The Epidemiology and Pathogenesis and Treatment of Pseudomonas aeruginosa Infections: An Update

Life-threatening periocular pseudomonal necrotizing fasciitis in an immunocompetent infant

Purpose

Necrotizing fasciitis, a severe soft tissue bacterial infection, is uncommon in the periocular region due to its rich blood supply. This report highlights a rare case in an immunocompetent infant.

Observations

A 10-month-old immunocompetent female exhibited fever, irritability, and right eyelid swelling post-fall. Despite initial treatment with cephalexin for presumed cellulitis, her condition rapidly deteriorated, suggesting necrotizing fasciitis. She stabilized after receiving broad-spectrum intravenous antibiotics and aggressive surgical debridement but later required orbital exenteration due to extensive tissue necrosis.

Conclusions and Importance

Periocular necrotizing fasciitis is exceedingly rare, particularly in immunocompetent individuals. Prompt diagnosis and treatment are critical to mitigate morbidity and mortality.

Revealing quorum-sensing networks in Pseudomonas aeruginosa infections through internal and external signals to prevent new resistance trends

In the context of growing antibiotic resistance in bacteria, the quorum-sensing (QS) system of Pseudomonas aeruginosa (P. aeruginosa) has become a target for new therapeutic strategies. QS is a crucial communication process and an essential pathogenic mechanism. This comprehensive review explores the critical role of QS in the pathogenesis of P. aeruginosa infections, including lung, burn, bloodstream, gastrointestinal, corneal, and urinary tract infections. In addition, this review delves into the complexity of the bacterial QS communication network and highlights the intricate mechanisms underlying these pathological processes. Notably, in addition to the four main QS systems, bacterial QS can interact with various external and internal signaling networks, such as host environments and nutrients in the external microbiome, as well as internal virulence regulation systems within bacteria. These elements can significantly influence the behavior and virulence of microbial communities. Therefore, this review reveals that inhibitors targeting singular QS pathways may inadvertently promote virulence in other pathways, leading to new trends in drug resistance. In response to evolving resistance challenges, this study proposes more cautious treatment strategies, including multitarget interventions and combination therapies, aimed at combating the escalating issue of resistance.

Chemical Synthesis of Conjugation-Ready Trisaccharides Corresponding to Biological Repeating Units of Pseudomonas aeruginosa Serotype 10 and 19 O-Antigens

Here we report the chemical synthesis of conjugation-ready trisaccharides, representing biological repeating units of Pseudomonas aeruginosa serotype 10 and 19 O-antigens. The α-d-QuiN3 glycosidic bond was stereoselectively synthesized through TMSI─Ph3P═O mediated 1,2-cis glycosylation. Selective oxidation of the C6-OH group at the disaccharide stage allowed for benzylidene-promoted construction of the α-l-GalN3 glycosidic bond and simplification of the postglycosylation process at the trisaccharide stage. The low reaction temperature and neighboring electron-donating effect facilitated the efficient synthesis of the trisaccharide.

Antibacterial and anti-biofilm efficacy of selenium nanoparticles against Pseudomonas aeruginosa: Characterization and in vitro analysis

Pseudomonas aeruginosa (P. aeruginosa), a Gram-negative opportunistic pathogen, poses significant treatment challenges due to its antibiotic resistance and biofilm formation. This study investigates the anti-bacterial and anti-biofilm activities of chemically synthesized selenium nanoparticles (SeNPs) against P. aeruginosa. SeNPs were synthesized using ascorbic acid as a reducing agent and characterized. Biofilm formation was quantified using a modified microtiter plate method, and the anti-biofilm efficacy of SeNPs was evaluated using confocal microscopy and SEM. The P. aeruginosa isolates exhibited high resistance to piperacillin-tazobactam (60 %) and ceftazidime (59 %). SeNPs demonstrated a round shape with a diameter of 15-18 nm. UV-Vis spectra showed a peak at 275 nm, and XRD analysis revealed crystalline peaks corresponding to selenium. The FTIR spectra confirmed the presence of various functional groups. SeNPs significantly reduced biofilm formation in a dose-dependent manner, with MIC50 and MIC90 values of 60 μg/mL and 80 μg/mL, respectively. Confocal microscopy and SEM analysis showed a notable decrease in biofilm thickness and bacterial adherence post-SeNPs treatment. These findings suggest that SeNPs could be a promising alternative or adjunctive treatment option for combating antibiotic-resistant P. aeruginosa infections. Further research is warranted to explore the clinical applications of SeNPs in treating biofilm-associated infections.

Proteomic approach to identify host cell attachment proteins provides protective Pseudomonas aeruginosa vaccine antigen FtsZ

Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen that causes severe nosocomial infections in susceptible individuals due to the emergence of multidrug-resistant strains. There are no approved vaccines against P. aeruginosa infections nor candidates in active clinical development, highlighting the need for novel candidates and strategies. Using a cell-blot proteomic approach, we reproducibly identified 49 proteins involved in interactions with human lung epithelial cells across four P. aeruginosa strains. Among these were cell division protein FtsZ and outer membrane protein OpmH. Escherichia coli BL21 cells overexpressing recombinant FtsZ or rOpmH showed a 66- and 15-fold increased ability to attach to 16HBE14o- cells, further supporting their involvement in host cell attachment. Both antigens led to proliferation of NK and CD8+ cytotoxic T cells, significant increases in the production of IFN-γ, IL-17A, TNF and IL-4 in immunised mice and elicited strong antigen-specific serological IgG1 and IgG2c responses. Immunisation with FtsZ significantly reduced bacterial burden in the lungs by 1.9-log CFU and dissemination to spleen by 1.8-log CFU. The protective antigen candidate, FtsZ, would not have been identified by traditional approaches relying on either virulence mechanisms or sequence-based predictions, opening new avenues in the development of an anti-P. aeruginosa vaccine.

Inhibition of Pseudomonas aeruginosa Carbonic Anhydrases, Exploring Ciprofloxacin Functionalization Toward New Antibacterial Agents: An In-Depth Multidisciplinary Study

Ciprofloxacin (CPX) is one of the most employed antibiotics in clinics to date. However, the rise of drug-resistant bacteria is dramatically impairing its efficacy, especially against life-threatening pathogens, such as Pseudomonas aeruginosa. This Gram-negative bacterium is an opportunistic pathogen, often infecting immuno-compromised patients with severe or fatal outcomes. The evidence of the possibility of exploiting Carbonic Anhydrase (CA, EC: 4.2.1.1) enzymes as pharmacological targets along with their role in P. aeruginosa virulence inspired the derivatization of CPX with peculiar CA-inhibiting chemotypes. Thus, a large library of CPX derivatives was synthesized and tested on a panel of bacterial CAs and human isoenzymes I and II. Selected derivatives were evaluated for antibacterial activity, revealing bactericidal and antibiofilm properties for some compounds. Importantly, promising preliminary absorption, distribution, metabolism, and excretion (ADME) properties in vitro were found and no cytotoxicity was detected for some representative compounds when tested in Galleria mellonella larvae.

Case Report: Pan-Drug Resistant Pseudomonas aeruginosa from a Child with an Infected Burn Wound at the University Teaching Hospital of Kigali, Rwanda

Background

Pseudomonas aeruginosa is a significant cause of morbidity and mortality in intensive care units, and is prevalent in nosocomial infections and cystic fibrosis. The increasing rates of antimicrobial resistance (AMR) complicate the treatment of P. aeruginosa infections, especially because of the multidrug resistance (MDR), extensively drug-resistant (XDR), and pan-drug resistant (PDR) strains.

Case Presentation

We report the case of a 4-year-old male with severe burns covering 45% of his body surface who developed nosocomial PDR P. aeruginosa infection at the University Teaching Hospital of Kigali (CHUK) in Rwanda. A wound culture yielded a PDR P. aeruginosa isolate that was resistant to all the tested antimicrobials, with intermediate resistance to colistin. However, the patient improved with a combination of ceftazidime and amikacin following cessation of fever and successful skin grafting. The patient was discharged on day 95.

Conclusion

P. aeruginosa is a common hospital-acquired pathogen that is particularly challenging to treat, owing to its antimicrobial resistance profile and biofilm production. Antibiotic-resistant strains are a significant public health threat, especially in pediatric burn units. This case underscores the critical need to strengthen infection prevention and control measures together with robust antimicrobial stewardship programs. Molecular characterization of this PDR strain will yield further details regarding its virulence and genotyping.

The identification of essential cellular genes is critical for validating drug targets

Accurately identifying biological targets is crucial for advancing treatment options. Essential genes, vital for cell or organism survival, hold promise as potential drug targets in disease treatment. Although many studies have sought to identify essential genes as therapeutic targets in medicine and bioinformatics, systematic reviews on their relationship with drug targets are relatively rare. This work presents a comprehensive analysis to aid in identifying essential genes as potential targets for drug discovery, encompassing their relevance, identification methods, successful case studies, and challenges. This work will facilitate the identification of essential genes as therapeutic targets, thereby boosting new drug development.

