Abstract:Pseudomonas aeruginosa is an opportunistic pathogen that causes severe airway infections in humans. These infections are usually difficult to treat and associated with high mortality rates. While colonizing the human airways, P. aeruginosa could accumulate genetic mutations that often lead to its better adaptability to the host environment. Understanding these evolutionary traits may provide important clues for the development of effective therapies to treat P. aeruginosa infections. In this study, 25 P. aerug… Show more
“…1). The closest genome to the PASGNDM group in the phylogenetic tree is PA_D1 (NZ_CP012585), which belongs to a group of P. aeruginosa strains isolated from ventilator-associated pneumonia patients in China 6 .Fig. 1Phylogenetic tree of PASGNDM345 and PASGNDM699 with 21 P. aeruginosa genomes.…”
Pseudomonas aeruginosa can cause life-threatening infections in immunocompromised patients. The first-line agents to treat P. aeruginosa infections are carbapenems. However, the emergence of carbapenem-resistant P. aeruginosa strains greatly compromised the effectiveness of carbapenem treatment, which makes the surveillance on their spreading and transmission important. Here we characterized the full-length genomes of two carbapenem-resistant P. aeruginosa clinical isolates that are capable of producing New Delhi metallo-β-lactamase-1 (NDM-1). We show that blaNDM-1 is carried by a novel integrative and conjugative element (ICE) ICETn43716385, which also carries the macrolide resistance gene msr(E) and the florfenicol resistance gene floR. By exogenously expressing msr(E) in P. aeruginosa laboratory strains, we show that Msr(E) can abolish azithromycin-mediated quorum sensing inhibition in vitro and anti-Pseudomonas effect in vivo. We conclude that ICEs are important in transmitting carbapenem resistance, and that anti-virulence treatment of P. aeruginosa infections using sub-inhibitory concentrations of macrolides can be challenged by horizontal gene transfer.
“…1). The closest genome to the PASGNDM group in the phylogenetic tree is PA_D1 (NZ_CP012585), which belongs to a group of P. aeruginosa strains isolated from ventilator-associated pneumonia patients in China 6 .Fig. 1Phylogenetic tree of PASGNDM345 and PASGNDM699 with 21 P. aeruginosa genomes.…”
Pseudomonas aeruginosa can cause life-threatening infections in immunocompromised patients. The first-line agents to treat P. aeruginosa infections are carbapenems. However, the emergence of carbapenem-resistant P. aeruginosa strains greatly compromised the effectiveness of carbapenem treatment, which makes the surveillance on their spreading and transmission important. Here we characterized the full-length genomes of two carbapenem-resistant P. aeruginosa clinical isolates that are capable of producing New Delhi metallo-β-lactamase-1 (NDM-1). We show that blaNDM-1 is carried by a novel integrative and conjugative element (ICE) ICETn43716385, which also carries the macrolide resistance gene msr(E) and the florfenicol resistance gene floR. By exogenously expressing msr(E) in P. aeruginosa laboratory strains, we show that Msr(E) can abolish azithromycin-mediated quorum sensing inhibition in vitro and anti-Pseudomonas effect in vivo. We conclude that ICEs are important in transmitting carbapenem resistance, and that anti-virulence treatment of P. aeruginosa infections using sub-inhibitory concentrations of macrolides can be challenged by horizontal gene transfer.
“…Several previous studies reported QS deficiency in antibiotic resistant clinical isolates and attributed the attenuated virulence of the strains to this mechanism, as these mutants are proposed to be social cheaters that exploit shared QS products without incurring metabolic costs to themselves (18-21). However, majority of these studies were based on comparative genomic analysis to identify mutations in the QS system genes, and the identified variations were mainly found in the master QS regulator LasR, including both lasR -null and various lasR point mutations.…”
Section: Discussionmentioning
confidence: 99%
“…These suggest the presence of a fitness trade-off that compromises the pathogenic potentials and virulence of MDR isolates. Several epidemiological survey and molecular evolutionary studies ascribed these phenotypes to quorum sensing (QS) deficiency in these strains (18-21), which is not unexpected since production of many virulence factors, such as exo-proteases, elastase, rhamnolipids, lectin, pyoverdine, pyocyanin, hydrogen cyanide etc. are primarily regulated by QS systems in P. aeruginosa (1).…”
22Pseudomonas aeruginosa is a prevalent and pernicious pathogen equipped with both extraordinary 23 capabilities to infect the host and to develop antimicrobials resistance (AMR). Monitoring the 24 emergence of AMR high risk clones and understanding the interplay of their pathogenicity and 25 antibiotic resistance is of paramount importance to avoid resistance dissemination and to control 26 P. aeruginosa infections. In this study, we report the identification of a multidrug resistant (MDR) 27 P. aeruginosa strain PA154197 isolated from a blood stream infection in Hong Kong. PA154197 28 belongs to a distinctive MLST550 clonal complex shared by two international P. aeruginosa 29 isolates VW0289 and AUS544. Comparative genome and transcriptome analysis with the 30 reference strain PAO1 led to the identification of a variety of genetic variations in antibiotic 31 resistance genes and the hyper-expression of three multidrug efflux pumps MexAB-OprM, 32 MexEF-OprN, and MexGHI-OpmD in PA154197. Unlike many resistant isolates displaying an 33 attenuated virulence, PA154197 produces a significantly high level of the P. aeruginosa major 34 virulence factor pyocyanin (PYO) and displays an uncompromised virulence compared to PAO1. 