The evolution of bacterial mutation rates under simultaneous selection by interspecific and social parasitism

Many bacterial populations harbour substantial numbers of hypermutable bacteria, in spite of hypermutation being associated with deleterious mutations. One reason for the persistence of hypermutators is the provision of novel mutations, enabling rapid adaptation to continually changing environments, for example coevolving virulent parasites. However, hypermutation also increases the rate at which intraspecific parasites (social cheats) are generated. Interspecific and intraspecific parasitism are therefore likely to impose conflicting selection pressure on mutation rate. Here, we combine theory and experiments to investigate how simultaneous selection from inter- and intraspecific parasitism affects the evolution of bacterial mutation rates in the plant-colonizing bacterium Pseudomonas fluorescens. Both our theoretical and experimental results suggest that phage presence increases and selection for public goods cooperation (the production of iron-scavenging siderophores) decreases selection for mutator bacteria. Moreover, phages imposed a much greater growth cost than social cheating, and when both selection pressures were imposed simultaneously, selection for cooperation did not affect mutation rate evolution. Given the ubiquity of infectious phages in the natural environment and clinical infections, our results suggest that phages are likely to be more important than social interactions in determining mutation rate evolution.

Early postoperative predictors of satisfaction following total knee arthroplasty

BACKGROUND

Despite the excellent total knee arthroplasty (TKA) results reported using traditional outcome measures, dissatisfaction rates of up to 30% are reported following surgery. Although several preoperative factors have been identified as possible predictors of satisfaction, there is conflicting evidence. Identification of dissatisfaction in the early postoperative assessment may therefore be an alternative consideration.

METHODS

We examined the relationship between 12-month satisfaction, and early post-operative outcomes in a cohort of 486 TKA patients. Preoperative, and postoperative outcome measures at 3- and 12-months (Oxford knee score, pain score, SF12, and knee motion), were analysed and compared between patients who were satisfied and dissatisfied at 12-months following TKA. Mean scores, and postoperative change in scores were calculated. Postoperative outcomes were examined for correlation with satisfaction, and multivariate logistic regression models used to identify potential predictors of dissatisfaction.

RESULTS

Overall satisfaction was 77.0%. No preoperative differences were observed between groups. Dissatisfaction was associated with worse postoperative status across all outcome measures (p<0.001), except the 3-month SF12-physical component (p=0.052). Dissatisfied patients demonstrated minimal further improvement or even worsening of outcome scores between 3- and 12-months postoperatively (p<0.02). Both the 3-month OKS (OR=1.15, p<0.001), and knee flexion (OR=1.03, p=0.009) were significant predictors of subsequent 12-month satisfaction.

CONCLUSIONS

Dissatisfaction following TKA is associated with worse outcomes as early as 3months following surgery, with minimal further improvement subsequently achieved at 12-months. Early postoperative assessment following TKA should therefore be considered, including clinical assessment, to identify those patients at risk of dissatisfaction.

The effects of age and gender on the diameter of the femoral canal in patients who undergo total hip replacement

With greater numbers of younger patients undergoing total hip replacement (THR), the effect of patient age on the diameter of the femoral canal may become more relevant. This study aimed to investigate the relationship between the diameter of the diaphysis of the femoral canal with increasing age in a large number of patients who underwent THR. A total of 1685 patients scheduled for THR had their femoral dimensions recorded from calibrated radiographs. There were 736 males and 949 females with mean ages of 67.1 years (34 to 92) and 70.2 years (29 to 92), respectively. The mean diameter of the femoral canal was 13.3 mm (8.0 to 23.0) for males and 12.7 mm (6.0 to 26.0) for females. There was a poor correlation between age and the diameter of the canal in males (r = 0.071, p = 0.05) but a stronger correlation in females (r = 0.31, p < 0.001). The diameter of the femoral canal diameter of a female patient undergoing THR could be predicted to increase by 3.2 mm between the ages of 40 and 80 years, in contrast a male would be expected to experience only a 0.6 mm increase during the same period. This increase in the diameter of the canal with age might affect the long-term survival of the femoral component in female patients.

Cementless fixation in Oxford unicompartmental knee replacement: a multicentre study of 1000 knees

The Cementless Oxford Unicompartmental Knee Replacement (OUKR) was developed to address problems related to cementation, and has been demonstrated in a randomised study to have similar clinical outcomes with fewer radiolucencies than observed with the cemented device. However, before its widespread use it is necessary to clarify contraindications and assess the complications. This requires a larger study than any previously published. We present a prospective multicentre series of 1000 cementless OUKRs in 881 patients at a minimum follow-up of one year. All patients had radiological assessment aligned to the bone-implant interfaces and clinical scores. Analysis was performed at a mean of 38.2 months (19 to 88) following surgery. A total of 17 patients died (comprising 19 knees (1.9%)), none as a result of surgery; there were no tibial or femoral loosenings. A total of 19 knees (1.9%) had significant implant-related complications or required revision. Implant survival at six years was 97.2%, and there was a partial radiolucency at the bone-implant interface in 72 knees (8.9%), with no complete radiolucencies. There was no significant increase in complication rate compared with cemented fixation (p = 0.87), and no specific contraindications to cementless fixation were identified. Cementless OUKR appears to be safe and reproducible in patients with end-stage anteromedial osteoarthritis of the knee, with radiological evidence of improved fixation compared with previous reports using cemented fixation.