Molecular Typing of Pseudomonas aeruginosa Isolates Collected in Abidjan Hospitals (Côte d'Ivoire) Using the Multiple-Locus Variable Number of Tandem Repeats Method

Background/objectives:Pseudomonas aeruginosa can cause community-acquired infections affecting various body sites. The present retrospective study investigated the genetic diversity of 173 isolates (166 clinical, 7 environmental) of P. aeruginosa collected from clinical pathology laboratories in Abidjan, Côte d'Ivoire (2001-2011). Methods: Multiple-Locus Variable Number of Tandem Repeats (VNTR) Analysis (MLVA) using 13 loci was applied to all isolates and compared to published MLVA data. The antibiotics status of the isolates was compiled when available and compared to published profiles. Results: Among 95 isolates analyzed for their antibiotics status, 14 displayed concerning resistance profiles: five multidrug-resistant (MDR) and nine extensively drug-resistant (XDR). MLVA typing revealed a high genetic diversity (>130 genotypes), with many genotypes represented by a single strain. Notably, thirteen clusters (≥4 related isolates) were observed. Some clusters displayed close genetic relatedness to isolates from France, Korea, and well-studied strains (ST560, LES and PA14). Comparative analysis suggested the presence of international high-risk MDR clones (CC233, CC111) in Côte d'Ivoire. Importantly, MLVA clustering revealed a close relationship of CC235-MDR strains with a locally identified cluster (group 9). Conclusions: These findings support MLVA as a reliable and cost-effective tool for low-resource settings, allowing the selection of relevant strains for future whole genome sequence analyses. This approach can improve outbreak investigations and public health interventions aimed at curbing MDR P. aeruginosa transmission within hospitals and at the national level.

Phage-Based Therapy in Combination with Antibiotics: A Promising Alternative against Multidrug-Resistant Gram-Negative Pathogens

The continued rise in antimicrobial resistance poses a serious threat to public health worldwide. The use of phages that can have bactericidal activity without disrupting the normal flora represents a promising alternative treatment method. This practice has been successfully applied for decades, mainly in Eastern Europe, and has recently been used as an emergency therapy for compassionate care in the United States. Here, we provide a comprehensive review of the pre-clinical and clinical applications of phage therapy concerning three major Gram-negative pathogens: Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. The advantages and the challenges of expanding the usage of phages as an alternative or adjunctive treatment for antimicrobial-resistant bacterial infections are discussed. We emphasize the virologic complexities of using the highly adaptable phage populations as molecular tools, along with antibiotic chemical compounds, to effectively combat rapidly coevolving pathogenic bacteria in the host microenvironment. Pre-clinical studies, isolated clinical reports and a few randomized clinical trials have shown that bacteriophages can be effective in treating multidrug-resistant bacterial infections. The ability of some phages to revert the resistance against antibiotics, and possibly also against the human complement and other phages, appears to be a great advantage of phage therapy despite the inevitable emergence of phage-resistant strains. Bacteriophages (or specific phage-derived products) can enhance antimicrobial efficacy by reducing bacterial virulence via the alteration of basic bacterial structures, primarily of the cellular wall and membrane. Although several issues remain open regarding their effective clinical application, it appears that phage-based therapeutics in combination with antibiotics can provide an effective solution to the spread of antimicrobial resistance.

Molecular characterization of clinically isolated Pseudomonas aeruginosa with varying resistance to ceftazidime-avibactam and ceftolozane-tazobactam collected as a part of the ATLAS global surveillance program from 2020 to 2021

Ceftazidime-avibactam (CZA) and ceftolozane-tazobactam (C/T) are important agents for treating multidrug-resistant P. aeruginosa infections. In this study, we evaluated the molecular characteristics of 300 globally collected clinical P. aeruginosa isolates non-susceptible (NS) to CZA, C/T, or both agents. Isolates were CZA-NS and C/T-NS (n = 57), CZA-susceptible (S) and C/T-NS (n = 145), or CZA-NS and C/T-S (n = 98) selected from the Antimicrobial Testing Leadership and Surveillance (ATLAS) surveillance program from 2020 to 2021. Characterization was by whole-genome sequencing. Analysis was performed to identify β-lactamase genes and mutations that impact efflux regulation, AmpC regulation, and target binding (PBP3). Of the 57 CZA-NS+C/T-NS isolates, 64.9% carried a metallo-β-lactamase (MBL), and a cumulative 84.2% carried any non-intrinsic β-lactamase [i.e., not Pseudomonas-derived cephalosporinase (PDC) or OXA-50-like]. Of the 145 CZA-S+C/T-NS isolates, 26.2% carried an extended-spectrum β-lactamase (ESBL) and no carbapenemase, 17.9% carried a serine-carbapenemase, and 42.1% were negative for non-intrinsic β-lactamases. Of 98 CZA-NS+C/T-S isolates, 34.7% carried mutations previously described as causing an upregulation of the MexAB-OprM efflux pump, while only 9.2% carried a non-intrinsic β-lactamase, and no resistance mechanism was identified in 29.6% of these isolates. MBLs were present in most isolates NS to both agents. More than half of the CZA-S+C/T-NS isolates carried serine β-lactamases. The most frequently identified resistance mechanism identified in CZA-NS+C/T-S isolates was a marker indicating the upregulation of MexAB-OprM. No mechanism was identified that is thought to support resistance to these agents in numerous isolates. This may be due in part to the fact that whole genome sequencing (WGS) cannot directly measure gene expression of chromosomal resistance mechanisms.

Three prolonged outbreaks of metallo-β-lactamase-producing Pseudomonas aeruginosa in an Upper Austrian hospital, 2017-2023

In spring 2022, an increase in metallo-β-lactamase-producing Pseudomonas aeruginosa (MBL-Pa) infections was detected in a hospital in Upper Austria. To identify the source of infection and to stop further transmissions, an epidemiological outbreak investigation including whole-genome sequencing (WGS)-based typing was conducted. The final case definition included cases admitted to the hospital between 2020 and 2023 with an MBL-Pa in one of the three genomic clusters identified. In addition, the investigation was extended to include historical cases from 2017. Core genome multilocus sequence typing was performed to assess the genetic relatedness between the isolates. Fifty-four clinical P. aeruginosa isolates and eight P. aeruginosa isolates from the hospital environment were obtained. All but nine isolates grouped into one of three genomic clusters (ST235/blaVIM-1, ST111/blaVIM-2, or ST621/blaIMP-13), which were considered to be distinct, prolonged outbreaks involving 47 out of 52 cases. The most likely source of infection for cluster 1 (ST111/blaVIM-2) and cluster 2 (ST235/blaVIM-1) was sinks in the intensive care unit (ICU) washroom. Cluster 3 clone (ST621/blaIMP-13) could have originated in the urology ward in 2020 and then spread to the ICU years later. However, the nosocomial origin of this clone could not be proven. In March 2023, following the implementation of control measures (gowning, patient isolation, screening, and daily disinfection), no further MLB-Pa was detected, and the outbreaks were considered to be over. As ICUs play an important role in the transmission of P. aeruginosa, emphasis should be placed on genomic surveillance, infection prevention, and control in such wards.

IMPORTANCE

The significance of our work lies in the successful resolution of three prolonged outbreaks of MBL-Pa infections in a hospital in Upper Austria. Through a comprehensive epidemiological investigation coupled with WGS-based typing of P. aeruginosa isolates, the study identified three distinct genomic clusters responsible for prolonged outbreaks involving 47 cases. The investigation pinpointed sinks in the ICU washroom as the likely source of infection for two of the clusters. The study demonstrates the effectiveness of control measures such as hand hygiene, gowning, patient isolation, screening, and disinfection in stopping further transmission and bringing the outbreaks to a close. This underscores the critical role of genomic surveillance and control measures, particularly in high-risk settings like ICUs, in reducing nosocomial transmission of MBL-Pa infections.

Immunostimulatory chimeric protein encapsulated in gelatin nanoparticles elicits protective immunity against Pseudomonas aeruginosa respiratory tract infection

This study presents the design and fabrication of an innovative vaccine candidate targeting Pseudomonas aeruginosa (P. aeruginosa). The vaccine consists of gelatin nanoparticles (GNPs) encapsulating a chimeric protein (CP) derived from the ExoS and OprI proteins from P. aeruginosa. The physicochemical properties of the GNPs were assessed using dynamic light scattering (DLS) and electron microscopy. The toxicity, encapsulation efficacy, release profile, and effectiveness of CP-encapsulated GNPs (CP-GNPs) in an animal model were investigated. The resulting nanovaccine demonstrated uniform spherical particles with an average size of 135 nm and an encapsulation efficiency of 85 %. The release assay revealed that 23 % of the antigen was released from the CP-GNPs after 20 days. The GNPs did not exhibit any toxic effects on L929 cells in vitro. The formulation induced both systemic and mucosal antibody responses. Additionally, CP-GNPs stimulated cytokine responses, including IFN-γ, IL-4, and IL-17, indicating the induction of both humoral (Th2) and cellular (Th1) responses. The CP-encapsulated GNPs formulation effectively protected the mice lungs against experimental respiratory tract infection, reducing colony count and inflammation. These findings suggest that CP-GNPs hold promise as a potential strategy for preventing respiratory tract infections caused by P. aeruginosa. Further research is needed to explore its clinical application.

