Mouse Model Of Skin Infection Research Articles

Discovery of Furanoquinone Derivatives as a Novel Class of DNA Polymerase and Gyrase Inhibitors for MRSA Eradication in Cutaneous Infection.

Methicillin-resistant Staphylococcus aureus (MRSA) is the primary microbe responsible for skin infections that are particularly difficult to eradicate. This study sought to inhibit planktonic and biofilm MRSA using furanoquinone-derived compounds containing imine moiety. A total of 19 furanoquinone analogs were designed, synthesized, and assessed for anti-MRSA potency. Among 19 compounds, (Z)-4-(hydroxyimino)naphtho[1,2-b]furan-5(4H)-one (HNF) and (Z)-4-(acetoxyimino)naphtho[1,2-b]furan-5(4H)-one (ANF) showed antibacterial activity superior to the others based on an agar diffusion assay. HNF and ANF exerted a bactericidal effect with a minimum inhibitory concentration (MIC) of 9.7 ∼ 19.5 and 2.4 ∼ 9.7 μg/ml, respectively. Both compounds were able to reduce the MRSA count by 1,000-fold in biofilm as compared to the control. In vivo efficacy was evaluated using a mouse model of skin infection. Topical application of lead compounds significantly suppressed abscess occurrence and the MRSA burden, and also ameliorated the skin-barrier function. The biochemical assay indicated the compounds’ inhibition of DNA polymerase and gyrase. In silico docking revealed a favorable interaction of the compounds with DNA polymerase and gyrase although the binding was not very strong. The total DNA analysis and proteomic data suggested a greater impairment of some proteins by HNF than ANF. In general, HNF and ANF were similarly potent in MRSA inhibition in vitro and in vivo. The findings demonstrated that there was room for structural modification of furanoquinone compounds that could be used to identify anti-MRSA agent candidates.

Clonal Vγ6+Vδ4+ T cells promote IL-17–mediated immunity against Staphylococcus aureus skin infection

T cell cytokines contribute to immunity against Staphylococcus aureus, but the predominant T cell subsets involved are unclear. In an S. aureus skin infection mouse model, we found that the IL-17 response was mediated by γδ T cells, which trafficked from lymph nodes to the infected skin to induce neutrophil recruitment, proinflammatory cytokines IL-1α, IL-1β, and TNF, and host defense peptides. RNA-seq for TRG and TRD sequences in lymph nodes and skin revealed a single clonotypic expansion of the encoded complementarity-determining region 3 amino acid sequence, which could be generated by canonical nucleotide sequences of TRGV5 or TRGV6 and TRDV4 However, only TRGV6 and TRDV4 but not TRGV5 sequences expanded. Finally, Vγ6+ T cells were a predominant γδ T cell subset that produced IL-17A as well as IL-22, TNF, and IFNγ, indicating a broad and substantial role for clonal Vγ6+Vδ4+ T cells in immunity against S. aureus skin infections.

An aryl isonitrile compound with an improved physicochemical profile that is effective in two mouse models of multidrug-resistant Staphylococcus aureus infection.

The aim of this study was to investigate the antibacterial activity of a synthetic aryl isonitrile compound (35) that was developed as part of a compound library to identify new antibacterial agents effective against methicillin-resistant Staphylococcus aureus (MRSA). Compound 35 was evaluated against MRSA isolates by the broth microdilution assay and for toxicity to mammalian keratinocytes using the MTS assay. A multistep resistance selection assay was conducted to investigate MRSA resistance development to 35. A Caco-2 bidirectional permeability assay was employed to evaluate the ability of 35 to permeate across the gastrointestinal tract, and compound 35 was incubated with human liver microsomes to determine susceptibility to hepatic metabolism. Finally, compound 35 was evaluated in an uncomplicated MRSA skin infection mouse model and an MRSA neutropenic thigh infection mouse model. Compound 35 inhibited the growth of MRSA clinical isolates at 2-4μM and was non-toxic to human keratinocytes. No resistance formation was observed with MRSA against compound 35 after 10 serial passages. In a murine skin wound model, compound 35 significantly reduced the burden of MRSA, similar to the antibiotic fusidic acid. Compound 35 exhibited a marked improvement both in permeability and stability to hepatic metabolism (half-life >11h) relative to the first-generation lead compound. In a neutropenic thigh infection mouse model, compound 35 successfully reduced the burden of MRSA in immunocompromised mice. In summary, compound 35 was identified as a new lead aryl isonitrile compound that warrants further investigation as a novel antibacterial agent.

