Pseudomonas aeruginosa at the dawn of a post-antibiotic era: clinical significance, resistance mechanisms, novel antibiotics and alternative treatments

Since their discovery, antibiotics have helped treat diseases prior to which many were untreatable, saving millions of lives. However, due to the overuse of antibiotics in medicine and agriculture, the advent of resistant strains of bacteria followed shortly after. The current antibiotic resistance crisis is bringing humanity closer to a post-antibiotic era, when all the advancements made by modern medicine could easily be reversed. Pseudomonas aeruginosa is a Gram-negative, rod-shaped bacterium, ubiquitous owing to its minimal nutritional and growth requirements. P. aeruginosa is one of the pathogens included in the priority list of the WHO, being assessed as critical due to its high antimicrobial resistance, leaving only a few effective treatment options to combat it. As an opportunistic pathogen, P. aeruginosa establishes infection in immunocompromised patients, primarily in hospital settings. In order to initiate infection, it requires several virulence factors that mediate the invasion of the pathogen into host cells. Owing to the multiple resistance mechanisms of P. aeruginosa, it has developed resistance to most classes of antibiotics. Due to its increased resistance, treating P. aeruginosa infections is a great challenge for clinicians. Several β-lactam/β-lactamase combinations have been approved and are available as treatment options, which overall show high efficacy against P. aeruginosa. Moreover, novel antibiotics are currently in development as possible antipseudomonal agents, including a Pseudomonas-specific formulation. In addition, new strategies such as bacteriophage therapy, pyocins or the inhibition of the quorum sensing system are being investigated for the treatment of P. aeruginosa infections.

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Evaluation of different phenotypic tests for detection of metallo-β-lactamases in imipenem-resistant Pseudomonas aeruginosa

Journal of Laboratory Physicians ◽

10.4103/jlp.jlp_118_16 ◽

2017 ◽

Vol 9 (04) ◽

pp. 249-253 ◽

Cited By ~ 5

Author(s):

Rohit Sachdeva ◽

Babita Sharma ◽

Rajni Sharma

Keyword(s):

Pseudomonas Aeruginosa ◽

Large Scale ◽

Wide Spectrum ◽

Carbapenem Resistance ◽

Resistance Mechanisms ◽

Clinical Samples ◽

Resistant Strains ◽

Synergy Test ◽

Phenotypic Tests ◽

Simple Screening

Abstract PURPOSE: Pseudomonas aeruginosa causes a wide spectrum of infections including bacteremia, pneumonia, urinary tract infection, etc., Metallo-beta-lactamase (MBL) producing P. aeruginosa is an emerging threat and cause of concern as they have emerged as one of the most feared resistance mechanisms. This study was designed to know the prevalence of MBL production in P. aeruginosa and to evaluate the four phenotypic tests for detection of MBL production in imipenem-resistant clinical isolates of P. aeruginosa. METHODS: Totally, 800 isolates of P. aeruginosa isolated from various clinical samples were evaluated for carbapenem resistance and MBL production. All imipenem-resistant strains were tested for carabapenemase production by modified Hodge test. Screening for MBL production was done by double-disc synergy test and combined disc test (CDT). Confirmation of MBL production was done by the E-test (Ab BioDisk, Solna, Sweden). RESULTS: Out of the 800 isolates of P. aeruginosa, 250 isolates were found resistant to imipenem. Based on the results of E-test, 147 (18.37%) isolates of P. aeruginosa were positive for MBL production. The CDT has the highest sensitivity and specificity for the detection of MBL production as compared to other tests. CONCLUSION: The results of this study are indicative that MBL production is an important mechanism of carbapenem resistance among P. aeruginosa. Use of simple screening test like CDT will be crucial step toward large-scale monitoring of these emerging resistant determinants. Phenotypic test for MBL production has to be standardized, and all the isolates should be routinely screened for MBL production.

