RESUMO
Lateral transduction (LT) is the process by which temperate phages mobilize large sections of bacterial genomes. Despite its importance, LT has only been observed during prophage induction. Here, we report that superantigen-carrying staphylococcal pathogenicity islands (SaPIs) employ a related but more versatile and complex mechanism of gene transfer to drive chromosomal hypermobility while self-transferring with additional virulence genes from the host. We found that after phage infection or prophage induction, activated SaPIs form concatamers in the bacterial chromosome by switching between parallel genomic tracks in replication bubbles. This dynamic life cycle enables SaPIbov1 to piggyback its LT of staphylococcal pathogenicity island vSaα, which encodes an array of genes involved in host-pathogen interactions, allowing both islands to be mobilized intact and transferred in a single infective particle. Our findings highlight previously unknown roles of pathogenicity islands in bacterial virulence and show that their evolutionary impact extends beyond the genes they carry.
Assuntos
Ilhas Genômicas , Fagos de Staphylococcus , Staphylococcus , Genoma Bacteriano , Staphylococcus/genética , Staphylococcus/patogenicidade , Virulência , Transdução GenéticaRESUMO
Human activities such as agriculturalization and domestication have led to the emergence of many new pathogens via host-switching events between humans, domesticated and wild animals. Staphylococcus aureus is a multi-host opportunistic pathogen with a global healthcare and economic burden. Recently, it was discovered that laboratory and wild rodents can be colonised and infected with S. aureus, but the origins and zoonotic potential of rodent S. aureus is unknown. In order to trace their evolutionary history, we employed a dataset of 1249 S. aureus genome sequences including 393 of isolates from rodents and other small mammals (including newly determined sequences for 305 isolates from 7 countries). Among laboratory mouse populations, we identified multiple widespread rodent-specific S. aureus clones that likely originated in humans. Phylogeographic analysis of the most common murine lineage CC88 suggests that it emerged in the 1980s in laboratory mouse facilities most likely in North America, from where it spread to institutions around the world, via the distribution of mice for research. In contrast, wild rodents (mice, voles, squirrels) were colonized with a unique complement of S. aureus lineages that are widely disseminated across Europe. In order to investigate the molecular basis for S. aureus adaptation to rodent hosts, genome-wide association analysis was carried out revealing a unique complement of bacteriophages associated with a rodent host ecology. Of note, we identified novel prophages and pathogenicity islands in rodent-derived S. aureus that conferred the potential for coagulation of rodent plasma, a key phenotype of abscess formation and persistence. Our findings highlight the remarkable capacity of S. aureus to expand into new host populations, driven by the acquisition of genes promoting survival in new host-species.
Assuntos
Infecções Estafilocócicas , Staphylococcus aureus , Animais , Staphylococcus aureus/genética , Staphylococcus aureus/virologia , Infecções Estafilocócicas/microbiologia , Infecções Estafilocócicas/veterinária , Camundongos , Roedores/microbiologia , Roedores/virologia , Bacteriófagos/genética , Humanos , Filogenia , Genoma Bacteriano , Fagos de Staphylococcus/genéticaRESUMO
Most new pathogens of humans and animals arise via switching events from distinct host species. However, our understanding of the evolutionary and ecological drivers of successful host adaptation, expansion, and dissemination are limited. Staphylococcus aureus is a major bacterial pathogen of humans and a leading cause of mastitis in dairy cows worldwide. Here we trace the evolutionary history of bovine S. aureus using a global dataset of 10,254 S. aureus genomes including 1,896 bovine isolates from 32 countries in 6 continents. We identified 7 major contemporary endemic clones of S. aureus causing bovine mastitis around the world and traced them back to 4 independent host-jump events from humans that occurred up to 2,500 y ago. Individual clones emerged and underwent clonal expansion from the mid-19th to late 20th century coinciding with the commercialization and industrialization of dairy farming, and older lineages have become globally distributed via established cattle trade links. Importantly, we identified lineage-dependent differences in the frequency of host transmission events between humans and cows in both directions revealing high risk clones threatening veterinary and human health. Finally, pangenome network analysis revealed that some bovine S. aureus lineages contained distinct sets of bovine-associated genes, consistent with multiple trajectories to host adaptation via gene acquisition. Taken together, we have dissected the evolutionary history of a major endemic pathogen of livestock providing a comprehensive temporal, geographic, and gene-level perspective of its remarkable success.