Delivery of novel vancomycin nanoplexes for combating methicillin resistant Staphylococcus aureus (MRSA) infections

The development of novel antibiotic systems is needed to address the methicillin-resistant Staphylococcus aureus (MRSA) infections. The aim of the study was to explore the novel nanoplex delivery method for vancomycin (VCM) against MRSA using dextran sulfate sodium salt (DXT) as a polyelectrolyte complexing agent. Nanoplexes were formulated by the self-assembling amphiphile polyelectrolyte complexation method and characterized. The size, polydispersity index (PDI), and zeta potential (ZP) of the optimized VCM nanoplexes were 84.6 ± 4.248 nm, 0.449 ± 0.024 and −33.0 ± 4.87 mV respectively, with 90.4 ± 0.77% complexation efficiency (CE %) and 62.3 ± 0.23% drug loading. The in vitro (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)tetrazolium (MTT) studies of the nanoplexes were found to be non-toxic against different mammalian cell lines tested and may confirm its biosafety. While the in vitro drug release studies demonstrated sustained slower release. The in silico study confirmed the spontaneous interaction of VCM with DXT in the presence of sodium chloride. A 6.24-fold enhancement was observed for VCM nanoplexes via in vitro antibacterial studies. Flow-cytometric analysis showed effective cell killing of 67% from VCM nanoplexes compared to 32.98% from the bare vancomycin at the minimum inhibitory concentration (MIC) of 1.25 μg/mL. The in vivo studies using BALB/c mouse skin infection model revealed that nanoplexes reduced MRSA burden by 2.3-folds compared to bare VCM. The novel nanoplexes have potential to be a promising delivery system to combat MRSA infections for improved treatment of bacterial infections.

Efflux pump-mediated resistance to antifungal compounds can be prevented by conjugation with triphenylphosphonium cation

Antifungal resistance due to upregulation of efflux pumps is prevalent in clinical Candida isolates. Potential efflux pump substrates (PEPSs), which are active against strains deficient in efflux pumps but inactive against wild-type strains, are usually missed in routine antifungal screening. Here we present a method for identification of PEPSs, and show that conjugation with mitochondria-targeting triphenylphosphonium cation (TPP+) can enhance or restore the compounds’ antifungal activity. The screening method involves co-culturing a wild-type C. albicans strain and a Cdr efflux pump-deficient strain, labelled with different fluorescent proteins. We identify several PEPSs from a library of natural terpenes, and restore their antifungal activity against wild-type and azole-resistant C. albicans by conjugation with TPP+. The most active conjugate (IS-2-Pi-TPP) kills C. albicans cells, prevents biofilm formation and eliminates preformed biofilms, without inducing significant resistance. The antifungal activity is accompanied by mitochondrial dysfunction and increased levels of intracellular reactive oxygen species. In addition, IS-2-Pi-TPP is effective against C. albicans in a mouse model of skin infection.