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Mechanisms of Resistance to Ceftolozane/Tazobactam in Pseudomonas aeruginosa: Results of the GERPA Multicenter Study

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01117-20 ◽

2020 ◽

Author(s):

Damien Fournier ◽

Romain Carrière ◽

Maxime Bour ◽

Emilie Grisot ◽

Pauline Triponney ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Hydrolytic Activity ◽

Resistance Mechanisms ◽

Group 3 ◽

High Production ◽

Resistant Strains ◽

Recycling Pathway ◽

French Hospital ◽

Almost All ◽

Moderately Resistant

Resistance mechanisms of Pseudomonas aeruginosa to ceftolozane/tazobactam (C/T) were assessed on a collection of 420 nonredundant strains non-susceptible to ceftazidime (MIC > 8 μg/ml) and/or imipenem (> 4 μg/ml), collected by 36 French hospital laboratories over a one month period (GERPA study). Rates of C/T resistance (MIC > 4/4 μg/ml) were equal to 10% in this population (42/420 strains), and 23.2% among the isolates resistant to both ceftazidime and imipenem (26/112). A first group of 21 strains (50%) was found to harbor various extended-spectrum β-lactamases (1 OXA-14; 2 OXA-19; 1 OXA-35; 1 GES-9; 3 PER-1), carbapenemases (2 GES-5; 1 IMP-8; 8 VIM-2), or both (1 VIM-2/OXA-35; 1 VIM-4/SHV-2a). All the strains of this group belonged to widely distributed epidemic clones (ST111, ST175, CC235, ST244, ST348, ST654), and were highly resistant to almost all the antibiotics tested except colistin. A second group was composed of 16 (38%) isolates moderately resistant to C/T (MIC from 8/4 to 16/4 μg/ml), of which 7 were related to international clones (ST111, ST253, CC274, ST352, ST386). As demonstrated by targeted mass spectrometry, cloxacillin-based inhibition tests and gene blaPDC deletion experiments, this resistance phenotype was correlated to an extremely high production of cephalosporinase PDC. In part accounting for this strong PDC upregulation, genomic analyses revealed the presence of mutations in regulator AmpR (D135N/G in 6 strains) and enzymes of the peptidoglycan recycling pathway such as AmpD, PBP4, and Mpl (9 strains). Finally, all the 5 (12%) remaining C/T resistant strains (group 3) appeared to encode PDC variants with mutations known to improve the hydrolytic activity of the β-lactamase to ceftazidime and C/T (F147L, ΔL223-Y226, E247K, N373I). Collectively, our results highlight the importance of both intrinsic and transferable mechanisms in C/T resistant P. aeruginosa. Which mutational events lead some clinical strains to massively produce the natural cephalosporinase PDC remains incompletely understood.

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PrtR Homeostasis Contributes to Pseudomonas aeruginosa Pathogenesis and Resistance against Ciprofloxacin

Infection and Immunity ◽

10.1128/iai.01388-13 ◽

2014 ◽

Vol 82 (4) ◽

pp. 1638-1647 ◽

Cited By ~ 28

Author(s):

Ziyu Sun ◽

Jing Shi ◽

Chang Liu ◽

Yongxin Jin ◽

Kewei Li ◽

...

Keyword(s):

Gene Expression ◽

Pseudomonas Aeruginosa ◽

Bacterial Colonization ◽

Mrna Level ◽

Sos Response ◽

Opportunistic Pathogen ◽

Host Cells ◽

Chronic Infections ◽

Mobility Shift ◽

Content Type

ABSTRACTPseudomonas aeruginosais an opportunistic pathogen that causes acute and chronic infections in humans. Pyocins are bacteriocins produced byP. aeruginosathat are usually released through lysis of the producer strains. Expression of pyocin genes is negatively regulated by PrtR, which gets cleaved under SOS response, leading to upregulation of pyocin synthetic genes. Previously, we demonstrated that PrtR is required for the expression of type III secretion system (T3SS), which is an important virulence component ofP. aeruginosa. In this study, we demonstrate that mutation inprtRresults in reduced bacterial colonization in a mouse acute pneumonia model. Examination of bacterial and host cells in the bronchoalveolar lavage fluids from infected mice revealed that expression of PrtR is induced by reactive oxygen species (ROS) released by neutrophils. We further demonstrate that treatment with hydrogen peroxide or ciprofloxacin, known to induce the SOS response and pyocin production, resulted in an elevated PrtR mRNA level. Overexpression of PrtR by atacpromoter repressed the endogenousprtRpromoter activity, and electrophoretic mobility shift assay revealed that PrtR binds to its own promoter, suggesting an autorepressive mechanism of regulation. A high level of PrtR expressed from a plasmid resulted in increased T3SS gene expression during infection and higher resistance against ciprofloxacin. Overall, our results suggest that the autorepression of PrtR contributes to the maintenance of a relatively stable level of PrtR, which is permissive to T3SS gene expression in the presence of ROS while increasing bacterial tolerance to stresses, such as ciprofloxacin, by limiting pyocin production.

