New Phytophthora species in Western Australia: Pathogenicity and control by phosphite in vitro and in planta

A number of new Phytophthora species to Western Australia, have been isolated from dying native species in southwest Western Australia (SWWA). However, little is known about their host range or whether the pathogenic species can be controlled by phosphite. The effect of phosphite on 23 Phytophthora species was investigated in vitro. On solid medium, EC50 values were 5 to >160 μg/ml phosphite, whilst in liquid medium buffered using 0.03 M MES (2-(N-morpholino) ethanesulfonic acid), EC50 values ranged from 30 to >900 μg/ml. Nineteen of 23 species displayed a much higher level of tolerance in buffered liquid medium to phosphite than in solid, or unbuffered liquid medium. Assessment of phosphite tolerance was more accurate using liquid, rather than solid medium. Casuarina obesa, Banksia littoralis, B. occidentalis, B. grandis, Lambetia inermis, Corymbia calophylla, and Eucalyptus marginata were screened in the glasshouse as possible susceptible hosts by inoculating soil with 22 Phytophthora species and assessing plant growth after 6 weeks. P. niederhauserii had a wide host range similar to P. cinnamomi. Other species that killed one or more hosts were P. elongata, P. boodjera, P. moyootj, P. constricta and P. rosacearum. No Phytophthora species tested killed C. calophylla. To test the effectiveness of phosphite as a control agent, Eucalyptus marginata, B. occidentalis, B. littoralis and L. inermis were sprayed with 0.5% phosphite seven days before soil inoculation with ten Phytophthora species. No phosphite-treated plants died, but in unprotected controls P. cinnamomi and P. neiderhauserii killed at least one host plant of all species, while plants of E. marginata were also killed by P.constricta, P. boodjera, P. elongata, and P. multivora. For P. constricta, P. boodjera, P. multivora, P. rosacearum and P. arenaria, for one or more host species, the reduction of shoot or root growth caused by the pathogen was not eliminated by spraying plants with phosphite. There was no relationship between phosphite tolerance in vitro (as determined by EC50) and the response to phosphite in planta: for example, P. gibbosa was highly tolerant in vitro but controlled by phosphite in planta. In L. inermis subsp. inermis all species of Phytophthora reduced root mass even in plants sprayed with phosphite. Phosphite prevented lesion development in E. marginata and B. occidentalis after underbark inoculation of with Phytophthora cinnamomi and P. niederhauserii

Towards a best practice methodology for the detection of Phytophthora species in soils

The genus Phytophthora contains species that are major pathogens worldwide, affecting a multitude of plant species across agriculture, horticulture, forestry, and natural ecosystems. Here, we concentrate on those species that are dispersed through soil and water, attacking the roots of the plants, causing them to rot and die. The intention of this study was to compare the soil baiting protocol developed by the Centre for Phytophthora Science and Management (CPSM) with two other baiting methods used in Australia. The aim was to demonstrate the effectiveness of each protocol for soil baiting Phytophthora species in different substrates. Three experiments were conducted: the first to test the sensitivity of each method to detect Phytophthora cinnamomi, the second to test the effect of substrate type (sand or loam), and the third to test the detection of species (P. cinnamomi, P. multivora, or P. pseudocryptogea). The specificity of different plant species baits was compared within and between the methods. Substrate type influenced isolation in all methods; however, the CPSM method was superior regardless of substrate, albeit slower than one of the other methods for one substrate. Comparing bait species between the three methods, Quercus ilex was the most attractive bait for P. cinnamomi, particularly in the CPSM method. The choice of protocol affected the isolation associated with each bait type. Overall, the multiple bait system used by CPSM was shown to provide the most sensitive and reliable detection of Phytophthora species from soil samples.info:eu-repo/semantics/publishedVersio

The ASOS Surgical Risk Calculator: development and validation of a tool for identifying African surgical patients at risk of severe postoperative complications

