http://hdl.handle.net/10397/1072 Search the Channel search http://repository.lib.polyu.edu.hk/jspui/simple-search http://hdl.handle.net/10397/5708 Title: Vancomycin intermediate-resistant Staphylococcus aureus : characterization of resistance development, detection and treatment strategies<br/><br/>Authors: Doddangoudar, Vijaya Chandranna<br/><br/>Abstract: Since the emergence of vancomycin non-susceptible Staphylococcus aureus (hVISA/VISA) efforts have been made to develop a reliable detection method, understand the mechanism of non-susceptibility development and loss, and improve the treatment of VISA infection. While several methods have been introduced for detection of hVISA/VISA, rapid and correct detection remains difficult due to their various limitations. These limitations could delay appropriate therapy. Therefore, a rapid and reliable resistance detection method is required. The genetic changes associated with development and loss of hVISA/VISA has been tracked in few strains and remains unclear. More work is required to identify important determinants associated with non-susceptibility. Identification of such changes could support development of a molecular detection method. Vancomycin remains the drug of choice for methicillin-resistant S. aureus (MRSA) treatment and with the high prevalence of MRSA in Hong Kong, it is not surprising that hVISA/VISA has been reported. VISA has been reported worldwide and determination of the level of hVISA/VISA in Hong Kong is important for formulating infection control guidelines. Additionally, resistance acquisition by MRSA against currently available antibiotics is of concern. Efforts have been made towards the development of new molecules and several new agents are in the pipeline, but such agents are expensive, have possible unknown side effects and may not be available for some time. In response to these problems, this work aimed to evaluate the spiral gradient endpoint (SGE) as a non-susceptibility detection method, further the understanding of non-susceptibility development and loss by examining genotypic and phenotypic changes, estimate hVISA/VISA prevalence in Hong Kong, and to study the effects of Traditional Chinese Medicine (TCM) herbal extracts alone and in combination with vancomycin against VISA.; SGE was found to have good reproducibility, there being excellent correlation between MICs generated by SGE and agar dilution (r² = 0.950). Tracking genotypic and phenotypic changes in both clinical and laboratory-induced VISA strains indicated the importance of mutations in vraS and graR during development and loss of non-susceptibility, in the development of stable phenotypes, and ability to reach an elevated MIC (20 mg/L) in the absence of vanA. This study has also demonstrated the role of stop codons in delaying non-susceptibility development and formation of stable phenotypes. The prevalence rate of hVISA/VISA in Hong Kong hospital was found to be 14.53% (48/330 isolates). Additionally, it was found that strains showing non-susceptible subpopulations rapidly progressed to non-susceptibility in the presence of 2 mg/L vancomycin and that SGE was effective in detecting such strains. Of the three TCM herbs investigated for antimicrobial activity, Radix scutellariae was found to be effective against VISA both alone and in combination with vancomycin at 2 g/L and 0.25 g/L respectively. In summary, SGE offers a reliable alternative for the detection of hVISA/VISA. Mutations in vraS and graR appear to be important for development of non-susceptibility. In particular the presence of stop codons in two component-regulatory systems appears to be important in non-susceptibility development and loss. The prevalence rate of vancomycin non-susceptibility in local isolates were relatively high and testing revealed additional strains with, resistant sub-populations which could rapidly progress to VISA. Antimicrobial-activity of RS indicated that this herb may have the potential to be used in treatment of MRSA and VISA infections, alone and in combination with vancomycin.<br/><br/>Description: xxxii, 376 leaves : ill. ; 30 cm.; PolyU Library Call No.: [THS] LG51 .H577P HTI 2012 Doddangoudar http://hdl.handle.net/10397/5707 Title: Involvement of CD44 during tumorigenic transformation of pre-cancerous human uroepithelial cells<br/><br/>Authors: Au, Yuen Ming<br/><br/>Abstract: Bladder cancer is a common disease in man aged over 50, making it the fourth most prevalent cancer in men. Superficial transition cell carcinoma contributes to 70% of clinical cases and is typically treated by transurethral resection (TUR) with or without Bacille Calmette-Guerin (BCG) treatment. However, effective treatment is hampered by the high cancer recurrence rate and around 30% of the patients may even progress to a high grade cancer making it the most expensive