Impact of sub-inhibitory antibiotics on fibronectin-mediated host cell adhesion and invasion by Staphylococcus aureus

<p>Abstract</p> <p>Background</p> <p><it>Staphylococcus aureus </it>is a well-armed pathogen prevalent in severe infections such as endocarditis and osteomyelitis. Fibronectin-binding proteins A and B, encoded by <it>fnb</it>A/B, are major pathogenesis determinants in these infections through their involvement in <it>S. aureus </it>adhesion to and invasion of host cells. Sub-minimum inhibitory concentrations (sub-MICs) of antibiotics, frequently occurring <it>in vivo </it>because of impaired drug diffusion at the infection site, can alter <it>S. aureus </it>phenotype. We therefore investigated their impact on <it>S. aureus </it>fibronectin-mediated adhesiveness and invasiveness.</p> <p>Methods</p> <p>After <it>in vitro </it>challenge of <it>S. aureus </it>8325-4 and clinical isolates with sub-MICs of major anti-staphylococcal agents, we explored <it>fnb</it>A/B transcription levels, bacterial adhesiveness to immobilised human fibronectin and human osteoblasts in culture, and bacterial invasion of human osteoblasts.</p> <p>Results</p> <p>Oxacillin, moxifloxacin and linezolid led to the development of a hyper-adhesive phenotype in the fibronectin adhesion assay that was consistent with an increase in <it>fnb</it>A/B transcription. Conversely, rifampin treatment decreased fibronectin binding in all strains tested without affecting <it>fnb</it>A/B transcription. Gentamicin and vancomycin had no impact on fibronectin binding or <it>fnb</it>A/B transcription levels. Only oxacillin-treated <it>S. aureus </it>displayed a significantly increased adhesion to cultured osteoblasts, but its invasiveness did not differ from that of untreated controls.</p> <p>Conclusion</p> <p>Our findings demonstrate that several antibiotics at sub-MICs modulate fibronectin binding in <it>S. aureus </it>in a drug-specific fashion. However, hyper- and hypo- adhesive phenotypes observed in controlled <it>in vitro </it>conditions were not fully confirmed in whole cell infection assays. The relevance of adhesion modulation during <it>in vivo </it>infections is thus still uncertain and requires further investigations.</p

Multicentre testing of the EUCAST broth microdilution reference method for MIC determination on mycobacterium tuberculosis

Objectives: the first objective of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) subcommittee for antimycobacterial susceptibility testing (AMST), launched in 2016, was to set a reference method for determining the MICs of antituberculous agents, since many protocols are used worldwide and a consensus one is needed for the determination of microbiological breakpoints. Methods: during 2017 and 2018, MIC determination protocols were evaluated prospectively in a multicentre study within the four AMST laboratories. MIC results were obtained for isoniazid, levofloxacin and amikacin on the reference strain Mycobacterium tuberculosis H37Rv ATCC 27294. Broth microdilution (BMD) in Middlebrook 7H9 and solid medium dilution (SMD) in Middlebrook 7H10 were performed using two inoculum concentrations. MICs were interpreted with regard to visual and 99% inhibition after 7, 14 or 21 days of incubation for BMD and 21 days for SMD. Results: following the EUCAST reference protocol, intra- and inter-assay agreements were within ±1 MIC dilution for >95% of the observations for the three drugs in both methods. MIC values, presented as MIC mode (range) for BMD and SMD respectively, were: 0.03 (0.015-0.06) mg/L and 0.12 (0.06-0.25) mg/L for isoniazid, 0.25 mg/L (0.25-0.5) and 0.5 mg/L (0.12-0.5) for levofloxacin, and 0.5 mg/L (0.5-1.0) and 0.5 mg/L (0.5-1.0) for amikacin. Conclusions: both SMD and BMD were reproducible and eligible as a reference method for MIC determination of the Mycobacterium tuberculosis complex (MTBC). BMD was finally selected as the EUCAST reference method. From now on it will be used to set epidemiological cut-off values and clinical breakpoints of new and old antituberculous agents

Antimicrobial susceptibility testing of mycobacterium tuberculosis complex isolates - the EUCAST broth microdilution reference method for MIC determination