Assuntos
Infecções Estafilocócicas , Staphylococcus aureus , Feminino , Humanos , Bovinos , Animais , Staphylococcus aureus/genética , Gado/genética , Infecções Estafilocócicas/epidemiologia , Infecções Estafilocócicas/veterinária , Infecções Estafilocócicas/genética , Genoma , Especificidade de HospedeiroRESUMO
Polymicrobial infection with Candida albicans and Staphylococcus aureus may result in a concomitant increase in virulence and resistance to antimicrobial drugs. This enhanced pathogenicity phenotype is mediated by numerous factors, including metabolic processes and direct interaction of S. aureus with C. albicans hyphae. The overall structure of biofilms is known to contribute to their recalcitrance to treatment, although the dynamics of direct interaction between species and how it contributes to pathogenicity is poorly understood. To address this, a novel time-lapse mesoscopic optical imaging method was developed to enable the formation of C. albicans/S. aureus whole dual-species biofilms to be followed. It was found that yeast-form or hyphal-form C. albicans in the biofilm founder population profoundly affects the structure of the biofilm as it matures. Different sub-populations of C. albicans and S. aureus arise within each biofilm as a result of the different C. albicans morphotypes, resulting in distinct sub-regions. These data reveal that C. albicans cell morphology is pivotal in the development of global biofilm architecture and the emergence of colony macrostructures and may temporally influence synergy in infection.
Assuntos
Candida albicans , Infecções Estafilocócicas , Hifas , Staphylococcus aureus , Imagem com Lapso de Tempo , BiofilmesRESUMO
Some bacteria can transfer to new host species, and this poses a risk to human health. Indeed, an estimated 60% of all human pathogens have originated from other animal species. Similarly, human-to-animal transitions are recognized as a major threat to sustainable livestock production, and emerging pathogens impose an increasing burden on crop yield and global food security. Recent advances in high-throughput sequencing technologies have enabled comparative genomic analyses of bacterial populations from multiple hosts. Such studies are providing new insights into the evolutionary processes that underpin the establishment of bacteria in new host niches. A better understanding of the genetic and mechanistic basis for bacterial host adaptation may reveal novel targets for controlling infection or inform the design of approaches to limit the emergence of new pathogens.
Assuntos
Adaptação Fisiológica/fisiologia , Bactérias , Fenômenos Fisiológicos Bacterianos , Evolução Biológica , Interações Hospedeiro-Patógeno/fisiologia , Animais , Bactérias/genética , Bactérias/metabolismo , HumanosRESUMO
The emergence of new pathogens is a major threat to public and veterinary health. Changes in bacterial habitat such as a switch in host or disease tropism are typically accompanied by genetic diversification. Staphylococcus aureus is a multi-host bacterial species associated with human and livestock infections. A microaerophilic subspecies, Staphylococcus aureus subsp. anaerobius, is responsible for Morel's disease, a lymphadenitis restricted to sheep and goats. However, the evolutionary history of S. aureus subsp. anaerobius and its relatedness to S. aureus are unknown. Population genomic analyses of clinical S. aureus subsp. anaerobius isolates revealed a highly conserved clone that descended from a S. aureus progenitor about 1000 years ago before differentiating into distinct lineages that contain African and European isolates. S. aureus subsp. anaerobius has undergone limited clonal expansion, with a restricted population size, and an evolutionary rate 10-fold slower than S. aureus. The transition to its current restricted ecological niche involved acquisition of a pathogenicity island encoding a ruminant host-specific effector of abscess formation, large chromosomal re-arrangements, and the accumulation of at least 205 pseudogenes, resulting in a highly fastidious metabolism. Importantly, expansion of ~87 insertion sequences (IS) located largely in intergenic regions provided distinct mechanisms for the control of expression of flanking genes, including a novel mechanism associated with IS-mediated anti-anti-sense decoupling of ancestral gene repression. Our findings reveal the remarkable evolutionary trajectory of a host-restricted bacterial pathogen that resulted from extensive remodelling of the S. aureus genome through an array of diverse mechanisms in parallel.