cancer to be treated. This study proposes that the high recurrence rate may be due to the presence of sensitized cell - urothelial cells that accumulated certain degree of genetic alternations but phenotypically similar to normal cells. Therefore, they can escape from the surgery removal and stem future tumor formations, i.e. cancer recurrence. However, little is known about the existence and properties of the sensitized cell. Identification and characterization this cell type will be crucial to develop means for recurrent prediction, monitoring and prevention. Information presented by this study is not only important for understanding the cancer development process but also useful for prediction of bladder cancer recurrences. An in vitro tumorigenic model involving two human uroepithelial cell lines at two different statuses, namely HUC-PC (pre-cancerous) and HUC-1 (normal) was used to study the transformation process. HUC-PC mimics the sensitized cell remained in bladder lining after TUR and tumorigenic transformation was triggered by the exposure of bladder carcinogen, 4-aminobiphenyl (ABP). Due to the fact that HUC-PC is sensitized to ABP and will transform to cancer state while HUC-1 will not, we can then target different molecules for their involvement in cancer development by comparing the molecular changes between two statuses of cell line.; The success of transformation process was confirmed by functional assays and cancer markers. In this study, HUC-PC was treated with tobacco carcinogen ABP at concentrations 200μM for 24hr. After 6 weeks of incubation, the tumorigenicity of cells was evaluated via functional assays. The results showed that the transformed HUC-PC displayed neoplastic transformation phenotype, as marked by their induced proliferation rate and invasion ability. In addition, bladder markers, survivin and telomerase, were also found highly expressed in the transformed HUC-PC, which further confirmed the success of the transformation process. During transformation, our target CD44 and its partner HA were quantified for evaluating their involvement in the process. Flow cytometry and RT-qPCR analyses showed that the transformed HUC-PC expressed increased levels of CD44 in the first week after exposure to 4-ABP. The elevated level of CD44 mRNA expression was great contributed by the CD44s instead of CD44v6 (exon v6 containing CD44 isoforms). In parallel, an increase in HA was found after the CD44 induction and maintained at a high level throughout the transformation process. Based on the above findings, we demonstrated that in vitro ABP exposure could neoplastically transform the pre-cancerous HUC-PC and suggested CD44 is involved in the initiation step of cancer development, possibly by interacting with HA.<br/><br/>Description: xvi, 152 leaves : ill. (chiefly col.) ; 30 cm.; PolyU Library Call No.: [THS] LG51 .H577M HTI 2012 Au http://hdl.handle.net/10397/5706 Title: Quantitative ultrasonic evaluation of bone growth in a rabbit tibial distraction model by comparing computed radiography and micro-computed tomography<br/><br/>Authors: Luk, Hon Kit<br/><br/>Abstract: Distraction osteogenesis (DO) has become the most popular orthopaedic treatment for correcting human limb discrepancies and deformities. However, a high post-operational complication rate has been reported during DO treatment. In these cases, delayed union or non-union of the bone callus is commonly due to the distraction protocol with the improper distraction rate or rhythm. Undesirable treatment outcomes can end up with the further remedial surgery such as the internal fixation of the distraction site. This may significantly delay the rehabilitation of DO patients and affect their quality of life. Thus, a closely monitoring of the bone callus growth condition during DO treatment, especially at the early treatment stage, is paramount important for informing the treatment progress and the prognosis of the treatment outcome. Optimization of the clinical distraction protocol or remedial measure can then be initiated at the early DO stage to alleviate the undesirable outcomes. Plain-film radiography is the conventional imaging modality to assess the bone callus growth during DO treatment. However, the detection of the subtle callus bone density changes during distraction period is a challenge to the plain-film radiography because of its sigmoid-shaped detector response. Computed radiography (CR) can provide a more linear detector response with the digital processing capability; however, its efficacy to assess the new bone formation at the early DO stage had not been well-studied yet. Previous in-vitro studies found that acoustic parameters could reflect the bone density, micro-structural and biomechanical properties of trabeculae. On the other hand, clinical studies had shown that ultrasonography could detect