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1.
Nat Commun ; 14(1): 1530, 2023 03 18.
Article in English | MEDLINE | ID: mdl-36934086

ABSTRACT

Even in the setting of optimal resuscitation in high-income countries severe sepsis and septic shock have a mortality of 20-40%, with antibiotic resistance dramatically increasing this mortality risk. To develop a reference dataset enabling the identification of common bacterial targets for therapeutic intervention, we applied a standardized genomic, transcriptomic, proteomic and metabolomic technological framework to multiple clinical isolates of four sepsis-causing pathogens: Escherichia coli, Klebsiella pneumoniae species complex, Staphylococcus aureus and Streptococcus pyogenes. Exposure to human serum generated a sepsis molecular signature containing global increases in fatty acid and lipid biosynthesis and metabolism, consistent with cell envelope remodelling and nutrient adaptation for osmoprotection. In addition, acquisition of cholesterol was identified across the bacterial species. This detailed reference dataset has been established as an open resource to support discovery and translational research.


Subject(s)
Sepsis , Staphylococcal Infections , Humans , Anti-Bacterial Agents/therapeutic use , Proteomics , Sepsis/microbiology , Bacteria , Escherichia coli , Klebsiella , Microbial Sensitivity Tests
2.
Nat Commun ; 14(1): 1051, 2023 02 24.
Article in English | MEDLINE | ID: mdl-36828918

ABSTRACT

A new variant of Streptococcus pyogenes serotype M1 (designated 'M1UK') has been reported in the United Kingdom, linked with seasonal scarlet fever surges, marked increase in invasive infections, and exhibiting enhanced expression of the superantigen SpeA. The progenitor S. pyogenes 'M1global' and M1UK clones can be differentiated by 27 SNPs and 4 indels, yet the mechanism for speA upregulation is unknown. Here we investigate the previously unappreciated expansion of M1UK in Australia, now isolated from the majority of serious infections caused by serotype M1 S. pyogenes. M1UK sub-lineages circulating in Australia also contain a novel toxin repertoire associated with epidemic scarlet fever causing S. pyogenes in Asia. A single SNP in the 5' transcriptional leader sequence of the transfer-messenger RNA gene ssrA drives enhanced SpeA superantigen expression as a result of ssrA terminator read-through in the M1UK lineage. This represents a previously unappreciated mechanism of toxin expression and urges enhanced international surveillance.


Subject(s)
Scarlet Fever , Streptococcal Infections , Humans , Streptococcus pyogenes/genetics , Scarlet Fever/epidemiology , Superantigens , Bacterial Proteins/genetics , United Kingdom , Exotoxins/genetics , Mutation , Australia
3.
Antibiotics (Basel) ; 11(4)2022 Mar 25.
Article in English | MEDLINE | ID: mdl-35453201

ABSTRACT

Gram-positive bacteria do not produce lipopolysaccharide as a cell wall component. As such, the polymyxin class of antibiotics, which exert bactericidal activity against Gram-negative pathogens, are ineffective against Gram-positive bacteria. The safe-for-human-use hydroxyquinoline analog ionophore PBT2 has been previously shown to break polymyxin resistance in Gram-negative bacteria, independent of the lipopolysaccharide modification pathways that confer polymyxin resistance. Here, in combination with zinc, PBT2 was shown to break intrinsic polymyxin resistance in Streptococcus pyogenes (Group A Streptococcus; GAS), Staphylococcus aureus (including methicillin-resistant S. aureus), and vancomycin-resistant Enterococcus faecium. Using the globally disseminated M1T1 GAS strain 5448 as a proof of principle model, colistin in the presence of PBT2 + zinc was shown to be bactericidal in activity. Any resistance that did arise imposed a substantial fitness cost. PBT2 + zinc dysregulated GAS metal ion homeostasis, notably decreasing the cellular manganese content. Using a murine model of wound infection, PBT2 in combination with zinc and colistin proved an efficacious treatment against streptococcal skin infection. These findings provide a foundation from which to investigate the utility of PBT2 and next-generation polymyxin antibiotics for the treatment of Gram-positive bacterial infections.