Amycomicin is a potent and specific antibiotic discovered with a targeted interaction screen

The rapid emergence of antibiotic-resistant pathogenic bacteria has accelerated the search for new antibiotics. Many clinically used antibacterials were discovered through culturing a single microbial species under nutrient-rich conditions, but in the environment, bacteria constantly encounter poor nutrient conditions and interact with neighboring microbial species. In an effort to recapitulate this environment, we generated a nine-strain actinomycete community and used 16S rDNA sequencing to deconvolute the stochastic production of antimicrobial activity that was not observed from any of the axenic cultures. We subsequently simplified the community to just two strains and identified Amycolatopsis sp. AA4 as the producing strain and Streptomyces coelicolor M145 as an inducing strain. Bioassay-guided isolation identified amycomicin (AMY), a highly modified fatty acid containing an epoxide isonitrile warhead as a potent and specific inhibitor of Staphylococcus aureus Amycomicin targets an essential enzyme (FabH) in fatty acid biosynthesis and reduces S. aureus infection in a mouse skin-infection model. The discovery of AMY demonstrates the utility of screening complex communities against specific targets to discover small-molecule antibiotics.

Identification of Novel Cryptic Multifunctional Antimicrobial Peptides from the Human Stomach Enabled by a Computational–Experimental Platform

Novel approaches are needed to combat antibiotic resistance. Here, we describe a computational-experimental framework for the discovery of novel cryptic antimicrobial peptides (AMPs). The computational platform, based on previously validated antimicrobial scoring functions, indicated the activation peptide of pepsin A, the main human stomach protease, and its N- and C-terminal halves as antimicrobial peptides. The three peptides from pepsinogen A3 isoform were prepared in a recombinant form using a fusion carrier specifically developed to express toxic peptides in Escherichia coli. Recombinant pepsinogen A3-derived peptides proved to be wide-spectrum antimicrobial agents with MIC values in the range 1.56-50 μM (1.56-12.5 μM for the whole activation peptide). Moreover, the activation peptide was bactericidal at pH 3.5 for relevant foodborne pathogens, suggesting that this new class of previously unexplored AMPs may contribute to microbial surveillance within the human stomach. The peptides showed no toxicity toward human cells and exhibited anti-infective activity in vivo, reducing by up to 4 orders of magnitude the bacterial load in a mouse skin infection model. These peptides thus represent a promising new class of antibiotics. We envision that computationally guided data mining approaches such as the one described here will lead to the discovery of antibiotics from previously unexplored sources.

Requirement and Synergistic Contribution of Platelet-Activating Factor Acetylhydrolase Sse and Streptolysin S to Inhibition of Neutrophil Recruitment and Systemic Infection by Hypervirulent emm3 Group A Streptococcus in Subcutaneous Infection of Mice.

Hypervirulent group A streptococcus (GAS) can inhibit neutrophil recruitment and cause systemic infection in a mouse model of skin infection. The purpose of this study was to determine whether platelet-activating factor acetylhydrolase Sse and streptolysin S (SLS) have synergistic contributions to inhibition of neutrophil recruitment and systemic infection in subcutaneous infection of mice by MGAS315, a hypervirulent genotype emm3 GAS strain. Deletion of sse and sagA in MGAS315 synergistically reduced the skin lesion size and GAS burden in the liver and spleen. However, the mutants were persistent at skin sites and had similar growth factors in nonimmune blood. Thus, the low numbers of Δsse ΔsagA mutants in the liver and spleen were likely due to their reduction in the systemic dissemination. Few intact and necrotic neutrophils were detected at MGAS315 infection sites. In contrast, many neutrophils and necrotic cells were present at the edge of Δsse mutant infection sites on day 1 and at the edge of and inside Δsse mutant infection sites on day 2. ΔsagA mutant infection sites had massive numbers of and few intact neutrophils at the edge and center of the infection sites, respectively, on day 1 and were full of intact neutrophils or necrotic cells on day 2. Δsse ΔsagA mutant infection sites had massive numbers of intact neutrophils throughout the whole infection site. These sse and sagA deletion-caused changes in the histological pattern at skin infection sites could be complemented. Thus, the sse and sagA deletions synergistically enhance neutrophil recruitment. These findings indicate that both Sse and SLS are required but that neither is sufficient for inhibition of neutrophil recruitment and systemic infection by hypervirulent GAS.