Assuntos
Genoma Bacteriano/genética , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/genética , Staphylococcus/genética , Animais , Evolução Biológica , Ecossistema , Genômica , Humanos , Gado , Filogenia , Transcriptoma , Sequenciamento Completo do GenomaRESUMO
BACKGROUND: The advent of low cost, high throughput DNA sequencing has led to the availability of thousands of complete genome sequences for a wide variety of bacterial species. Examining and interpreting genetic variation on this scale represents a significant challenge to existing methods of data analysis and visualisation. RESULTS: Starting with the output of standard pangenome analysis tools, we describe the generation and analysis of interactive, 3D network graphs to explore the structure of bacterial populations, the distribution of genes across a population, and the syntenic order in which those genes occur, in the new open-source network analysis platform, Graphia. Both the analysis and the visualisation are scalable to datasets of thousands of genome sequences. CONCLUSIONS: We anticipate that the approaches presented here will be of great utility to the microbial research community, allowing faster, more intuitive, and flexible interaction with pangenome datasets, thereby enhancing interpretation of these complex data.
Assuntos
Genoma Bacteriano , Sequenciamento de Nucleotídeos em Larga Escala , Bactérias/genética , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Análise de Sequência de DNA/métodosRESUMO
Staphylococcus aureus is a leading cause of bovine mastitis worldwide. Despite some improved understanding of disease pathogenesis, progress towards new methods for the control of intramammary infections (IMI) has been limited, particularly in the field of vaccination. Although herd management programs have helped to reduce the number of clinical cases, S. aureus mastitis remains a major disease burden. This review summarizes the past 16 years of research on bovine S. aureus population genetics, and molecular pathogenesis that have been conducted worldwide. We describe the diversity of S. aureus associated with bovine mastitis and the geographical distribution of S. aureus clones in different continents. We also describe studies investigating the evolution of bovine S. aureus and the importance of host-adaptation in its emergence as a mastitis pathogen. The available information on the prevalence of virulence determinants and their functional relevance during the pathogenesis of bovine mastitis are also discussed. Although traits such as biofilm formation and innate immune evasion are critical for the persistence of bacteria, the current understanding of the key host-pathogen interactions that determine the outcome of S. aureus IMI is very limited. We suggest that greater investment in research into the genetic and molecular basis of bovine S. aureus pathogenesis is essential for the identification of novel therapeutic and vaccine targets.
Assuntos
Doenças dos Bovinos , Mastite Bovina , Infecções Estafilocócicas , Animais , Bovinos , Feminino , Mastite Bovina/microbiologia , Infecções Estafilocócicas/microbiologia , Infecções Estafilocócicas/veterinária , Staphylococcus aureus/genética , Fatores de Virulência/genéticaRESUMO
Fibrinogen is an essential part of the blood coagulation cascade and a major component of the extracellular matrix in mammals. The interface between fibrinogen and bacterial pathogens is an important determinant of the outcome of infection. Here, we demonstrate that a canine host-restricted skin pathogen, Staphylococcus pseudintermedius, produces a cell wall-associated protein (SpsL) that has evolved the capacity for high strength binding to canine fibrinogen, with reduced binding to fibrinogen of other mammalian species including humans. Binding occurs via the surface-expressed N2N3 subdomains, of the SpsL A-domain, to multiple sites in the fibrinogen α-chain C-domain by a mechanism analogous to the classical dock, lock, and latch binding model. Host-specific binding is dependent on a tandem repeat region of the fibrinogen α-chain, a region highly divergent between mammals. Of note, we discovered that the tandem repeat region is also polymorphic in different canine breeds suggesting a potential influence on canine host susceptibility to S. pseudintermedius infection. Importantly, the strong host-specific fibrinogen-binding interaction of SpsL to canine fibrinogen is essential for bacterial aggregation and biofilm formation, and promotes resistance to neutrophil phagocytosis, suggesting a key role for the interaction during pathogenesis. Taken together, we have dissected a bacterial surface protein-ligand interaction resulting from the co-evolution of host and pathogen that promotes host-specific innate immune evasion and may contribute to its host-restricted ecology.
