Search

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., Author summary The emergence of new pathogens is a major threat to public and veterinary health. Some bacteria such as Staphylococcus aureus, have the capacity to infect many different host species including humans and livestock while others such as the closely-related S. aureus subsp. anaerobius, associated with a single type of pathology called Morel’s disease in small ruminants, are highly niche-restricted. However, our understanding of the genetic basis for such differences in bacterial host-tropism is very limited. Here, we discovered that S. aureus subsp. anaerobius evolved from an S. aureus ancestor and underwent an array of extensive changes to its genome that accompanied the transition to its current restricted lifestyle. We observed genome decay involving loss of function of hundreds of genes, large intra-chromosomal rearrangements affecting most of the genome, acquisition of a pathogenicity island, and expansion of large numbers of insertion sequences that are inserted at intergenic sites around the genome. Importantly, we found that IS elements affect the expression of neighbouring genes in different ways including a novel mechanism of IS-enabled disruption of ancestral gene repression. Taken together, we provide a remarkable example of radical genomic changes associated with evolutionary transition from a multi-host to highly restricted host ecology.

Conjugation has classically been considered the main mechanism driving plasmid transfer in nature. Yet bacteria frequently carry so-called non-transmissible plasmids, raising questions about how these plasmids spread. Interestingly, the size of many mobilisable and non-transmissible plasmids coincides with the average size of phages (~40 kb) or that of a family of pathogenicity islands, the phage-inducible chromosomal islands (PICIs, ~11 kb). Here, we show that phages and PICIs from Staphylococcus aureus can mediate intra- and inter-species plasmid transfer via generalised transduction, potentially contributing to non-transmissible plasmid spread in nature. Further, staphylococcal PICIs enhance plasmid packaging efficiency, and phages and PICIs exert selective pressures on plasmids via the physical capacity of their capsids, explaining the bimodal size distribution observed for non-conjugative plasmids. Our results highlight that transducing agents (phages, PICIs) have important roles in bacterial plasmid evolution and, potentially, in antimicrobial resistance transmission., Nature Communications, 12, ISSN:2041-1723

A model of bacterial host switching provides a window into the population dynamics of host adaptation., While many bacterial pathogens are restricted to single host species, some have the capacity to undergo host switches, leading to the emergence of new clones that are a threat to human and animal health. However, the bacterial traits that underpin a multihost ecology are not well understood. Following transmission to a new host, bacterial populations are influenced by powerful forces such as genetic drift that reduce the fixation rate of beneficial mutations, limiting the capacity for host adaptation. Here, we implement a novel experimental model of bacterial host switching to investigate the ability of the multihost pathogen Staphylococcus aureus to adapt to new species under continuous population bottlenecks. We demonstrate that beneficial mutations accumulated during infection can overcome genetic drift and sweep through the population, leading to host adaptation. Our findings highlight the remarkable capacity of some bacteria to adapt to distinct host niches in the face of powerful antagonistic population forces.

24 páginas, 6 figuras, 3 tablas, The dUTPase (Dut) enzymes, encoded by almost all free-living organisms and some viruses, prevent the misincorporation of uracil into DNA. We previously proposed that trimeric Duts are regulatory proteins involved in different cellular processes; including the phage-mediated transfer of the Staphylococcus aureus pathogenicity island SaPIbov1. Recently, it has been shown that the structurally unrelated dimeric Dut encoded by phage ϕNM1 is similarly able to mobilize SaPIbov1, suggesting dimeric Duts could also be regulatory proteins. How this is accomplished remains unsolved. Here, using in vivo, biochemical and structural approaches, we provide insights into the signaling mechanism used by the dimeric Duts to induce the SaPIbov1 cycle. As reported for the trimeric Duts, dimeric Duts contain an extremely variable region, here named domain VI, which is involved in the regulatory capacity of these enzymes. Remarkably, our results also show that the dimeric Dut signaling mechanism is modulated by dUTP, as with the trimeric Duts. Overall, our results demonstrate that although unrelated both in sequence and structure, dimeric and trimeric Duts control SaPI transfer by analogous mechanisms, representing a fascinating example of convergent evolution. This conserved mode of action highlights the biological significance of Duts as regulatory molecules., This work was supported by grants, BIO2013-42619-P and BIO2016-78571-P, from the Ministerio de Economia y Competitividad (Spain) and grant Prometeo II/2014/029 from Valencian Government (Spain) to AM, and grants MR/M003876/1 from the Medical Research Council (UK), BB/N002873/1, from the Biotechnology and Biological Sciences Research Council (BBSRC, UK), and ERC-ADG-2014 Proposal n° 670932 Dut-signal from EU to JRP. EM was supported by CSIC JAE-Doc postdoctoral contract (Programa «Junta para la Ampliación de Estudios») co-funded by the European Social Fund. JRC and CA were supported by FPU13/02880 and FPI BES-2014-068617 predoctoral fellowships respectively. X-ray diffraction data collection was supported by Diamond Light Source block allocation group (BAG) Proposal, MX14739, and Spanish Synchrotron Radiation Facility ALBA Proposal 2016071762. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under BioStruct-X, grant agreement N°283570. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