Interleukin-36\u03b2 provides protection against HSV-1 infection, but does not modulate initiation of adaptive immune responses

Interleukin-36 (IL-36) represents three cytokines, IL-36α, IL-36β and IL-36γ, which bind to the same receptor, IL-1RL2; however, their physiological function(s) remain poorly understood. Here, the role of IL-36 in immunity against HSV-1 was examined using the flank skin infection mouse model. Expression analyses revealed increased levels of IL-36α and IL-36β mRNA in infected skin, while constitutive IL-36γ levels remained largely unchanged. In human keratinocytes, IL-36α mRNA was induced by HSV-1, while IL-1β and TNFα increased all three IL-36 mRNAs. The dominant alternative splice variant of human IL-36β mRNA was isoform 2, which is the ortholog of the known mouse IL-36β mRNA. Mice deficient in IL-36β, but not IL-36α or IL-36γ, succumbed more frequently to HSV-1 infection than wild type mice. Furthermore, IL-36β−/− mice developed larger zosteriform skin lesions along infected neurons. Levels of HSV-1 specific antibodies, CD8+ cells and IFNγ-producing CD4+ cells were statistically equal in wild type and IL-36β−/− mice, suggesting similar initiation of adaptive immunity in the two strains. This correlated with the time at which HSV-1 genome and mRNA levels in primary skin lesions started to decline in both wild type and IL-36β−/− mice. Our data indicate that IL-36β has previously unrecognized functions protective against HSV-1 infection.

Characterization of a PVL-negative community-acquired methicillin-resistant Staphylococcus aureus strain of sequence type 88 in China

Sequence type 88 community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strain SR434, isolated from an outpatient with skin and soft tissue infection, was subjected to whole genome sequencing, antimicrobial susceptibility testing, mouse skin infection model and hemolysis analysis to identify its virulence and resistance determinants. MRSA strain SR434 is resistant to clindamycin, erythromycin and fosfomycin. Four plasmids with resistance genes were identified in this strain, including a 20,658bp blaZ-carrying plasmid, a 2473bp ermC-carrying plasmid, a 2622bp fosB7-carrying plasmid (86% identity with plasmid in a ST2590 MRSA strain) and a 4817bp lnuA-carrying plasmid (99% identity with pLNU4 from bovine coagulase-nagetive Staphylococci). This strain contains staphylococcal cassette chromosome mec type IV and does not contain arginine catabolic mobile element or Panton-Valentine-Leukocidin. SR434 harbors genomic islands νSaα, νSaβ, νSaγ and ΦSa3 and pathogenicity islands νSa2 that carries genes encoding toxic shock syndrome toxin 1, superantigen enterotoxin C and superantigen enterotoxin L. Mouse skin infection model results show that SR434 had similar virulence potential causing invasive skin infection as a PVL-negative epidemic Korea clone HL1 (ST72). CA-MRSA strain of ST88 lineage might be a great concern for its high virulence. PVL has limited contribution to virulence phenotype among this lineage.

Streptococcus pyogenes Endopeptidase O Contributes to Evasion from Complement-mediated Bacteriolysis via Binding to Human Complement Factor C1q