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Significant differences in type IV pilin allele distribution among Pseudomonas aeruginosa isolates from cystic fibrosis (CF) versus non-CF patients

Microbiology ◽

10.1099/mic.0.26822-0 ◽

2004 ◽

Vol 150 (5) ◽

pp. 1315-1326 ◽

Cited By ~ 101

Author(s):

Julianne V. Kus ◽

Elizabeth Tullis ◽

Dennis G. Cvitkovitch ◽

Lori L. Burrows

Keyword(s):

Cystic Fibrosis ◽

Pseudomonas Aeruginosa ◽

Opportunistic Pathogen ◽

Host Cells ◽

Phylogenetic Groups ◽

Allele Distribution ◽

Specific Pcr ◽

Type Iv ◽

Accessory Genes ◽

Group I

Type IV pili (TFP) are important colonization factors of the opportunistic pathogen Pseudomonas aeruginosa, involved in biofilm formation and attachment to host cells. This study undertook a comprehensive analysis of TFP alleles in more than 290 environmental, clinical, rectal and cystic fibrosis (CF) isolates of P. aeruginosa. Based on the results, a new system of nomenclature is proposed, in which P. aeruginosa TFP are divided into five distinct phylogenetic groups. Each pilin allele is stringently associated with characteristic, distinct accessory genes that allow the identification of the allele by specific PCR. The invariant association of the pilin and accessory genes implies horizontal transfer of the entire locus. Analysis of pilin allele distribution among isolates from various sources revealed a striking bias in the prevalence of isolates with group I pilin genes from CF compared with non-CF human sources (P<0·0001), suggesting this particular pilin type, which can be post-translationally modified by glycosylation via the action of TfpO (PilO), may confer a colonization or persistence advantage in the CF host. This allele was also predominant in paediatric CF isolates (29 of 43; 67·4 %), showing that this bias is apparent early in colonization. Group I pilins were also the most common type found in environmental isolates tested. To the authors' knowledge, this is the first example of a P. aeruginosa virulence factor allele that is strongly associated with CF isolates.

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Syndecan 1 Shedding Contributes to Pseudomonas aeruginosa Sepsis

Infection and Immunity ◽

10.1128/iai.73.12.7914-7921.2005 ◽

2005 ◽

Vol 73 (12) ◽

pp. 7914-7921 ◽

Cited By ~ 45

Author(s):

Allan Haynes ◽

Frank Ruda ◽

Jeffrey Oliver ◽

Abdul N. Hamood ◽

John A. Griswold ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Thermal Injury ◽

