Justin Glavis-Bloom

Of Model Hosts and Man: Using Caenorhabditis elegans, Drosophila melanogaster and Galleria mellonella as Model Hosts for Infectious Disease Research

The use of invertebrate model hosts has increased in popularity due to numerous advantages of invertebrates over mammalian models, including ethical, logistical and budgetary features. This review provides an introduction to three model hosts, the nematode Caenorhabditis elegans, the fruit fly Drosophila melanogaster and the larvae of Galleria mellonella, the greater wax moth. It highlights principal experimental advantages of each model, for C. elegans the ability to run high-throughput assays, for D. melanogaster the evolutionarily conserved innate immune response, and for G. mellonella the ability to conduct experiments at 37°C and easily inoculate a precise quantity of pathogen. It additionally discusses recent research that has been conducted with each host to identify pathogen virulence factors, study the immune response, and evaluate potential antimicrobial compounds, focusing principally on fungal pathogens.

Invertebrate models of fungal infection

The morbidity, mortality and economic burden associated with fungal infections, together with the emergence of fungal strains resistant to current antimicrobial agents, necessitate broadening our understanding of fungal pathogenesis and discovering new agents to treat these infections. Using invertebrate hosts, especially the nematode Caenorhabditis elegans and the model insects Drosophila melanogaster and Galleria mellonella, could help achieve these goals. The evolutionary conservation of several aspects of the innate immune response between invertebrates and mammals makes the use of these simple hosts an effective and fast screening method for identifying fungal virulence factors and testing potential antifungal compounds. The purpose of this review is to compare several model hosts that have been used in experimental mycology to-date and to describe their different characteristics and contribution to the study of fungal virulence and the detection of compounds with antifungal properties. This article is part of a Special Issue entitled: Animal Models of Disease.

Fusarium infection: report of 26 cases and review of 97 cases from the literature.

AbstractFusarium species is a ubiquitous fungus that causes opportunistic infections. We present 26 cases of invasive fusariosis categorized according to the European Organization for Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG) criteria of fungal infections. All cases (20 proven and 6 probable) were treated from January 2000 until January 2010. We also review 97 cases reported since 2000. The most important risk factors for invasive fusariosis in our patients were compromised immune system, specifically lung transplantation (n = 6) and hematologic malignancies (n = 5), and burns (n = 7 patients with skin fusariosis), while the most commonly infected site was the skin in 11 of 26 patients. The mortality rates among our patients with disseminated, skin, and pulmonary fusariosis were 50%, 40%, and 37.5%, respectively. Fusarium solani was the most frequent species, isolated from 49% of literature cases. Blood cultures were positive in 82% of both current study and literature patients with disseminated fusariosis, while the remaining 16% had 2 noncontiguous sites of infection but negative blood cultures. Surgical removal of focal lesions was effective in both current study and literature cases.Skin lesions in immunocompromised patients should raise the suspicion for skin or disseminated fusariosis. The combination of medical monotherapy with voriconazole or amphotericin B and surgery in such cases is highly suggested.

Nationwide implementation of integrated community case management of childhood illness in Rwanda

Between 2008 and 2011, Rwanda introduced iCCM of childhood illness nationwide. One year after iCCM rollout, community-based treatment for diarrhea and pneumonia had increased significantly, and under-5 mortality and overall health facility use had declined significantly. Between 2008 and 2011, Rwanda introduced iCCM of childhood illness nationwide. One year after iCCM rollout, community-based treatment for diarrhea and pneumonia had increased significantly, and under-5 mortality and overall health facility use had declined significantly. ABSTRACT Background: Between 2008 and 2011, Rwanda introduced integrated community case management (iCCM) of childhood illness nationwide. Community health workers in each of Rwandas nearly 15,000 villages were trained in iCCM and equipped for empirical diagnosis and treatment of pneumonia, diarrhea, and malaria; for malnutrition surveillance; and for comprehensive reporting and referral services. Methods: We used data from the Rwanda health management information system (HMIS) to calculate monthly all-cause under-5 mortality rates, health facility use rates, and community-based treatment rates for childhood illness in each district. We then compared a 3-month baseline period prior to iCCM implementation with a seasonally matched comparison period 1 year after iCCM implementation. Finally, we compared the actual changes in all-cause child mortality and health facility use over this time period with the changes that would have been expected based on baseline trends in Rwanda. Results: The number of children receiving community-based treatment for diarrhea and pneumonia increased significantly in the 1-year period after iCCM implementation, from 0.83 cases/1,000 child-months to 3.80 cases/1,000 child-months (P = .01) and 0.25 cases/1,000 child-months to 5.28 cases/1,000 child-months (P<.001), respectively. On average, total under-5 mortality rates declined significantly by 38% (P<.001), and health facility use declined significantly by 15% (P = .006). These decreases were significantly greater than would have been expected based on baseline trends. Conclusions: This is the first study to demonstrate decreases in both child mortality and health facility use after implementing iCCM of childhood illness at a national level. While our study design does not allow for direct attribution of these changes to implementation of iCCM, these results are in line with those of prior studies conducted at the sub-national level in other low-income countries.