Multifaceted strategies for alleviating Pseudomonas aeruginosa infection by targeting protease activity: Natural and synthetic molecules

Pseudomonas aeruginosa has become a top-priority pathogen in the health sector because it is ubiquitous, has high metabolic/genetic versatility, and is identified as an opportunistic pathogen. The production of numerous virulence factors by P. aeruginosa was reported to act individually or cooperatively to make them robots invasion, adherences, persistence, proliferation, and protection against host immune systems. P. aeruginosa produces various kinds of extracellular proteases such as alkaline protease, protease IV, elastase A, elastase B, large protease A, Pseudomonas small protease, P. aeruginosa aminopeptidase, and MucD. These proteases effectively allow the cells to invade and destroy host cells. Thus, inhibiting these protease activities has been recognized as a promising approach to controlling the infection caused by P. aeruginosa. The present review discussed in detail the characteristics of these proteases and their role in infection to the host system. The second part of the review discussed the recent updates on the multiple strategies for attenuating or inhibiting protease activity. These strategies include the application of natural and synthetic molecules, as well as metallic/polymeric nanomaterials. It has also been reported that a propeptide present in the middle domain of protease IV also attenuates the virulence properties and infection ability of P. aeruginosa.

Interactions between Pseudomonas aeruginosa and six opportunistic pathogens cover a broad spectrum from mutualism to antagonism

Bacterial infections often involve more than one pathogen. While it is well established that polymicrobial infections can impact disease outcomes, we know little about how pathogens interact and affect each other's behaviour and fitness. Here, we used a microscopy approach to explore interactions between Pseudomonas aeruginosa and six human opportunistic pathogens that often co-occur in polymicrobial infections: Acinetobacter baumannii, Burkholderia cenocepacia, Escherichia coli, Enterococcus faecium, Klebsiella pneumoniae, and Staphylococcus aureus. When following growing microcolonies on agarose pads over time, we observed a broad spectrum of species-specific ecological interactions, ranging from mutualism to antagonism. For example, P. aeruginosa engaged in a mutually beneficial interaction with E. faecium but suffered from antagonism by E. coli. While we found little evidence for active directional growth towards or away from cohabitants, we observed that some pathogens increased growth in double layers in response to competition and that physical forces due to fast colony expansion had a major impact on fitness. Overall, our work provides an atlas of pathogen interactions, highlighting the diversity of potential species dynamics that may occur in polymicrobial infections. We discuss possible mechanisms driving pathogen interactions and offer predictions of how the different ecological interactions could affect virulence.

Structural and functional diversity of Resistance-Nodulation-Division (RND) efflux pump transporters with implications for antimicrobial resistance

SUMMARYThe discovery of bacterial efflux pumps significantly advanced our understanding of how bacteria can resist cytotoxic compounds that they encounter. Within the structurally and functionally distinct families of efflux pumps, those of the Resistance-Nodulation-Division (RND) superfamily are noteworthy for their ability to reduce the intracellular concentration of structurally diverse antimicrobials. RND systems are possessed by many Gram-negative bacteria, including those causing serious human disease, and frequently contribute to resistance to multiple antibiotics. Herein, we review the current literature on the structure-function relationships of representative transporter proteins of tripartite RND efflux pumps of clinically important pathogens. We emphasize their contribution to bacterial resistance to clinically used antibiotics, host defense antimicrobials and other biocides, as well as highlighting structural similarities and differences among efflux transporters that help bacteria survive in the face of antimicrobials. Furthermore, we discuss technical advances that have facilitated and advanced efflux pump research and suggest future areas of investigation that will advance antimicrobial development efforts.

Predicting Pseudomonas aeruginosa drug resistance using artificial intelligence and clinical MALDI-TOF mass spectra

Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) is widely used in clinical microbiology laboratories for bacterial identification but its use for detection of antimicrobial resistance (AMR) remains limited. Here, we used MALDI-TOF MS with artificial intelligence (AI) approaches to successfully predict AMR in Pseudomonas aeruginosa, a priority pathogen with complex AMR mechanisms. The highest performance was achieved for modern β-lactam/β-lactamase inhibitor drugs, namely, ceftazidime/avibactam and ceftolozane/tazobactam. For these drugs, the model demonstrated area under the receiver operating characteristic curve (AUROC) of 0.869 and 0.856, specificity of 0.925 and 0.897, and sensitivity of 0.731 and 0.714, respectively. As part of this work, we developed dynamic binning, a feature engineering technique that effectively reduces the high-dimensional feature set and has wide-ranging applicability to MALDI-TOF MS data. Compared to conventional feature engineering approaches, the dynamic binning method yielded highest performance in 7 of 10 antimicrobials. Moreover, we showcased the efficacy of transfer learning in enhancing the AUROC performance for 8 of 11 antimicrobials. By assessing the contribution of features to the model's prediction, we identified proteins that may contribute to AMR mechanisms. Our findings demonstrate the potential of combining AI with MALDI-TOF MS as a rapid AMR diagnostic tool for Pseudomonas aeruginosa.IMPORTANCEPseudomonas aeruginosa is a key bacterial pathogen that causes significant global morbidity and mortality. Antimicrobial resistance (AMR) emerges rapidly in P. aeruginosa and is driven by complex mechanisms. Drug-resistant P. aeruginosa is a major challenge in clinical settings due to limited treatment options. Early detection of AMR can guide antibiotic choices, improve patient outcomes, and avoid unnecessary antibiotic use. Matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) is widely used for rapid species identification in clinical microbiology. In this study, we repurposed mass spectra generated by MALDI-TOF and used them as inputs for artificial intelligence approaches to successfully predict AMR in P. aeruginosa for multiple key antibiotic classes. This work represents an important advance toward using MALDI-TOF as a rapid AMR diagnostic for P. aeruginosa in clinical settings.

Effect of Lactiplantibacillus plantarum cell-free culture on bacterial pathogens isolated from cystic fibrosis patients: in vitro and in vivo studies

This study aimed to investigate the effects of the cell-free supernatant of Lactiplantibacillus plantarum ATCC® 10241TM on the biofilm-forming capacity of Pseudomonas aeruginosa strains isolated from cystic fibrosis (CF) patients. In addition, the study evaluated the in vivo potential of the cell-free supernatant to modulate inflammation and reduce lung damage in mice infected with P. aeruginosa strains or co-challenged with P. aeruginosa and the Streptococcus milleri group (SMG). The results showed that CF-derived P. aeruginosa strains can infect the respiratory tract of adult mice, inducing local inflammation and lung damage. The severity of these infections was exacerbated when P. aeruginosa was co-administered with SMG. Notably, nebulization with the cell-free supernatant of L. plantarum produced beneficial effects, reducing respiratory infection severity and inflammatory responses induced by P. aeruginosa, both alone or in combination with SMG. Reduced bacterial loads and lung damage were observed in supernatant-treated mice compared to controls. Although further mechanistic studies are necessary, the results show that the cell-free supernatant of L. plantarum ATCC® 10241TM is an interesting adjuvant alternative to treat P. aeruginosa respiratory infections and superinfections in CF patients.

Effectiveness of water system chemical disinfection against Pseudomonas aeruginosa infections, despite a not-so-obvious connection

BACKGROUND

Pseudomonas aeruginosa is a well-recognized opportunistic pathogen frequently responsible for hospital-acquired infections. Acquisition routes of P aeruginosa are both endogenous and exogenous, including transmission from a portion of the hospital water system.

METHODS

The impact of disinfection procedures of the water system and description routes of P aeruginosa transmission in a surgical intensive care unit over a 2-year period were investigated. Two distinct periods A and B were considered, respectively, before and after the disinfection. Fourier transform infrared spectroscopy was used to compare isolates recovered from patients and tap water.

RESULTS

Overall, 21.3% of tap water samples were positive but with a significantly lower rate in period B. Concomitantly, the prevalence of patients positive for P aeruginosa decreased from 2.6% to 1%, suggesting a correlation between the presence of environmental sources and patient contaminations. The results revealed that 18% of patients were involved in cross-transmission events not related to any isolate recovered from water, suggesting transmission through care practices. Conversely, only 1 environmental transmission event was suspected in a patient.

CONCLUSIONS

Although the link between the hospital environment and patients was unclear, HCW-associated care practices could be related to contaminated point-of-use waters and then indirect spreading to patients.

The influence of pre- and postnatal exposure to air pollution and green spaces on infant's gut microbiota: Results from the MAMI birth cohort study

BACKGROUND

Animal and human studies indicate that exposure to air pollution and natural environments might modulate the gut microbiota, but epidemiological evidence is very scarce.

