scholarly journals Iron Depletion Enhances Production of Antimicrobials by Pseudomonas aeruginosa

2015 ◽  
Vol 197 (14) ◽  
pp. 2265-2275 ◽  
Author(s):  
Angela T. Nguyen ◽  
Jace W. Jones ◽  
Max A. Ruge ◽  
Maureen A. Kane ◽  
Amanda G. Oglesby-Sherrouse
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Iron Depletion ◽  
Content Type ◽  
Regulatory Pathways ◽  
Enhanced Production ◽  
Antimicrobial Metabolites ◽  
Polymicrobial Infections

ABSTRACTCystic fibrosis (CF) is a heritable disease characterized by chronic, polymicrobial lung infections. WhileStaphylococcus aureusis the dominant lung pathogen in young CF patients,Pseudomonas aeruginosabecomes predominant by adulthood.P. aeruginosaproduces a variety of antimicrobials that likely contribute to this shift in microbial populations. In particular, secretion of 2-alkyl-4(1H)-quinolones (AQs) contributes to lysis ofS. aureusin coculture, providing an iron source toP. aeruginosabothin vitroandin vivo. We previously showed that production of one such AQ, thePseudomonasquinolone signal (PQS), is enhanced by iron depletion and that this induction is dependent upon the iron-responsive PrrF small RNAs (sRNAs). Here, we demonstrate that antimicrobial activity againstS. aureusduring coculture is also enhanced by iron depletion, and we provide evidence that multiple AQs contribute to this activity. Strikingly, aP. aeruginosaΔprrFmutant, which produces very little PQS in monoculture, was capable of mediating iron-regulated growth suppression ofS. aureus. We show that the presence ofS. aureussuppresses the ΔprrF1,2mutant's defect in iron-regulated PQS production, indicating that a PrrF-independent iron regulatory pathway mediates AQ production in coculture. We further demonstrate that iron-regulated antimicrobial production is conserved in multipleP. aeruginosastrains, including clinical isolates from CF patients. These results demonstrate that iron plays a central role in modulating interactions ofP. aeruginosawithS. aureus. Moreover, our studies suggest that established iron regulatory pathways of these pathogens are significantly altered during polymicrobial infections.IMPORTANCEChronic polymicrobial infections involvingPseudomonas aeruginosaandStaphylococcus aureusare a significant cause of morbidity and mortality, as the interplay between these two organisms exacerbates infection. This is in part due to enhanced production of antimicrobial metabolites byP. aeruginosawhen these two species are cocultured. Using both established and newly developed coculture techniques, this report demonstrates that iron depletion increasesP. aeruginosa's ability to suppress growth ofS. aureus. These findings present a novel role for iron in modulating microbial interaction and provide the basis for understanding how essential nutrients drive polymicrobial infections.

scholarly journals Exogenous Alginate Protects Staphylococcus aureus from Killing by Pseudomonas aeruginosa

2019 ◽  
Vol 202 (8) ◽  
Author(s):  
Courtney E. Price ◽  
Dustin G. Brown ◽  
Dominique H. Limoli ◽  
Vanessa V. Phelan ◽  
George A. O’Toole
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Physical Space ◽  
Late Time ◽  
Protective Effects ◽  
Content Type ◽  
Alginate Production ◽  
The Impact

