Introduction: Bloodstream infection (BSI) is an important cause of morbidity and mortality in children (1). There are few descriptions of Escherichia coli (E. coli) BSI in children, particularly in Africa, yet E. coli is increasing in importance as a cause of antibiotic-resistant infection in paediatric settings. Methods: In this retrospective, descriptive study aspects of E. coli BSI epidemiology are described over a 10-year period including incidence risk, risk factors for extended spectrum β-lactamase (ESBL)- producing E. coli BSI, antibiotic susceptibility of the bacterial isolates and outcome including risk factors for severe disease. Results: There were 583 new E. coli BSI episodes among 217,483 admissions, an overall incidence risk of 2.7 events/1,000 hospital admissions. Of 455 of these E. coli BSI episodes that were analysed, 136 (29.9%) were caused by ESBL-producing isolates. Risk factors for ESBL-producing E. coli BSI included hospitalization in the 28-day period preceding E. coli BSI episodes and having an underlying chronic illness other than HIV infection at the time of the E. coli BSI. None of the E. coli isolates were resistant to carbapenems or colistin. The mortality rate was 5.9% and admission to the intensive care unit was required in 12.3% of BSI episodes. Predictors of severe disease included age less than 1 month, hospitalization in the 28-day period preceding E. coli BSI and BSI without a definable focus. Conclusions: These findings extend our understanding of E. coli BSI in a sub-Saharan African setting, provide useful information that can guide empiric treatment choices for community- and hospitalacquired BSI and help inform prevention strategies.

It is, perhaps, ironical. that while influenza was probably the first animal virus to be studied in detail there is still little known concerning its behaviour. In many ways it represents a model of difficult immunization problems. Now that so many of the most lethal and dramatic of the infectious diseases are susceptible to control attention is being focused upon the control of the next rank of disorders. This includes those conditions which cause ill-health and discomfort only to such an extent that the cost and severity of measures of prevention must be carefully weighed against the effects of the disease process itself. The solution of the technical, administrative and ethical problems of influenza control will, in addition, greatly assist the struggle against numerous other ailments.

Includes abstract. Includes bibliographical references.

Includes abstract. Includes bibliographical references.

Background: The paucibacillary nature of paediatric pulmonary tuberculosis (PTB) makes microbiological diagnosis difficult and limits the usefulness of microbiology for assessing treatment efficacy. Clinical response to treatment has thus been used by clinicians to monitor disease activity, as well as by researchers in clinical case definitions of intrathoracic TB to differentiate those with unconfirmed PTB from those with other lower respiratory tract infections (LRTIs). There is, however, limited data on the expected pattern and timing of resolution of symptoms and signs, and whether this does indeed differ between those with PTB and those without. Objectives: To longitudinally investigate clinical response to TB treatment in children treated for PTB, to compare this to the clinical course of children with other LRTIs, and to identify factors associated with persistence of symptoms and signs. Methods: This study is a secondary analysis of data collected prospectively in a TB diagnostic study from 1 February 2009 to 31 December 2018. We enrolled children ≤15 years with features suggestive of PTB. Study participants were categorized into 3 groups according to NIH consensus definitions; confirmed PTB, unconfirmed PTB and unlikely PTB. Children were followed at 1 and 3 months after enrolment. Those with confirmed or unconfirmed TB were also followed at 6 months. At enrolment and follow-up symptoms of PTB were recorded using a standardized questionnaire and physical examination was done including anthropometry and respiratory parameters. Data were analysed using STATA version 16.1. The effect of potential predictors of persistence of symptoms and signs was explored with univariable and multivariable logistic regression modelling. Results: Two thousand and nineteen children were included in this analysis, 427 (21%) with confirmed PTB, 810 (40%) with unconfirmed PTB, and 782 (39%) with unlikely PTB. Symptoms resolved rapidly in the vast majority of participants. At 1 month, 9.2% (129/1402) of all participants who had a cough and 11.1% (111/999) of those with loss of appetite at baseline reported no improvement in these symptoms. At 3 months this declined to 2.0% (24/1222) and 2.6% (23/886) respectively, with no differences between the groups. Clinical signs persisted in a greater proportion of participants. At 3 months, tachypnoea persisted in 56.7% (410/723) of participants. Abnormal auscultatory findings (including wheeze, crackles, reduced breath sounds or abnormal breath sounds) similarly persisted in almost a third of participants, with greater proportion in the confirmed group (37.1%) than unconfirmed (23.0%) and unlikely (26.2%) groups (p=0.002). Children living with HIV and those with abnormal baseline chest radiographs had greater odds of persistence of signs or symptoms (including cough, loss of appetite, abnormal auscultatory findings, or no weight improvement if underweight at baseline). No features of clinical response differentiated those with PTB from those without. Conclusion: Symptoms resolved rapidly in the majority of children investigated for PTB whilst clinical signs took longer to resolve. The timing and pattern of resolution of symptoms and signs cannot differentiate those with PTB from those without – and is thus not a suitable parameter for confirming disease classification in paediatric TB research.