OBJECTIVES

To assess the potential impact of pre- and postnatal exposure to air pollution and green spaces on infant gut microbiota assembly and trajectories during the first year of life.

METHODS

MAMI ("MAternal MIcrobes") birth cohort (Valencia, Spain, N = 162) was used to study the impact of environmental exposure (acute and chronic) on infant gut microbiota during the first year of life (amplicon-based 16S rRNA sequencing). At 7 days and at 1, 6 and 12 months, residential pre- and postnatal exposure to air pollutants (NO2, black carbon -BC-, PM2.5 and O3) and green spaces indicators (NDVI and area of green spaces at 300, 500 and 1000 m buffers) were obtained. For the association between exposures and alpha diversity indicators linear regression models (cross-sectional analyses) and mixed models, including individual as a random effect (longitudinal analyses), were applied. For the differential taxon analysis, the ANCOM-BC package with a log count transformation and multiple-testing corrections were used.

RESULTS

Acute exposure in the first week of life and chronic postnatal exposure to NO2 were associated with a reduction in microbial alpha diversity, while the effects of green space exposure were not evident. Acute and chronic (prenatal or postnatal) exposure to NO2 resulted in increased abundance of Haemophilus, Akkermansia, Alistipes, Eggerthella, and Tyzerella populations, while increasing green space exposure associated with increased Negativicoccus, Senegalimassilia and Anaerococcus and decreased Tyzzerella and Lachnoclostridium populations.

DISCUSSION

We observed a decrease in the diversity of the gut microbiota and signs of alteration in its composition among infants exposed to higher levels of NO2. Increasing green space exposure was also associated with changes in gut microbial composition. Further research is needed to confirm these findings.

Dosing Evaluation of Ceftazidime-Avibactam in Intensive Care Unit Patients Based on Pharmacokinetic/Pharmacodynamic (PK/PD) Modeling and Simulation

P. aeruginosa is the most common microorganism involved in many ICU-acquired infections. A correct dosage regimen is pivotal to avoiding resistance development, worse outcomes and higher mortality rates. The aim of this study was to perform a pharmacokinetic-pharmacodynamic (PK/PD) evaluation of recommended dosing regimens of ceftazidime-avibactam (CAZ-AVI) in ICU patients with different degrees of renal function for a specific strain of Pseudomonas aeruginosa. A semi-mechanistic PK/PD model has been developed. It allows for the simulation of CAZ-AVI steady-state plasma level curves and the evolution of bacterial growth curves. The percentage of bacterial load reduction and the value of the recommended PK/PD indices have been taken into account to define the success or failure of the regimens. Probabilistic analysis was performed using Monte Carlo simulations of two populations: control and ICU. In both populations, dosing regimens endorsed for patients with CLcr higher than 10 mL/min reach the PK/PD indices recommended, T > MIC > 90% and Cmin/MIC > 1.3. While dosage regimens endorsed for patients with CLcr of 10 mL/min or lower fail (T > MIC < 60% and Cmin/MIC < 0.35). However, proposed dosing regimens based on shortening dosing intervals for these patients would be successful, increasing bacterial load reduction by almost 50% and reaching the proposed PK/PD indices. Therefore, CAZ-AVI dosing strategies based on model-informed precision dosing (MIPD) could directly influence the efficacy of results in ICU patients with renal insufficiency.

In the Depths of Wash Water: Isolation of Opportunistic Bacteria from Fresh-Cut Processing Plants

The fruit and vegetable industry in post-harvest processing plants is characterized by a substantial consumption of water resources. Wash waters may serve as an environment for the periodic or permanent habitation of microorganisms, particularly if biofilm forms on the inner walls of tanks and flushing channels. Despite the implementation of integrated food safety monitoring systems in numerous countries, foodborne pathogens remain a global public health and food safety concern, particularly for minimally processed food products such as vegetables and fruits. This necessitates the importance of studies that will explore wash water quality to safeguard minimally processed food against foodborne pathogen contamination. Therefore, the current study aimed to isolate and identify bacteria contaminating the wash waters of four fresh-cut processing plants (Poland) and to evaluate the phenotypic antibiotic resistance profiles in selected species. Bacteria were isolated using membrane filtration and identified through mass spectrometry, followed by antibiotic susceptibility testing according to EUCAST guidelines. The results revealed that the level of contamination with total aerobic bacteria in the water ranged from 1.30 × 106 cfu/mL to 2.54 × 108 cfu/mL. Among the isolates, opportunistic pathogens including Enterococcus faecalis, Pseudomonas aeruginosa, Klebsiella oxytoca, Klebsiella pneumoniae, Serratia marcescens, and Proteus vulgaris strains were identified. An especially noteworthy result was the identification of cefepime-resistant K. oxytoca isolates. These findings highlight the importance of monitoring the microbial microflora in minimally processed foods and the need for appropriate sanitary control procedures to minimize the risk of pathogen contamination, ensuring that products remain safe and of high quality throughout the supply chain.

Glycomimetics as Candidates for Treatment and Prevention of Catheter-associated Biofilms Formed by Pseudomonas aeruginosa

Bacteria develop biofilms for protection and persistent colonization. Biofilms of pathogenic bacteria can lead to serious medical problems. Bacterial biofilms on catheters used in the treatment of urinary tract diseases represent a major challenge for antibiotic therapy. Several attempts to eradicate biofilms using classical antibiotics and various alternatives, including antibiotic treatment of surfaces, surfaces that release silver ions, and surfaces with anti-adhesive properties, have not shown clinical efficacy in biofilm prevention or removal. Pseudomonas aeruginosa is one of the most problematic biofilm-forming uropathogens and accounts for approximately 10% of urinary tract infections. Novel glycomimetics that inhibit bacterial lectins have shown promising results in the prevention of P. aeruginosa biofilms and in interference with bacterial virulence. This mini-review summarizes the status of glycomimetic development and provides a perspective on their use in clinical practice. PATIENT SUMMARY: For patients with recurrent urinary tract infections and patients needing long-term catheter use to manage urinary problems, biofilms formed by bacteria can be a problem and are difficult to treat. New compounds that mimic carbohydrates, called glycomimetics, have shown promise in inhibiting these bacteria and the biofilms they form. More research on these compounds is needed before they can be used to treat patients.

Identification of antimicrobial-susceptible Pseudomonas aeruginosa RpoA variant strains through positional conservation pattern

BACKGROUND

Bacterial RNA polymerase (RNAP) is a promising target for antimicrobial chemotherapy due to its indispensable role in bacterial growth and survival. Among its components, only the rpoB gene encoding the β-subunit is known for its association with rifampicin resistance. We recently identified a variant of the RNAP α-subunit (RpoA) in Pseudomonas aeruginosa, conferring heightened bacterial susceptibility to antimicrobials. This susceptibility was attributed to the specific down-regulation of the MexEF-OprN efflux pump.

OBJECTIVES

We asked how to distinguish antimicrobial-susceptible variant strains from clinical isolates.

METHODS

In this study, we identified various P. aeruginosa RpoA variants from clinical sources. Using the sequence alignment of different bacterial RpoA species, we computed the positional conservation of substitutions in RpoA variants using Shannon Entropy.

RESULTS

Our findings revealed that selective RpoA variant strains exhibited distinct profiles of antimicrobial susceptibility. Notably, RpoA variant strains, containing single-substitutions in the C-terminal domain (α-CTD) but not the N-terminal domain (α-NTD), showed attenuated MexEF-OprN expression and increased susceptibility to MexEF-OprN-specific antibiotics. Furthermore, we observed a close correlation between the susceptibility of these α-CTD RpoA variant strains to antibiotics and the conservation degrees of positional substitutions.

CONCLUSIONS

Our findings demonstrate the prevalence of antimicrobial-susceptible RpoA variant strains among P. aeruginosa clinical isolates. The identified positional conservation pattern in our study facilitates the rapid classification of RpoA variant strains with distinct drug resistances. Given the high conservation of RNAP across bacterial species, our findings open a new therapeutic perspective for precisely and efficiently combating pathogenic RpoA variant strains with specific antimicrobials.