Midupper Arm Circumference Outperforms Weight-Based Measures of Nutritional Status in Children with Diarrhea

BACKGROUND Undernutrition contributes to 45% of all deaths in children <5 y of age worldwide, with a large proportion of those deaths caused by diarrhea. However, no validated tools exist for assessing undernutrition in children with diarrhea and possible dehydration. OBJECTIVE This study assessed the validity of different measures of undernutrition in children with diarrhea. METHODS A prospective cohort study was conducted at an urban hospital in Bangladesh. Children <60 mo of age presenting to the hospital rehydration unit with acute diarrhea were eligible for enrollment. Study staff randomly selected 1196 children for screening, of which 1025 were eligible, 850 were enrolled, and 721 had complete data for analysis. Anthropometric measurements, including weight-for-age z score (WAZ), weight-for-length z score (WLZ), midupper arm circumference (MUAC), and midupper arm circumference z score (MUACZ), were calculated pre- and posthydration in all patients. Measurements were evaluated for their ability to correctly identify undernutrition in children with varying degrees of dehydration. RESULTS Of the 721 patients with full data for analysis, the median percent dehydration was 4%. Of the 4 measures evaluated, MUAC and MUACZ demonstrated 92-94% agreement pre- and posthydration compared with 69-76% for WAZ and WLZ. Although each 1% change in hydration status was found to change weight-for-age by 0.0895 z scores and weight-for-length by 0.1304 z scores, MUAC and MUACZ were not significantly affected by dehydration status. Weight-based measures misclassified 12% of children with severe underweight and 14% with severe acute malnutrition (SAM) compared with only 1-2% for MUAC and MUACZ. CONCLUSIONS MUAC and MUACZ were the most accurate predictors of undernutrition in children with diarrhea. WAZ and WLZ were significantly affected by dehydration status, leading to the misdiagnosis of many patients on arrival with severe underweight and SAM. This trial was registered at clinicaltrials.gov as NCT02007733.

C. elegans for anti-infective discovery.

Widespread use of antimicrobial agents has led to the emergence of multidrug resistant pathogens, which are becoming increasingly common in clinical practice. This underscores the need to discover novel anti-infective compounds. The soil-living nematode Caenorhabditis elegans has proved to be an excellent model host in the search for such compounds. Indeed, this alternative host is successfully being used to identify traditional microbicidal agents, including antihelminthic compounds, as well as novel agents that attenuate microbial virulence or enhance the hosts immune response. Thanks to numerous advantageous features, including its amenability to high-throughput automated screens that allow for the detection of bioactive products among thousands of tested substances, the C. elegans model is now in the spotlight of scientific attention.

Using C. elegans for antimicrobial drug discovery.

Introduction: The number of microorganism strains with resistance to known antimicrobials is increasing. Therefore, there is a high demand for new, non-toxic and efficient antimicrobial agents. Research with the microscopic nematode Caenorhabditis elegans can address this high demand for the discovery of new antimicrobial compounds. In particular, C. elegans can be used as a model host for in vivo drug discovery through high-throughput screens of chemical libraries. Areas covered: This review introduces the use of substitute model hosts and especially C. elegans in the study of microbial pathogenesis. The authors also highlight recently published literature on the role of C. elegans in drug discovery and outline its use as a promising host with unique advantages in the discovery of new antimicrobial drugs. Expert opinion: Caenorhabditis elegans can be used, as a model host, to research many diseases, including fungal infections and Alzheimers disease. In addition, high-throughput techniques for screening chemical libraries can also be facilitated. Nevertheless, C. elegans and mammals have significant differences that both limit the use of the nematode in research and the degree by which results can be interpreted. That being said, the use of C. elegans in drug discovery still holds promise and the field continues to grow, with attempts to improve the methodology already underway.