Opportunistic Pathogen ◽

Multiple Organ ◽

Innate Immune ◽

Host Cells ◽

Ectodomain Shedding ◽

Systemic Spread ◽

Immunocompromised State ◽

First Time

ABSTRACT The innate immune system is comprised of many components that function coordinately to prevent bacterial sepsis. However, thermal injury suppresses many of these factors, and the opportunistic pathogen Pseudomonas aeruginosa takes advantage of this condition, making it one of the leading causes of morbidity and mortality in the setting of thermal injury. P. aeruginosa is extremely efficient at colonizing burn wounds, spreading systemically, and causing sepsis, which often results in a systemic inflammatory response, multiple-organ failure, and death. The pathogenicity of P. aeruginosa is due to the arsenal of virulence factors produced by the pathogen and the immunocompromised state of the host. Syndecan 1 is a major heparan sulfate proteoglycan present on many host cells involved in thermal injury. Syndecan 1 anchored to the cell surface can be cleaved in a process termed ectodomain shedding. Syndecan 1 shedding results in the release of intact, soluble proteoglycan ectodomains that have diverse roles in innate immunity. Here we show for the first time that thermal injury results in shedding of syndecan 1 from host tissue. Our data show that syndecan 1 null mice are significantly less susceptible to P. aeruginosa infection than their wild-type counterparts, as demonstrated by (i) significantly lower mortality; (ii) absence of systemic spread of P. aeruginosa; and (iii) significant reductions in some proinflammatory cytokines. These results suggest that shed syndecan 1 plays an important role in the pathogenesis of P. aeruginosa infection of thermal injury and that syndecan 1-neutralizing agents may be effective supplements to current P. aeruginosa treatments.

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Inference of the phenotypic resistance profile of Pseudomonas aeruginosa through an interpretative reading of the antibiogram in a pediatric hospital. 2006-2014.

Revista de la Facultad de Medicina ◽

10.15446/revfacmed.v64n3.51770 ◽

2016 ◽

Vol 64 (3) ◽

pp. 409

Author(s):

Juan Jailer Arango ◽

Aura Lucia Leal ◽

Maria Del Pilar Montilla ◽

German Camacho Moreno

Keyword(s):

Pseudomonas Aeruginosa ◽

High Capacity ◽

Pediatric Intensive Care ◽

Opportunistic Pathogen ◽

Resistance Mechanisms ◽

Cross Sectional Study ◽

Cross Sectional ◽

Resistance Phenotype ◽

Phenotypic Resistance ◽

Male Subjects

Introduction: Pseudomonas aeruginosa behaves as an opportunistic pathogen involved in hospital infections, with high capacity to generate resistance to antibiotic treatment. The interpretative reading of the antibiogram makes possible inferring these resistance mechanisms and establishing appropriate antibiotic treatment.Objective: The interpretative reading of the antibiogram seeks to infer the resistance phenotype of P. aeruginosa at Fundación Hospital de la Misericordia (HOMI, by its acronym in Spanish) between 2006 and 2014.Materials and methods: Descriptive cross-sectional study where a search of positive antibiogram reports for P. aeruginosa was performed. The resistance phenotype was deduced based on the interpretative reading of the antibiogram.Results: A sample of 463 positive antibiograms for P. aeruginosa was obtained; these samples were taken from children aged 0 to 17, showing a higher prevalence among infants and toddlers. The antibiograms mainly came from male subjects (62.2%). The most frequent hospitalization services were: PICU —pediatric intensive care unit— (30.2%) and general hospitalization (27.3%). The most common sources of isolation were: blood (24.4%) and urine (23.8%). 11 phenotypes were characterized, being the most common: natural phenotype (63.2%), loss of porin OprD (5.7%) and partial and full AmpC derepression (8.4% and 8.2%, respectively).Conclusion: Isolation of P. aeruginosa at HOMI predominantly shows a natural phenotype. The interpretative reading of the antibiogram allowed inferring 11 phenotypes.

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725. WCK 5222 (Cefepime/Zidebactam): An In Vitro Assessment of Activity Compared with Current Dual-Antibiotic Options Against Multidrug-Resistant Pseudomonas aeruginosa

Open Forum Infectious Diseases ◽

10.1093/ofid/ofz360.793 ◽

2019 ◽

Vol 6 (Supplement_2) ◽

pp. S325-S325

Author(s):

Elias M Mullane ◽

Lindsay M Avery ◽

David P Nicolau

Keyword(s):