Streptococcus pyogenes secretes various virulence factors for evasion from complement-mediated bacteriolysis. However, full understanding of the molecules possessed by this organism that interact with complement C1q, an initiator of the classical complement pathway, remains elusive. In this study, we identified an endopeptidase of S. pyogenes, PepO, as an interacting molecule, and investigated its effects on complement immunity and pathogenesis. Enzyme-linked immunosorbent assay and surface plasmon resonance analysis findings revealed that S. pyogenes recombinant PepO bound to human C1q in a concentration-dependent manner under physiological conditions. Sites of inflammation are known to have decreased pH levels, thus the effects of PepO on bacterial evasion from complement immunity was analyzed in a low pH condition. Notably, under low pH conditions, PepO exhibited a higher affinity for C1q as compared with IgG, and PepO inhibited the binding of IgG to C1q. In addition, pepO deletion rendered S. pyogenes more susceptible to the bacteriocidal activity of human serum. Also, observations of the morphological features of the pepO mutant strain (ΔpepO) showed damaged irregular surfaces as compared with the wild-type strain (WT). WT-infected tissues exhibited greater severity and lower complement activity as compared with those infected by ΔpepO in a mouse skin infection model. Furthermore, WT infection resulted in a larger accumulation of C1q than that with ΔpepO. Our results suggest that interaction of S. pyogenes PepO with C1q interferes with the complement pathway, which enables S. pyogenes to evade complement-mediated bacteriolysis under acidic conditions, such as seen in inflammatory sites.

CapB2 Expression Is Associated with Staphylococcus aureus Pathogenicity.

CapB2 is recognized as a tyrosine kinase and is likely a vital factor in extracellular polysaccharide synthesis in Staphylococcus aureus, but its pathogenicity function and regulatory mechanism remain obscure. Here, we demonstrate that CapB2 enhances bacterial virulence in a murine model. Mice infected with the wild type SA75 strain exhibited significantly larger (P < 0.05) skin lesions from days 4 to 7 of infection than those challenged with the capB2 mutant strain. The effect on virulence was reverted by restoring the capB2 mutation to the wild type. The related components of the wild type SA75 cell wall in the capB2 mutant strain (SA75ΔcapB2) were thinner than wild type SA75 strain and the capB2 mutant complemented strain (SA75ΔcapB2-C), which was determined by the transmission electron microscopy. The survival percentages of the wild type strain SA75 and SA75ΔcapB2-C were significantly higher relative to SA75ΔcapB2. The results of qRT-PCR studies also indicated that mutations in regulatory gene sarA led to a drastic increase in capB2 gene transcription, with a 326-fold increase of growth at 6 h compared with the wild type strain, suggesting that sarA is a major negative regulator of capB2 expression. Taken together, these results demonstrate that the expression of CapB2 promotes S. aureus virulence in a mouse model of skin infection, and that capB2 gene transcription is regulated negatively by SarA.

Antisense locked nucleic acids targeting agrA inhibit quorum sensing and pathogenesis of community-associated methicillin-resistant Staphylococcus aureus.

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is commonly associated with nonnosocomial skin and soft tissue infections due to its virulence, which is mainly controlled by the accessory gene regulator (agr) quorum sensing (QS) system. In this study (KFF)3 K peptide-conjugated locked nucleic acids (PLNAs) targeting agrA mRNA were developed to inhibit agr activity and arrest the pathogenicity of CA-MRSA. Two PLNAs were designed, and synthesized, after predicting the secondary structure of agrA mRNA. The influence on bacterial growth was tested using a growth curve assay. RT-qPCR, haemolysis assay, lactate dehydrogenase release assay and chemotaxis assay were used to evaluate the effects of the PLNAs on inhibiting agr QS. A mouse skin infection model was employed to test the protective effect of the PLNAs invivo. None of the PLNAs were found to be bacteriostatic or bactericidal invitro. However, one PLNA, PLNA34, showed strong ability to suppress expression of agrA and the effector molecule RNAIII in USA300 LAC strain. Furthermore, PLNA34 inhibited the expression of virulence genes that are upregulated by agr, including hla, psmα, psmβ and pvl. The haemolytic activity of the supernatants from PLNA34-treated bacteria was also dramatically reduced, as well as the capacity to lyse and recruit neutrophils. Moreover, PLNA34 showed high levels of protection in the CA-MRSA mouse skin infection model. The anti-agrA PLNA34 can effectively inhibit the agr QS and suppress CA-MRSA pathogenicity. agrA is a promising target for the development of antisense oligonucleotides to block agr QS.