13 páginas, 5 figuras, 3 tablas, material suplementario en NAR online, We have recently proposed that the trimeric staphylococcal phage encoded dUTPases (Duts) are signaling molecules that act analogously to eukaryotic G-proteins, using dUTP as a second messenger. To perform this regulatory role, the Duts require their characteristic extra motif VI, present in all the staphylococcal phage coded trimeric Duts, as well as the strongly conserved Dut motif V. Recently, however, an alternative model involving Duts in the transfer of the staphylococcal islands (SaPIs) has been suggested, questioning the implication of motifs V and VI. Here, using state-of the-art techniques, we have revisited the proposed models. Our results confirm that the mechanism by which the Duts derepress the SaPI cycle depends on dUTP and involves both motifs V and VI, as we have previously proposed. Surprisingly, the conserved Dut motif IV is also implicated in SaPI derepression. However, and in agreement with the proposed alternative model, the dUTP inhibits rather than inducing the process, as we had initially proposed. In summary, our results clarify, validate and establish the mechanism by which the Duts perform regulatory functions., Ministerio de Economia y Competitividad (Spain) [BIO2013-42619-P to A.M.]; Medical Research Council (UK) [MR/M003876/1]; ERC-ADG-2014 Dut-signal (from EU) [Proposal no 670932 to J.R.P]; CSIC JAE-Doc Postdoctoral contract (Programa «Junta para la Ampliación de Estudios»), European Social Fund (to E.M.); FPU13/02880 (to J.R.C.), FPI BES-2014-068617 Predoctoral Fellowships (to C.A.). Diamond Light Source block allocation group (BAG) Proposal [MX10121]; Spanish Synchrotron Radiation Facility ALBA Proposal [2014060897]; European Community's Seventh Framework Programme [FP7/2007-2013]; BioStruct-X [283570]. Funding for open access charge: Ministerio de Economia y Competitividad (Spain) [BIO2013-42619-P to A.M.]; Medical Research Council (UK) [MR/M003876/1]; ERC-ADG-2014 Dut-signal (from EU) [Proposal no 670932 to J.R.P].

