Effects of chelators (desferal, deferiprone & deferaairox) on the growth of klebsiella and aeromonas isolated from transfusion dependent thalassemia patients

Poster Presentation (Doctor’s Session)Infection is among the leading causes of death for thalassemia major patients. The known predisposing factors of infection include prior splenectomy, iron overload and use of iron chelator such as desferal (desferrioxamine). While encapsulated organisms frequently found in splenectomized patients were readily controlled by prophylactic vaccination and vigilant antibiotic treatment, ferrophilic organisms such as Yersinia and Klebsiella remains common among Thalassemic patients. The inductive iron overloaded environment favours the growth of these organisms but their growth is also affected by the environment temperature. For example, Yersinia infection is more prevalent in temperate regions and Klebsiella infection is commonly found in subtropical areas. Furthermore, the use of iron chelator in the form of desferal further aggravates the risk of Yersinia infection. It is because the iron membrane transport protein siderophore found in desferal can be adopted by the bacteria for iron acquisition. However, oral chelators such as deferiprone do not enhance growth of Yersinia in vitro or in vivo. In order to find out whether such observation can be extended to Klebsiella and Aeromona infection, in vitro culture assay using Klebsiella pneumoniae and Aeromonas hydrophila obtained directly from our transfusion dependent thalassaemic patients were performed. The growth rates of the bacteria under iron rich, iron poor with or without different chelators were assessed. The growth rates were analyzed by both: (1) optic density of bacterial broth; and (2) colony count by bacterial agar plate. We found that the growth of Klebsiella was marginally enhanced by desferal in vitro when compared to Yersinia. Such unfavourable effect was not found in either deferiprone or deferasirox in vitro. On the other hand, the growth of Aeromonas was not affected by the presence of any of the 3 chelators. Therefore, we suggested that factors other than desferal may account for the increase prevalence of Klebsiella and Aeromonas infection among Asian thalassemic patients. It also suggests that oral chelators are safe for thalassemic patients during febrile illness. Unlike desferal, withholding iron chelator during infectious period may not be mandatory. But care has to be exercised especially for patients on deferiprone, since neutropenia has to be ruled out during febrile illness. This project was supported by the Children's Thalassaemia Foundationspublished_or_final_versio

Automatic detection and classification of nasopharyngeal carcinoma on PET/CT with support vector machine

Purpose: Positron emission tomography/computed tomography (PET/CT) has established values for imaging of head and neck cancers, including the nasopharyngeal carcinoma (NPC), utilizing both morphologic and functional information. In this paper, we introduce a computerized system for automatic detection of NPC, targeting both the primary tumor and regional nodal metastasis, on PET/CT. Methods: Candidate lesions were extracted based on the features from both PET and CT images and a priori knowledge of anatomical features and subsequently classified by a support vector machine algorithm. The system was validated with 25 PET/CT examinations from 10 patients suffering from NPC. Lesions manually contoured by experienced radiologists were used as the gold standard. Results: Results showed that the system successfully identified all 53 hypermetabolic lesions larger than 1 cm in size and excluded normal physiological uptake in brown fat, muscles, bone marrow, brain, and salivary glands. Conclusion: The system combined both imaging features and a priori clinical knowledge for classification between pathological and physiological uptake. Preliminary results showed that the system was highly accurate and promising for adoption in clinical use. © The Author(s) 2011.published_or_final_versionSpringer Open Choice, 25 May 201

Susceptibility weighted imaging (SWI) for the assessment of iron loading in the brain of beta-thalassemia major patients

postprintThe 2010 Joint Annual Meeting of ISMRM-ESMRMB, Stockholm, Sweden, 1-7 May 2010

Genetic algorithm supported by graphical processing unit improves the exploration of effective connectivity in functional brain imaging

published_or_final_versio

Distinctive patterns of macrolide-lincosamide-streptogramin resistance phenotypes and determinants amongst Staphylococcus aureus populations in Hong Kong

postprin

Streptococcus pneumonia serotype 19A bacteremia in a child fully immunized with 10-valent pneumococcal conjugate vaccine

postprin

Characterization of white matter reorganization in neonatal hypoxic-ischemic cerebral injury using diffusion tensor imaging

Animal Models of Ischemia: Characterization - Poster presentationThis study employs in vivo diffusion tensor imaging (DTI) to understand the late changes in white matter (WM) injury and reorganization in the rat brain upon neonatal hypoxic-ischemic cerebral injury. In particular, detailed inspection of the color-encoded fractional anisotropy (FA) map of the principal eigenvector was performed to compare the orientations of the high FA fibers at the perilesional areas with the WM microstructures in the contralateral hemisphere. In addition to the differences in DTI parameters in the microstructures between both hemispheres, results showed that the perilesional areas had similar fiber orientations as the contralateral external capsule in the anterior section of the brain, and as the internal capsule and the fimbria of hippocampus in the posterior section. We demonstrated that DTI can detect the microstructure and orientations of WM fiber changes at the perilesional areas in vivo, and can be used for non-invasive evaluation of HI brain injuries and reorganization.published_or_final_versionThe 17th Scientific Meeting & Exhibition of the International Society of Magnetic Resonance in Medicine (ISMRM), Honolulu, HI., 18-24 April 2009. In Proceedings of ISMRM 17th Scientific Meeting & Exhibition, 2009, p. 327

The colonization pattern by resistant microorganisms in an adult intensive care unit (ICU)

published_or_final_versio

Population-based hospitalization incidence of respiratory viruses in community-acquired pneumonia in children younger than 5 years of age

published_or_final_versio