Global reprogramming of virulence and antibiotic resistance in Pseudomonas aeruginosa by a single nucleotide polymorphism in elongation factor, fusA1

Clinical isolates of the opportunistic pathogen Pseudomonas aeruginosa from patients with cystic fibrosis (CF) frequently contain mutations in the gene encoding an elongation factor, FusA1. Recent work has shown that fusA1 mutants often display elevated aminoglycoside resistance due to increased expression of the efflux pump, MexXY. However, we wondered whether these mutants might also be affected in other virulence-associated phenotypes. Here, we isolated a spontaneous gentamicin-resistant fusA1 mutant (FusA1^P443L) in which mexXY expression was increased. Proteomic and transcriptomic analyses revealed that the fusA1 mutant also exhibited discrete changes in the expression of key pathogenicity-associated genes. Most notably, the fusA1 mutant displayed greatly increased expression of the Type III secretion system (T3SS), widely considered to be the most potent virulence factor in the P. aeruginosa arsenal, and also elevated expression of the Type VI (T6) secretion machinery. This was unexpected because expression of the T3SS is usually reciprocally coordinated with T6 secretion system expression. The fusA1 mutant also displayed elevated exopolysaccharide production, dysregulated siderophore production, elevated ribosome synthesis, and transcriptomic signatures indicative of translational stress. Each of these phenotypes (and almost all of the transcriptomic and proteomic changes associated with the fusA1 mutation) were restored to levels comparable with that in the progenitor strain by expression of the WT fusA1 gene in trans, indicating that the mutant gene is recessive. Our data show that in addition to elevating antibiotic resistance through mexXY expression (and also additional contributory resistance mechanisms), mutations in fusA1 can lead to highly selective dysregulation of virulence gene expression.

A case-control study of employment status and mortality in a cohort of Australian youth

Recent studies have demonstrated a link in young populations between unemployment and ill health. The purpose of this study is to correlate mortality with employment status in two cohorts of young Australian males, aged 17-25 years, from 1984 to 1988. Two youth cohorts consisting of an initially unemployed sample (n = 1424 males) and a population sample (n = 4573 males), were surveyed annually throughout the study period. Those lost to follow-up during the survey period were matched with death registries across Australia. Employment status was determined from weekly diaries and death certificates and was designated as: employed or student; unemployed; not in the work force (excluding students). Conditional logistic regression, using age- and cohort- matched cases (deaths) and controls (alive), was used to estimate the odds ratio (OR) of dying with regard to employment status, taking into account potential confounders such as ethnicity, aboriginality, educational attainment, pre-existing health problems, socio-economic status of parents, and other factors. Twenty three male survey respondents were positively matched to death registry records. Compared to those employed or students (referent group), significantly elevated ORs were found to be associated with neither being in the workforce nor a student for all cause, external cause, and external cause mortality other than suicide. Odds ratios were adjusted for age, survey cohort, ethnicity, pre-existing physical and mental health status, education level, and socio-economic status of parent(s). A statistically significant increasing linear trend in odds ratios of male mortality for most cause groups was found across the employment categories, from those employed or student (lowest ORs), through those unemployed, to those not in the workforce (highest ORs). Suicide was higher, but not statistically significantly, in those unemployed or not in the workforce. Suicide also was associated, though not significantly, with the respondent not living with their parents when they were 14 years of age. No association was found between mortality and past unemployment experience, as measured by length of time spent unemployed, or the number of spells of unemployment experienced during the survey. The results of this study underscore the elevated risk to survival in young males as a consequence of being neither employed nor a student.

A cohort study of unemployment as a cause of psychological disturbance in Australian youth

Data from the Australian Longitudinal Survey, conducted by the Commonwealth Department of Employment, Education and Training, were analysed to estimate relative risk of psychological disturbance accompanying unemployment in young people aged 15-24 years. Two cohorts were surveyed annually over 4 years during the mid-to-late-1980s; one from the general 15-24 year-old population (N = 8995), and the other selected from Commonwealth Employment Service records (N = 2403). Such large respondent numbers allowed control of confounding by exclusion to isolate employment transition groups suitable for hypothesis testing and quantification of causal relationships. Psychological morbidity was measured using binary outcomes of the 12 item psychological component of the General Health Questionnaire. Excluded from the analysis were those who: suffered from pre-existing physical health problems; were dissatisfied in their job; were self-employed; underwent marriage breakdown during the inter-survey period; had become widowed during the inter-survey period. A Bayesian probabilistic approach was used to calculate probabilities of psychologically normal respondents becoming psychologically morbid, given prior transition from employment to unemployment. Mantel-Haenszel analysis was utilised to estimate relative risks in comparison to a control group of those remaining employed, after controlling for age and gender. An overall relative risk of becoming psychologically disturbed as a consequence of becoming unemployed was estimated to be 1.51 (95% CI: 1.15-1.99). The overall relative risk of recovery from psychological disturbance upon re-employment in those with psychological disturbance was estimated to be 1.63 (95% CI: 1.08-2.48). Residual psychological effects of past unemployment experience and the effects of long-term unemployment were investigated, but found to be non-significant in this study. There was some evidence of psychological adaptation to unemployment, but this was statistically insignificant. Unemployment was a significant cause of psychological disturbance in young people who were initially employed, not suffering physical ill-health, and psychologically normal; conversely, re-employment reversed the effect.

Blood utilisation in open heart surgery at Green Lane Hospital

Blood utilization in 166 patients who underwent open heart surgery over a period of three months in 1980 at Green Lane Hospital has been surveyed. Over two-thirds of the operations were for coronary artery disease. For each hospitalized patient an average of 2.55 units of homologous blood were used. Including blood products, the total demand on the blood transfusion service was 3.55 donors/patient. Regular autologous transfusion of oxygenator blood post-bypass was a major factor in reducing blood usage. No blood was used in 23% of the bypass procedures and 13% of patients did not receive any homologous blood or blood products.