Evaluation of chlorogenic acid and carnosol for anti-efflux pump and anti-biofilm activities against extensively drug-resistant strains of Staphylococcus aureus and Pseudomonas aeruginosa

Efflux pumps and biofilm play significant roles in bacterial antibiotic resistance. This study investigates the potential of chlorogenic acid (CGA) and carnosol (CL), as phenolic and diterpene compounds, respectively, for their inhibitory effects on efflux pumps. Among the 12 multidrug-resistant (MDR) strains of Staphylococcus aureus and Pseudomonas aeruginosa isolated from nosocomial skin infections, eight strains were identified as extensively drug resistant (XDR) using the disc diffusion method. The presence of efflux pumps in MDR strains of S. aureus and P. aeruginosa was screened using carbonyl cyanide-m-chlorophenylhydrazone. Between the 12 MDR strains of S. aureus and P. aeruginosa, 80% (4 out of 5) of the S. aureus strains and 85.7% (6 out of 7) of the P. aeruginosa strains exhibited active efflux pumps associated with gentamicin resistance. The checkerboard assay results, in combination with gentamicin, demonstrated that CGA exhibited a reduction in the minimum inhibitory concentration (MIC) for XDR S. aureus strain. Similarly, CL showed a synergistic effect and reduced the MIC for both XDR strains of S. aureus and P. aeruginosa. Flow cytometry was used to examine efflux pump activity at sub-MIC concentrations of 1/8, 1/4, and 1/2 MIC in comparison to the control. In XDR S. aureus, CGA demonstrated 39%, 70%, and 19% inhibition, while CL exhibited 74%, 73.5%, and 62% suppression. In XDR P. aeruginosa, CL exhibited inhibition rates of 25%, 10%, and 15%. The inhibition of biofilm formation was assessed using the microtiter plate method, resulting in successful inhibition of biofilm formation. Finally, the MTT assay was conducted, and it confirmed minimal cytotoxicity. Given the significant reduction in efflux pump activity and biofilm formation observed with CGA and CL in this study, these compounds can be considered as potential inhibitors of efflux pumps and biofilm formation, offering potential strategies to overcome antimicrobial resistance.

IMPORTANCE

In summary, CGA and CL demonstrated promising potentiating antimicrobial effects against XDR strains of Staphylococcus aureus and Pseudomonas aeruginosa, suggesting their probably potential as candidates for addressing nosocomial pathogens. They exhibited significant suppression of efflux pump activity, indicating a possible successful inhibition of this mechanism. Moreover, all substances effectively inhibited biofilm formation, while showing minimal cytotoxicity. However, further advancement to clinical trials is needed to evaluate the feasibility of utilizing CGA and CL for reversing bacterial XDR efflux and determining their efficacy against biofilms. These trials will provide valuable insights into the practical applications of these compounds in combating drug-resistant infections.

Methyl gallate attenuates virulence and decreases antibiotic resistance in extensively drug-resistant Pseudomonasaeruginosa

Pseudomonas aeruginosa infections have become a serious threat to public health due to the increasing emergence of extensively antibiotic-resistant strains and high mortality rates. Therefore, the search for new therapeutic alternatives has become crucial. In this study, the antivirulence and antibacterial activity of methyl gallate was evaluated against six clinical isolates of extensively antibiotic-resistant P. aeruginosa. Methyl gallate exhibited minimal inhibitory concentrations of 256-384 μg/mL; moreover, the use of subinhibitory concentrations of the compound inhibited biofilm formation, swimming, swarming, proteolytic activity, and pyocyanin production. Methyl gallate plus antipseudomonal antibiotics showed a synergistic effect by reduced the MICs of ceftazidime, gentamicin and meropenem. Furthermore, the potential therapeutic effect of methyl gallate was demonstrated in an infection model. This study evidenced the antivirulence and antimicrobial activity of methyl gallate as a therapeutic alternative against P. aeruginosa.

Inorganic nanoparticles: An effective antibiofilm strategy

Biofilm is a common problem associated with human health. Pathogenicity and increase in resistance of bacteria require urgent development of effective ways for the treatment of bacterial diseases. Different strategies have been developed for the treatment of bacterial infections among which nanoparticles have shown greater prospects in battling with infections. Biofilms are resistant microbial colonies that possess resistance and, hence, cannot be killed by conventional drugs. Nanoparticles offer new avenues for treating biofilm-related infections involving multi-drug resistant organisms. They possess great antibiofilm properties, disrupting cell architecture and preventing colony formation. Green-synthesised nanoparticles are more effective and less toxic to human cells than commercially available or chemically synthesised antibiofilm nanoparticles. This review summarises the antibiofilm efficiency of plant-mediated nanoparticles and knowledge about biofilm inhibition.

Antimicrobial photodynamic effect of the photosensitizer riboflavin, alone and in combination with colistin, against pandrug-resistant Pseudomonas aeruginosa clinical isolates

INTRODUCTION

Development of multi-, extensively-, and pandrug-resistant (MDR, XDR, and PDR) strains of Pseudomonas aeruginosa remains a major problem in medical care. The present study evaluated the effect of antimicrobial photodynamic therapy (aPDT) as a monotherapy and in combination with colistin against P. aeruginosa isolates.

METHODS

Two P. aeruginosa isolates recovered from patients with respiratory tract infections were examined in this study. Minimum inhibitory concentration (MIC) of colistin was determined by the colistin broth disk elution (CBDE) and the reference broth microdilution (rBMD) methods. aPDT was performed using the photosensitizer (Ps) riboflavin at several concentrations and a light-emitting diode (LED) emitting blue light for different irradiation times with or without colistin at 1/2 × MIC concentration.

RESULTS

Both PA1 and PA2 isolates were identified as colistin-resistant P. aeruginosa with a MIC ≥4 μg/mL by the CBDE and MICs of 512 μg/mL and 256 μg/mL, respectively, by the rBMD. In aPDT, neither riboflavin nor LED light alone had antibacterial effects. The values of colony forming units per milliliter (CFU/mL) in both isolates were significantly reduced by LED + Ps treatments in a time-dependent manner (LED irradiation time) and dose-dependent manner (Ps concentration). In comparison with control, treatment with Ps (50 μM) + LED (120 s) and Ps (100 μM) + LED (120 s) resulted in 0.27 log10 CFU/mL and 0.43 log10 CFU/mL reductions in PA1, and 0.28 log10 CFU/mL and 0.34 log10 CFU/mL reductions in PA2, respectively, (P < 0.01). The best results were obtained after the combination of aPDT followed by colistin, which increased bacterial reduction, resulting in a 0.41-0.7 log10 CFU/mL reduction for PA1 and 0.35-0.83 log10 CFU/mL reduction for PA2 (P = 0.001).

CONCLUSIONS

This study suggests the potential implications of aPDT in combination with antibiotics, such as colistin for treatment of difficult-to-treat P. aeruginosa infections.

Acanthamoebae as a protective reservoir for Pseudomonas aeruginosa in a clinical environment

BACKGROUND

Pseudomonas aeruginosa is a growing concern in healthcare-associated infections and poses significant risk to those with serious underlying health conditions. The antimicrobial resistance traits of the pathogen and ability to form biofilms make effective mitigation and disinfection strategies difficult. Added to this challenge is the role that free-living amoebae such as Acanthamoeba play in the detection, disinfection and transmission of P. aeruginosa. P. aeruginosa can survive intracellularly within amoebae, which has the potential to limit detectability and permit transmission into high-risk areas.

METHODS/FINDINGS

We screened for the presence of Acanthamoeba spp. and P. aeruginosa within a functioning general hospital in Scotland using a culture and molecular approach, noting their presence at several sites over a four-month period, particularly within floor drains connecting patient rooms. In addition, microbiome analysis revealed that amoebae harbour a unique microbial community comprised primarily of Pseudomonas spp. that were not readily detected using microbiome sequencing techniques on environmental swabs. Having demonstrated that both organisms were consistently present in hospital settings, we investigated the relationship between acanthamoeba and P. aeruginosa in the laboratory, showing that (i) acanthamoeba growth rate is increased in the presence of pseudomonas biofilms and viable pseudomonas persist within the amoebae and (ii) hydrogen peroxide-based disinfectants are significantly less effective against an isolate of P. aeruginosa in the presence of acanthamoeba than when the bacteria are incubated alone.

CONCLUSIONS

These findings suggest that amoebae, and other protists, can influence the detection and persistence of P. aeruginosa in high-risk areas and should be considered when implementing mitigation strategies.

Efflux pump-mediated resistance to new beta lactam antibiotics in multidrug-resistant gram-negative bacteria

The emergence and spread of bacteria resistant to commonly used antibiotics poses a critical threat to modern medical practice. Multiple classes of bacterial efflux pump systems play various roles in antibiotic resistance, and members of the resistance-nodulation-division (RND) transporter superfamily are among the most important determinants of efflux-mediated resistance in gram-negative bacteria. RND pumps demonstrate broad substrate specificities, facilitating extrusion of multiple chemical classes of antibiotics from the bacterial cell. Several newer beta-lactams and beta-lactam/beta-lactamase inhibitor combinations (BL/BLI) have been developed to treat infections caused by multidrug resistant bacteria. Here we review recent studies that suggest RND efflux pumps in clinically relevant gram-negative bacteria may play critical but underappreciated roles in the development of resistance to beta-lactams and novel BL/BLI combinations. Improved understanding of the genetic and structural basis of RND efflux pump-mediated resistance may identify new antibiotic targets as well as strategies to minimize the emergence of resistance.