ABSTRACT Cystic fibrosis (CF) patients chronically infected with both Pseudomonas aeruginosa and Staphylococcus aureus have worse health outcomes than patients who are monoinfected with either P. aeruginosa or S. aureus. We showed previously that mucoid strains of P. aeruginosa can coexist with S. aureus in vitro due to the transcriptional downregulation of several toxic exoproducts typically produced by P. aeruginosa, including siderophores, rhamnolipids, and HQNO (2-heptyl-4-hydroxyquinoline N-oxide). Here, we demonstrate that exogenous alginate protects S. aureus from P. aeruginosa in both planktonic and biofilm coculture models under a variety of nutritional conditions. S. aureus protection in the presence of exogenous alginate is due to the transcriptional downregulation of pvdA, a gene required for the production of the iron-scavenging siderophore pyoverdine as well as the downregulation of the PQS (Pseudomonas quinolone signal) (2-heptyl-3,4-dihydroxyquinoline) quorum sensing system. The impact of exogenous alginate is independent of endogenous alginate production. We further demonstrate that coculture of mucoid P. aeruginosa with nonmucoid P. aeruginosa strains can mitigate the killing of S. aureus by the nonmucoid strain of P. aeruginosa, indicating that the mechanism that we describe here may function in vivo in the context of mixed infections. Finally, we investigated a panel of mucoid clinical isolates that retain the ability to kill S. aureus at late time points and show that each strain has a unique expression profile, indicating that mucoid isolates can overcome the S. aureus-protective effects of mucoidy in a strain-specific manner. IMPORTANCE CF patients are chronically infected by polymicrobial communities. The two dominant bacterial pathogens that infect the lungs of CF patients are P. aeruginosa and S. aureus, with ∼30% of patients coinfected by both species. Such coinfected individuals have worse outcomes than monoinfected patients, and both species persist within the same physical space. A variety of host and environmental factors have been demonstrated to promote P. aeruginosa-S. aureus coexistence, despite evidence that P. aeruginosa kills S. aureus when these organisms are cocultured in vitro. Thus, a better understanding of P. aeruginosa-S. aureus interactions, particularly mechanisms by which these microorganisms are able to coexist in proximal physical space, will lead to better-informed treatments for chronic polymicrobial infections.

scholarly journals Disruption of Cross-Feeding Inhibits Pathogen Growth in the Sputa of Patients with Cystic Fibrosis

mSphere ◽  
2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Jeffrey M. Flynn ◽  
Lydia C. Cameron ◽  
Talia D. Wiggen ◽  
Jordan M. Dunitz ◽  
William R. Harcombe ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Antibiotic Susceptibility ◽  
Susceptibility Testing ◽  
Anaerobic Bacteria ◽  
Content Type ◽  
Growth Environment ◽  
Polymicrobial Infections

ABSTRACT A critical limitation in the management of chronic polymicrobial infections is the lack of correlation between antibiotic susceptibility testing (AST) and patient responses to therapy. Underlying this disconnect is our inability to accurately recapitulate the in vivo environment and complex polymicrobial communities in vitro. However, emerging evidence suggests that, if modeled and tested accurately, interspecies relationships can be exploited by conventional antibiotics predicted to be ineffective by standard AST. As an example, under conditions where Pseudomonas aeruginosa relies on cocolonizing organisms for nutrients (i.e., cross-feeding), multidrug-resistant P. aeruginosa may be indirectly targeted by inhibiting the growth of its metabolic partners. While this has been shown in vitro using synthetic bacterial communities, the efficacy of a “weakest-link” approach to controlling host-associated polymicrobial infections has not yet been demonstrated. To test whether cross-feeding inhibition can be leveraged in clinically relevant contexts, we collected sputa from cystic fibrosis (CF) subjects and used enrichment culturing to isolate both P. aeruginosa and anaerobic bacteria from each sample. Predictably, both subpopulations showed various antibiotic susceptibilities when grown independently. However, when P. aeruginosa was cultured and treated under cooperative conditions in which it was dependent on anaerobic bacteria for nutrients, the growth of both the pathogen and the anaerobe was constrained despite their intrinsic antibiotic resistance profiles. These data demonstrate that the control of complex polymicrobial infections may be achieved by exploiting obligate or facultative interspecies relationships. Toward this end, in vitro susceptibility testing should evolve to more accurately reflect in vivo growth environments and microbial interactions found within them. IMPORTANCE Antibiotic efficacy achieved in vitro correlates poorly with clinical outcomes after treatment of chronic polymicrobial diseases; if a pathogen demonstrates susceptibility to a given antibiotic in the lab, that compound is often ineffective when administered clinically. Conversely, if a pathogen is resistant in vitro, patient treatment with that same compound can elicit a positive response. This discordance suggests that the in vivo growth environment impacts pathogen antibiotic susceptibility. Indeed, here we demonstrate that interspecies relationships among microbiotas in the sputa of cystic fibrosis patients can be targeted to indirectly inhibit the growth of Pseudomonas aeruginosa. The therapeutic implication is that control of chronic lung infections may be achieved by exploiting obligate or facultative relationships among airway bacterial community members. This strategy is particularly relevant for pathogens harboring intrinsic multidrug resistance and is broadly applicable to chronic polymicrobial airway, wound, and intra-abdominal infections.