Assuntos
Proteínas de Bactérias/imunologia , Biofilmes/crescimento & desenvolvimento , Fibrinogênio/imunologia , Evasão da Resposta Imune , Imunidade Inata , Staphylococcus/fisiologia , Animais , Proteínas de Bactérias/genética , Galinhas , Cães , Fibrinogênio/genética , HumanosRESUMO
Staphylococcus aureus is a major human pathogen and an important cause of livestock infections. The first S. aureus genomes to be published, 15 years ago, provided the first view of genome structure and gene content. Since then, thousands of genomes from a wide array of strains from different sources have been sequenced. Comparison of these sequences has resulted in broad insights into population structure, bacterial evolution, clone emergence and expansion, and the molecular basis of niche adaptation. Furthermore, this information is now being applied clinically in outbreak investigations to inform infection control measures and to determine appropriate treatment regimens. In this review, we summarize some of the broad insights into S. aureus biology gained from the analysis of genomes and discuss future directions and opportunities in this dynamic field of research.
Assuntos
Genoma Bacteriano , Infecções Estafilocócicas/microbiologia , Infecções Estafilocócicas/veterinária , Staphylococcus aureus/genética , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Evolução Molecular , Genômica , Humanos , Gado/microbiologia , Staphylococcus aureus/metabolismo , Fatores de Virulência/genética , Fatores de Virulência/metabolismoRESUMO
Bacterial superantigens (SAgs) cause Vß-dependent T-cell proliferation leading to immune dysregulation associated with the pathogenesis of life-threatening infections such as toxic shock syndrome, and necrotizing pneumonia. Previously, we demonstrated that staphylococcal enterotoxin-like toxin X (SElX) from Staphylococcus aureus is a classical superantigen that exhibits T-cell activation in a Vß-specific manner, and contributes to the pathogenesis of necrotizing pneumonia. Here, we discovered that SElX can also bind to neutrophils from human and other mammalian species and disrupt IgG-mediated phagocytosis. Site-directed mutagenesis of the conserved sialic acid-binding motif of SElX abolished neutrophil binding and phagocytic killing, and revealed multiple glycosylated neutrophil receptors for SElX binding. Furthermore, the neutrophil binding-deficient mutant of SElX retained its capacity for T-cell activation demonstrating that SElX exhibits mechanistically independent activities on distinct cell populations associated with acquired and innate immunity, respectively. Finally, we demonstrated that the neutrophil-binding activity rather than superantigenicity is responsible for the SElX-dependent virulence observed in a necrotizing pneumonia rabbit model of infection. Taken together, we report the first example of a SAg, that can manipulate both the innate and adaptive arms of the human immune system during S. aureus pathogenesis.
