The Use of Positron Emission Tomography in the Diagnosis of Prosthetic Arteriovenous Hemodialysis Graft Infection: A Case Study

Patients on chronic hemodialysis (HD) required efficient arterio-venous access. Different types of vascular access are commonly used, such as native arteriovenous (AV) fistula, prosthetic AV graft, central venous catheter, or temporary and tunnelled cuffed catheters. Vascular access—related morbidity remains the major issue for patients requiring long-term therapy. Vascular access infection constitutes the most challenging and life-threatening complication of vascular access and causes significant morbidity, loss of access and mortality. Vascular access infection is defined as local signs at the vascular access site or a positive blood culture with no know source other than the vascular access. The critical issue in the management of AV graft infection is the need to remove the infection and to maintain HD access with reduced morbidity. The diagnosis of infected AV graft is not always easy, especially with low-grade infection or atypical presentation. Fluorodeoxyglucose positron emission tomography (FDG-PET) is an imaging method that uses a radioactively labelled tracer (18 fluorodeoxy glucose) which is taken up by tissue with high metabolic activity, such as neoplastic and inflammatory lesions. FDG-PET has been proposed to visualise localisation of infection in patients with suspected prosthetic graft infection. We report a case of methicilin resistant staphylococcus aureus (MRSA) hemodialysis access infection without local inflammatory signs diagnosed on the PET-CT.

Aortic stent graft infection in a patient with Marfan syndrome

Endovascular repair of raptured abdominal aortic aneurysm （AAA） has been adopted clinically. It is especially suitable for the patients who are at high surgical risk or fulfil the technical requirements for endovascular therapy. The use of endoprostheses, however, may raise the risk of infection, as occurred in our AAA patient with Marfan syndrome who had stent-graft infection as a result of Salmonella choleraesuis.

Two bacterial infection models in tree shrew for evaluating the efficacy of antimicrobial agents

Animal models are essential for the development of new anti-infectious drugs.Although some bacterial infection models have been established in rodents,small primate models are rare.Here,we report on two bacterial infection models established in tree shrew（Tupaia belangeri chinensis）.A burnt skin infection model was induced by dropping 5×106 CFU of Staphylococcus aureus on the surface of a wound after a third degree burn.This dose of S.aureus caused persistent infection for 7 days and obvious inflammatory response was observed 4 days after inoculation.A Dacron graft infection model,2×106 CFU of Pseudomonas aeruginosa also caused persistent infection for 6 days,with large amounts of pus observed 3 days after inoculation.These models were used to evaluate the efficacy of levofloxacin（LEV） and cefoperazone（CPZ）,which reduced the viable bacteria in skin to 4log10 and 5log10 CFU/100 mg tissue,respectively.The number of bacteria in graft was significantly reduced by 4log10 CFU/mL treatment compared to the untreated group（P0.05）.These results suggest that two bacterial infection models were successfully established in tree shrew using P.aeruginosa and S.aureus.In addition,tree shrew was susceptible to P.aeruginosa and S.aureus,thus making it an ideal bacterial infection animal model for the evaluation of new antimicrobials.

Role of vector resistance and grafting infection in Huanglongbing control models

Citrus huanglongbing(HLB)is one of the most devastating diseases affecting citrus almost worldwide due to the lack of a cure.To better understand the impact of insecticide resistance and grafting infection on the spread of HLB disease,a vector-borne compartmental model is formulated to describe the transmission dynamics of HLB between citrus and Asian citrus psyllid(ACP).The basic reproduction number R0 is computed by using the next generation matrix approach,which is a threshold value of the uniform persistence and disappearance of HLB disease.By applying the sensitivity analysis of R0,we obtain some parameters with the most significant influence on the transmission dynamics of HLB.Moreover,we also obtain that grafting infection has the least influence on the transmission dynamics of HLB.Additionally,a time-dependent control model of HLB to minimize the cost of implementing control efforts and infected trees and ACPs is formulated.By using Pontryagin's Minimum Principle,we obtain the optimal integrated strategy and prove the uniqueness of optimal control solution.The simulation results illustrate that the strategy involving two time-dependent optimal controls is the most effective to suppress the spread of the disease.However,insecticide spraying is more effective measure compared with infected tree removing.

A Rapid Identification Method for Germplasm Materials Resistant to Citrus Huanglongbing Disease

[Objectives]This study was conducted to develop a rapid identification method for citrus germline materials resistant to Huanglongbing disease and lay a basis for accelerating citrus breeding for resistance to Huanglongbing and increasing the breeding efficiency.[Methods]Thirty-six citrus germplasms suspected to be resistant to citrus Huanglongbing disease were collected.The method of direct high grafting to citrus trees infected with Huanglongbing pathogen was adopted.The resistance of the test materials was identified and evaluated by field symptoms combined with quantitative PCR.It was defined as the top grafting identification method.[Results]The test materials that were grafted in spring started to germinate after one month,and three months late(June 5,2018)typical mottled yellowing on leaves was observed on KH-14 for the first time.After four months(July 5,2018)of top grafting,typical mottled yellowing occurred on 23 materials,and 11 materials showed no such symptom.After six months(September 4,2018)of top grafting,although the growth of KH-18,KH-12,KHY-4,KHY-5 and KHY-6 were normal,yellowing was observed on their leaves.Only KH-21 grew well,and showed no yellow shoots and yellowing leaves.It was identified as the material with resistance to Huanglongbing disease.Quantitative PCR tests on the above six materials showed that KH-21 was negative and other five were positive.Real-time fluorescence quantitative PCR test indicated that the average Huanglongbing bacteria amount in KH-21 was 1870.0 cell/μg DNA,and the average Huanglongbing bacteria amount in the control material was 372285.5 cell/μg DNA,indicating KH-21 was resistant to Huanglongbing bacteria.[Conclusions]The method for infecting bacteria by top grafting takes six months,can detect large amount of seedlings,and is time-saving,efficient,cost-saving and accurate.This method can quickly identify the resistance of citrus varieties to citrus Huanglongbing disease,and can be popularized and used in the identification of citrus Huanglongbing disease resistance.