The Potential of Phage Treatment to Inactivate Planktonic and Biofilm-Forming Pseudomonas aeruginosa

Pseudomonas aeruginosa is a common cause of hospital-acquired infections and exhibits a strong resistance to antibiotics. An alternative treatment option for bacterial infections is the use of bacteriophages (or phages). In this study, two distinct phages, VB_PaD_phPA-G (phPA-G) and VB_PaN_phPA-Intesti (phPA-Intesti), were used as single suspensions or in a phage cocktail to inactivate the planktonic cells and biofilms of P. aeruginosa. Preliminary experiments in culture medium showed that phage phPA-Intesti (reductions of 4.5-4.9 log CFU/mL) outperformed phPA-G (reductions of 0.6-2.6 log CFU/mL) and the phage cocktail (reduction of 4.2 log CFU/mL). Phage phPA-Intesti caused a maximum reduction of 5.5 log CFU/cm2 in the P. aeruginosa biofilm in urine after 4 h of incubation. The combination of phage phPA-Intesti and ciprofloxacin did not improve the efficacy of bacterial inactivation nor reduce the development of resistant mutants. However, the development of resistant bacteria was lower in the combined treatment with the phage and the antibiotic compared to treatment with the antibiotic alone. This phage lacks known toxins, virulence, antibiotic resistance, and integrase genes. Overall, the results suggest that the use of phage phPA-Intesti could be a potential approach to control urinary tract infections (UTIs), namely those caused by biofilm-producing and multidrug-resistant strains of P. aeruginosa.

Electrochemical Detection of Pseudomonas aeruginosa Quorum Sensing Molecule (S)-N-Butyryl Homoserine Lactone Using Molecularly Imprinted Polymers

Pseudomonas aeruginosa is a multidrug-resistant Gram-negative bacterium that poses a significant threat to public health, necessitating rapid and on-site detection methods for rapid recognition. The goal of the project is therefore to indirectly detect the presence of P. aeruginosa in environmental water samples targeting one of its quorum-sensing molecules, namely, (S)-N-butyryl homoserine lactone (BHL). To this aim, molecularly imprinted polymers (MIPs) were synthesized via bulk free-radical polymerization using BHL as a template molecule. The obtained MIP particles were immobilized onto screen-printed electrodes (MIP-SPEs), and the BHL rebinding was analyzed via electrochemical impedance spectroscopy (EIS). To study the specificity of the synthesized MIPs, isotherm curves were built after on-point rebinding analysis performed via LC-MS measurements for both MIPs and NIPs (nonimprinted polymers, used as a negative control), obtaining an imprinting factor (IF) of 2.8 (at C f = 0.4 mM). The MIP-SPEs were integrated into an electrochemical biosensor with a linear range of 1 × 101-1 × 103 nM and a limit of detection (LoD) of 31.78 ± 4.08 nM. Selectivity measurements were also performed after choosing specific interferent molecules, such as structural analogs and potential interferents, followed by on-point analysis performed in spiked tap water to prove the sensor's potential to detect the presence of the quorum-sensing molecule in environmentally related real-life samples.

Control of phosphodiesterase activity in the regulator of biofilm dispersal RbdA from Pseudomonas aeruginosa

The switch between planktonic and biofilm lifestyle correlates with intracellular concentration of the second messenger bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP). While bacteria possess cyclase and phosphodiesterase enzymes to catalyse formation or hydrolysis of c-di-GMP, both enzymatic domains often occur in a single protein. It is tacitly assumed that one of the two enzymatic activities is dominant, and that additional domains and protein interactions enable responses to environmental conditions and control activity. Here we report the structure of the phosphodiesterase domain of the membrane protein RbdA (regulator of biofilm dispersal) in a dimeric, activated state and show that phosphodiesterase activity is controlled by the linked cyclase. The phosphodiesterase region around helices α5/α6 forms the dimer interface, providing a rationale for activation, as this region was seen in contact with the cyclase domain in an auto-inhibited structure previously described. Kinetic analysis supports this model, as the activity of the phosphodiesterase alone is lower when linked to the cyclase. Analysis of a computed model of the RbdA periplasmatic domain reveals an all-helical architecture with a large binding pocket that could accommodate putative ligands. Unravelling the regulatory circuits in multi-domain phosphodiesterases like RbdA is important to develop strategies to manipulate or disperse bacterial biofilms.

Genomic Insights into Pediococcus pentosaceus ENM104: A Probiotic with Potential Antimicrobial and Cholesterol-Reducing Properties

Pediococcus pentosaceus, which often occurs in fermented foods, is characterized by numerous positive effects on the human health, such as the presence of possible probiotic abilities, the reduction of cholesterol levels, satisfactory antimicrobial activity, and certain therapeutic functions. This study was conducted with the goal of describing the genomic content of Pediococcus pentosaceus ENM104, a strain known for its inhibitory effects against pathogenic bacteria and its remarkable probiotic potential, including the induction of significant reductions in cholesterol levels and the production of γ-aminobutyric acid (GABA). The P. pentosaceus ENM104 chromosome is circular. The chromosome is 1,734,928 bp with a GC content of 37.2%. P. pentosaceus also harbors a circular plasmid, pENM104, that is 71,811 bp with a GC content of 38.1%. Functional annotations identified numerous genes associated with probiotic traits, including those involved in stress adaptation (e.g., heat stress: htpX, dnaK, and dnaJ), bile tolerance (e.g., ppaC), vitamin biosynthesis (e.g., ribU, ribZ, ribF, and btuD), immunomodulation (e.g., dltA, dltC, and dltD), and bacteriocin production (e.g., pedA). Notably, genes responsible for lowering cholesterol levels (bile salt hydrolase, bsh) and GABA synthesis (glutamate/GABA antiporter, gadC) were also identified. The in vitro assay results using cell-free supernatants of P. pentosaceus ENM104 revealed antibacterial activity against carbapenem-resistant bacteria, such as Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii, and the inhibition zone diameter increased progressively over time. This comprehensive study provides valuable insights into the molecular characteristics of P. pentosaceus ENM104, emphasizing its potential as a probiotic. Its notable cholesterol-lowering, GABA-producing, and antimicrobial capabilities suggest promising applications in the pharmaceutical and food industries. Future research should focus on further exploring these functional properties and assessing the strain's efficacy in clinical settings.

Murepavadin Enhances the Killing Efficacy of Ciprofloxacin against Pseudomonas aeruginosa by Inhibiting Drug Efflux

Pseudomonas aeruginosa is a multidrug-resistant Gram-negative pathogen and one of the leading causes of ventilator-associated pneumonia and infections in patients with chronic obstructive pulmonary disease and cystic fibrosis. Murepavadin is a peptidomimetic that specifically targets outer-membrane lipopolysaccharide transport protein LptD of P. aeruginosa. In this study, we find that murepavadin enhances the bactericidal efficacy of ciprofloxacin. We further demonstrate that murepavadin increases intracellular accumulation of ciprofloxacin by suppressing drug efflux. In addition, the murepavadin-ciprofloxacin combination exhibits a synergistic bactericidal effect in an acute murine pneumonia model. In conclusion, our results identify an effective drug combination for the treatment of P. aeruginosa infections.

Genomic Insights into Vietnamese Extended-Spectrum β-Lactamase-9-Producing Extensively Drug-Resistant Pseudomonas aeruginosa Isolates Belonging to the High-Risk Clone ST357 Obtained from Bulgarian Intensive Care Unit Patients

Extensively drug-resistant P. aeruginosa (XDR-PA) has been highlighted as a serious public health threat. The present study aimed to explore the genomic characteristics of two Vietnamese extended-spectrum β-lactamase-9 (VEB-9)-producing XDR-PA isolates from Bulgaria in comparison to all blaVEB-9-positive strains with available genomes. The isolates designated Pae51 and Pae52 were obtained from tracheobronchial aspirates of intensive care unit (ICU) patients. Antimicrobial susceptibility testing, whole-genome sequencing, RT-qPCR, and phylogenomic analysis were performed. Pae51 and Pae52 were resistant to most antipseudomonal β-lactams including carbapenems, aminoglycosides, and fluoroquinolones but remained susceptible to colistin and cefiderocol. Numerous resistance determinants were detected: blaVEB-9, blaPDC-3, blaOXA-10, blaOXA-50, aac(6')-II, ant(2″)-Ia, ant(3″)-IIa, aph(3')-IIb, cprP, catB7, dfrB2, sul1, fosA, and tet(A). Both isolates carried complex integrons with blaVEB-9 and tet(A) embedded next to the conservative 3' end sequences. A variety of virulence factors were also identified, including the type III secretion system exotoxin U. Pae51 and Pae52 differed by only four SNPs and belonged to the high-risk clone ST357. To our knowledge, this is the first report of blaVEB-9-positive XDR-PA isolates in Bulgaria presenting a detailed genomic analysis. The development of novel antimicrobial strategies for such pathogens should be an essential part of infection control stewardship practices in ICU wards.

