Evolution and host-specific adaptation of Pseudomonas aeruginosa.

The major human bacterial pathogen Pseudomonas aeruginosa causes multidrug-resistant infections in people with underlying immunodeficiencies or structural lung diseases such as cystic fibrosis (CF). We show that a few environmental isolates, driven by horizontal gene acquisition, have become dominant epidemic clones that have sequentially emerged and spread through global transmission networks over the past 200 years. These clones demonstrate varying intrinsic propensities for infecting CF or non-CF individuals (linked to specific transcriptional changes enabling survival within macrophages); have undergone multiple rounds of convergent, host-specific adaptation; and have eventually lost their ability to transmit between different patient groups. Our findings thus explain the pathogenic evolution of P. aeruginosa and highlight the importance of global surveillance and cross-infection prevention in averting the emergence of future epidemic clones.

Comprehensive global genome dynamics of Chlamydia trachomatis show ancient diversification followed by contemporary mixing and recent lineage expansion.

Chlamydia trachomatis is the world's most prevalent bacterial sexually transmitted infection and leading infectious cause of blindness, yet it is one of the least understood human pathogens, in part due to the difficulties of in vitro culturing and the lack of available tools for genetic manipulation. Genome sequencing has reinvigorated this field, shedding light on the contemporary history of this pathogen. Here, we analyze 563 full genomes, 455 of which are novel, to show that the history of the species comprises two phases, and conclude that the currently circulating lineages are the result of evolution in different genomic ecotypes. Temporal analysis indicates these lineages have recently expanded in the space of thousands of years, rather than the millions of years as previously thought, a finding that dramatically changes our understanding of this pathogen's history. Finally, at a time when almost every pathogen is becoming increasingly resistant to antimicrobials, we show that there is no evidence of circulating genomic resistance in C. trachomatis.

Genome-Based Infection Tracking Reveals Dynamics of Clostridium difficile Transmission and Disease Recurrence.

BACKGROUND: Accurate tracking of Clostridium difficile transmission within healthcare settings is key to its containment but is hindered by the lack of discriminatory power of standard genotyping methods. We describe a whole-genome phylogenetic-based method to track the transmission of individual clones in infected hospital patients from the epidemic C. difficile 027/ST1 lineage, and to distinguish between the 2 causes of recurrent disease, relapse (same strain), or reinfection (different strain). METHODS: We monitored patients with C. difficile infection in a UK hospital over a 2-year period. We performed whole-genome sequencing and phylogenetic analysis of 108 strains isolated from symptomatic patients. High-resolution phylogeny was integrated with in-hospital transfers and contact data to create an infection network linking individual patients and specific hospital wards. RESULTS: Epidemic C. difficile 027/ST1 caused the majority of infections during our sampling period. Integration of whole-genome single nucleotide polymorphism (SNP) phylogenetic analysis, which accurately discriminated between 27 distinct SNP genotypes, with patient movement and contact data identified 32 plausible transmission events, including ward-based contamination (66%) or direct donor-recipient contact (34%). Highly contagious donors were identified who contributed to the persistence of clones within distinct hospital wards and the spread of clones between wards, especially in areas of intense turnover. Recurrent cases were identified between 4 and 26 weeks, highlighting the limitation of the standard <8-week cutoff used for patient diagnosis and management. CONCLUSIONS: Genome-based infection tracking to monitor the persistence and spread of C. difficile within healthcare facilities could inform infection control and patient management.

Emergence and global spread of epidemic healthcare-associated Clostridium difficile.

Epidemic C. difficile (027/BI/NAP1) has rapidly emerged in the past decade as the leading cause of antibiotic-associated diarrhea worldwide. However, the key events in evolutionary history leading to its emergence and the subsequent patterns of global spread remain unknown. Here, we define the global population structure of C. difficile 027/BI/NAP1 using whole-genome sequencing and phylogenetic analysis. We show that two distinct epidemic lineages, FQR1 and FQR2, not one as previously thought, emerged in North America within a relatively short period after acquiring the same fluoroquinolone resistance-conferring mutation and a highly related conjugative transposon. The two epidemic lineages showed distinct patterns of global spread, and the FQR2 lineage spread more widely, leading to healthcare-associated outbreaks in the UK, continental Europe and Australia. Our analysis identifies key genetic changes linked to the rapid transcontinental dissemination of epidemic C. difficile 027/BI/NAP1 and highlights the routes by which it spreads through the global healthcare system.

Characterization of the yehUT two-component regulatory system of Salmonella enterica Serovar Typhi and Typhimurium.

Proteins exhibiting hyper-variable sequences within a bacterial pathogen may be associated with host adaptation. Several lineages of the monophyletic pathogen Salmonella enterica serovar Typhi (S. Typhi) have accumulated non-synonymous mutations in the putative two-component regulatory system yehUT. Consequently we evaluated the function of yehUT in S. Typhi BRD948 and S. Typhimurium ST4/74. Transcriptome analysis identified the cstA gene, encoding a carbon starvation protein as the predominantly yehUT regulated gene in both these serovars. Deletion of yehUT had no detectable effect on the ability of these mutant Salmonella to invade cultured epithelial cells (S. Typhi and S. Typhimurium) or induce colitis in a murine model (S. Typhimurium only). Growth, metabolic and antimicrobial susceptibility tests identified no obvious influences of yehUT on these phenotypes.

Evidence in court: witness preparation and cross-examination style effects on adult witness accuracy.

Witnesses play a clear and pivotal role in the criminal justice system and there is an obvious public interest in identifying procedures that both undermine and maximize the quality of evidence received by the criminal courts. This paper reports an investigation into the effects of witness familiarization and cross-examination type on adult witness accuracy that situates outcomes in both legal and psychological context. 60 mock witnesses observed a crime event and each witness was then cross-examined by a practising barrister in a moot courtroom according to two conditions - either via a scripted complex version of cross-examination or by a simpler but equivalent scripted examination. Mock witnesses were also allocated to two further conditions - half the participants received a guidance booklet on cross-examination and the other half received no familiarization to the process. Study outcomes showed that familiarization of witnesses to cross-examination processes increased accurate responses and reduced errors. The guidance seemingly allowed accessibility to cognitive information that enabled witnesses to process information more effectively. On this basis, advance written information about the nature of the cross-examination and potentially misleading tactics used by advocates could help to immunize against negative lawyerly influence.

Meeting the mental health needs of people with chronic obstructive pulmonary disease: a qualitative study.

OBJECTIVES: This study aimed to understand the mental health needs of people living with chronic obstructive pulmonary disease: what they were experiencing, what they wanted (or did not want) which might be described as 'felt need', what they had accessed or received ('expressed need') and how, from their perspective, their emotional needs might be more effectively met by health care services. METHODS: Qualitative study with 14 patients with a confirmed diagnosis of chronic obstructive pulmonary disease, where a member of the clinical team had recognised that the patient was suffering from associated emotional distress. RESULTS: Three themes emerged: a sense of assuming a different identity as the disease challenged abilities, the experience of social isolation with fear of dependence and barriers the participants encountered acting as obstacles to coping, adapting and accessing treatments. There were mixed feelings about the value of talking about problems, with both psychological and physical barriers strongly militating against both expression of need and utilization of care offered. CONCLUSIONS: Innovative research and clinical care should be aimed towards development of skills, strategies and systems required to engage sensitively and negotiate needs for care, in a patient-centred manner, with people who do not necessarily see the need to ask for emotional support.