The Population Structure of Acinetobacter baumannii: Expanding Multiresistant Clones from an Ancestral Susceptible Genetic Pool

Outbreaks of hospital infections caused by multidrug resistant Acinetobacter baumannii strains are of increasing concern worldwide. Although it has been reported that particular outbreak strains are geographically widespread, little is known about the diversity and phylogenetic relatedness of A. baumannii clonal groups. Sequencing of internal portions of seven housekeeping genes (total 2,976 nt) was performed in 154 A. baumannii strains covering the breadth of known diversity and including representatives of previously recognized international clones, and in 19 representatives of other Acinetobacter species. Restricted amounts of diversity and a star-like phylogeny reveal that A. baumannii is a genetically compact species that suffered a severe bottleneck in the recent past, possibly linked to a restricted ecological niche. A. baumannii is neatly demarcated from its closest relative (genomic species 13TU) and other Acinetobacter species. Multilocus sequence typing analysis demonstrated that the previously recognized international clones I to III correspond to three clonal complexes, each made of a central, predominant genotype and few single locus variants, a hallmark of recent clonal expansion. Whereas antimicrobial resistance was almost universal among isolates of these and a novel international clone (ST15), isolates of the other genotypes were mostly susceptible. This dichotomy indicates that antimicrobial resistance is a major selective advantage that drives the ongoing rapid clonal expansion of these highly problematic agents of nosocomial infections

Toward programmatic research on virtue assessment: Challenges and prospects

Poor construct definition has characterized research on virtue, beginning with Hartshorne and May’s honesty studies and continuing to the present. Recently, scholars have begun to define virtues in ways that improve the prospects for measuring virtue constructs, but a coordinated, programmatic approach is necessary for success in virtue measurement. A brief overview of the construct of virtue includes six key elements that can structure virtue assessment design. Recent research on the trait/situation problem suggests that situational factors do not obviate traits. Veridicality issues such as social desirability and positive illusions are significant challenges for self-report virtue measurement. In summary self-report measures, these challenges can be met with a number of methods, including directly assessing social desirability and item construction to remove social desirability. These challenges can also be met using other-reports, experience sampling, or experimental procedures. A brief discussion of construct validity in virtue measurement leads to the conclusion that many studies with a variety of methods are necessary to establish valid measures of virtue