Synthesis, Characterization, and Biological Evaluation of Chitosan Nanoparticles Cross-Linked with Phytic Acid and Loaded with Colistin against Extensively Drug-Resistant Bacteria

The natural evolution of microorganisms, as well as the inappropriate use of medicines, have accelerated the problem of drug resistance to many of the antibiotics employed today. Colistin, a lipopeptide antibiotic used as a last resort against multi-resistant strains, has also begun to present these challenges. Therefore, this study was focused on establishing whether colistin associated with chitosan nanoparticles could improve its antibiotic activity on an extremely resistant clinical isolate of Pseudomonas aeruginosa, which is a clinically relevant Gram-negative bacterium. For this aim, nanoparticulate systems based on phytic acid cross-linked chitosan and loaded with colistin were prepared by the ionic gelation method. The characterization included particle size, polydispersity index-PDI, and zeta potential measurements, as well as thermal (DSC) and spectrophotometric (FTIR) analysis. Encapsulation efficiency was assessed by the bicinchoninic acid (BCA) method, while the antimicrobial evaluation was made following the CLSI guidelines. The results showed that colistin-loaded nanoparticles were monodispersed (PDI = 0.196) with a particle size of around 266 nm and a positive zeta potential (+33.5 mV), and were able to associate with around 65.8% of colistin and decrease the minimum inhibitory concentration from 16 μg/mL to 4 μg/mL. These results suggest that the association of antibiotics with nanostructured systems could be an interesting alternative to recover the antimicrobial activity on resistant strains.

Respiratory tract infections: an update on the complexity of bacterial diversity, therapeutic interventions and breakthroughs

Respiratory tract infections (RTIs) have a significant impact on global health, especially among children and the elderly. The key bacterial pathogens Streptococcus pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae, Staphylococcus aureus and non-fermenting Gram Negative bacteria such as Acinetobacter baumannii and Pseudomonas aeruginosa are most commonly associated with RTIs. These bacterial pathogens have evolved a diverse array of resistance mechanisms through horizontal gene transfer, often mediated by mobile genetic elements and environmental acquisition. Treatment failures are primarily due to antimicrobial resistance and inadequate bacterial engagement, which necessitates the development of alternative treatment strategies. To overcome this, our review mainly focuses on different virulence mechanisms and their resulting pathogenicity, highlighting different therapeutic interventions to combat resistance. To prevent the antimicrobial resistance crisis, we also focused on leveraging the application of artificial intelligence and machine learning to manage RTIs. Integrative approaches combining mechanistic insights are crucial for addressing the global challenge of antimicrobial resistance in respiratory infections.

An unnatural amino acid dependent, conditional Pseudomonas vaccine prevents bacterial infection

Live vaccines are ideal for inducing immunity but suffer from the need to attenuate their pathogenicity or replication to preclude the possibility of escape. Unnatural amino acids (UAAs) provide a strategy to engineer stringent auxotrophies, yielding conditionally replication incompetent live bacteria with excellent safety profiles. Here, we engineer Pseudomonas aeruginosa to maintain auxotrophy for the UAA p-benzoyl-L-phenylalanine (BzF) through its incorporation into the essential protein DnaN. In vivo evolution using an Escherichia coli-based two-hybrid selection system enabled engineering of a mutant DnaN homodimeric interface completely dependent on a BzF-specific interaction. This engineered strain, Pa Vaccine, exhibits undetectable escape frequency (<10-11) and shows excellent safety in naïve mice. Animals vaccinated via intranasal or intraperitoneal routes are protected from lethal challenge with pathogenic P. aeruginosa PA14. These results establish UAA-auxotrophic bacteria as promising candidates for bacterial vaccine therapy and outline a platform for expanding this technology to diverse bacterial pathogens.

Prospects of Pseudomonas in Microbial Fuel, Bioremediation, and Sustainability

Microbial applications in agriculture and industry have gained significant attention due to their potential to address environmental challenges and promote sustainable development. Among these, the genus Pseudomonas stands out as a promising candidate for various biotechnological uses, thanks to its metabolic flexibility, resilience, and adaptability to diverse environments. This review provides a comprehensive overview of the current state and future prospects of microbial fuel production, bioremediation, and sustainable development, focusing on the pivotal role of Pseudomonas species. We emphasize the importance of microbial fuel as a renewable energy source and discuss recent advancements in enhancing biofuel generation using Pseudomonas strains. Additionally, we explore the critical role of Pseudomonas in bioremediation processes, highlighting its ability to degrade a wide spectrum of pollutants, including hydrocarbons, pesticides, and heavy metals, thereby reducing environmental contamination. Despite significant progress, several challenges remain. These include refining microbial strains for optimal process efficiency and addressing ecological considerations. Nonetheless, the diverse capabilities of Pseudomonas offer promising avenues for innovative solutions to pressing environmental issues, supporting the transition to a more sustainable future.

Resistance to ceftazidime-avibactam and other new β-lactams in Pseudomonas aeruginosa clinical isolates: a multi-center surveillance study

New β-lactam-β-lactamase inhibitor combinations represent last-resort antibiotics to treat infections caused by multidrug-resistant Pseudomonas aeruginosa. Carbapenemase gene acquisition can limit their spectrum of activity, and reports of resistance toward these new molecules are increasing. In this multi-center study, we evaluated the prevalence of resistance to ceftazidime-avibactam (CZA) and comparators among P. aeruginosa clinical isolates from bloodstream infections, hospital-acquired or ventilator-associated pneumonia, and urinary tract infections, circulating in Southern Italy. We also investigated the clonality and content of relevant β-lactam resistance mechanisms of CZA-resistant (CZAR) isolates. A total of 120 P. aeruginosa isolates were collected. CZA was among the most active β-lactams, retaining susceptibility in the 81.7% of cases, preceded by cefiderocol (95.8%) and followed by ceftolozane-tazobactam (79.2%), meropenem-vaborbactam (76.1%), imipenem-relebactam (75%), and aztreonam (69.6%). Among non-β-lactams, colistin and amikacin were active against 100% and 85.8% of isolates respectively. In CZAR strains subjected to whole-genome sequencing (n = 18), resistance was mainly due to the expression of metallo-β-lactamases (66.6% VIM-type and 5.5% FIM-1), followed by PER-1 (16.6%) and GES-1 (5.5%) extended-spectrum β-lactamases, mostly carried by international high-risk clones (ST111 and ST235). Of note, two strains producing the PER-1 enzyme were resistant to all β-lactams, including cefiderocol. In conclusion, the CZA resistance rate among P. aeruginosa clinical isolates in Southern Italy remained low. CZAR isolates were mostly metallo-β-lactamases producers and belonging to ST111 and ST253 epidemic clones. It is important to implement robust surveillance systems to monitor emergence of new resistance mechanisms and to limit the spread of P. aeruginosa high-risk clones.

IMPORTANCE

Multidrug-resistant Pseudomonas aeruginosa infections are a growing threat due to the limited therapeutic options available. Ceftazidime-avibactam (CZA) is among the last-resort antibiotics for the treatment of difficult-to-treat P. aeruginosa infections, although resistance due to the acquisition of transferable β-lactamase genes is increasing. With this work, we report that CZA represents a highly active antipseudomonal β-lactam compound (after cefiderocol), and that metallo-β-lactamases (VIM-type) and extended-spectrum β-lactamases (GES and PER-type) production is the major factor underlying CZA resistance in isolates from Southern Italian hospitals. In addition, we reported that such resistance mechanisms were mainly carried by the international high-risk clones ST111 and ST235.

Antibacterial Interactions of Ethanol-Dispersed Multiwalled Carbon Nanotubes with Staphylococcus aureus and Pseudomonas aeruginosa

Infectious diseases are acknowledged as one of the leading causes of death worldwide. Statistics show that the annual death toll caused by bacterial infections has reached 14 million, most of which are caused by drug-resistant strains. Bacterial antibiotic resistance is currently regarded as a compelling problem with dire consequences, which motivates the urgent identification of alternative ways of fighting bacteria. Various types of nanomaterials have been reported to date as efficient antibacterial solutions. Among these, carbon-based nanomaterials, such as carbon nanodots, carbon graphene oxide, and carbon nanotubes (CNTs), have been shown to be effective in killing a wide panel of pathogenic bacteria. With this study, we aim to provide additional insights into this topic of research by investigating the antibacterial activity of a specific type of multiwalled CNTs, with diameters from 50 to 150 nm, against two representative opportunistic pathogens, i.e., the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Pseudomonas aeruginosa, both included among the top antibiotic-resistant pathogens. We also test the synergistic effect of CNTs with different antibiotics commonly used in the treatment of infections caused by S. aureus and/or P. aeruginosa. Additionally, a novel approach for quantitatively analyzing bacterial aggregation in brightfield microscopy images was implemented. This method was utilized to assess the effectiveness of CNTs, either alone or in combination with antibiotics, in dispersing bacterial aggregates. Finally, atomic force microscopy coupled with a newly devised image analysis pipeline was used to examine any potential morphological changes in bacterial cells following exposure to CNTs and antibiotics.