Pseudomonas Aeruginosa ◽

Opportunistic Pathogen ◽

Multidrug Resistant ◽

Gradient Diffusion ◽

Resistant Strains ◽

In Vitro Assessment ◽

Poor Outcomes ◽

Resistance Rates ◽

Selection Of

Abstract Background Pseudomonas aeruginosa (PSA) is an opportunistic pathogen known to cause complications in critically ill patients worldwide. In those at risk of infection with multidrug-resistant strains (MDR-PSA), dual antibiotic therapy is often considered. However, this practice may contribute to rising resistance rates and poor outcomes if empirical selection is suboptimal. WCK 5222 (cefepime/zidebactam), a novel β-lactam/β-lactam enhancer, may offer a solution. Methods Minimum inhibitory concentrations (MICs) were determined for WCK 5222, amikacin (AMK), fosfomycin (FOF), cefepime (FEP), ceftolozane/tazobactam (C/T), and meropenem (MEM) against 18 clinical PSA isolates using gradient diffusion strip (GDS) methods. Activities of FEP, C/T, and MEM in combination with AMK and FOF were assessed using GDS for isolates nonsusceptible to the β-lactam (MICs >8 mg/L, >4/4 mg/L, and >2 mg/L, respectively). Synergy was defined as a fractional inhibitory concentration index ≤ 0.5. Instances of restored β-lactam susceptibility when tested in combination were compared with the proportion of WCK 5222 MICs ≤ 8 mg/L. Results WCK 5222 MICs ranged from 2 to 32 mg/L (MIC50, 8 mg/L). Rates of susceptibility were: AMK (67%), FOF (44%, MIC ≤ 64 mg/L), FEP (6%), C/T (33%), MEM (0%). Combinations with C/T most frequently demonstrated synergy (C/T-FOF, 42%; C/T-AMK, 33%) and restored C/T susceptibility was observed in 42% of assessments with FOF and in 50% with AMK. For FEP combinations, synergy was observed in 29% and 18% of assessments with FOF and AMK, respectively, with restored susceptibility in 6% for both combinations. Synergy occurred in 11% and 6% of assessments of MEM with FOF and AMK, respectively, with zero instances of restored susceptibility. In total, β-lactam susceptibility was restored in 14% (13/94) of combinations compared with 78% (14/18) of WCK 5222 MICs ≤ 8 mg/L. Conclusion In a selection of MDR-PSA isolates that included carbapenem- and C/T-resistant strains, WCK 5222 MICs ≤ 8 mg/L (cefepime susceptible) were observed more frequently than restoration of susceptibility in select β-lactams in combination with FOF or AMK. WCK 5222 monotherapy may offer enhanced coverage of MDR-PSA over empirically selected combination therapies. Disclosures All authors: No reported disclosures.

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A new regulator of pathogenicity (bvlR) is required for full virulence and tight microcolony formation in Pseudomonas aeruginosa

Microbiology ◽

10.1099/mic.0.075291-0 ◽

2014 ◽

Vol 160 (7) ◽

pp. 1488-1500 ◽

Cited By ~ 12

Author(s):

Ronan R. McCarthy ◽

Marlies J. Mooij ◽

F. Jerry Reen ◽

Olivier Lesouhaitier ◽

Fergal O’Gara

Keyword(s):

Pseudomonas Aeruginosa ◽

Transcriptional Repression ◽

Transcriptional Regulators ◽

Opportunistic Pathogen ◽

Host Cells ◽

Cell Contact ◽

Virulence Determinants ◽

Surface Attachment ◽

Global Regulators ◽

Virulence Regulator

LysR-type transcriptional regulators (LTTRs) are the most common family of transcriptional regulators found in the opportunistic pathogen Pseudomonas aeruginosa. They are known to regulate a wide variety of virulence determinants and have emerged recently as positive global regulators of pathogenicity in a broad spectrum of important bacterial pathogens. However, in spite of their key role in modulating expression of key virulence determinants underpinning pathogenic traits associated with the process of infection, surprisingly few are found to be transcriptionally altered by contact with host cells. BvlR (PA14_26880) an LTTR of previously unknown function, has been shown to be induced in response to host cell contact, and was therefore investigated for its potential role in virulence. BvlR expression was found to play a pivotal role in the regulation of acute virulence determinants such as type III secretion system and exotoxin A production. BvlR also played a key role in P. aeruginosa pathogenicity within the Caenorhabditis elegans acute model of infection. Loss of BvlR led to an inability to form tight microcolonies, a key step in biofilm formation in the cystic fibrosis lung, although surface attachment was increased. Unusually for LTTRs, BvlR was shown to exert its influence through the transcriptional repression of many genes, including the virulence-associated cupA and alg genes. This highlights the importance of BvlR as a new virulence regulator in P. aeruginosa with a central role in modulating key events in the pathogen–host interactome.