4.
mBio ; 13(1): e0351721, 2022 02 22.
Article in English | MEDLINE | ID: mdl-35012353

ABSTRACT

Acinetobacter baumannii causes high mortality in ventilator-associated pneumonia patients, and antibiotic treatment is compromised by multidrug-resistant strains resistant to ß-lactams, carbapenems, cephalosporins, polymyxins, and tetracyclines. Among COVID-19 patients receiving ventilator support, a multidrug-resistant A. baumannii secondary infection is associated with a 2-fold increase in mortality. Here, we investigated the use of the 8-hydroxyquinoline ionophore PBT2 to break the resistance of A. baumannii to tetracycline class antibiotics. In vitro, the combination of PBT2 and zinc with either tetracycline, doxycycline, or tigecycline was shown to be bactericidal against multidrug-resistant A. baumannii, and any resistance that did arise imposed a fitness cost. PBT2 and zinc disrupted metal ion homeostasis in A. baumannii, increasing cellular zinc and copper while decreasing magnesium accumulation. Using a murine model of pulmonary infection, treatment with PBT2 in combination with tetracycline or tigecycline proved efficacious against multidrug-resistant A. baumannii. These findings suggest that PBT2 may find utility as a resistance breaker to rescue the efficacy of tetracycline-class antibiotics commonly employed to treat multidrug-resistant A. baumannii infections. IMPORTANCE Within intensive care unit settings, multidrug-resistant (MDR) Acinetobacter baumannii is a major cause of ventilator-associated pneumonia, and hospital-associated outbreaks are becoming increasingly widespread. Antibiotic treatment of A. baumannii infection is often compromised by MDR strains resistant to last-resort ß-lactam (e.g., carbapenems), polymyxin, and tetracycline class antibiotics. During the on-going COVID-19 pandemic, secondary bacterial infection by A. baumannii has been associated with a 2-fold increase in COVID-19-related mortality. With a rise in antibiotic resistance and a reduction in new antibiotic discovery, it is imperative to investigate alternative therapeutic regimens that complement the use of current antibiotic treatment strategies. Rescuing the efficacy of existing therapies for the treatment of MDR A. baumannii infection represents a financially viable pathway, reducing time, cost, and risk associated with drug innovation.


Subject(s)
Acinetobacter Infections , Acinetobacter baumannii , COVID-19 , Pneumonia, Ventilator-Associated , Humans , Animals , Mice , Tigecycline/pharmacology , Pneumonia, Ventilator-Associated/drug therapy , Pneumonia, Ventilator-Associated/microbiology , Tetracycline/pharmacology , Pandemics , Acinetobacter Infections/microbiology , Drug Resistance, Multiple, Bacterial , Anti-Bacterial Agents/pharmacology , Carbapenems/pharmacology , beta-Lactams/pharmacology , Microbial Sensitivity Tests , Zinc/pharmacology
5.
Sci Transl Med ; 12(570)2020 11 18.
Article in English | MEDLINE | ID: mdl-33208501

ABSTRACT

The emergence of polymyxin resistance in carbapenem-resistant and extended-spectrum ß-lactamase (ESBL)-producing bacteria is a critical threat to human health, and alternative treatment strategies are urgently required. We investigated the ability of the hydroxyquinoline analog ionophore PBT2 to restore antibiotic sensitivity in polymyxin-resistant, ESBL-producing, carbapenem-resistant Gram-negative human pathogens. PBT2 resensitized Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa to last-resort polymyxin class antibiotics, including the less toxic next-generation polymyxin derivative FADDI-287, in vitro. We were unable to select for mutants resistant to PBT2 + FADDI-287 in polymyxin-resistant E. coli containing a plasmid-borne mcr-1 gene or K. pneumoniae carrying a chromosomal mgrB mutation. Using a highly invasive K. pneumoniae strain engineered for polymyxin resistance through mgrB mutation, we successfully demonstrated the efficacy of PBT2 + polymyxin (colistin or FADDI-287) for the treatment of Gram-negative sepsis in immunocompetent mice. In comparison to polymyxin alone, the combination of PBT2 + polymyxin improved survival and reduced bacterial dissemination to the lungs and spleen of infected mice. These data present a treatment modality to break antibiotic resistance in high-priority polymyxin-resistant Gram-negative pathogens.