In vivo antibacterial activity of Garcinia mangostana pericarp extract against methicillin-resistant Staphylococcus aureus in a mouse superficial skin infection model

Context: Garcinia mangostana Linn. (Guttiferae) (GM) pericarp has been shown to exhibit good in vitro antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA); however, there is currently no available information regarding its in vivo antibacterial activity.Objective: To examine in vivo antibacterial activity of G. mangostana extract against MRSA.Materials and methods: GM pericarp was extracted by ethanol (GM-EtOH) and methanol (GM-MeOH). The crude extracts were examined for in vitro antibacterial activity against MRSA using broth microdilution assay. The in vivo antibacterial activity of 10% GM-EtOH against MRSA was determined in a tape stripping mouse model of superficial skin infection for 9 days by evaluating transepidermal water loss (TEWL) and performing colony counts from cultured swabs.Results: GM-EtOH showed greater in vitro activity against MRSA than GM-MeOH in broth microdilution assay with minimum inhibitory concentration 17 versus 20 μg/mL and minimum bactericidal concentration 30 versus 35 μg/mL, respectively. The GM-EtOH (13.20 ± 0.49%) contained α-mangostin more than the GM-MeOH (9.83 ± 0.30%). In the tape stripping mouse model, 10% GM-EtOH reduced the number of MRSA colonies (0–1) recovered from infected wounds (>100 colonies) on the first day of treatment, restored TEWL to normal levels on the fourth day, and had completely healed the wounds by day 9.Conclusion: GM-EtOH showed promising in vivo antibacterial activity against MRSA in a superficial skin infection model in mice. It is of interest to develop a topical formulation of GM-EtOH to further study its potential as a novel antibacterial agent.

K1K8: an Hp1404-derived antibacterial peptide.

As an alternative class of antimicrobial agents used to overcome drug-resistant infections, antimicrobial peptides (AMPs) have recently gained significant attention. In this study, we designed an improved antimicrobial peptide, K1K8, based on the molecular template of Hp1404. Compared to the wild-type Hp1404, K1K8 showed an improved antibacterial spectrum in vitro, a lower hemolytic activity, and an enhanced serum stability. Importantly, K1K8 also decreased methicillin-resistant Staphylococcus aureus (MRSA) bacterial counts in the wounded region in a mouse skin infection model. Interestingly, K1K8 did not induce bacterial resistance or non-specific immune response reactions. Moreover, the peptide killed bacterial cells mainly by disrupting the bacterial membrane. In summary, K1K8 has the potential to be used as an improved anti-infection agent for topical use, which opens an avenue that potential anti-infection drugs may be designed and developed from the molecular templates of AMPs.

An Aromatic Hydroxyamide Attenuates Multiresistant Staphylococcus aureus Toxin Expression.

Methicillin-resistant Staphylococcus aureus (MRSA) causes severe infections with only few effective antibiotic therapies currently available. To approach this challenge, chemical entities with a novel and resistance-free mode of action are desperately needed. Here, we introduce a new hydroxyamide compound that effectively reduces the expression of devastating toxins in various S. aureus and MRSA strains. The molecular mechanism was investigated by transcriptome analysis as well as by affinity-based protein profiling. Down-regulation of several pathogenesis associated genes suggested the inhibition of a central virulence-related pathway. Mass spectrometry-based chemical proteomics revealed putative molecular targets. Systemic treatment with the hydroxyamide showed significant reduction of abscess sizes in a MRSA mouse skin infection model. The absence of resistance development in vitro further underlines the finding that targeting virulence could lead to prolonged therapeutic options in comparison to antibiotics that directly address bacterial survival.

Antibacterial activity and therapeutic efficacy of Fl-P(R)P(R)P(L)-5, a cationic amphiphilic polyproline helix, in a mouse model of staphylococcal skin infection.