El objetivo del presente estudio fue estimar la prevalencia de bacterias patógenas de mastitis en muestras de leche de tanque en tambos ubicados en la cuenca lechera central Argentina. Además, se evaluó el desempeño de tres medios de cultivo, dos estándar (Baird Parker y agar sangre) y uno comercial (Compact Dry “Nissui”), para realizar el recuento, aislamiento e identifi cación de Sta-phylococcus aureus. Entre las muestras con aislamiento de patógenos mayores, la prevalencia de S. aureus, Streptococcus agalactiae, Streptococcus uberis y Streptococcus dysgalactiae fue del 50%, 5,45%, 31.82% y 12.72% respectivamente. Ninguna muestra fue positiva para Mycoplasma spp. Al comparar los medios para aislamiento de S. aureus se observó una concordancia moderada a baja entre Baird Parker (BP) y Agar Sangre (AS), mayor que la observada entre Baird Parker y Compact Dry “Nissui” (CSA). Al comparar el porcentaje de recuperación, ninguna de las dos técnicas AS y CSA difi rió de BP la cual fue intermedia a las otras dos, obteniéndose recuentos más bajos en AS que en CSA. Estos resultados evidencian que aún persisten elevadas prevalencias de los principales agentes patógenos de mastitis y su control es importante para mejorar la calidad microbiológica de la leche cruda. Los tres medios ensayados fueron adecuados para la detección de S. aureus en leche de tanque The objective of this study was to determine the prevalence of major mastitis pathogens in bulk tank milk from dairy herds located in the central dairy area of Argentina. In addition, performance of three culture media, two standard (Baird Parker and blood agar) and one commercial (Dry Compact “Nissui”) for Staphylococcus aureus detection and enumeration was evaluated. Prevalence of S. aureus, Streptococcus agalactiae, Streptococcus uberis and Streptococcus dysgalactiae was 50%, 5.45%, 31.82 and 12.72, respectively, while Mycoplasma spp. was not detected. Regarding culture media performance, accordance between Baird Parker and blood agar was moderate to low, although higher than the one observed between Baird Parker and Compact Dry “Nissui”. Colony recovery percent on blood agar or Compact Dry “Nissui” did not differ from Baird Parker, being higher on Compact Dry “Nissui” and lower on blood agar. These results stress the need to control major mastitis contagious pathogens in the central dairy area. All culture media evaluated were found suitable for detection and enumeration of S. aureus in bulk tank milk EEA Rafaela Fil: Neder, Veronica Elizabeth. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina Fil: Signorini, Marcelo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Cuatrin, Alejandra. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina Fil: Gianre, Vilma Rita. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina. Fil: Calvinho, Luis Fernando. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentina. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias; Argentina

En este artículo se describe la síntesis y caracterización de un nuevo complejo de paladio(II), [Pd(Ph2PzTSC)2], con el ligante 1,3-difenilpirazol-4-carboxaldehído tiosemicarbazona (Ph2PzTSC) como una estrategia para mejorar la actividad antimicrobiana del complejo formado. La coordinación del ion metálico y el efecto sinérgico entre estos, conduce a mejorar la actividad biológica del complejo. El ligante se coordina al ion metálico de modo bidentado a través del átomo de nitrógeno del azometino y del azufre en forma de tiol, por la desprotonación del grupo NH-C=S. La actividad antimicrobiana de estos compuestos fueevaluada frente a bacterias Gram-negativas(Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa) yGram-positivas(Staphylococcus aureus, Bacillus thuringensis) y dos levaduras (Candida albicans y Saccharomyces cerevisiae). Cuando fueron comparados los resultados de la actividad antimicrobiana con la actividad del ligante libre, se observó que la coordinación del Pd(II) mejoró la actividad. This article describes the synthesis and characterization of a new complex, [Pd(Ph2PzTSC)2], formed between palladium(II) and 1,3-diphenylpyrazole-4-carboxaldehyde thiosemicarba-zone ligand as a strategy for antimicrobial activity improve-ment the synthesized complex. The metal coordination leads to an improvement of ligand pharmacological activities and synergistic effects involving both metal ion as the ligand. The bidentate ligand is coordinated to metal ion through the azomethine nitrogen atoms and the sulphur in the form of thiol by deprotonation of the NH-C=S group. The antimicro-bial activity of these new compounds was evaluated against gram-negative (Escherichia coli, Klebsiella pneumoniaeand Pseudomonas aeruginosa) and gram-positive (Staphy-lococcus aureus and Bacillus thuringiensis) bacteria and two yeasts strains (Candida albicans and Saccharomyces cerevisiae). A comparison between the antimicrobial activity of the complex and that of the free ligand revealed that the coordination of Pd(II) improved the activity. Incluye referencias bibliográficas