Subject(s)
Escherichia coli Proteins , Neurodegenerative Diseases , Pharmaceutical Preparations , Sepsis , Animals , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/therapeutic use , Bacteria , Colistin/pharmacology , Drug Repositioning , Drug Resistance, Bacterial , Drug Resistance, Multiple, Bacterial , Escherichia coli , Escherichia coli Proteins/pharmacology , Klebsiella pneumoniae , Mice , Microbial Sensitivity Tests , Sepsis/drug therapy
6.
J Invest Dermatol ; 139(6): 1284-1293, 2019 06.
Article in English | MEDLINE | ID: mdl-30543898

ABSTRACT

Group A Streptococcus causes severe invasive infections, including necrotizing fasciitis. The expression of an array of virulence factors targeting specific host immune functions impedes successful bacterial clearance. The virulence factor streptococcal DNase Sda1 was previously shown to interfere with the entrapment of bacteria through neutrophil extracellular traps and TLR9 signaling. In this study, we showed that plasmacytoid dendritic cells are recruited to the infected tissue during group A streptococcal necrotizing fasciitis. We found that the streptococcal DNase Sda1 impairs plasmacytoid dendritic cell recruitment by reducing IFN-1 levels at the site of infection. We found that streptococcal DNase Sda1 interferes with stabilization of the DNA by the host molecule HMGB1 protein, which may account for decreased IFN-1 levels at the site of infection.


Subject(s)
Dendritic Cells/immunology , Deoxyribonuclease I/metabolism , Fasciitis, Necrotizing/immunology , Interferon-alpha/immunology , Streptococcal Infections/immunology , A549 Cells , Animals , Biopsy , DNA/metabolism , DNA Fragmentation , Deoxyribonuclease I/immunology , Disease Models, Animal , Fascia/cytology , Fascia/immunology , Fascia/microbiology , Fascia/pathology , Fasciitis, Necrotizing/microbiology , Fasciitis, Necrotizing/pathology , HMGB1 Protein/metabolism , Healthy Volunteers , Humans , Interferon-alpha/metabolism , Mice , Mice, Knockout , Primary Cell Culture , Prospective Studies , Receptor, Interferon alpha-beta/genetics , Skin/cytology , Skin/immunology , Skin/microbiology , Skin/pathology , Streptococcal Infections/microbiology , Streptococcal Infections/pathology , Streptococcus pyogenes/immunology , Streptococcus pyogenes/metabolism
7.
Front Microbiol ; 9: 2927, 2018.
Article in English | MEDLINE | ID: mdl-30538696

ABSTRACT

The increasing number of multidrug-resistant bacteria intensifies the need to develop new antimicrobial agents. Endolysins are bacteriophage-derived enzymes that degrade the bacterial cell wall and hold promise as a new class of highly specific and versatile antimicrobials. One major limitation to the therapeutic use of endolysins is their often short serum circulation half-life, mostly due to kidney excretion and lysosomal degradation. One strategy to increase the half-life of protein drugs is fusion to the albumin-binding domain (ABD). By high-affinity binding to serum albumin, ABD creates a complex with large hydrodynamic volume, reducing kidney excretion and lysosomal degradation. The aim of this study was to investigate the in vitro antibacterial activity and in vivo biodistribution and half-life of an engineered variant of the Staphylococcus aureus phage endolysin LysK. The ABD sequence was introduced at different positions within the enzyme, and lytic activity of each variant was determined in vitro and ex vivo in human serum. Half-life and biodistribution were assessed in vivo by intravenous injection of europium-labeled proteins into C57BL/6 wild-type mice. Our data demonstrates that fusion of the endolysin to ABD improves its serum circulation half-life and reduces its deposition in the kidneys in vivo. The most active construct reduced S. aureus counts in human serum ex vivo by 3 logs within 60 min. We conclude that ABD fusions provide an effective strategy to extend the half-life of antibacterial enzymes, supporting their therapeutic potential for treatment of systemic bacterial infections.