Assuntos
Enterotoxinas/metabolismo , Exfoliatinas/farmacologia , Neutrófilos/efeitos dos fármacos , Infecções Estafilocócicas , Superantígenos/farmacologia , Animais , Exfoliatinas/metabolismo , Humanos , Ativação Linfocitária/imunologia , Neutrófilos/imunologia , Coelhos , Receptores de Antígenos de Linfócitos T alfa-beta/imunologia , Staphylococcus aureus/química , Staphylococcus aureus/metabolismo , Superantígenos/imunologiaRESUMO
Evasion of autophagy is key for intracellular survival of bacteria in host cells, but its involvement in persistent infection by Helicobacter pylori, a bacterium identified to invade gastric epithelial cells, remains obscure. The aim of this study was to functionally characterize the role of autophagy in H. pylori infection. Autophagy was assayed in H. pylori-infected human gastric epithelium and the functional role of autophagy was determined via genetic or pharmacological ablation of autophagy in mouse and cell line models of H. pylori infection. Here, we showed that H. pylori inhibited lysosomal function and thereby promoted the accumulation of autophagosomes in gastric epithelial cells. Importantly, inhibiting autophagosome formation by pharmacological inhibitors or genetic ablation of BECN1 or ATG5 reduced H. pylori intracellular survival, whereas inhibition of lysosomal functions exerted an opposite effect. Further experiments demonstrated that H. pylori inhibited lysosomal acidification and the retrograde trafficking of mannose-6-phosphate receptors, both of which are known to positively regulate lysosomal function. We conclude that H. pylori subverts autophagy into a pro-survival mechanism through inhibition of lysosomal clearance of autophagosomes. Disruption of autophagosome formation offers a novel strategy to reduce H. pylori colonization in human stomachs. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Assuntos
Autofagossomos/microbiologia , Autofagia , Mucosa Gástrica/microbiologia , Infecções por Helicobacter/microbiologia , Helicobacter pylori/crescimento & desenvolvimento , Lisossomos/microbiologia , Animais , Autofagossomos/patologia , Proteína 5 Relacionada à Autofagia/genética , Proteína 5 Relacionada à Autofagia/metabolismo , Proteína Beclina-1/genética , Proteína Beclina-1/metabolismo , Estudos de Casos e Controles , Linhagem Celular , Mucosa Gástrica/patologia , Infecções por Helicobacter/genética , Infecções por Helicobacter/patologia , Interações Hospedeiro-Patógeno , Humanos , Concentração de Íons de Hidrogênio , Lisossomos/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Viabilidade Microbiana , Transporte Proteico , Receptor IGF Tipo 2/metabolismoRESUMO
Staphylococcus pseudintermedius is the leading cause of pyoderma in dogs and is often associated with recurrent skin infections that require prolonged antibiotic therapy. High levels of antibiotic use have led to multidrug resistance, including the emergence of epidemic methicillin-resistant clones. Our understanding of the pathogenesis of S. pseudintermedius skin infection is very limited, and the identification of the key host-pathogen interactions underpinning infection could lead to the design of novel therapeutic or vaccine-based approaches for controlling disease. Here, we employ a novel murine cutaneous-infection model of S. pseudintermedius and investigate the role of the two cell wall-associated proteins (SpsD and SpsL) in skin disease pathogenesis. Experimental infection with wild-type S. pseudintermedius strain ED99 or a gene-deletion derivative deficient in expression of SpsD led to a focal accumulation of neutrophils and necrotic debris in the dermis and deeper tissues of the skin characteristic of a classical cutaneous abscess. In contrast, mice infected with mutants deficient in SpsL or both SpsD and SpsL developed larger cutaneous lesions with distinct histopathological features of regionally extensive cellulitis rather than focal abscessation. Furthermore, comparison of the bacterial loads in S. pseudintermedius-induced cutaneous lesions revealed a significantly increased burden of bacteria in the mice infected with SpsL-deficient mutants. These findings reveal a key role for SpsL in murine skin abscess formation and highlight a novel function for a bacterial surface protein in determining the clinical outcome and pathology of infection caused by a major canine pathogen.