The antibacterial activities and therapeutic efficacy of the cationic, unnatural proline-rich peptide Fl-PRPRPL-5 were evaluated against multidrug-resistant Staphylococcus aureus in a mouse model of skin infection. Fl-PRPRPL-5 showed potent activity against all clinical isolates of S. aureus tested, including methicillin- and vancomycin-resistant S. aureus (MRSA and VRSA, respectively). Fl-PRPRPL-5 was also superior in clearing established in vitro biofilms of S. aureus and Staphylococcus epidermidis, compared with the established antimicrobials mupirocin and vancomycin. Additionally, topical treatment of an MRSA-infected wound with Fl-PRPRPL-5 enhanced wound closure and significantly reduced bacterial load. Finally, 0.5% Fl-PRPRPL-5 significantly reduced the levels of the inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1 beta (IL-1β) in wounds induced by MRSA skin infection. In conclusion, the results of this study suggest the potential application of Fl-PRPRPL-5 in the treatment of staphylococcal skin infections.

Strain Specific Phage Treatment for Staphylococcus aureus Infection Is Influenced by Host Immunity and Site of Infection.

The response to multi-drug resistant bacterial infections must be a global priority. While mounting resistance threatens to create what the World Health Organization has termed a “post-antibiotic era”, the recent discovery that antibiotic use may adversely impact the microbiome adds further urgency to the need for new developmental approaches for anti-pathogen treatments. Methicillin-resistant Staphylococcus aureus (MRSA), in particular, has declared itself a serious threat within the United States and abroad. A potential solution to the problem of antibiotic resistance may not entail looking to the future for completely novel treatments, but instead looking into our history of bacteriophage therapy. This study aimed to test the efficacy, safety, and commercial viability of the use of phages to treat Staphylococcus aureus infections using the commercially available phage SATA-8505. We found that SATA-8505 effectively controls S. aureus growth and reduces bacterial viability both in vitro and in a skin infection mouse model. However, this killing effect was not observed when phage was cultured in the presence of human whole blood. SATA-8505 did not induce inflammatory responses in peripheral blood mononuclear cultures. However, phage did induce IFN gamma production in primary human keratinocyte cultures and induced inflammatory responses in our mouse models, particularly in a mouse model of chronic granulomatous disease. Our findings support the potential efficacy of phage therapy, although regulatory and market factors may limit its wider investigation and use.

Plasminogen activation by staphylokinase enhances local spreading of S. aureus in skin infections.

BackgroundStaphylococcus aureus (S. aureus) is a frequent cause of skin and soft tissue infections. A unique feature of S. aureus is the combined presence of coagulases that trigger fibrin formation and of the plasminogen activator staphylokinase (SAK). Whereas the importance of fibrin generation for S. aureus virulence has been established, the role of SAK remains unclear.We studied the role of plasminogen activation by SAK in a skin infection model in mice and evaluated the impact of alpha-2-antiplasmin (α2AP) deficiency on the spreading and proteolytic activity of S. aureus skin infections. The species-selectivity of SAK was overcome by adenoviral expression of human plasminogen. Bacterial spread and density was assessed non-invasively by imaging the bioluminescence of S. aureus Xen36.ResultsSAK-mediated plasmin activity increased the local invasiveness of S. aureus, leading to larger lesions with skin disruption as well as decreased bacterial clearance by the host. Even though fibrin and bacterial surfaces protected SAK-mediated plasmin activity from inhibition by α2AP, the deficiency of α2AP resulted in increased bacterial spreading. SAK-mediated plasmin also induced secondary activation of gelatinases, shown both in vitro and in lesions from the in vivo model.ConclusionSAK contributes to the phenotype of S. aureus skin infections by enhancing bacterial spreading as a result of fibrinolytic and proteolytic activation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-014-0310-7) contains supplementary material, which is available to authorized users.

Sequence-Specific Antibiotics

Modified CRISPR-Cas nucleases target pathogens or resistance genes for sequence-specific destruction.