The interplay between microevolution and community structure in microbial populations

The structure of microbial communities is key to their functionality. However, this structure is likely to be influenced by adaptive genetic change in members of the community, which can occur over a matter of days. Changes in community structure can in turn influence the evolutionary trajectories of species within the community, further altering community structure. Microbial communities provide evidence for this interplay between rapid evolution and community structure. To date, studies are primarily limited to simple in vitro systems, but we suggest similar processes are inevitably operating in both natural and derived communities, which are important for biotechnology.

Patterns of chemotherapy treatment for women with invasive epithelial ovarian cancer--a population-based study

OBJECTIVE

Ovarian cancer five-year survival is poor at <40%. In the absence of effective screening or new treatments, ensuring all women receive optimal treatment is one avenue to improve survival. There is little population-based information regarding the primary chemotherapy treatment that women with epithelial ovarian cancer receive. This information is essential to identify potential gaps in care.

METHODS

Cancer registries identified all women diagnosed with invasive epithelial ovarian cancer in Australia in 2005 (n=1192). Histopathology, chemotherapy and comorbidity information was abstracted from medical records. Multivariable logistic regression was used to identify factors associated with chemotherapy commencement, regimen, and completion.

RESULTS

Women >70 years (p<0.0001), those with high-grade, stage IA/IB cancers (vs. stages IC-IV, p=0.003) and those with mucinous cancers (p=0.0002) were less likely to start chemotherapy. Most treated women received platinum-based drugs (97%), but only 68% received combination carboplatin-paclitaxel and only half completed six cycles without treatment modification/delay. Approximately 19% received single-agent carboplatin: mostly those aged >70 (p<0.0001) and/or with co-morbidities (p<0.0001). Age was the strongest predictor of completing six cycles of combination therapy.

CONCLUSIONS

For specific patient groups, particularly older women, there is notable variation from standard treatment. Understanding how treatment variations affect survival and determining optimal regimens for these groups are research priorities.

Prognostic significance of 11q23 aberrations in adult acute myeloid leukemia and the role of allogeneic stem cell transplantation

The clinical features and outcomes of 148 patients with acute myeloid leukemia (AML) and 11q23 chromosomal abnormalities were compared with those of 2640 patients with non-11q23 AML. Patients with t(9;11) ), t(6;11) or other 11q23 balanced translocations (t(11;v)(q23;v)) presented at a younger age and with higher percentage of bone marrow blasts. Unbalanced 11q23 abnormalities were commonly associated with deletions of chromosomes 5q, 7q and/or complex karyotypes. In multivariate analysis, when compared with patients with non-11q23 AML and unfavorable-risk karyotype, there was a significant difference in overall survival (OS) for patients with t(9;11) (P=0.004), whereas there were no differences in OS for patients with t(6;11) (P=0.62), t(11;19) (P=0.20) and unbalanced 11q23 aberrations (P=0.85) or t(11;v)(q23;v) (P=0.59), indicating that t(9;11) has an independent intermediate prognostic significance, with all others being poor prognostic factors for OS; this was further confirmed by comparing them with patients with non-11q23 AML and intermediate-risk karyotype. Using intention-to treat analysis based on donor availability, we also noted that allogeneic stem cell transplant in first remission had a significant benefit toward improving OS (P<0.001) and relapse-free survival (P<0.001) in patients with AML and 11q23 abnormalities.

Modifiable factors delaying early discharge following primary joint arthroplasty

AIMS

Recent NHS reforms have incentivised reduction in length of stay, with the UK department of health expecting health trusts to reduce bed days and ultimately reduce overall costs. The aim of this study was to identify avoidable causes for protracted hospital admission following total hip arthroplasty (THA) or total knee arthroplasty (TKA) within a fast-track unit.

METHODS

During a 6-month period, 535 consecutive patients underwent primary THA or TKA under the care of a single surgeon. All patients with a post-operative stay of greater than 72 h were identified, and reasons for delayed discharge were determined.