Assuntos
Abscesso/patologia , Proteínas de Bactérias/metabolismo , Proteínas de Membrana/metabolismo , Infecções Cutâneas Estafilocócicas/patologia , Staphylococcus/patogenicidade , Fatores de Virulência/metabolismo , Abscesso/microbiologia , Animais , Carga Bacteriana , Proteínas de Bactérias/genética , Modelos Animais de Doenças , Deleção de Genes , Histocitoquímica , Proteínas de Membrana/genética , Camundongos , Pele/microbiologia , Pele/patologia , Infecções Cutâneas Estafilocócicas/microbiologia , Staphylococcus/genética , Staphylococcus/crescimento & desenvolvimento , Fatores de Virulência/genéticaRESUMO
Superantigens (SAgs) represent a diverse family of bacterial toxins that induce Vß-specific T cell proliferation associated with an array of important diseases in humans and animals, including mastitis of dairy cows. However, an understanding of the diversity and distribution of SAg genes among bovine Staphylococcus aureus strains and their role in the pathogenesis of mastitis is lacking. Population genomic analysis of 195 bovine S. aureus isolates representing 57 unique sequence types revealed that strains encode 2 to 13 distinct SAgs and that the majority of isolates contain 5 or more SAg genes. A genome-scale analysis of bovine reference strain RF122 revealed a complement of 11 predicted SAg genes, which were all expressed in vitro Detection of specific antibodies in convalescent cows suggests expression of 7 of 11 SAgs during natural S. aureus infection. We determined the Vß T cell activation profile for all functional SAgs encoded by RF122, revealing evidence for bovine host-specific activity among the recently identified RF122-encoded SAgs SElY and SElZ. Remarkably, we discovered that some strains have evolved the capacity to stimulate the entire T cell repertoire of cattle through an array of diverse SAgs, suggesting a key role in bovine immune evasion.
Assuntos
Antígenos de Bactérias/imunologia , Ativação Linfocitária , Staphylococcus aureus/imunologia , Superantígenos/imunologia , Linfócitos T/imunologia , Animais , Bovinos , Proliferação de Células , Evasão da Resposta Imune , Mastite Bovina/patologia , Infecções Estafilocócicas/patologia , Infecções Estafilocócicas/veterináriaRESUMO
Legionella longbeachae is the primary cause of legionellosis in Australasia and Southeast Asia and an emerging pathogen in Europe and the United States; however, our understanding of the population diversity of L. longbeachae from patient and environmental sources is limited. We analyzed the genomes of 64 L. longbeachae isolates, of which 29 were from a cluster of legionellosis cases linked to commercial growing media in Scotland in 2013 and 35 were non-outbreak-associated isolates from Scotland and other countries. We identified extensive genetic diversity across the L. longbeachae species, associated with intraspecies and interspecies gene flow, and a wide geographic distribution of closely related genotypes. Of note, we observed a highly diverse pool of L. longbeachae genotypes within compost samples that precluded the genetic establishment of an infection source. These data represent a view of the genomic diversity of L. longbeachae that will inform strategies for investigating future outbreaks.
Assuntos
Genoma Bacteriano , Genômica , Legionella longbeachae/genética , Legionelose/microbiologia , Austrália/epidemiologia , Análise por Conglomerados , Biologia Computacional/métodos , Fluxo Gênico , Variação Genética , Genômica/métodos , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Legionella longbeachae/classificação , Legionelose/epidemiologia , Nova Zelândia/epidemiologia , Filogenia , Plasmídeos/genética , RNA Bacteriano , RNA Ribossômico 16S , Recombinação Genética , Escócia/epidemiologia , Sorogrupo , Estados Unidos/epidemiologiaRESUMO
Hospital-associated methicillin-resistant Staphylococcus aureus (MRSA) strains typically express high-level, homogeneous (HoR) ß-lactam resistance, whereas community-associated MRSA (CA-MRSA) more commonly express low-level heterogeneous (HeR) resistance. Expression of the HoR phenotype typically requires both increased expression of the mecA gene, carried on the staphylococcal cassette chromosome mec element (SCCmec), and additional mutational event(s) elsewhere on the chromosome. Here the oxacillin concentration in a chemostat culture of the CA-MRSA strain USA300 was increased from 8 µg/ml to 130 µg/ml over 13 days to isolate highly oxacillin-resistant derivatives. A stable, small-colony variant, designated HoR34, which had become established in the chemostat culture was found to have acquired mutations in gdpP, clpX, guaA, and camS Closer inspection of the genome sequence data further revealed that reads covering SCCmec were â¼10 times overrepresented compared to other parts of the chromosome. Quantitative PCR (qPCR) confirmed >10-fold-higher levels of mecA DNA on the HoR34 chromosome, and MinION genome sequencing verified the presence of 10 tandem repeats of the SCCmec element. qPCR further demonstrated that subculture of HoR34 in various concentrations of oxacillin (0 to 100 µg/ml) was accompanied by accordion-like contraction and amplification of the SCCmec element. Although slower growing than strain USA300, HoR34 outcompeted the parent strain in the presence of subinhibitory oxacillin. These data identify tandem amplification of the SCCmec element as a new mechanism of high-level methicillin resistance in MRSA, which may provide a competitive advantage for MRSA under antibiotic selection.