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Exoenzyme Y Contributes to End-Organ Dysfunction Caused by Pseudomonas aeruginosa Pneumonia in Critically Ill Patients: An Exploratory Study

Toxins ◽

10.3390/toxins12060369 ◽

2020 ◽

Vol 12 (6) ◽

pp. 369

Author(s):

Brant M. Wagener ◽

Naseem Anjum ◽

Sarah C. Christiaans ◽

Morgan E. Banks ◽

Jordan C. Parker ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Organ Dysfunction ◽

Virulence Factors ◽

Opportunistic Pathogen ◽

Lavage Fluid ◽

Host Cells ◽

Clinical Isolates ◽

Icu Patients ◽

Edema Factor ◽

Host Infection

Pseudomonas aeruginosa is an opportunistic pathogen that causes pneumonia in immunocompromised and intensive care unit (ICU) patients. During host infection, P. aeruginosa upregulates the type III secretion system (T3SS), which is used to intoxicate host cells with exoenzyme (Exo) virulence factors. Of the four known Exo virulence factors (U, S, T and Y), ExoU has been shown in prior studies to associate with high mortality rates. Preclinical studies have shown that ExoY is an important edema factor in lung infection caused by P. aeruginosa, although its importance in clinical isolates of P. aeruginosa is unknown. We hypothesized that expression of ExoY would be highly prevalent in clinical isolates and would significantly contribute to patient morbidity secondary to P. aeruginosa pneumonia. A single-center, prospective observational study was conducted at the University of Alabama at Birmingham Hospital. Mechanically ventilated ICU patients with a bronchoalveolar lavage fluid culture positive for P. aeruginosa were included. Enrolled patients were followed from ICU admission to discharge and clinical P. aeruginosa isolates were genotyped for the presence of exoenzyme genes. Ninety-nine patients were enrolled in the study. ExoY was present in 93% of P. aeruginosa clinical isolates. Moreover, ExoY alone (ExoY+/ExoU−) was present in 75% of P. aeruginosa isolates, compared to 2% ExoU alone (ExoY−/ExoU+). We found that bacteria isolated from human samples expressed active ExoY and ExoU, and the presence of ExoY in clinical isolates was associated with end-organ dysfunction. This is the first study we are aware of that demonstrates that ExoY is important in clinical outcomes secondary to nosocomial pneumonia.

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Neutron crystallography reveals novel mechanisms used by Pseudomonas aeruginosa for host-cell binding

10.1101/2021.09.24.461693 ◽

2021 ◽

Author(s):

Lukas Gajdos ◽

Matthew P Blakeley ◽

Michael Haertlein ◽

V Trevor Forsyth ◽

Juliette M Devos ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Calcium Ions ◽

Bacterial Infections ◽

Opportunistic Pathogen ◽

Host Cells ◽

Carbohydrate Binding ◽

Hydrogen Atoms ◽

High Affinity ◽

Structural Details ◽

Neutron Crystallography

The opportunistic pathogen Pseudomonas aeruginosa, a major cause of nosocomial infections, uses carbohydrate-binding proteins (lectins) as part of its binding to host cells. The fucose-binding lectin, LecB, displays a unique carbohydrate-binding site that incorporates two closely located calcium ions bridging between the ligand and protein, providing specificity and unusually high affinity. Here, we investigate the mechanisms involved in binding based on neutron crystallography studies of a fully deuterated LecB/fucose/calcium complex. The neutron structure, which includes the positions of all the hydrogen atoms, reveals that the high affinity of binding may be related to the occurrence of a low barrier hydrogen bond induced by the proximity of the two calcium ions, the presence of coordination rings between the sugar, calcium and LecB, and the dynamic behaviour of bridging water molecules at room temperature. These key structural details may assist in the design of anti-adhesive compounds to combat multi-resistance bacterial infections.

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