8.
Am J Pathol ; 188(7): 1517-1523, 2018 07.
Article in English | MEDLINE | ID: mdl-29684366

ABSTRACT

Streptococcal necrotizing fasciitis (NF) causes high morbidity and mortality despite state-of-the-art therapy. Low incidence and rapid disease progression, necessitating immediate initiation of therapy, have proven challenging aspects for setting up prospective randomized trials. This has resulted in little therapeutic progress over the past decade. The validation of reliable murine NF models to study both pathogenesis and optimized therapeutic regimens of streptococcal NF are thus essential. In this study, we characterized a murine NF model and compared the pathology with an in-depth tissue analysis of streptococcal NF in patients. We found that the streptococcal murine NF model closely reflected all histologic characteristics encountered in human streptococcal NF. This murine NF model helps understanding of human NF pathology better in a time-dependent manner and will allow studying novel therapeutic options in the future.


Subject(s)
Disease Models, Animal , Fasciitis, Necrotizing/pathology , Streptococcal Infections/pathology , Streptococcus pyogenes/pathogenicity , Adult , Aged , Aged, 80 and over , Animals , Fasciitis, Necrotizing/complications , Fasciitis, Necrotizing/microbiology , Female , Humans , Male , Mice , Mice, Inbred C57BL , Middle Aged , Prognosis , Retrospective Studies , Streptococcal Infections/complications , Streptococcal Infections/microbiology
9.
J Infect Dis ; 217(2): 270-279, 2018 01 04.
Article in English | MEDLINE | ID: mdl-29099935

ABSTRACT

Background: Necrotizing fasciitis (NF) retains a very high mortality rate despite prompt and adequate antibiotic treatment and surgical debridement. Necrotizing fasciitis has recently been associated with Streptococcus dysgalactiae subspecies equisimilis (SDSE). Methods: We investigated the causes of a very severe clinical manifestation of SDSE-NF by assessing both host and pathogen factors. Results: We found a lack of streptokinase-function blocking antibodies in the patient resulting in increased streptokinase-mediated fibrinolysis and bacterial spread. At the same time, the clinical SDSE isolate produced very high levels of streptokinase. Exogenous immunoglobulin Gs (ex-IgGs) efficiently blocked streptokinase-mediated fibrinolysis in vitro, indicating a protective role against the action of streptokinase. In vivo, SDSE infection severity was also attenuated by ex-IgGs in a NF mouse model. Conclusions: These findings illustrate for the first time that the lack of specific antibodies against streptococcal virulence factors, such as streptokinase, may contribute to NF disease severity. This can be counteracted by ex-IgGs.


Subject(s)
Antibodies, Bacterial/immunology , Fasciitis, Necrotizing/pathology , Streptococcal Infections/pathology , Streptococcus/pathogenicity , Streptokinase/antagonists & inhibitors , Virulence Factors/antagonists & inhibitors , Adult , Animals , Fasciitis, Necrotizing/microbiology , Female , Fibrinolytic Agents/immunology , Fibrinolytic Agents/metabolism , Host-Pathogen Interactions , Humans , Mice, Inbred C57BL , Streptococcal Infections/microbiology , Streptococcus/immunology , Streptokinase/immunology , Virulence Factors/immunology
10.
J Infect Dis ; 215(2): 269-277, 2017 01 15.
Article in English | MEDLINE | ID: mdl-27247345

ABSTRACT

Group A Streptococcus (GAS) has acquired an arsenal of virulence factors, promoting life-threatening invasive infections such as necrotizing fasciitis. Current therapeutic regimens for necrotizing fasciitis include surgical debridement and treatment with cell wall-active antibiotics. Addition of clindamycin (CLI) is recommended, although clinical evidence is lacking. Reflecting the current clinical dilemma, an observational study showed that only 63% of the patients with severe invasive GAS infection received CLI. This work thus aimed to address whether CLI improves necrotizing fasciitis outcome by modulating virulence factors of CLI-susceptible and CLI-resistant GAS in vitro and in vivo. Treatment with CLI reduced extracellular DNase Sda1 and streptolysin O (SLO) activity in vivo, whereas subinhibitory CLI concentrations induced expression and activity of SLO, DNase, and Streptococcus pyogenes cell envelope protease in vitro. Our in vivo results suggest that CLI should be administered as soon as possible to patients with necrotizing fasciitis, while our in vitro studies emphasize that a high dosage of CLI is essential.