Assuntos
Cromossomos Bacterianos/genética , Resistência a Meticilina/genética , Staphylococcus aureus Resistente à Meticilina/genética , Antibacterianos/farmacologia , Proteínas de Bactérias/genética , DNA Bacteriano/genética , Meticilina/farmacologia , Resistência a Meticilina/efeitos dos fármacos , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos , Infecções Estafilocócicas/tratamento farmacológico , Infecções Estafilocócicas/microbiologia , beta-Lactamas/farmacologiaRESUMO
The widespread use of antibiotics in association with high-density clinical care has driven the emergence of drug-resistant bacteria that are adapted to thrive in hospitalized patients. Of particular concern are globally disseminated methicillin-resistant Staphylococcus aureus (MRSA) clones that cause outbreaks and epidemics associated with health care. The most rapidly spreading and tenacious health-care-associated clone in Europe currently is EMRSA-15, which was first detected in the UK in the early 1990s and subsequently spread throughout Europe and beyond. Using phylogenomic methods to analyze the genome sequences for 193 S. aureus isolates, we were able to show that the current pandemic population of EMRSA-15 descends from a health-care-associated MRSA epidemic that spread throughout England in the 1980s, which had itself previously emerged from a primarily community-associated methicillin-sensitive population. The emergence of fluoroquinolone resistance in this EMRSA-15 subclone in the English Midlands during the mid-1980s appears to have played a key role in triggering pandemic spread, and occurred shortly after the first clinical trials of this drug. Genome-based coalescence analysis estimated that the population of this subclone over the last 20 yr has grown four times faster than its progenitor. Using comparative genomic analysis we identified the molecular genetic basis of 99.8% of the antimicrobial resistance phenotypes of the isolates, highlighting the potential of pathogen genome sequencing as a diagnostic tool. We document the genetic changes associated with adaptation to the hospital environment and with increasing drug resistance over time, and how MRSA evolution likely has been influenced by country-specific drug use regimens.
Assuntos
Genoma Bacteriano , Staphylococcus aureus Resistente à Meticilina/genética , Infecções Estafilocócicas/epidemiologia , Análise por Conglomerados , Farmacorresistência Bacteriana/genética , Genômica , Genótipo , Humanos , Staphylococcus aureus Resistente à Meticilina/classificação , Pandemias , Filogenia , Filogeografia , Infecções Estafilocócicas/transmissão , Reino Unido/epidemiologiaRESUMO
BACKGROUND: Worldwide, there is a wealth of literature examining patient-level risk factors for methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia. At the hospital-level it is generally accepted that MRSA bacteraemia is more common in larger hospitals. In Scotland, size does not fully explain all the observed variation among hospitals. The aim of this study was to identify risk factors for the presence and rate of MRSA bacteraemia cases in Scottish mainland hospitals. Specific hypotheses regarding hospital size, type and connectivity were examined. METHODS: Data from 198 mainland Scottish hospitals (defined as having at least one inpatient per year) were analysed for financial year 2007-08 using logistic regression (Model 1: presence/absence of MRSA bacteraemia) and Poisson regression (Model 2: rate of MRSA bacteraemia). The significance of risk factors representing various measures of hospital size, type and connectivity were investigated. RESULTS: In Scotland, size was not the only significant risk factor identified for the presence and rate of MRSA bacteraemia. The probability of a hospital having at least one case of MRSA bacteraemia increased with hospital size only if the hospital exceeded a certain level of connectivity. Higher levels of MRSA bacteraemia were associated with the large, highly connected teaching hospitals with high ratios of patients to domestic staff. CONCLUSIONS: A hospital's level of connectedness within a network may be a better measure of a hospital's risk of MRSA bacteraemia than size. This result could be used to identify high risk hospitals which would benefit from intensified infection control measures.