scholarly journals In Vitro Activity of Rifabutin and Rifampin against Antibiotic-Resistant Acinetobacter baumannii, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae

mSphere ◽  
2021 ◽  
Author(s):  
Bosul Lee ◽  
Jun Yan ◽  
Amber Ulhaq ◽  
Sarah Miller ◽  
Wonjae Seo ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Klebsiella Pneumoniae ◽  
General Effect ◽  
In Vitro Activity ◽  
Antibiotic Resistant ◽  
Content Type

Rifabutin has been recently described as a potential adjunctive therapy for antibiotic-resistant A. baumannii infections due to hypersensitivity in iron-depleted media, which may more closely mimic an in vivo environment. Here, we report that this hyperactivity is specific for A. baumannii , rather than being a general effect for other pathogens.

scholarly journals Staphylococcus aureus Serves as an Iron Source for Pseudomonas aeruginosa during In Vivo Coculture

2005 ◽  
Vol 187 (2) ◽  
pp. 554-566 ◽  
Author(s):  
Lauren M. Mashburn ◽  
Amy M. Jett ◽  
Darrin R. Akins ◽  
Marvin Whiteley
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Pathogenic Bacteria ◽  
Iron Acquisition ◽  
Low Oxygen ◽  
Dialysis Membrane ◽  
Opportunistic Human Pathogen ◽  
The Impact

ABSTRACT Pseudomonas aeruginosa is a gram-negative opportunistic human pathogen often infecting the lungs of individuals with the heritable disease cystic fibrosis and the peritoneum of individuals undergoing continuous ambulatory peritoneal dialysis. Often these infections are not caused by colonization with P. aeruginosa alone but instead by a consortium of pathogenic bacteria. Little is known about growth and persistence of P. aeruginosa in vivo, and less is known about the impact of coinfecting bacteria on P. aeruginosa pathogenesis and physiology. In this study, a rat dialysis membrane peritoneal model was used to evaluate the in vivo transcriptome of P. aeruginosa in monoculture and in coculture with Staphylococcus aureus. Monoculture results indicate that approximately 5% of all P. aeruginosa genes are differentially regulated during growth in vivo compared to in vitro controls. Included in this analysis are genes important for iron acquisition and growth in low-oxygen environments. The presence of S. aureus caused decreased transcription of P. aeruginosa iron-regulated genes during in vivo coculture, indicating that the presence of S. aureus increases usable iron for P. aeruginosa in this environment. We propose a model where P. aeruginosa lyses S. aureus and uses released iron for growth in low-iron environments.

scholarly journals Role of BrnQ1 and BrnQ2 in Branched-Chain Amino Acid Transport and Virulence in Staphylococcus aureus

2014 ◽  
Vol 83 (3) ◽  
pp. 1019-1029 ◽  
Author(s):  
Julienne C. Kaiser ◽  
Sameha Omer ◽  
Jessica R. Sheldon ◽  
Ian Welch ◽  
David E. Heinrichs
Keyword(s):  
Staphylococcus Aureus ◽  
Virulence Gene ◽  
Defined Medium ◽  
Infection Model ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Branched Chain Amino Acid ◽  
Branched Chain

