, among additional potential advantages shared with other facultative intracellular pathogens. For this review, we compiled studies that observe intracellular P. aeruginosa across strains, cell types, and experimental systems in vitro, as well as contextualize these findings with the few studies that report similar observations in vivo. We also seek to address key findings that drove the perception that P. aeruginosa remains extracellular in order to reconcile what is currently understood about intracellular pathogenesis and highlight open questions regarding its contribution to disease.

Edible Medicinal Guava Fruit (Psidium guajava L.) Are a Source of Anti-Biofilm Compounds against Pseudomonas aeruginosa

Psidium guajava is one of the most common edible medicinal plants frequently used in Malagasy traditional medicine to treat gastrointestinal infections. In order to evaluate their probable antibacterial activities, three organic extracts (successive extractions by hexane, dichloromethane, and ethanol) of ripe guava fruits were assessed for their bactericidal and anti-virulence properties against P. aeruginosa PAO1. Although these three extracts have shown no direct antibacterial activity (MIC of 1000 µg/mL) and, at the non-bactericidal concentration of 100 µg/mL, no impact on the production of major P. aeruginosa PAO1 virulence factors (pyocyanin and rhamnolipids), the hexane and dichloromethane extracts showed significant anti-biofilm properties and the dichloromethane extract disrupted the P. aeruginosa PAO1 swarming motility. Bioguided fractionation of the dichloromethane extract led to the isolation and identification of lycopene and β-sitosterol-β-D-glucoside as major anti-biofilm compounds. Interestingly, both compounds disrupt P. aeruginosa PAO1 biofilm formation and maintenance with IC50 of 1383 µM and 131 µM, respectively. More interestingly, both compounds displayed a synergistic effect with tobramycin with a two-fold increase in its effectiveness in killing biofilm-encapsulated P. aeruginosa PAO1. The present study validates the traditional uses of this edible medicinal plant, indicating the therapeutic effectiveness of guava fruits plausibly through the presence of these tri- and tetraterpenoids, which deserve to be tested against pathogens generally implicated in diarrhea.

Antimicrobial resistance of Pseudomonas aeruginosa: navigating clinical impacts, current resistance trends, and innovations in breaking therapies

Pseudomonas aeruginosa, a Gram-negative bacterium, is recognized for its adaptability and opportunistic nature. It poses a substantial challenge in clinical settings due to its complicated antibiotic resistance mechanisms, biofilm formation, and capacity for persistent infections in both animal and human hosts. Recent studies revealed a potential zoonotic transmission of P. aeruginosa between animals, the environment, and human populations which highlights awareness of this microbe. Implementation of the One Health approach, which underscores the connection between human, animal, and environmental health, we aim to offer a comprehensive perspective on the current landscape of P. aeruginosa management. This review presents innovative strategies designed to counteract P. aeruginosa infections. Traditional antibiotics, while effective in many cases, are increasingly compromised by the development of multidrug-resistant strains. Non-antibiotic avenues, such as quorum sensing inhibition, phage therapy, and nanoparticle-based treatments, are emerging as promising alternatives. However, their clinical application encounters obstacles like cost, side effects, and safety concerns. Effectively addressing P. aeruginosa infections necessitates persistent research efforts, advancements in clinical development, and a comprehension of host-pathogen interactions to deal with this resilient pathogen.

A human urothelial microtissue model reveals shared colonization and survival strategies between uropathogens and commensals

Urinary tract infection is among the most common infections worldwide, typically studied in animals and cell lines with limited uropathogenic strains. Here, we assessed diverse bacterial species in a human urothelial microtissue model exhibiting full stratification, differentiation, innate epithelial responses, and urine tolerance. Several uropathogens invaded intracellularly, but also commensal Escherichia coli, suggesting that invasion is a shared survival strategy, not solely a virulence hallmark. The E. coli adhesin FimH was required for intracellular bacterial community formation, but not for invasion. Other shared lifestyles included filamentation (Gram-negatives), chaining (Gram-positives), and hijacking of exfoliating cells, while biofilm-like aggregates were formed mainly with Pseudomonas and Proteus. Urothelial cells expelled invasive bacteria in Rab-/LC3-decorated structures, while highly cytotoxic/invasive uropathogens, but not commensals, disrupted host barrier function and strongly induced exfoliation and cytokine production. Overall, this work highlights diverse species-/strain-specific infection strategies and corresponding host responses in a human urothelial microenvironment, providing insights at the microtissue, cell, and molecular level.

