Community-acquired methicillin-resistant staphylococcus aureus: diagnosis and treatment update for plastic surgeons

LEARNING OBJECTIVES:: After studying this article, the participant should be able to: 1. Identify risk factors associated with community-acquired methicillin-resistant Staphylococcus aureus. 2. Recognize the clinical presentation of patients with community-acquired methicillin-resistant S. aureus. 3. Understand the treatment and indications for decolonization of patients who have community-acquired methicillin-resistant S. aureus infections. SUMMARY:: Community-acquired methicillin-resistant Staphylococcus aureus has evolved over the past 10 years as a new health threat seen by plastic surgeons and is an increasing cause of soft-tissue infections. This pathogen has several distinct virulence factors and unique antimicrobial susceptibilities that distinguish methicillin-resistant S. aureus from traditional hospital-acquired methicillin-resistant S. aureus. This article reviews the epidemiology, risk factors, clinical presentation, and treatment of community-acquired methicillin-resistant S. aureus.     

Contrasting phylogeographies inferred for the two alpine sister species Cardamine resedifolia and C. alpina (Brassicaceae)

Aim We use Cardamine alpina and C. resedifolia as models to address the detailed history of disjunctions in the European alpine system. These species grow on siliceous bedrock: C. alpina in the Alps and Pyrenees, and C. resedifolia in several mountain ranges from the Sierra Nevada to the Balkans. We explore differentiation among their disjunct populations as well as within the contiguous Alpine and Pyrenean ranges, and compare the phylogeographical histories of these diploid sister species. We also include samples of the closely related, arctic diploid C. bellidifolia in order to explore its origin and post‐glacial establishment. Location European alpine system, Norway and Iceland. Methods We employed amplified fragment length polymorphisms (AFLPs). AFLP data were analysed using principal coordinates analysis, neighbour joining and Bayesian clustering, and measures of diversity and differentiation were computed. Results For the snow‐bed species C. alpina (27 populations, 203 plants) we resolved two strongly divergent lineages, corresponding to the Alps and the Pyrenees. Although multiple glacial refugia were invoked in the Pyrenees, we inferred only a single one in the Maritime Alps – from which rapid post‐glacial colonization of the entire Alps occurred, accompanied by a strong founder effect. For C. resedifolia (33 populations, 247 plants), which has a broader ecological amplitude and a wider distribution, the genetic structuring was rather weak and did not correspond to the main geographical disjunctions. This species consists of two widespread and largely sympatric main genetic groups (one of them subdivided into four geographically more restricted groups), and frequent secondary contacts exist between them. Main conclusions The conspicuously different histories of these two sister species are likely to be associated with their different ecologies. The more abundant habitats available for C. resedifolia may have increased the probability of its gradual migration during colder periods and also of successful establishment after long‐distance dispersal, whereas C. alpina has been restricted by its dependence on snow‐beds. Surprisingly, the arctic C. bellidifolia formed a very divergent lineage with little variation, contradicting a scenario of recent, post‐glacial migration from the Alps or Pyrenees.     

Genome size in Hieracium subgenus Hieracium (Asteraceae) is strongly correlated with major phylogenetic groups

Background and Aims

Hieracium subgenus Hieracium is one of the taxonomically most intricate groups of vascular plants, due to polyploidy and a diversity of breeeding systems (sexuality vs. apomixis). The aim of the present study was to analyse nuclear genome size in a phylogenetic framework and to assess relationships between genome size and ploidy, breeding system and selected ecogeographic features.

Methods

Holoploid and monoploid genome sizes (C- and Cx-values) of 215 cultivated plants from 89 field populations of 42 so-called ‘basic’ Hieracium species were determined using propidium iodide flow cytometry. Chromosome counts were available for all analysed plants, and all plants were tested experimentally for their mode of reproduction (sexuality vs. apomixis). For constructing molecular phylogenetic trees, the external transcribed spacer region of nuclear ribosomal DNA was used.

Key Results

The mean 2C values differed up to 2·37-fold among different species (from 7·03 pg in diploid to 16·67 in tetraploid accessions). The 1Cx values varied 1·22-fold (between 3·51 and 4·34 pg). Variation in 1Cx values between conspecific (species in a broad sense) accessions ranged from 0·24% to 7·2%. Little variation (not exceeding the approximate measurement inaccurracy threshold of 3·5%) was found in 33 species, whereas variation higher than 3·5% was detected in seven species. Most of the latter may have a polytopic origin. Mean 1Cx values of the three cytotypes (2n, 3n and 4n) differed significantly (average of 3·93 pg in diploids, 3·82 pg in triploids and 3·78 pg in tetraploids) indicating downsizing of genomes in polyploids. The pattern of genome size variation correlated well with two major phylogenetic clades which were composed of species with western or eastern European origin. The monoploid genome size in the ‘western’ species was significantly lower than in the ‘eastern’ ones. Correlation of genome size with latitude, altitude and selected ecological characters (light and temperature) was not significant. A longitudinal component was only apparent for the whole data set, but absent within the major lineages.

Conclusions

Phylogeny was the most important factor explaining the pattern of genome size variation in Hieracium sensu stricto, species of western European origin having significantly lower genome size in comparison with those of eastern European origin. Any correlation with ecogeographic variables, including longitude, was outweighed by the divergence of the genus into two major phylogenetic lineages.Key words: Apomixis, chromosome numbers, Compositae, genome size, hawkweeds, Hieracium subgenus Hieracium, mode of reproduction, nuclear DNA content, phylogeny, polyploidy