The branched-chain amino acids (BCAAs; Ile, Leu, and Val) not only are important nutrients for the growth ofStaphylococcus aureusbut also are corepressors for CodY, which regulates virulence gene expression, implicating BCAAs as an important link between the metabolic state of the cell and virulence. BCAAs are either synthesized intracellularly or acquired from the environment.S. aureusencodes three putative BCAA transporters, designated BrnQ1, BrnQ2, and BrnQ3; their functions have not yet been formally tested. In this study, we mutated all threebrnQparalogs so as to characterize their substrate specificities and their roles in growthin vitroandin vivo. We demonstrated that in the community-associated, methicillin-resistantS. aureus(CA-MRSA) strain USA300, BrnQ1 is involved in uptake of all three BCAAs, BrnQ2 transports Ile, and BrnQ3 does not have a significant role in BCAA transport under the conditions tested. Of the three, only BrnQ1 is essential for USA300 to grow in a chemically defined medium that is limited for Leu or Val. Interestingly, we observed that abrnQ2mutant grew better than USA300 in media limited for Leu and Val, owing to the fact that this mutation leads to overexpression ofbrnQ1. In a murine infection model, thebrnQ1mutant was attenuated, but in contrast,brnQ2mutants had significantly increased virulence compared to that of USA300, a phenotype we suggest is at least partially linked to enhancedin vivoscavenging of Leu and Val through BrnQ1. These data uncover a hitherto-undiscovered connection between nutrient acquisition and virulence in CA-MRSA.

scholarly journals Evaluation of Antibiotics Active against Methicillin-Resistant Staphylococcus aureus Based on Activity in an Established Biofilm

2016 ◽  
Vol 60 (10) ◽  
pp. 5688-5694 ◽  
Author(s):  
Daniel G. Meeker ◽  
Karen E. Beenken ◽  
Weston B. Mills ◽  
Allister J. Loughran ◽  
Horace J. Spencer ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Biofilm Formation ◽  
Limit Of Detection ◽  
Relative Activity ◽  
Methicillin Resistant ◽  
Content Type ◽  
Comparable Activity ◽  
Antibiotic Delivery

ABSTRACTWe usedin vitroandin vivomodels of catheter-associated biofilm formation to compare the relative activity of antibiotics effective against methicillin-resistantStaphylococcus aureus(MRSA) in the specific context of an established biofilm. The results demonstrated that, underin vitroconditions, daptomycin and ceftaroline exhibited comparable activity relative to each other and greater activity than vancomycin, telavancin, oritavancin, dalbavancin, or tigecycline. This was true when assessed using established biofilms formed by the USA300 methicillin-resistant strain LAC and the USA200 methicillin-sensitive strain UAMS-1. Oxacillin exhibited greater activity against UAMS-1 than LAC, as would be expected, since LAC is an MRSA strain. However, the activity of oxacillin was less than that of daptomycin and ceftaroline even against UAMS-1. Among the lipoglycopeptides, telavancin exhibited the greatest overall activity. Specifically, telavancin exhibited greater activity than oritavancin or dalbavancin when tested against biofilms formed by LAC and was the only lipoglycopeptide capable of reducing the number of viable bacteria below the limit of detection. With biofilms formed by UAMS-1, telavancin and dalbavancin exhibited comparable activity relative to each other and greater activity than oritavancin. Importantly, ceftaroline was the only antibiotic that exhibited greater activity than vancomycin when testedin vivoin a murine model of catheter-associated biofilm formation. These results emphasize the need to consider antibiotics other than vancomycin, most notably, ceftaroline, for the treatment of biofilm-associatedS. aureusinfections, including by the matrix-based antibiotic delivery methods often employed for local antibiotic delivery in the treatment of these infections.

scholarly journals The 5′ NAD Cap of RNAIII Modulates Toxin Production in Staphylococcus aureus Isolates

2019 ◽  
Vol 202 (6) ◽  
Author(s):  
Hector Gabriel Morales-Filloy ◽  
Yaqing Zhang ◽  
Gabriele Nübel ◽  
Shilpa Elizabeth George ◽  
Natalya Korn ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Secondary Structure ◽  
Quorum Sensing ◽  
Opportunistic Pathogen ◽  
Toxin Production ◽  
Dual Function ◽  
Content Type ◽  
The Stability