Scope:Several methods are used worldwide for antibiotic susceptibility testing (AST) for theMycobac-terium tuberculosiscomplex (MTBC). The variability in the results obtained with these methods hamperssetting epidemiological cut-off (ECOFF) values and clinical breakpoints according to EUCAST guidelines.Methods for susceptibility testing and determination of the minimal inhibitory concentrations (MICs)need to be standardized for MTBC isolates for old and new agents. Our objective was to establish astandardized reference method for MIC determination for MTBC.Methods:The EUCAST antimycobacterial susceptibility testing subcommittee (AMST) compared pro-tocols of MIC determination with regard to medium, inoculum preparation, antituberculous agentpreparation, incubation, reading of the results and interpretation.Recommendations:The EUCAST reference method of MIC determination for MTBC is the broth micro-dilution method in Middlebrook 7H9-10% OADC medium. Thefinal inoculum is a 105CFU/mL suspension,obtained from a 10 2dilution of a 0.5 McFarland suspension prepared after vortexing bacterial colonieswith glass beads before suspending them in sterile water. The culture is maintained in a U-shaped 96-well polystyrene microtitre sterile plate with a lid incubated at 36 ±1 C. Reading is done using aninverted mirror as soon as the 1:100 diluted control (i.e. 103CFU/mL suspension) shows visual growth.The MIC, expressed in mg/L, is the lowest concentration that inhibits visual growth.MycobacteriumtuberculosisH37Rv ATCC 27294 is used as the reference strain and its targeted MIC values are within therange 0.03e0.12 for isoniazid, 0.12e0.5 for levofloxacin and 0.25e1 mg/L for amikacin.Conclusions:The EUCAST reference method for MTBC was endorsed by EUCAST after public consultationand will from now on be used to define EUCAST ECOFFs and clinical breakpoints. This reference methodis not primarily intended to be used under routine conditions and the AST methods will need to b

Community-Acquired Methicillin-Resistant Staphylococcus aureus Carrying Panton-Valentine Leukocidin Genes: Worldwide Emergence

Infections caused by community-acquired (CA)-methicillin resistant Staphylococcus aureus (MRSA) have been reported worldwide. We assessed whether any common genetic markers existed among 117 CA-MRSA isolates from the United States, France, Switzerland, Australia, New Zealand, and Western Samoa by performing polymerase chain reaction for 24 virulence factors and the methicillin-resistance determinant. The genetic background of the strain was analyzed by pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). The CA-MRSA strains shared a type IV SCCmec cassette and the Panton-Valentine leukocidin locus, whereas the distribution of the other toxin genes was quite specific to the strains from each continent. PFGE and MLST analysis indicated distinct genetic backgrounds associated with each geographic origin, although predominantly restricted to the agr3 background. Within each continent, the genetic background of CA-MRSA strains did not correspond to that of the hospital-acquired MRSA

Rapid detection of Staphylococcus aureus Panton-Valentine leukocidin in clinical specimens by enzyme-linked immunosorbent assay and immunochromatographic tests

10.1128/JCM.02274-09Journal of Clinical Microbiology4841384-139

Novel methodologies for biomarker discovery in atherosclerosis

Identification of subjects at increased risk for cardiovascular events plays a central role in the worldwide efforts to improve prevention, prediction, diagnosis, and prognosis of cardiovascular disease and to decrease the related costs. Despite their high predictive value on population level, traditional risk factors fail to fully predict individual risk. This position paper provides a summary of current vascular biomarkers other than the traditional risk factors with a special focus on the emerging −omics technologies. The definition of biomarkers and the identification and use of classical biomarkers are introduced, and we discuss the limitations of current biomarkers such as high sensitivity C-reactive protein (hsCRP) or N-terminal pro-brain natriuretic peptide (NT-proBNP). This is complemented by circulating plasma biomarkers, including high-density lipoprotein (HDL), and the conceptual shift from HDL cholesterol levels to HDL composition/function for cardiovascular risk assessment. Novel sources for plasma-derived markers include microparticles, microvesicles, and exosomes and their use for current omics-based analytics. Measurement of circulating micro-RNAs, short RNA sequences regulating gene expression, has attracted major interest in the search for novel biomarkers. Also, mass spectrometry and nuclear magnetic resonance spectroscopy have become key complementary technologies in the search for new biomarkers, such as proteomic searches or identification and quantification of small metabolites including lipids (metabolomics and lipidomics). In particular, pro-inflammatory lipid metabolites have gained much interest in the cardiovascular field. Our consensus statement concludes on leads and needs in biomarker research for the near future to improve individual cardiovascular risk predictio

