Pseudomonas aeruginosa:pathogenesis,virulence factors,antibiotic resistance,interaction with host,technology advances and emerging therapeutics

Pseudomonas aeruginosa(P.aeruginosa)is a Gram-negative opportunistic pathogen that infects patients with cystic fibrosis,burn wounds,immunodeficiency,chronic obstructive pulmonary disorder(COPD),cancer,and severe infection requiring ventilation,such as COVID-19.P.aeruginosa is also a widely-used model bacterium for all biological areas.In addition to continued,intense efforts in understanding bacterial pathogenesis of P.aeruginosa including virulence factors(LPS,quorum sensing,two-component systems,6 type secretion systems,outer membrane vesicles(OMVs),CRISPR-Cas and their regulation),rapid progress has been made in further studying host-pathogen interaction,particularly host immune networks involving autophagy,inflammasome,noncoding RNAs,cGAS,etc.Furthermore,numerous technologic advances,such as bioinformatics,metabolomics,scRNA-seq,nanoparticles,drug screening,and phage therapy,have been used to improve our understanding of P.aeruginosa pathogenesis and host defense.Nevertheless,much remains to be uncovered about interactions between P.aeruginosa and host immune responses,including mechanisms of drug resistance by known or unannotated bacterial virulence factors as well as mammalian cell signaling pathways.The widespread use of antibiotics and the slow development of effective antimicrobials present daunting challenges and necessitate new theoretical and practical platforms to screen and develop mechanism-tested novel drugs to treat intractable infections,especially those caused by multi-drug resistance strains.Benefited from has advancing in research tools and technology,dissecting this pathogen’s feature has entered into molecular and mechanistic details as well as dynamic and holistic views.Herein,we comprehensively review the progress and discuss the current status of P.aeruginosa biophysical traits,behaviors,virulence factors,invasive regulators,and host defense patterns against its infection,which point out new directions for future investigation and add to the design of novel and/or alternative therapeutics to combat this clinically significant pathogen.

Discovery of synergistic activity of fluoroquinolones in combination with antimicrobial peptides against clinical polymyxin-resistant Pseudomonas aeruginosa DK2

Polymyxin B(PB),as the last-line of defense against multidrug-resistant Gram-negative bacteria,has caused resistance to P.aeruginosa recently.Fortunately,synergistic treatment could preserve the last class of antibiotics and reduce the emergency of drug resistance.Here,we performed a screen of 970 approved drugs synergized with PB against the P.aeruginosa DK2,which is severely resistant to PB,MIC=512μg/mL.Encouragingly,we found fluoroquinolones could synergy with PB and achieved an obvious reduction in MIC of PB below the clinical susceptible breakpoint(2 μg/mL).Especially,gemifloxacin achieved the highest synergistic effect with PB,leading to a 4096-fold MIC reduction(reduced from512 μg/mL to 0.125 μg/mL).Furthermore,synergistic effect was also observed in the combination of gemifloxacin and colistin.Finally,outer membrane permeabilization assay showed that gemifloxacin could increase the permeability of bacterial cell membranes for P.aeruginosa which partly explained the synergy mechanism.These results indicate that fluoroquinolones represent attractive synergists to address the emerging threat of polymyxin-resistant infections.

Histamine activates HinK to promote the virulence of Pseudomonas aeruginosa

During infections,bacteria stimulate host cells to produce and release histamine,which is a key mediator of vital cellular processes in animals.However,the mechanisms underlying the bacterial cell’s ability to sense and respond to histamine are poorly understood.Herein,we show that HinK,a Lys R-type transcriptional regulator,is required to evoke responses to histamine in Pseudomonas aeruginosa,an important human pathogen.HinK directly binds to and activates the promoter of genes involved in histamine uptake and metabolism,iron acquisition,and Pseudomonas quinolone signal(PQS)biosynthesis.The transcriptional regulatory activity of HinK is induced when histamine is present,and it occurs when HinK binds with imidazole-4-acetic acid(Im AA),a histamine metabolite whose production in P.aeruginosa depends on the HinK-activated histamine uptake and utilization operon hin DAC-pa0222.Importantly,the inactivation of HinK inhibits diverse pathogenic phenotypes of P.aeruginosa.These results suggest that histamine acts as an interkingdom signal and provide insights into the mechanism used by pathogenic bacteria to exploit host regulatory signals to promote virulence.

A novel copper-sensing two-component system for inducing Dsb gene expression in bacteria

In nature, bacteria must sense copper and tightly regulate gene expression to evade copper toxicity. Here,we identify a new copper-responsive two-component system named DsbRS in the important human pathogen Pseudomonas aeruginosa;in this system, DsbS is a sensor histidine kinase, and DsbR, its cognate response regulator, directly induces the transcription of genes involved in protein disulfide bond formation(Dsb)(i.e., the dsbDEG operon and dsbB). In the absence of copper, DsbS acts as a phosphatase toward DsbR, thus blocking the transcription of Dsb genes. In the presence of copper, the metal ion directly binds to the sensor domain of DsbS, and the Cys82 residue plays a critical role in this process. The copperbinding behavior appears to inhibit the phosphatase activity of DsbS, leading to the activation of DsbR.The copper resistance of the dsbRS knock-out mutant is restored by the ectopic expression of the dsbDEG operon, which is a DsbRS major target. Strikingly, cognates of the dsbRS-dsbDEG pair are widely distributed across eubacteria. In addition, a DsbR-binding site, which contains the consensus sequence 5’-TTA-N8-TTAA-3’, is detected in the promoter region of dsbDEG homologs in these species. These findings suggest that the regulation of Dsb genes by DsbRS represents a novel mechanism by which bacterial cells cope with copper stress.