Introducción: Las infecciones intrahospitalarias constituyen un problema de salud pública mundial, la diseminación de bacterias patógenas a partir del personal de salud, ha sido el enfoque de numerosas investigaciones que buscan mejorar la calidad de vida de los pacientes. Objetivo: Determinar la frecuencia de portadores de Staphylococcus aureus en fosas nasales del personal que labora en las unidades de cuidados intensivos, infectología pediátrica y lactario en un Hospital en Santander. Metodología: Se estudiaron muestras provenientes de fosas nasales de 87 trabajadores del Hospital. Las cepas aisladas se identificaron mediante las pruebas bioquímicas y posteriormente, se determinó el perfil de susceptibilidad ante diferentes antibióticos, se realizó test D a las cepas de S. aureus. Resultados: La frecuencia de portadores de bacterias patógenas fue 41,4%; el patógeno aislado con mayor frecuencia fue S. aureus (72%), donde el porcentaje de S. aureus meticilino-resistentes (SARM) fue de 11,6%, Enterobacter aerogenes (6%), Proteus mirabilis (2,3%), Haemophylus influenzae (1,1%), Citrobacter koseri (1,1%) y Providencia rettgeri (1,1%). Conclusión: S. aureus es el agente aislado con mayor frecuencia de las fosas nasales del personal de salud y la presencia de SARM es preocupante por su resistencia a los antibióticos, lo que dificulta su tratamiento. Este hecho evidencia la necesidad de actuar con un carácter preventivo, en el cual el control de portadores es crítico y debe asociarse con medidas de bioseguridad que establezcan barreras más eficientes, para reducir la diseminación del microorganismo y la ocurrencia de infecciones intrahospitalarias. Salud UIS 2011; 43 (2): 111-117 Introduction: Nosocomial infections are a public health problem worldwide, its spread start from health personnel carrier of pathogenic bacteria, it has been the focus of a large number of research to improve the quality of life of the patients. Objective: To determine the frequency of nasal carriers of Staphylococcus aureus in the personnel that works in intensive care units (adults ICU and pediatric ICU), pediatric infectology and lactary in a Hospital in Santander. Methodology: Nasal samples from 87 workers from of the Hospital were studied. Isolated strains were identified by the corresponding biochemical tests and subsequently determined their susceptibility profiles to different antibiotics and test D for S. aureus. Results: The frequency of nasal carriers of pathogenic bacteria was 41.4%; it was found that S. aureus was the most isolated pathogenic microorganism, with a frequency of (72%). The percentage of meticilin resistant S. aureus (MRSA) was 11.6% , Enterobacter aerogenes (6%), Proteus mirabilis (2.3%); Haemophylus influenzae (1.1%); Citrobacter koseri (1.1%) and Providencia rettgeri (1.1%). Conclusion: S. aureus is the most frequently isolated agent in health personnel's nasal nostrils and the presence of MRSA is worrying, additionally, it presents characteristic of resistance to antibiotics, making harder its treatment. This fact evidences the necessity to act with a preventive character, in which the control of carriers is critical and it should be associated with biosecurity measures to establish effective barriers to reduce the dissemination of the microorganism and occurrence of nosocomial infections. Salud UIS 2011; 43 (2): 111-117

En la presente investigación fueron aisladas cepas de campo de Staphyloccous aureus de 27 vacas con mastitis, que representan a 12 hatos lecheros; las cepas de campo se seleccionaron de un total de casi 3.000 cepas aisladas. Las cepas fueron sujetas a las pruebas de Reacción en Cadena con Polimerasa (PCR) para detectar las toxinas codificadas por los genes SEA, SEB, SEC, SED, SEE, SEG, SEJ y el TST. Las cepas fueron investigadas mediante la técnica de fingerprinting, con la electroforesis de campos pulsátiles (PFGE). El monitoreo de los genes que codifican las toxinas fue negativo, con excepción de la SEI, la cual fue detectada en una cepa. Es muy significativo hacer notar que los resultados obtenidos mediante el análisis de PFGE indican que hay una relación estrecha entre las cepas de campo de S. aureus responsables de la mastitis de las vacas lecheras en el Occidente de México. In the present work, Staphyloccous aureus field strains were isolated from 27 mastitic cows representing 12 dairy herds. This was selected of almost 3,000 field strains of mastitic cows. The strains were subjected to different Polymerase Chain Reaction (PCR) to detect the toxin encoding genes SEA, SEB, SEC, SED, SEE, SEG, SEJ and TST genes. The investigated strains were then subjected to fingerprinting by the means of Pulse Field Gel Electrophoresis (PFGE). The screening for the previously mentioned toxin encoding genes revealed the absence of all toxin encoding genes with the exception of SEI which could be detected in a single strain. Meanwhile, the data obtained through the PFGE analysis indicated the close relationship of S. aureus field strains responsible for the induction of mastitis in western Mexico. 308-316 hcastane@cucba.udg.mx Bimestral