Subject(s)
Anti-Bacterial Agents/pharmacology , Clindamycin/pharmacology , Fasciitis, Necrotizing/drug therapy , Streptococcal Infections/drug therapy , Streptococcus pyogenes/drug effects , Virulence Factors/antagonists & inhibitors , Animals , Anti-Bacterial Agents/administration & dosage , Clindamycin/administration & dosage , Disease Models, Animal , Fasciitis, Necrotizing/microbiology , Female , Humans , Mice, Inbred C57BL , Streptococcal Infections/microbiology , Treatment Outcome
11.
Immunity ; 45(1): 172-84, 2016 07 19.
Article in English | MEDLINE | ID: mdl-27438770

ABSTRACT

Neutrophils are the first immune cells recruited to sites of inflammation and infection. However, patients with allergic disorders such as atopic dermatitis show a paucity of skin neutrophils and are prone to bacterial skin infections, suggesting that allergic inflammation curtails neutrophil responses. Here we have shown that the type 2 cell signature cytokine interleukin-4 (IL-4) hampers neutrophil expansion and migration by antagonizing granulocyte colony-stimulating factor (G-CSF) and chemokine receptor-mediated signals. Cutaneous bacterial infection in mice was exacerbated by IL-4 signaling and improved with IL-4 inhibition, each outcome inversely correlating with neutrophil migration to skin. Likewise, systemic bacterial infection was worsened by heightened IL-4 activity, with IL-4 restricting G-CSF-induced neutrophil expansion and migration to tissues by affecting CXCR2-CXCR4 chemokine signaling in neutrophils. These effects were dependent on IL-4 acting through type 2 IL-4 receptors on neutrophils. Thus, targeting IL-4 might be beneficial in neutropenic conditions with increased susceptibility to bacterial infections.


Subject(s)
Inflammation/immunology , Listeria monocytogenes/physiology , Listeriosis/immunology , Neutrophils/immunology , Receptors, Cell Surface/metabolism , Streptococcal Infections/immunology , Streptococcus pyogenes/physiology , Animals , Bacterial Load , Cell Movement , Cell Proliferation , Cells, Cultured , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Mice, Knockout , Receptors, Cell Surface/genetics , Signal Transduction , Th2 Cells/immunology
12.
J Infect Dis ; 214(2): 321-8, 2016 07 15.
Article in English | MEDLINE | ID: mdl-27338768

ABSTRACT

BACKGROUND: Neutrophils and monocytes are crucial for controlling bacterial infections. More-frequent bacterial infections are accordingly encountered in neutropenic patients undergoing chemotherapy. This is not the case for pegylated interferon α (IFN-α)-induced neutropenia. We hypothesized that IFN-α induces a compensatory innate antibacterial state that prevents bacterial infections despite the neutropenia. METHODS: To investigate whether patients with hepatitis C virus infection treated with IFN-α killed group A Streptococcus (GAS) better than before initiating therapy, whole blood was used to perform ex vivo GAS killing assays before, during, and after IFN-α therapy. RESULTS: We found that IFN-α therapy enhanced GAS killing in whole blood ex vivo despite the decreased neutrophil and monocyte numbers during IFN-α therapy. IFN-α also boosted neutrophil- and monocyte-mediated GAS killing in vitro. Underlying mechanisms included increased production of the antibacterial properdin, a regulator of the complement activation, as well as reactive oxygen species. CONCLUSIONS: These findings help to explain the rather discrepant facts of neutropenia but preserved antibacterial immune defenses in patients treated with IFN-α.