RESULTS

The majority of arthroplasty patients were discharged within 3 days post-operatively. Twenty-one per cent of THA patients and 25 % of TKA patients remained as inpatients for greater than 72 h. For the THA population, this equates to 43 % of bed days used by 21 % of patients, and for the TKA population, 44 % of bed days were used by 25 % of patients. The major factor within both groups for delayed discharge was attributed to inadequate social support.

CONCLUSIONS

Delayed discharge can never be totally prevented. This unit aims to develop improvement in social work provision, with a greater focus on pre-admission discharge planning to reduce the number of delayed discharges and ultimately reduce the cost burden of joint replacement surgery. It is not conducive with the ethos of fast-track arthroplasty to only identify social circumstances upon admission.

On-off intermittency in an optically injected semiconductor laser

We report on the observation of on-off intermittency in an optically injected dual-mode semiconductor laser. It is shown that quasi-single-mode chaotic dynamics of the injected mode are accompanied by intermittent and irregular bursts of the intensity of the uninjected mode. We define a threshold intensity of the uninjected mode to distinguish laminar and bursting states of the system. For small values of the threshold parameter we observe excellent agreement with the predictions of theory for the distribution of the laminar phase durations. For larger values of the threshold parameter, a gap appears in the distribution of laminar phase durations. Numerical simulations demonstrate that this gap is a consequence of the fact that in this case the on states of the system define large intensity spikes, which can belong either to the same or to distinct bursts away from the single-mode manifold.

Selective, novel spleen tyrosine kinase (Syk) inhibitors suppress chronic lymphocytic leukemia B-cell activation and migration

Syk is a protein tyrosine kinase that couples B-cell receptor (BCR) activation with downstream signaling pathways, affecting cell survival and proliferation. Moreover, Syk is involved in BCR-independent functions, such as B-cell migration and adhesion. In chronic lymphocytic leukemia (CLL), Syk becomes activated by external signals from the tissue microenvironment, and was targeted in a first clinical trial with R788 (fostamatinib), a relatively nonspecific Syk inhibitor. Here, we characterize the activity of two novel, highly selective Syk inhibitors, PRT318 and P505-15, in assays that model CLL interactions with the microenvironment. PRT318 and P505-15 effectively antagonize CLL cell survival after BCR triggering and in nurse-like cell-co-cultures. Moreover, they inhibit BCR-dependent secretion of the chemokines CCL3 and CCL4 by CLL cells, and leukemia cell migration toward the tissue homing chemokines CXCL12, CXCL13, and beneath stromal cells. PRT318 and P505-15 furthermore inhibit Syk and extracellular signal-regulated kinase phosphorylation after BCR triggering. These findings demonstrate that the selective Syk inhibitors PRT318 and P505-15 are highly effective for inhibition of CLL survival and tissue homing circuits, and support the therapeutic development of these agents in patients with CLL, other B-cell malignancies and autoimmune disorders.

The stability of markers in dried-blood spots for recommended newborn screening disorders in the United States

OBJECTIVE

We aimed to measure separately the contributions of heat and humidity to changes in levels of 34 markers of inborn disorders in dried-blood-spot (DBS) samples.

DESIGN AND METHODS

We stored paired sets of DBSs at 37°C for predetermined intervals in low-humidity and high-humidity environments. Marker levels of all samples in each complete sample set were measured in a single analytic run.

RESULTS

During the 30 ± 5 day studies, galactose-1-phosphate uridyltransferase and biotinidase lost almost 65% of initial activities in low-humidity storage; most of the degradation in 27 other markers was attributable to adverse effects of high-humidity storage; seven markers in DBSs stored at high humidity lost more than 90% of initial levels by the end of the study and 4 of the 7 lost more than 50% of initial levels within the first week of storage.

CONCLUSIONS

Minimizing both humidity and temperature in DBS transportation and storage environments is essential to maintaining sample integrity.

KIR2DS1 genotype predicts for complete cytogenetic response and survival in newly diagnosed chronic myeloid leukemia patients treated with imatinib

Natural killer (NK) cells are expanded in chronic myeloid leukemia (CML) patients on tyrosine kinase inhibitors (TKI) and exert cytotoxicity. The inherited repertoire of killer immunoglobulin-like receptors (KIR) may influence response to TKI. We investigated the impact of KIR-genotype on outcome in 166 chronic phase CML patients on first-line imatinib treatment. We validated our findings in an independent patient group. On multivariate analysis, KIR2DS1 genotype (RR=1.51, P=0.03) and Sokal risk score (low-risk RR=1, intermediate-risk RR=1.53, P=0.04, high-risk RR=1.69, P=0.034) were the only independent predictors for failure to achieve complete cytogenetic response (CCyR). Furthermore, KIR2DS1 was the only factor predicting shorter progression-free (PFS) (RR=3.1, P=0.03) and overall survival (OS) (RR=2.6, P=0.04). The association between KIR2DS1 and CCyR, PFS and OS was validated by KIR genotyping in 174 CML patients on first-line imatinib in the UK multi-center SPIRIT-1 trial; in this cohort, KIR2DS1(+) patients had significantly lower 2-year probabilities of achieving CCyR (76.9 vs 87.9%, P=0.003), PFS (85.3 vs 98.1%, P=0.007) and OS (94.4 vs 100%, P=0.015) than KIR2DS1(-) patients. The impact of KIR2DS1 on CCyR was greatest when the ligand for the corresponding inhibitory receptor, KIR2DL1, was absent (P=0.00006). Our data suggest a novel role for KIR-HLA immunogenetics in CML patients on TKI.