Accuracy of Inferior Vena Cava Ultrasound for Predicting Dehydration in Children with Acute Diarrhea in Resource-Limited Settings

Introduction Although dehydration from diarrhea is a leading cause of morbidity and mortality in children under five, existing methods of assessing dehydration status in children have limited accuracy. Objective To assess the accuracy of point-of-care ultrasound measurement of the aorta-to-IVC ratio as a predictor of dehydration in children. Methods A prospective cohort study of children under five years with acute diarrhea was conducted in the rehydration unit of the International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b). Ultrasound measurements of aorta-to-IVC ratio and dehydrated weight were obtained on patient arrival. Percent weight change was monitored during rehydration to classify children as having “some dehydration” with weight change 3–9% or “severe dehydration” with weight change > 9%. Logistic regression analysis and Receiver-Operator Characteristic (ROC) curves were used to evaluate the accuracy of aorta-to-IVC ratio as a predictor of dehydration severity. Results 850 children were enrolled, of which 771 were included in the final analysis. Aorta to IVC ratio was a significant predictor of the percent dehydration in children with acute diarrhea, with each 1-point increase in the aorta to IVC ratio predicting a 1.1% increase in the percent dehydration of the child. However, the area under the ROC curve (0.60), sensitivity (67%), and specificity (49%), for predicting severe dehydration were all poor. Conclusions Point-of-care ultrasound of the aorta-to-IVC ratio was statistically associated with volume status, but was not accurate enough to be used as an independent screening tool for dehydration in children under five years presenting with acute diarrhea in a resource-limited setting.

Characteristics and Outcomes of Pediatric Patients With Ebola Virus Disease Admitted to Treatment Units in Liberia and Sierra Leone: A Retrospective Cohort Study

Background. The clinical and virologic characteristics of Ebola virus disease (EVD) in children have not been thoroughly documented. Methods. Consecutive children aged <18 years with real-time polymerase chain reaction (RT-PCR)–confirmed EVD were enrolled retrospectively in 5 Ebola treatment units in Liberia and Sierra Leone in 2014/2015. Data collection and medical management were based on standardized International Medical Corps protocols. We performed descriptive statistics, multivariate logistic regression, and Kaplan-Meier survival analyses. Results. Of 122 children enrolled, the median age was 7 years and one-third were aged <5 years. The female-to-male ratio was 1.3. The most common clinical features at triage and during hospitalization were fever, weakness, anorexia, and diarrhea, although 21% of patients were initially afebrile and 6 patients remained afebrile. Bleeding was rare at presentation (5%) and manifested subsequently in fewer than 50%. The overall case fatality rate was 57%. Factors associated with death in bivariate analyses were age <5 years, bleeding at any time during hospitalization, and high viral load. After adjustment with logistic regression modeling, the odds of death were 14.8-fold higher if patients were aged <5 years, 5-fold higher if the patient had any evidence of bleeding, and 5.2-fold higher if EVD RT-PCR cycle threshold value was ⩽20. Plasmodium parasitemia had no impact on EVD outcomes. Conclusions. Age <5 years, bleeding, and high viral loads were poor prognostic indicators of children with EVD. Research to understand mechanisms of these risk factors and the impact of dehydration and electrolyte imbalance will improve health outcomes.

Using Caenorhabditis elegans for antimicrobial drug discovery

Introduction: The number of microorganism strains with resistance to known antimicrobials is increasing. Therefore, there is a high demand for new, non-toxic and efficient antimicrobial agents. Research with the microscopic nematode Caenorhabditis elegans can address this high demand for the discovery of new antimicrobial compounds. In particular, C. elegans can be used as a model host for in vivo drug discovery through high-throughput screens of chemical libraries. Areas covered: This review introduces the use of substitute model hosts and especially C. elegans in the study of microbial pathogenesis. The authors also highlight recently published literature on the role of C. elegans in drug discovery and outline its use as a promising host with unique advantages in the discovery of new antimicrobial drugs. Expert opinion: Caenorhabditis elegans can be used, as a model host, to research many diseases, including fungal infections and Alzheimers disease. In addition, high-throughput techniques for screening chemical libraries can also be facilitated. Nevertheless, C. elegans and mammals have significant differences that both limit the use of the nematode in research and the degree by which results can be interpreted. That being said, the use of C. elegans in drug discovery still holds promise and the field continues to grow, with attempts to improve the methodology already underway.