Facile Modification of Medical-Grade Silicone for Antimicrobial Effectiveness and Biocompatibility: A Potential Therapeutic Strategy against Bacterial Biofilms

A one-step modification of biomedical silicone tubing with N,N-dimethyltetradecylamine, C14, results in a composition designated WinGard-1 (WG-1, 1.1 wt % C14). A surface-active silicon-amine phase (SAP) is proposed to account for increased wettability and increased surface charge. To understand the mechanism of antimicrobial effectiveness, several procedures were employed to detect whether C14 leaching occurred. An immersion-growth (IG) test was developed that required knowing the bacterial Minimum Inhibitory Concentrations (MICs) and Minimum Biocidal Concentrations (MBCs). The C14 MIC and MBC for Gm- uropathogenic E. coli (UPEC), commonly associated with catheter-associated urinary tract infections (CAUTI), were 10 and 20 μg/mL, respectively. After prior immersion of WG-1 silicone segments in a growth medium from 1 to 28 d, the IG test for the medium showed normal growth for UPEC over 24 h, indicating that the concentration of C14 must be less than the MIC, 10 μg/mL. GC-MS and studies of the medium inside and outside a dialysis bag containing WG-1 silicone segments supported de minimis leaching. Consequently, a 5 log UPEC reduction (99.999% kill) in 24 h using the shake flask test (ASTM E2149) cannot be due to leaching and is ascribed to contact kill. Interestingly, although the MBC was greater than 100 μg/mL for Pseudomonas aeruginosa, WG-1 silicone affected an 80% reduction via a 24 h shake flask test. For other bacteria and Candida albicans, greater than 99.9% shake flask kill may be understood by proposing increased wettability and concentration of charge illustrated in the TOC. De minimis leaching places WG-1 silicone at an advantage over conventional anti-infectives that rely on leaching of an antibiotic or heavy metals such as silver. The facile process for preparation of WG-1 silicone combined with biocidal effectiveness comprises progress toward the goals of device designation from the FDA for WG-1 and clearance.

Ants of Mexico: Distribution and species richness in environments with varying levels of human impact

Background

Anthropogenic disturbance, primarily driven by land-use changes, has caused alterations in ecosystems and biodiversity, including the ant community. Therefore, the aim of this study was to analyse the current landscape of ant species richness and distribution in environments with varying degrees of disturbance in Mexico. Additionally, we sought to identify ant species of ecological, economic and health significance within the country.

New information

The present study shows that Mexico has a total of 33,286 records of 1,104 ant species belonging to 10 subfamilies. These species were recorded in a wide variety of environments with different levels of human impact. It was observed that both highly-disturbed environments and undisturbed environments had the highest number of ant records. In undisturbed environments, greater species richness was recorded, with a total of 704 species. Furthermore, the most representative ant species for the country were identified in ecological, economic and human health contexts. Within these species, a group composed of four exotic species (Tapinomamelanocephalum, Paratrechinalongicornis, Wasmanniaauropunctata and Linepithemahumile) deserves special attention, as they have achieved extensive dispersion throughout the country and have been associated with negative impacts in ecological, economic and human health realms.

Proteomic profiling spotlights the molecular targets and the impact of the natural antivirulent umbelliferone on stress response, virulence factors, and the quorum sensing network of Pseudomonas aeruginosa

Pseudomonas aeruginosa easily adapts to newer environments and acquires several genome flexibilities to overcome the effect of antibiotics during therapeutics, especially in cystic fibrosis patients. During adaptation to the host system, the bacteria employ various tactics including virulence factor production and biofilm formation to escape from the host immune system and resist antibiotics. Hence, identifying alternative strategies to combat recalcitrant pathogens is imperative for the successful elimination of drug-resistant microbes. In this context, this study portrays the anti-virulence efficacy of umbelliferone (UMB) against P. aeruginosa. UMB (7-hydroxy coumarin) is pervasively found among the plant family of Umbelliferae and Asteraceae. The UMB impeded biofilm formation in the P. aeruginosa reference strain and clinical isolates on polystyrene and glass surfaces at the concentration of 125 µg/ml. Global proteomic analysis of UMB-treated cells revealed the downregulation of major virulence-associated proteins such as RhlR, LasA, AlgL, FliD, Tpx, HtpG, KatA, FusA1, Tsf, PhzM, PhzB2, CarB, DctP, MtnA, and MscL. A functional interaction study, gene ontology, and KEGG pathway analysis revealed that UMB could modulate the global regulators, enzymes, co-factors, and transcription factors related to quorum sensing (QS), stress tolerance, siderophore production, motility, and microcolony formation. In vitro biochemical assays further affirmed the anti-virulence efficacy of UMB by reducing pyocyanin, protease, elastase, and catalase production in various strains of P. aeruginosa. Besides the antibiofilm activity, UMB-treated cells exhibited enhanced antibiotic susceptibility to various antibiotics including amikacin, kanamycin, tobramycin, ciprofloxacin, and cefotaxime. Furthermore, in vitro cytotoxicity analysis revealed the biocompatibility of UMB, and the IC₅₀ value was determined to be 249.85 µg/ml on the HepG2 cell line. Altogether, the study substantiates the anti-virulence efficacy of UMB against P. aeruginosa, and the proteomic analysis reveals the differential expression of the regulators related to QS, stress response, and motility factors.