Background: The African Surgical Outcomes Study (ASOS) showed that surgical patients in Africa have a mortality twice the global average. Existing risk assessment tools are not valid for use in this population because the pattern of risk for poor outcomes differs from high-income countries. The objective of this study was to derive and validate a simple, preoperative risk stratification tool to identify African surgical patients at risk for in-hospital postoperative mortality and severe complications. Methods: ASOS was a 7-day prospective cohort study of adult patients undergoing surgery in Africa. The ASOS Surgical Risk Calculator was constructed with a multivariable logistic regression model for the outcome of in-hospital mortality and severe postoperative complications. The following preoperative risk factors were entered into the model; age, sex, smoking status, ASA physical status, preoperative chronic comorbid conditions, indication for surgery, urgency, severity, and type of surgery. Results: The model was derived from 8799 patients from 168 African hospitals. The composite outcome of severe postoperative complications and death occurred in 423/8799 (4.8%) patients. The ASOS Surgical Risk Calculator includes the following risk factors: age, ASA physical status, indication for surgery, urgency, severity, and type of surgery. The model showed good discrimination with an area under the receiver operating characteristic curve of 0.805 and good calibration with c-statistic corrected for optimism of 0.784. Conclusions: This simple preoperative risk calculator could be used to identify high-risk surgical patients in African hospitals and facilitate increased postoperative surveillance. © 2018 British Journal of Anaesthesia. Published by Elsevier Ltd. All rights reserved.Medical Research Council of South Africa gran

Maternal and neonatal outcomes after caesarean delivery in the African Surgical Outcomes Study: a 7-day prospective observational cohort study.

BACKGROUND: Maternal and neonatal mortality is high in Africa, but few large, prospective studies have been done to investigate the risk factors associated with these poor maternal and neonatal outcomes. METHODS: A 7-day, international, prospective, observational cohort study was done in patients having caesarean delivery in 183 hospitals across 22 countries in Africa. The inclusion criteria were all consecutive patients (aged ≥18 years) admitted to participating centres having elective and non-elective caesarean delivery during the 7-day study cohort period. To ensure a representative sample, each hospital had to provide data for 90% of the eligible patients during the recruitment week. The primary outcome was in-hospital maternal mortality and complications, which were assessed by local investigators. The study was registered on the South African National Health Research Database, number KZ_2015RP7_22, and on ClinicalTrials.gov, number NCT03044899. FINDINGS: Between February, 2016, and May, 2016, 3792 patients were recruited from hospitals across Africa. 3685 were included in the postoperative complications analysis (107 missing data) and 3684 were included in the maternal mortality analysis (108 missing data). These hospitals had a combined number of specialist surgeons, obstetricians, and anaesthetists totalling 0·7 per 100 000 population (IQR 0·2-2·0). Maternal mortality was 20 (0·5%) of 3684 patients (95% CI 0·3-0·8). Complications occurred in 633 (17·4%) of 3636 mothers (16·2-18·6), which were predominantly severe intraoperative and postoperative bleeding (136 [3·8%] of 3612 mothers). Maternal mortality was independently associated with a preoperative presentation of placenta praevia, placental abruption, ruptured uterus, antepartum haemorrhage (odds ratio 4·47 [95% CI 1·46-13·65]), and perioperative severe obstetric haemorrhage (5·87 [1·99-17·34]) or anaesthesia complications (11·47 (1·20-109·20]). Neonatal mortality was 153 (4·4%) of 3506 infants (95% CI 3·7-5·0). INTERPRETATION: Maternal mortality after caesarean delivery in Africa is 50 times higher than that of high-income countries and is driven by peripartum haemorrhage and anaesthesia complications. Neonatal mortality is double the global average. Early identification and appropriate management of mothers at risk of peripartum haemorrhage might improve maternal and neonatal outcomes in Africa. FUNDING: Medical Research Council of South Africa.Medical Research Council of South Africa