Difference in the Breast Milk Proteome between Allergic and Non-Allergic Mothers

Breastfeeding has been linked to a reduction in the prevalence of allergy and asthma. However, studies on this relationship vary in outcome, which may partly be related to differences in breast milk composition. In particular breast milk composition may differ between allergic and non-allergic mothers. Important components that may be involved are breast milk proteins, as these are known to regulate immune development in the newborn. The objective of this study was therefore to explore differences in the proteins of breast milk from 20 allergic and non-allergic mothers. The results from this comparison may then be used to generate hypotheses on proteins associated with allergy in their offspring.Milk samples from allergic and non-allergic mothers were obtained from the PIAMA project, a prospective birth cohort study on incidence, risk factors, and prevention of asthma and inhalant allergy. Non-targeted proteomics technology, based on liquid chromatography and mass spectrometry, was used to compare breast milk from allergic and non-allergic mothers.Nineteen proteins, out of a total of 364 proteins identified in both groups, differed significantly in concentration between the breast milk of allergic and non-allergic mothers. Protease inhibitors and apolipoproteins were present in much higher concentrations in breast milk of allergic than non-allergic mothers. These proteins have been suggested to be linked to allergy and asthma.The non-targeted milk proteomic analysis employed has provided new targets for future studies on the relation between breast milk composition and allergy

A genome-wide association study follow-up suggests a possible role for PPARG in systemic sclerosis susceptibility

Introduction: A recent genome-wide association study (GWAS) comprising a French cohort of systemic sclerosis (SSc) reported several non-HLA single-nucleotide polymorphisms (SNPs) showing a nominal association in the discovery phase. We aimed to identify previously overlooked susceptibility variants by using a follow-up strategy.&lt;p&gt;&lt;/p&gt; Methods: Sixty-six non-HLA SNPs showing a P value &#60;10-4 in the discovery phase of the French SSc GWAS were analyzed in the first step of this study, performing a meta-analysis that combined data from the two published SSc GWASs. A total of 2,921 SSc patients and 6,963 healthy controls were included in this first phase. Two SNPs, PPARG rs310746 and CHRNA9 rs6832151, were selected for genotyping in the replication cohort (1,068 SSc patients and 6,762 healthy controls) based on the results of the first step. Genotyping was performed by using TaqMan SNP genotyping assays. Results: We observed nominal associations for both PPARG rs310746 (PMH = 1.90 × 10-6, OR, 1.28) and CHRNA9 rs6832151 (PMH = 4.30 × 10-6, OR, 1.17) genetic variants with SSc in the first step of our study. In the replication phase, we observed a trend of association for PPARG rs310746 (P value = 0.066; OR, 1.17). The combined overall Mantel-Haenszel meta-analysis of all the cohorts included in the present study revealed that PPARG rs310746 remained associated with SSc with a nominal non-genome-wide significant P value (PMH = 5.00 × 10-7; OR, 1.25). No evidence of association was observed for CHRNA9 rs6832151 either in the replication phase or in the overall pooled analysis.&lt;p&gt;&lt;/p&gt; Conclusion: Our results suggest a role of PPARG gene in the development of SSc

Panton-Valentine Leukocidin Does Play a Role in the Early Stage of Staphylococcus aureus Skin Infections: A Rabbit Model

Despite epidemiological data linking necrotizing skin infections with the production of Panton-Valentine leukocidin (PVL), the contribution of this toxin to the virulence of S. aureus has been highly discussed as a result of inconclusive results of in vivo studies. However, the majority of these results originate from experiments using mice, an animal species which neutrophils - the major target cells for PVL - are highly insensitive to the action of this leukocidin. In contrast, the rabbit neutrophils have been shown to be as sensitive to PVL action as human cells, making the rabbit a better experimental animal to explore the PVL role. In this study we examined whether PVL contributes to S. aureus pathogenicity by means of a rabbit skin infection model. The rabbits were injected intradermally with 108 cfu of either a PVL positive community-associated methicillin-resistant S. aureus isolate, its isogenic PVL knockout or a PVL complemented knockout strain, and the development of skin lesions was observed. While all strains induced skin infection, the wild type strain produced larger lesions and a higher degree of skin necrosis compared to the PVL knockout strain in the first week after the infection. The PVL expression in the rabbits was indirectly confirmed by a raise in the serum titer of anti-LukS-PV antibodies observed only in the rabbits infected with PVL positive strains. These results indicate that the rabbit model is more suitable for studying the role of PVL in staphylococcal diseases than other animal models. Further, they support the epidemiological link between PVL producing S. aureus strains and necrotizing skin infections

Global Distribution of Panton-Valentine Leukocidin–positive Methicillin-resistant Staphylococcus aureus, 2006

Some formerly continent-specific clones have now spread around the worl