the new bone formation during fracture healing. The results suggest that combining ultrasonography and acoustic parameters measurement has the potential to determine the callus growth condition in a qualitative and quantitative manner, respectively during DO treatment. In the present study, CR, ultrasound (US) and micro-computed tomography (uCT) were applied to an animal DO model. A comparative evaluation of the efficacies in using CR and the combined US approach as the callus monitoring tool during DO treatment was conducted. The objectives of this study were: (i) to temporally and regionally compare among CR images, 2D and 3D US images acquired during DO treatment; (ii) to determine the reliability of the regional acoustic parameters measurement and to study the temporal callus growth changes by regional radiographic and acoustic parameters measured during DO treatment; (iii) to predict the bone density, micro-structural and biomechanical properties of the consolidated bone callus by radiographic and acoustic parameters measured during DO treatment. Seven male New Zealand white rabbits were operated with the tibial DO surgical procedures. After 7-day latency, right tibiae were distracted at 1.0 mm/day, up to 12.0 mm, and followed with a four-week consolidation. Callus growth condition was evaluated by CR and US at a 3-day and weekly interval during distraction and consolidation periods, respectively. Besides the images taken by CR and US during the treatment, the calibrated aluminum step-wedge thickness (AlTh) , as a surrogate measurement of the bone mineral density (BMD), and acoustic parameters including speed of sound (SoScal), integrated reflection coefficient (IRC), integrated backscattering (IBScorr) and integrated attenuation (IA) were acquired from CR and US images, respectively. These parameters were measured at the distal, middle and proximal regions of the callus. At the end of the four-week consolidation, distracted tibiae were dissected and scanned by uCT for evaluating the bone density, micro-structural and biomechanical properties of the consolidated callus.; Findings showed that the callus density changes were not demonstrated by CR during distraction period. However, the callus echogenicity shown in the US images increased regionally and temporally at the same period. 2D US showed that echogenic foci in the distraction gap initially occurred as the speckled appearance. Later, they developed as an echogenic boundary at the anterior superficial surface of the distal and proximal callus regions but not at the middle one. 3D US even exhibited an undulating pattern in the callus echogenicity across the distracting bone callus. Such observation was further supported by the similar patterns of SoScal, IRC and IA measured across the distraction gap during distraction period. These findings indicated that the continuous callus mineralization and its differential pattern had been initiated during distraction period and could be detected by US, but not by CR. During consolidation period, however, only a hyper-echogenic line or surface could be observed at all three callus regions by 2D and 3D US, respectively. Instead, CR could provide the important radiographic characteristics of the bone callus growth such as the callus mineralization, bridging and corticalization at the late DO stage. Quantitatively, regional AlTh did not demonstrate significant trend changes (p>0.05) at the early DO stage. Instead, there were significant trend increases of regional SoScal, IRC and IA at this stage (p<0.05), and the measurement of these regional parameters were reliable (most ICC values> 0.7). This indicated that acoustic parameters were more sensitive to detect the growth changes of the distracting callus than AlTh. They might further help in studying the effectiveness of the pharmaceutical and biophysical intervention on the bone healing at the early DO stage. Furthermore, these acoustic parameters measured at this stage could significantly contribute up to 65%, 66% and 43% variances of the bone density, micro-structural and biomechanical properties of the consolidated callus, respectively (p<0.05). However, these consolidated callus properties were weakly predicted by AlTh measured at the same stage (r²<0.09, p>0.05). This implied that the measurement of the callus acoustic parameters measured at the early DO stage could provide the prognosis of the treatment outcome, which was evident in their predictions to the uCT-derived consolidated callus properties. But this was not the case in AlTh measured during the same period. The predictive values of the acoustic parameters measured at the late DO stage showed relatively weak predictions to the consolidated callus properties (adjusted R²<0.42, p<0.05). At the same period, AlTh not just showed the significant increases at all three callus