ABSTRACT Nicotinamide adenosine dinucleotide (NAD) has been found to be covalently attached to the 5′ ends of specific RNAs in many different organisms, but the physiological consequences of this modification are largely unknown. Here, we report the occurrence of several NAD-RNAs in the opportunistic pathogen Staphylococcus aureus. Most prominently, RNAIII, a central quorum-sensing regulator of this bacterium’s physiology, was found to be 5′ NAD capped in a range from 10 to 35%. NAD incorporation efficiency into RNAIII was found to depend in vivo on the −1 position of the P3 promoter. An increase in RNAIII’s NAD content led to a decreased expression of alpha- and delta-toxins, resulting in reduced cytotoxicity of the modified strains. These effects seem to be caused neither by changes in RNAIII’s secondary structure nor by a different translatability upon NAD attachment, as indicated by unaltered patterns in in vitro chemical probing and toeprinting experiments. Even though we did not observe any effect of this modification on RNAIII’s secondary structure or translatability in vitro, additional unidentified factors might account for the modulation of exotoxins in vivo. Ultimately, the study constitutes a step forward in the discovery of new roles of the NAD molecule in bacteria. IMPORTANCE Numerous organisms, including bacteria, are endowed with a 5′ NAD cap in specific RNAs. While the presence of the 5′ NAD cap modulates the stability of the modified RNA species, a significant biological function and phenotype have not been assigned so far. Here, we show the presence of a 5′ NAD cap in RNAIII from S. aureus, a dual-function regulatory RNA involved in quorum-sensing processes and regulation of virulence factor expression. We also demonstrate that altering the natural NAD modification ratio of RNAIII leads to a decrease in exotoxin production, thereby modulating the bacterium’s virulence. Our work unveils a new layer of regulation of RNAIII and the agr system that might be linked to the redox state of the NAD molecule in the cell.

scholarly journals Three-Dimensional In Vitro Staphylococcus aureus Abscess Communities Display Antibiotic Tolerance and Protection from Neutrophil Clearance

2020 ◽  
Vol 88 (11) ◽  
Author(s):  
Marloes I. Hofstee ◽  
Martijn Riool ◽  
Igors Terjajevs ◽  
Keith Thompson ◽  
Martin J. Stoddart ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Immune Cells ◽  
Early Stage ◽  
Three Dimensional ◽  
Collagen Gel ◽  
Maximum Size ◽  
Human Neutrophils ◽  
Content Type

ABSTRACT Staphylococcus aureus is a prominent human pathogen in bone and soft-tissue infections. Pathophysiology involves abscess formation, which consists of central staphylococcal abscess communities (SACs), surrounded by a fibrin pseudocapsule and infiltrating immune cells. Protection against the ingress of immune cells such as neutrophils, or tolerance to antibiotics, remains largely unknown for SACs and is limited by the lack of availability of in vitro models. We describe a three-dimensional in vitro model of SACs grown in a human plasma-supplemented collagen gel. The in vitro SACs reached their maximum size by 24 h and elaborated a fibrin pseudocapsule, as confirmed by electron and immunofluorescence microscopy. The in vitro SACs tolerated 100× the MIC of gentamicin alone and in combination with rifampin, while planktonic controls and mechanically dispersed SACs were efficiently killed. To simulate a host response, SACs were exposed to differentiated PLB-985 neutrophil-like (dPLB) cells and to primary human neutrophils at an early stage of SAC formation or after maturation at 24 h. Both cell types were unable to clear mature in vitro SACs, but dPLB cells prevented SAC growth upon early exposure before pseudocapsule maturation. Neutrophil exposure after plasmin pretreatment of the SACs resulted in a significant decrease in the number of bacteria within the SACs. The in vitro SAC model mimics key in vivo features, offers a new tool to study host-pathogen interactions and drug efficacy assessment, and has revealed the functionality of the S. aureus pseudocapsule in protecting the bacteria from host phagocytic responses and antibiotics.

scholarly journals Characterization of Intracellular Growth RegulatoricgRby Utilizing Transcriptomics To Identify Mediators of Pathogenesis in Shigella flexneri