The role of extracellular structures in Clostridioides difficile biofilm formation

C. difficile infection (CDI) is a costly and increasing burden on the healthcare systems of many developed countries due to the high rates of nosocomial infections. Despite the availability of several antibiotics with high response rates, effective treatment is hampered by recurrent infections. One potential mechanism for recurrence is the existence of C. difficile biofilms in the gut which persist through the course of antibiotics. In this review, we describe current developments in understanding the molecular mechanisms by which C. difficile biofilms form and are stabilized through extracellular biomolecular interactions.

Hospital and municipal wastewater as a source of carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa in the environment: a review

The increase in the prevalence of carbapenem-resistant Gram-negative bacteria, in particular Acinetobacter baumannii (CRAB) and Pseudomonas aeruginosa (CRPA), poses a serious threat for public health worldwide. This article reviews the alarming data on the prevalence of infections caused by CRAB and CRPA pathogens and their presence in hospital and municipal wastewater, and it highlights the environmental impact of antibiotic resistance. The article describes the key role of antibiotic resistance genes (ARGs) in the acquisition of carbapenem resistance and sheds light on bacterial resistance mechanisms. The main emphasis was placed on the transfer of ARGs not only in the clinical setting, but also in the environment, including water, soil, and food. The aim of this review was to expand our understanding of the global health risks associated with CRAB and CRPA in hospital and municipal wastewater and to analyze the spread of these micropollutants in the environment. A review of the literature published in the last decade will direct research on carbapenem-resistant pathogens, support the implementation of effective preventive measures and interventions, and contribute to the development of improved strategies for managing this problem.

Guidelines for Antibiotics Prescription in Critically Ill Patients

How to cite this article: Khilnani GC, Tiwari P, Mittal S, Kulkarni AP, Chaudhry D, Zirpe KG, et al. Guidelines for Antibiotics Prescription in Critically Ill Patients. Indian J Crit Care Med 2024;28(S2):S104-S216.

Genomic Comparative of Pseudomonas aeruginosa Small Colony Variant, Mucoid and Non-mucoid Phenotypes Obtained from a Patient with Cystic Fibrosis During Respiratory Exacerbations

Pseudomonas aeruginosa, the most prevalent opportunistic pathogen in chronic obstructive pulmonary disease, associated with high morbidity and mortality in patients with cystic fibrosis (CF), is practically impossible to be eradicated from the airways in chronicity. Its extraordinary genomic plasticity is possibly associated with high antimicrobial resistance, virulence factors, and its phenotypic diversity. The occurrence of P. aeruginosa isolates promoting airway infection, showing mucoid, non-mucoid, and small colony variant (SCV) phenotypes, was observed simultaneously, in the present study, in sputum cultures obtained from a male CF young patient with chronic pulmonary infection for over a decade. The isolates belonged to a new ST (2744) were obtained in two moments of exacerbation of the respiratory disease, in which he was hospitalized. Genetic background and phenotypic analysis indicated that the isolates exhibited multi- and pan-antimicrobial resistant profiles, as well as non-susceptible to polymyxin and predominantly hypermutable (HPM) phenotypes. Whole genome sequencing showed variations in genome sizes, coding sequences and their determinants of resistance and virulence. The annotated genomes were compared for antimicrobial resistance, hypermutability, and SCV characteristics. We highlight the lack of reported genetic determinants of SCV emergence and HPM phenotypes, which can be explained in part due to the very short time between collections of isolates. To the best of our knowledge, this is the first report of genome sequencing of P. aeruginosa SCV from a CF patient in Brazil.

Enhancing acute inflammatory and sepsis treatment: superiority of membrane receptor blockade

Conditions such as acute pancreatitis, ulcerative colitis, delayed graft function and infections caused by a variety of microorganisms, including gram-positive and gram-negative organisms, increase the risk of sepsis and therefore mortality. Immune dysfunction is a characterization of sepsis, so timely and effective treatment strategies are needed. The conventional approaches, such as antibiotic-based treatments, face challenges such as antibiotic resistance, and cytokine-based treatments have shown limited efficacy. To address these limitations, a novel approach focusing on membrane receptors, the initiators of the inflammatory cascade, is proposed. Membrane receptors such as Toll-like receptors, interleukin-1 receptor, endothelial protein C receptor, μ-opioid receptor, triggering receptor expressed on myeloid cells 1, and G-protein coupled receptors play pivotal roles in the inflammatory response, offering opportunities for rapid regulation. Various membrane receptor blockade strategies have demonstrated efficacy in both preclinical and clinical studies. These membrane receptor blockades act as early stage inflammation modulators, providing faster responses compared to conventional therapies. Importantly, these blockers exhibit immunomodulatory capabilities without inducing complete immunosuppression. Finally, this review underscores the critical need for early intervention in acute inflammatory and infectious diseases, particularly those posing a risk of progressing to sepsis. And, exploring membrane receptor blockade as an adjunctive treatment for acute inflammatory and infectious diseases presents a promising avenue. These novel approaches, when combined with antibiotics, have the potential to enhance patient outcomes, particularly in conditions prone to sepsis, while minimizing risks associated with antibiotic resistance and immune suppression.

Effect of Xylitol on Inhibition and Eradication of Pseudomonas aeruginosa PAO1 and Methicillin-Resistant Staphylococcus aureus Biofilms in an Alginate Bead Model

Biofilms formed by Pseudomonas aeruginosa and Staphylococcus aureus, along with their antibiotic tolerance have posed challenges to treatment strategies for lung, wound, and other infections, particularly when co-infecting. In the present study, the inhibitory effect of xylitol on biofilm formation, as well as its eradication potential on pre-established biofilms formed by P. aeruginosa strain PAO1, methicillin-resistant S. aureus, and a mix of both species in an alginate bead model were tested. Xylitol concentrations of 2, 1, and 0.5 M reduced biofilm formation by P. aeruginosa strain PAO1, methicillin-resistant S. aureus, and the mixed-species biofilm in a concentration-dependent manner. Additionally, biofilms formed by these species were subjected to treatment with xylitol. Xylitol was also capable of eradicating biofilms established by P. aeruginosa strain PAO1, methicillin-resistant S. aureus, and the mixed-species biofilm by at least 20%, with the most effective eradication observed for P. aeruginosa strain PAO1. The present study indicates the effectiveness of xylitol as both an inhibitory and eradicating agent against biofilms formed by P. aeruginosa strain PAO1, methicillin-resistant S. aureus, and a mix of both species in an alginate bead model, which mimics the in vivo characteristics of P. aeruginosa aggregates.

Enhancing the antimicrobial activity of silver nanoparticles against pathogenic bacteria by using Pelargonium sidoides DC extract in microwave assisted green synthesis

This study presents an optimized microwave-assisted method for the green synthesis of silver nanoparticles (AgNPs) using a root extract obtained from Pelargonium sidoides DC. The influence of temperature, reagent concentration, and irradiation time was systematically investigated to enhance synthesis yield. Characterization techniques including XRD, UV-vis, FTIR, XPS, and zetametry were employed to confirm the successful formation of nanoparticles with a metallic silver core (∼17 nm) functionalized with organic molecules derived from the plant extract. The cytotoxicity of AgNPs was assessed using a cell viability assay, while the Minimum Inhibitory Concentration (MIC) of nanoformulation against pathogenic bacteria, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and the carbapenem-resistant Klebsiella pneumoniae (KPC), was determined using the Broth microdilution method. The nanoformulation synthesized with P. sidoides extract exhibited a dose-dependent response, demonstrating superior antimicrobial efficacy compared to the pure plant extract in most cases. The MIC values ranged from 0.85 to 17.1 μg mL-1, with particularly strong performance against the drug resistant KPC strain. The enhanced antimicrobial effect is attributed to the synergistic action of the metallic silver core and phytochemicals from P. sidoides on the surface of nanoparticles, which also contribute to notable colloidal stability of AgNPs at physiological pH levels.

Phage Therapy in a Burn Patient Colonized with Extensively Drug-Resistant Pseudomonas aeruginosa Responsible for Relapsing Ventilator-Associated Pneumonia and Bacteriemia

Pseudomonas aeruginosa is one of the main causes of healthcare-associated infection in Europe that increases patient morbidity and mortality. Multi-resistant pathogens are a major public health issue in burn centers. Mortality increases when the initial antibiotic treatment is inappropriate, especially if the patient is infected with P. aeruginosa strains that are resistant to many antibiotics. Phage therapy is an emerging option to treat severe P. aeruginosa infections. It involves using natural viruses called bacteriophages, which have the ability to infect, replicate, and, theoretically, destroy the P. aeruginosa population in an infected patient. We report here the case of a severely burned patient who experienced relapsing ventilator-associated pneumonia associated with skin graft infection and bacteremia due to extensively drug-resistant P. aeruginosa. The patient was successfully treated with personalized nebulized and intravenous phage therapy in combination with immunostimulation (interferon-γ) and last-resort antimicrobial therapy (imipenem-relebactam).