Within-Host Dynamics of Multi-Species Infections: Facilitation, Competition and Virulence

Host individuals are often infected with more than one parasite species (parasites defined broadly, to include viruses and bacteria). Yet, research in infection biology is dominated by studies on single-parasite infections. A focus on single-parasite infections is justified if the interactions among parasites are additive, however increasing evidence points to non-additive interactions being the norm. Here we review this evidence and theoretically explore the implications of non-additive interactions between co-infecting parasites. We use classic Lotka-Volterra two-species competition equations to investigate the within-host dynamical consequences of various mixes of competition and facilitation between a pair of co-infecting species. We then consider the implications of these dynamics for the virulence (damage to host) of co-infections and consequent evolution of parasite strategies of exploitation. We find that whereas one-way facilitation poses some increased virulence risk, reciprocal facilitation presents a qualitatively distinct destabilization of within-host dynamics and the greatest risk of severe disease

Is undertransfusion a problem in modern clinical practice?

BACKGROUND: Significant progress has been made in reducing inappropriate transfusion of blood products. However, there is also a need to monitor for their underutilization in patients who would benefit from transfusion. This study aimed to develop a method to monitor for undertransfusion and conduct a preliminary examination of whether it is a problem in modern clinical practice. STUDY DESIGN AND METHODS: All patients with a hemoglobin (Hb) concentration below 6 g/dL or platelet (PLT) count of fewer than 10 × 10(9) /L were identified during a 1-month period in an academic medical center in the United Kingdom. Patients who were transfused within 72 hours of the low reading were excluded from further analysis. For all other patients, records were examined against predefined criteria to ascertain whether the reason for nonadministration of transfusion was justified. RESULTS: During the study period there were 63 eligible Hb readings and 130 eligible PLT counts in 93 patients. Of these, 36 patients were not transfused within 72 hours of the low reading. The majority of nonadministration (n = 28) was justified by either an additional Hb or an additional PLT count on repeat sampling being above the transfusion threshold or the transfusion being medically inappropriate. No documentation was found to indicate that any cases of nonadministration of blood were unjustified. CONCLUSION: This study did not find that patients with low Hb readings or PLT counts were inappropriately undertransfused. However, systems similar to those described in this study should be developed to monitor for inappropriate undertransfusion as well as continuing efforts to monitor for and reduce inappropriate overtransfusion

The impact of electronic decision support and electronic remote blood issue on transfusion practice.

OBJECTIVES: To assess the impact on transfusion practice of a two-stage electronic intervention: the introduction of a decision support system (DSS) followed by the addition of electronic remote blood issue (ERBI). BACKGROUND: With increasing evidence to show the benefit of restrictive transfusion policies, it is important to ascertain which interventions can increase clinician compliance with their implementation. A DSS provides patient-specific recommendations to clinicians. ERBI reduces delays in acquiring blood and may alter the transfusion behaviour of clinicians. METHODS: All electronically requested blood transfusions administered outside of surgical theatres or recovery were identified in an orthopaedic hospital. These were divided into three time periods corresponding to pre-intervention, the successive introduction of DSS alone and DSS with ERBI. Pre- and post-transfusion haemoglobin (Hb) concentration levels, and the number of units ordered and transfused were recorded. RESULTS: A total of 204 transfusions for 92 patients were assessed; 38 of 85 (45%) transfusions in the first time period were compliant. This did not significantly change after introduction of the DSS, but with DSS and ERBI together significantly increased to 39 of 60 (65%) (P < 0·05). Mean pre-transfusion Hb reduced from 8·24 g dl(-1) in the first time period to 7·67 g dl(-1) in the third (P < 0·0001). There was no significant change in overall blood usage, although ERBI significantly reduced the amount of unused blood orders from 70 to 25%. CONCLUSION: Electronic DSS was not sufficient to change practice in the form implemented in this study. ERBI can contribute to significant improvements in blood usage as well as the efficiency of blood provision