2013 ◽  
Vol 81 (9) ◽  
pp. 3068-3076 ◽  
Author(s):  
Carolyn R. Morris ◽  
Christen L. Grassel ◽  
Julia C. Redman ◽  
Jason W. Sahl ◽  
Eileen M. Barry ◽  
...  
Keyword(s):  
High Throughput ◽  
High Throughput Sequencing ◽  
Diarrheal Disease ◽  
Intracellular Growth ◽  
Bioinformatics Analyses ◽  
Content Type ◽  
Regulatory Pathways

ABSTRACTShigellaspecies Gram-negative bacteria which cause a diarrheal disease, known as shigellosis, by invading and destroying the colonic mucosa and inducing a robust inflammatory response. With no vaccine available, shigellosis annually kills over 600,000 children in developing countries. This study demonstrates the utility of combining high-throughput bioinformatic methods within vitroandin vivoassays to provide new insights into pathogenesis. Comparisons ofin vivoandin vitrogene expression identified genes associated with intracellular growth. Additional bioinformatics analyses identified genes that are present inS. flexneriisolates but not in the three otherShigellaspecies. Comparison of these two analyses revealed nine genes that are differentially expressed during invasion and that are specific toS. flexneri. One gene, a DeoR family transcriptional regulator with decreased expression during invasion, was further characterized and is now designatedicgR, forintracellulargrowthregulator. Deletion oficgRcaused no difference in growthin vitrobut resulted in increased intracellular replication in HCT-8 cells. Furtherin vitroandin vivostudies using high-throughput sequencing of RNA transcripts (RNA-seq) of an isogenic ΔicgRmutant identified 34 genes that were upregulated under both growth conditions. This combined informatics and functional approach has allowed the characterization of a gene and pathway previously unknown inShigellapathogenesis and provides a framework for further identification of novel virulence factors and regulatory pathways.

Favorable effects in vitro and in vivo of two clinical isolates of Pseudomonas aeruginosa on nutritionally deficient Staphylococcus aureus strains

1973 ◽  
Vol 19 (8) ◽  
pp. 973-981 ◽  
Author(s):  
T. Gadbois ◽  
J. De Repentigny ◽  
L. G. Mathieu
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Peritoneal Cavity ◽  
Pathogenic Bacteria ◽  
Bacterial Species ◽  
Mixed Cultures ◽  
Rabbit Skin ◽  
Metabolic Activities

We have studied aspects of interbacterial ecology with nutritionally dependent Staphylococcus aureus strains; they were grown in association with Pseudomonas aeruginosa in systems of mixed cultures and infections in vitro in a semisynthetic medium and in vivo in mouse peritoneal cavity and rabbit skin. In mixed cultures and in P. aeruginosa culture filtrates, thymine and tryptophan deficiencies in staphylococci were partly overcome. This is probably because P. aeruginosa supplied the essential metabolites required to ensure growth; however, other metabolic activities could also be involved. Other experiments showed that the sensitivity of thymineless staphylococci to nucleoside inhibitions was alleviated. In mixed infections with P. aeruginosa, the S. aureus thymineless strain has shown a greater ability to survive in the peritoneal cavity of mice than when injected alone, even when one species was injected after the other with different doses of bacteria. The examination of the liquid from the peritoneal cavity of infected mice by fluorescence microscopy after fluorochroming with acridine orange or auramine O has revealed that Pseudomonas endotoxin seems to damage leucocytes and consequently reduces the phagocytosis of Staphylococcus cells.Necrosis in rabbit skin was mainly due to S. aureus when both species were injected together intradermally; the thymineless strain was less harmful than the parent strain.It seems that survival and even growth of nutritionally dependent strains of a bacterial species can be favored by the metabolic activities of another species in mixed cultures and infections, in this instance S. aureus by P. aeruginosa. This phenomenon among others could be a determinant of bacterial pathogenicity for nutritionally dependent pathogenic bacteria; thus associated organisms could determine the effective pathogenicity of nutritionally dependent bacteria by contributing essential nutrilites at the site where infection is initiated.

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