Subject(s)
Immunologic Factors/metabolism , Interferon-alpha/metabolism , Microbial Viability , Neutropenia , Streptococcus pyogenes/immunology , Blood Bactericidal Activity , Hepatitis C/drug therapy , Humans , Immunologic Factors/adverse effects , Interferon-alpha/administration & dosage , Interferon-alpha/adverse effects , Streptococcus pyogenes/physiology
13.
PLoS Pathog ; 11(4): e1004818, 2015 Apr.
Article in English | MEDLINE | ID: mdl-25927232

ABSTRACT

Uropathogenic E. coli (UPEC) is the primary cause of urinary tract infections (UTI) affecting approximately 150 million people worldwide. Here, we revealed the importance of transcriptional regulator hypoxia-inducible factor-1 α subunit (HIF-1α) in innate defense against UPEC-mediated UTI. The effects of AKB-4924, a HIF-1α stabilizing agent, were studied using human uroepithelial cells (5637) and a murine UTI model. UPEC adherence and invasion were significantly reduced in 5637 cells when HIF-1α protein was allowed to accumulate. Uroepithelial cells treated with AKB-4924 also experienced reduced cell death and exfoliation upon UPEC challenge. In vivo, fewer UPEC were recovered from the urine, bladders and kidneys of mice treated transurethrally with AKB-4924, whereas increased bacteria were recovered from bladders of mice with a HIF-1α deletion. Bladders and kidneys of AKB-4924 treated mice developed less inflammation as evidenced by decreased pro-inflammatory cytokine release and neutrophil activity. AKB-4924 impairs infection in uroepithelial cells and bladders, and could be correlated with enhanced production of nitric oxide and antimicrobial peptides cathelicidin and ß-defensin-2. We conclude that HIF-1α transcriptional regulation plays a key role in defense of the urinary tract against UPEC infection, and that pharmacological HIF-1α boosting could be explored further as an adjunctive therapy strategy for serious or recurrent UTI.


Subject(s)
Escherichia coli Infections/metabolism , Hypoxia-Inducible Factor 1, alpha Subunit/metabolism , Immunity, Innate , Urinary Tract Infections/metabolism , Uropathogenic Escherichia coli/immunology , Urothelium/metabolism , Administration, Intravesical , Animals , Anti-Bacterial Agents/administration & dosage , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/therapeutic use , Antimicrobial Cationic Peptides/agonists , Antimicrobial Cationic Peptides/metabolism , Bacterial Adhesion/drug effects , Cell Line , Escherichia coli Infections/immunology , Escherichia coli Infections/microbiology , Escherichia coli Infections/prevention & control , Female , Host-Pathogen Interactions/drug effects , Humans , Hypoxia-Inducible Factor 1, alpha Subunit/agonists , Hypoxia-Inducible Factor 1, alpha Subunit/genetics , Immunity, Innate/drug effects , Mice, Inbred C57BL , Mice, Knockout , Nitric Oxide/agonists , Nitric Oxide/metabolism , Piperazines/administration & dosage , Piperazines/pharmacology , Piperazines/therapeutic use , Protein Stability/drug effects , Pyridones/administration & dosage , Pyridones/pharmacology , Pyridones/therapeutic use , RNA, Messenger/metabolism , Urinary Tract Infections/immunology , Urinary Tract Infections/microbiology , Urinary Tract Infections/prevention & control , Uropathogenic Escherichia coli/drug effects , Urothelium/drug effects , Urothelium/immunology , Urothelium/microbiology
14.
mBio ; 6(2): e00133, 2015 Mar 10.
Article in English | MEDLINE | ID: mdl-25759502