35 Further analysis revealed that the secondary quorum sensing system Pqs which primarily controls 36 the PYO production is hyper-active in PA154197 independent of the master QS systems Las and 37 Rhl. Together, these investigations disclose a unique, uncoupled QS mediated pathoadaptation 38 mechanism in clinical P. aeruginosa which may account for the high pathogenic potentials and 39 antibiotics resistance in the MDR isolate PA154197. 40 41 Pseudomonas aeruginosa is a ubiquitous Gram-negative pathogen that causes a variety of 42 notorious infections in humans such as ventilator-associated pneumonia, lung infections of cystic 43 fibrosis (CF) patients, burn wound infection, and various sepsis syndromes. It is the second leading 44 cause of hospital-acquired infections and is especially problematic in ICUs, where it is the leading 45 cause of pneumonia among pediatric patients and is responsible for a large number of urinary tract 46 (10% in US and 19% in Europe), blood stream (3% in US and 10% in Europe), eye, ear, nose, and47 throat infections (1-3). Compounding the burden of these infections is the extraordinary capability 48 of the pathogen to develop antibiotic and multidrug resistance (MDR) even during the course of 49 antibiotics therapy. P. aeruginosa is one of the "ESKAPE" (Enterococcus spp., Staphylococcus 50 aureus, Klebsiella spp., Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter 51 spp.) organisms which are recognized by the WHO as an alarming threat to the global public heath 52 associated with antimicrobial resistance (AMR). As a consequence, the diseases outcome of the P. 53 aeruginosa infections is the complex interplay of the pathogen (its pathogenicity and virulence), 54 hospital environments (antibiotic therapies and the emergence of AMR), and the patie...
“…In many different contexts, the gene that encodes one of the key transcriptional regulators involved in QS, lasR , frequently sustains loss-of-function mutations. LasR-defective (LasR-) strains of P. aeruginosa are commonly isolated from the lungs of individuals with CF (10-12) and other pulmonary diseases (13, 14), implanted device infections (5, 15), acute corneal ulcers (16), and the environment (16).…”
1 Pseudomonas aeruginosa strains with loss-of-function mutations in the transcription factor 2 are frequently encountered in the clinic and the environment. Among the characteristics common 3 to LasR-defective (LasR-) strains is increased activity of the transcription factor Anr, relative to 4 their LasR+ counterparts, in low oxygen conditions. One of the Anr-regulated genes that was 5 highly induced in the LasR-strains encoded a putative oxygen-binding hemerythrin encoded by 6 PA14_42860 (PA1673) which we named mhr for microoxic hemerythrin. Purified P. aeruginosa 7 Mhr protein contained the predicted di-iron center and binds oxygen with a Kd of 1 µM. Both Anr 8 and Mhr were necessary for fitness in lasR+ and lasR mutant strains in colony biofilms grown in 9 microoxic conditions, and the effects were more striking in the lasR mutant. Among genes in the 10 Anr regulon, mhr was most closely co-regulated with the Anr-controlled high affinity cytochrome 11 c oxidase genes and in the absence of high affinity cytochrome c oxidase activity, deletion of mhr 12 no longer caused a fitness disadvantage suggesting that Mhr works in concert with microoxic 13 respiration. We demonstrate that Anr and Mhr contribute to LasR-strain fitness even in the 14 normoxic biofilm conditions, and metabolomics data indicate that in a lasR mutant, expression of 15 Anr-regulated mhr leads to differences in metabolism in cells grown on LB and artificial sputum 16 medium. Together these data indicate that increased Anr activity in microoxically-grown lasR 17 mutants confers an advantage in part for its regulation of the O2 binding protein Mhr.
18
Significance
19Pseudomonas aeruginosa, a versatile bacterium that both lives in environmental habitats 20 and causes life-threatening opportunistic infections, uses quorum sensing to coordinate gene 21 expression with cell density. The lasR gene, which encodes a quorum sensing regulator, is often 22 deleteriously mutated in clinical isolates. Interestingly, LasR-strains have high activity of the 23 oxygen-sensitive transcription factor Anr in microoxic conditions. This report identifies and 24 characterizes an Anr-regulated microoxic hemerythrin that reversibly binds oxygen. We showed 25 both anr and mhr are critical to fitness in microoxia, and these genes uniquely benefit LasR-26 strains in normoxia. Our findings enrich our understanding of the success of P. aeruginosa as a 27 pulmonary resident through its propensity to lose LasR functionality in the context of low-oxygen 28 infection environments.
30 31Pseudomonas aeruginosa is a devastating pathogen for healthcare systems worldwide 32 and causes opportunistic infections at multiple body sites that are extremely difficult to treat. P.
33aeruginosa is especially damaging within the context of the genetic disease cystic fibrosis (CF),
34where it establishes chronic infections of the airway and is a major predictor of morbidity and 35 mortality (1, 2). The success of P. aeruginosa in disease is due to a confluence of factors,
36including intrinsic an...
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