CD4+ T cells and macrophages are the principal targets of HIV-1. They can be productively infected with the virus and transfer virions to contacting bystander cells. It has been suggested that soon after initial infection, free virions and virus-bearing or infected T cells and macrophages can enter the brain, triggering a cascade of inflammatory signals and recruitment of other immune cells. Chronic inflammation and increased viral antigens in the brain lead to HIV-1 associated neuropathy. Once free virions or infected cells enter the central nervous system, the first type of brain cells that they are likely to encounter are astrocytes, which extend endfeet around the blood vessels. These cells have been observed to contain virions and viral products, but their permissivity to productive infection has not been clearly demonstrated. By contrast, productive infection of resident microglia and perivascular macrophages is well established. Here, I investigate the permissivity of astrocytes to HIV-1 infection and found no evidence of infection by the free route. However, I found that astrocytes intimately contact HIV-1 infected macrophages and CD4+ T cells and, in some cases, extend filopodial membrane toward the infected cell. In astrocyte-T cell contact sites, termed synapses, virions appear to move along the astrocytic filopodia from the T cell to the astrocyte. In this case, the target cell mediated viral transfer across the intercellular gap. HIV-1-infected macrophages released virus that associated with astrocytes, remaining either on the surface of the astrocytes or within intracellular compartments. HIV-1 bound to astrocytes could be transmitted efficiently to permissive cells in trans. However, astrocyte-associated virus was sensitive to inhibitors including proteases and neutralizing antibodies, suggesting a surface-accessible compartment. This work provides insight into mechanisms of HIV-1 spread in the brain from infected CD4+ T cells and macrophages to astrocytes and their potential as virus reservoirs. I also optimized high resolution, correlative focused ion beam scanning electron microscopy technology to answer fundamental biological questions. I demonstrate the application of the technology to study skeletal muscle cell differentiation mechanisms. I combine the power of genetic mapping with structural analysis to qualitatively and quantitatively describe cellular states and functions. Using semi-automatic image processing analysis, I was able to compute high volumes of data and generate statistics that relate quantitative measurements of cellular structures to functions. The toolset developed here will be instrumental in studying cells and tissues in both research and clinical applications.

No description available.

No description available.

Emerging diseases are an increasingly important public health problem. This research investigates space-time disease surveillance for emerging infectious diseases. A system was developed in Sri Lanka monitoring clinical diagnoses in cattle, poultry and buffalo. Veterinarians submitted surveys using mobile phones and GPS. This surveillance system proved to be both feasible and acceptable and provided timely information on animal health patterns in Sri Lanka. A critical review of software and methods for space-time disease surveillance provides guidance on the selection and implementation of appropriate analytic methods for surveillance data. For the data collected in this research, a hidden Markov model is developed which estimates region-specific prevalence estimates after controlling for sentinel-level factors. The use of cluster detection methods in surveillance research is demonstrated using data from an outbreak of suspected leptospirosis in Sri Lanka in 2005-2009. / Graduate

Polymyxins have previously been described to have activity against M. tuberculosis (M. tb), but further research was abandoned due to systemic toxicity concerns to achieve the required MIC. Colistin methanesulfonate (CMS), a polymyxin, is well tolerated when inhaled directly into the lungs, resulting in high local concentrations. Reported here for the first time are the MIC and MBC data for CMS, CST and PST determined by the microtiter Alamar Blue® assay (MABA) against H37Ra and multi-drug-resistant (MDR) M. tb. Additionally determined is how the MIC of CMS would be affected by the presence of pulmonary surfactant (PS) and if any synergy with isoniazid (INH) and rifampicin (RIF) exists. The effect of CMS on the ultrastructure of M. tb was also determined. MICs for CMS, CST and PST were determined to be too high for systemic use. CMS can, however, be administered by inhalation allowing for high local concentrations with reduced systemic toxicity. The MIC for CMS was antagonised eight fold in PS. For synergy, indifference was determined for both H37Ra and MDR M. tb. Time-kill assays revealed a bactericidal killing effect when CMS was used together with INH against H37Ra M. tb while no enhanced effect of CMS with INH or RIF was observed against MDR M. tb. The resistant effects caused by rpoB and katG mutations could not be overcome. With regard to H37Ra M. tb, ultrastructure analysis suggests that the disruption of the capsule layer (CL) and cytoplasmic membrane (CM) by CMS may enhance the uptake of INH. These findings may provide insight for further investigations of CMS against M. tb. / Thesis (PhD)--University of Pretoria, 2016. / Medical Microbiology / Unrestricted