ABSTRACT

UNLABELLED: The M1T1 clone of group A Streptococcus (GAS) is associated with severe invasive infections, including necrotizing fasciitis and septicemia. During invasive M1T1 GAS disease, mutations in the covRS regulatory system led to upregulation of an ADP-ribosyltransferase, SpyA. Surprisingly, a GAS ΔspyA mutant was resistant to killing by macrophages and caused higher mortality with impaired bacterial clearance in a mouse intravenous challenge model. GAS expression of SpyA triggered macrophage cell death in association with caspase-1-dependent interleukin 1ß (IL-1ß) production, and differences between wild-type (WT) and ΔspyA GAS macrophage survival levels were lost in cells lacking caspase-1, NOD-like receptor protein 3 (NLRP3), apoptosis-associated speck-like protein (ASC), or pro-IL-1ß. Similar in vitro findings were identified in macrophage studies performed with pseudomonal exotoxin A, another ADP-ribosylating toxin. Thus, SpyA triggers caspase-1-dependent inflammatory cell death in macrophages, revealing a toxin-triggered IL-1ß-dependent innate immune response pathway critical in defense against invasive bacterial infection. IMPORTANCE: Group A Streptococcus (GAS) is a leading human pathogen capable of producing invasive infections even in healthy individuals. GAS bacteria produce a toxin called SpyA that modifies host proteins through a process called ADP ribosylation. We describe how macrophages, frontline defenders of the host innate immune system, respond to SpyA by undergoing a specialized form of cell death in which they are activated to release the proinflammatory cytokine molecule interleukin 1ß (IL-1ß). Release of IL-1ß activates host immune cell clearance of GAS, as we demonstrated in tissue culture models of macrophage bacterial killing and in vivo mouse infectious-challenge experiments. Similar macrophage responses to a related toxin of Pseudomonas bacteria were also shown. Thus, macrophages recognize certain bacterial toxins to activate a protective immune response in the host.


Subject(s)
ADP Ribose Transferases/immunology , Interleukin-1beta/metabolism , Macrophages/immunology , Macrophages/microbiology , Streptococcus pyogenes/enzymology , Streptococcus pyogenes/immunology , ADP Ribose Transferases/genetics , Animals , Cell Survival , Disease Models, Animal , Gene Deletion , Mice , Streptococcal Infections/immunology , Streptococcal Infections/microbiology , Streptococcus pyogenes/genetics , Virulence
15.
Mol Cell Proteomics ; 13(5): 1262-72, 2014 May.
Article in English | MEDLINE | ID: mdl-24567418

ABSTRACT

Molecular genetic analysis indicates that the problematic human bacterial pathogen methicillin-resistant Staphylococcus aureus possesses more than 2000 open reading frames in its genome. This number of potential gene products, coupled with intrinsic mechanisms of posttranslational modification, endows methicillin-resistant Staphylococcus aureus with a highly complex biochemical repertoire. Recent proteomic and metabolomic advances have provided methodologies to better understand and characterize the biosynthetic factors released by microbial organisms. Here, the emerging tool of mass spectrometry-based molecular networking was used to visualize and map the repertoire of biosynthetic factors produced by a community-associated methicillin-resistant Staphylococcus aureus strain representative of the epidemic USA300 clone. In particular, the study focused on elucidating the complexity of the recently discovered phenol soluble modulin family of peptides when placed under various antibiotic treatment stresses. Novel PSM truncated variant peptides were captured, and the type of variants that were clustered by the molecular networks platform changed in response to the different antibiotic treatment conditions. After discovery, a group of the peptides were selected for functional analysis in vitro. The peptides displayed bioactive properties including the ability to induce proinflammatory responses in human THP-1 monocytes. Additionally, the tested peptides did not display antimicrobial activity as previously reported for other phenol soluble modulin truncated variants. Our findings reveal that the PSM family of peptides are quite structurally diverse, and suggest a single phenol soluble modulin parent peptide can functionally spawn differential bioactivities in response to various external stimuli.


Subject(s)
Anti-Infective Agents/pharmacology , Mass Spectrometry/methods , Methicillin-Resistant Staphylococcus aureus/drug effects , Peptides/metabolism , Phenol/chemistry , Virulence Factors/metabolism , Amino Acid Sequence , Cell Line , Gene Regulatory Networks , Genetic Variation , Humans , Methicillin-Resistant Staphylococcus aureus/metabolism , Monocytes/immunology , Peptides/chemistry , Protein Interaction Maps , Proteomics , Sequence Homology, Amino Acid , Virulence Factors/chemistry
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