regions (p<0.05), but their values measured at the end of the consolidation period also predicted strongly to the bone density (r²>0.70, p<0.01), micro-structural (r²>0.70, p<0.01) and biomechanical properties (r²>0.75, p<0.01) of the consolidated callus. In summary, the present study was the first imaging study to compare CR and US in evaluating the bone callus growth in a rabbit tibial distraction model. Results indicated that the combined US approach was not just sensitive to the early callus growth changes, but it also provided the early prediction of the consolidated callus properties. This might inform clinicians about the appropriateness of the patient's distraction protocol. Such US approach could act as an effective qualitative and quantitative assessment of the early callus growth condition. Also, it could be practiced frequently to reduce the use of X-ray at the early DO stage. Nevertheless, clinical study should be contemplated so as to verify the potential value of measuring the callus acoustic properties at the early DO stage as evident in the present study.<br/><br/>Description: xxi, 218 p. : ill. (some col.) ; 30 cm.; PolyU Library Call No.: [THS] LG51 .H577M HTI 2012 Luk http://hdl.handle.net/10397/5705 Title: Could clinical ultrasound improve the fitting of spinal orthosis for patients with AIS?<br/><br/>Authors: Li, Meng<br/><br/>Abstract: Adolescent idiopathic scoliosis (AIS) is described as a structural, lateral, rotated deformity of the spine that arises in children during puberty with unknown causes. Spinal orthosis is generally applied onto the patients with AIS to mechanically support the scoliotic spine and prevent further deterioration. The outcome of orthotic intervention for AIS is considered being associated with accurate orthosis fitting and patients' treatment compliance. In current practice, pre-brace X-ray images are used as references for clinicians to design orthotic intervention, however, the optimum location of pressure pads for maximum deformity control may not be determined because the referred X-ray is not a real-time presentation of the spinal curvature (once forces are applied, the spinal deformities could change three dimensionally). The most commonly used method to assess scoliotic curvature in radiography is the Cobb's method. Besides, spinous process angle (SPA) was proposed to be an alternative method to assess spinal curvature. A correlation study was conducted using X-ray images from 43 patients with AIS, including 37 major curves at the pre-brace stage, and 21 major curves at the in-brace stage. A new method was developed to study the correlation between Cobb's angle and SPA. Intra-rater and Inter-rater reliabilities of this method were found to be high (ICCs>0.9, p<0.05). The results of this study indicated that there was a significant correlation (r=0.80 for the pre-brace stage and r=0.87 for the in-brace stage, p<0.05) between Cobb's angle and SPA for patients with AIS. The findings contribute strong evidence to support this new method for assessing scoliosis.; With the advancement of clinical ultrasound, tracing spinal processes along a scoliotic spine becomes possible, which means SPA can be obtained from ultrasound images. This study aimed to apply 3-dimensional ultrasound (3-D US) technique to monitor the fitting method of spinal orthoses for patients with AIS. By means of ultrasound assessments, SPA could be examined and used as the parameter to evaluate the optimal location for pressure pad. Angle calculation software was developed to measure SPA in this study. Ultrasound-assisted fitting method was conducted on 21 patients as a test group, while conventional fitting method was conducted on 60 patients as a control group. Within these 21 patients in test group, there were 13 patients who were required to adjust the location of pressure pad to achieve better curvature correction. The mean immediate correction (Cobb's angle measured from radiographs) of test group (mean thoracic curve correction: 11.5°, mean lumbar curve correction: 11.0°) was found significantly higher than that of control group (mean thoracic curve correction: 5.6°, mean lumbar curve correction: 6.0°) for both thoracic and lumbar curvature (p<0.005), which indicated that ultrasound-assisted fitting method of spinal orthosis was effective and helpful to 61.9% patients in this study. According to these findings, 3-D US can be further developed to assess spinal curvature especially for determining the optimal location for pressure pad. In summary, 3-D US is proposed to be a non-invasive, effective and real-time approach to assess scoliotic spine in routine clinical visit and helpful to improve the effectiveness of orthotic treatment for scoliosis.<br/><br/>Description: xiv, 116 leaves : ill. (some col.) ; 30 cm.; PolyU Library Call No.: [THS] LG51 .H577M HTI 2012 Li