Assuntos
Bacteriemia/epidemiologia , Staphylococcus aureus Resistente à Meticilina/isolamento & purificação , Infecções Estafilocócicas/epidemiologia , Adulto , Idoso , Bacteriemia/diagnóstico , Bacteriemia/microbiologia , Análise Fatorial , Feminino , Hospitais de Ensino/estatística & dados numéricos , Humanos , Masculino , Staphylococcus aureus Resistente à Meticilina/genética , Staphylococcus aureus Resistente à Meticilina/fisiologia , Pessoa de Meia-Idade , Fatores de Risco , Escócia/epidemiologia , Infecções Estafilocócicas/diagnóstico , Infecções Estafilocócicas/microbiologiaRESUMO
In this study, we investigated the cell wall-anchored fibronectin-binding proteins SpsD and SpsL from the canine commensal and pathogen Staphylococcus pseudintermedius for their role in promoting bacterial invasion of canine progenitor epidermal keratinocytes (CPEK). Invasion was examined by the gentamicin protection assay and fluorescence microscopy. An ΔspsD ΔspsL mutant of strain ED99 had a dramatically reduced capacity to invade CPEK monolayers, while no difference in the invasion level was observed with single mutants. Lactococcus lactis transformed with plasmids expressing SpsD and SpsL promoted invasion, showing that both proteins are important. Soluble fibronectin was required for invasion, and an RGD-containing peptide or antibodies recognizing the integrin α5ß1 markedly reduced invasion, suggesting an important role for the integrin in this process. Src kinase inhibitors effectively blocked internalization, suggesting a functional role for the kinase in invasion. In order to identify the minimal fibronectin-binding region of SpsD and SpsL involved in the internalization process, recombinant fragments of both proteins were produced. The SpsD520-846 and SpsL538-823 regions harboring the major fibronectin-binding sites inhibited S. pseudintermedius internalization. Finally, the effects of staphylococcal invasion on the integrity of different cell lines were examined. Because SpsD and SpsL are critical factors for adhesion and invasion, blocking these processes could provide a strategy for future approaches to treating infections.
Assuntos
Proteínas de Bactérias/metabolismo , Doenças do Cão/microbiologia , Células Epiteliais/microbiologia , Fibronectinas/metabolismo , Infecções Estafilocócicas/veterinária , Staphylococcus/metabolismo , Animais , Proteínas de Bactérias/genética , Linhagem Celular , Parede Celular/genética , Parede Celular/metabolismo , Doenças do Cão/metabolismo , Cães , Ligação Proteica , Infecções Estafilocócicas/metabolismo , Infecções Estafilocócicas/microbiologia , Staphylococcus/genética , Staphylococcus/patogenicidade , VirulênciaRESUMO
In order to cause colonization and invasive disease, pathogenic bacteria secrete proteins that modulate host immune defences. Identification and characterization of these proteins leads to a better understanding of the pathological processes underlying infectious and inflammatory diseases and is essential in the development of new strategies for their prevention and treatment. Current techniques to functionally characterize these proteins are laborious and inefficient. Here we describe a high-throughput functional selection strategy using phage display in order to identify immune evasion proteins. Using this technique we identified two previously uncharacterized proteins secreted by Staphylococcus aureus, SElX and SSL6 that bind to neutrophil surface receptors. SElX binds PSGL-1 on neutrophils and thereby inhibits the interaction between PSGL-1 and P-selectin, a crucial step in the recruitment of neutrophils to the site of infection. SSL6 is the first bacterial protein identified that binds CD47, a widely expressed cell surface protein recently described as an interesting target in anti-cancer therapy. Our findings provide new insights into the pathogenesis of S. aureus infections and support phage display as an efficient method to identify bacterial secretome proteins interacting with humoral or cellular immune components.