Undergraduate medical education in substance use in Ireland: a review of the literature and discussion paper

BACKGROUND

Medical complications of substance use are a considerable cause of morbidity and the role of the physician in the care of such problems has consistently been demonstrated. Appropriate knowledge and skills are necessary to carry out this role.

AIMS

To review the literature on training undergraduate medical students in identifying and managing substance misuse and to discuss the implications of this literature for Irish medical education.

METHODS

A search of the literature was performed using keywords; "substance-related disorders", "undergraduate" and "curriculum". All abstracts were reviewed and the full text of relevant abstracts was studied and references reviewed for further articles.

RESULTS

Despite an increase in prevalence of the problem of drug and alcohol use in Ireland and the UK, this has not been reflected in undergraduate medical curricula. In the UK, minimal time is devoted to formal teaching of medical undergraduates in the area of substance misuse and many doctors do not have the appropriate knowledge, skills, attitudes and confidence to treat patients with such problems. In Ireland, no data has reported formal undergraduate teaching hours in the area of drug and alcohol misuse. Internationally, substance abuse curricula have been developed and implemented in medical schools in the United States and Australia.

CONCLUSION

While substance misuse is increasing in prevalence, this is not reflected in the composition of medical curricula, especially in Ireland. International best practice whereby undergraduate curricula that adequately address substance misuse and related issues are systematically developed and implemented, is recommended for adoption by Irish medical schools.

Patent ductus arteriosus hemodynamics in very premature infants treated with poractant alfa or beractant for respiratory distress syndrome

OBJECTIVE

Respiratory distress syndrome (RDS), requiring mechanical ventilation and exogenous surfactant treatment, and patent ductus arteriosus (PDA), are common co-morbidities in very premature infants. The effects of intra-tracheal surfactant administration on the cardiovascular and pulmonary systems in very premature infants with RDS and PDAs are not well characterized. We evaluated the effects of poractant alfa and beractant, surfactants with different rapidity of onset and duration of action, in very premature infants with RDS. To assess whether there were differences in PDA hemodynamics in very premature infants with RDS treated with poractant alfa and beractant during the first week of life and to assess whether poractant alfa or beractant had a direct effect on PDAs and PDA hemodynamics following the second dose of surfactant.

STUDY DESIGN

We studied 50 in-born, very premature infants with RDS, 24 0 of 7 to 29 6 of 7 weeks gestation, treated with poractant alfa or beractant, in an open label, 1:1, randomized clinical trial. A subgroup of 16 patients with severe RDS, treated with a second dose of surfactant, had echocardiographical assessments before and 20 to 30 min after the second dose of surfactant.

RESULT

There were 25 infants treated with poractant alfa (27.1±1.6 weeks, birth weight 930±231 g) and 25 treated with beractant (26.7±1.7 weeks, P=0.407 and birth weight 898±282 g, P=0.666). Clinically significant PDAs were diagnosed and treated in 8 of 25 (32%) of the poractant alfa and 19 of 25 (76%) of the beractant group (P=0.002). Indomethacin treatment was slightly earlier (3.4±2.5 days) in the poractant alfa than in the beractant group (5.1±4.9 days, P=0.038). Right ventricle pressure (RVP)/systolic arterial pressure (SAP) ratio in the first week was slightly lower in the poractant alfa (64±20%) than in the beractant (78±26%, P=0.048) group. Following a second dose of surfactant, neither poractant alfa nor beractant changed PDA flow. These hemodynamic observations were associated with less respiratory support in the poractant alfa group, allowing earlier extubation (13 of 25 at 48 h and 15 of 25 at 72 h), than in the beractant group (6 of 25 at 48 h, P=0.044, and 8 of 25 at 72 h, P=0.049).

CONCLUSION

The more rapid improvement in pulmonary function in the poractant alfa-treated infants was associated with a lower RVP/SAP ratio and a corresponding earlier treatment with indomethacin. Neither surfactant had a significant direct effect on PDA hemodynamics. The lower frequency of clinically significant PDAs in the poractant alfa compared with the beractant group may represent an indirect effect of the differences in the pulmonary improvement induced by the two surfactants.