Medicine & Health

Publication Search Results

Now showing 1 - 3 of 3
  • (2023) Zillur Rahman, Kazi Mohammad
    Thesis
    Current healthcare infection surveillance rarely monitors the distribution of antimicrobial resistance (AMR) in bacteria beyond clinical settings in Australia and overseas. This results in a significant gap in our ability to fully understand and manage the spread of AMR in the general community. This thesis explores whether wastewater-based monitoring could reveal geospatial-temporal and demographic trends of antibiotic-resistant bacteria in the urban area of Greater Sydney, Australia. Untreated wastewater from 25 wastewater treatment plants sampled between 2017 and 2019 consistently contained extended-spectrum β-lactamases-producing Enterobacteriaceae (ESBL-E) isolates, suggesting its endemicity in the community. Carbapenem-resistant Enterobacteriaceae (CRE), vancomycin-resistant enterococci (VRE), and methicillin-resistant Staphylococcus aureus (MRSA) isolates were occasionally detected. Demographic and healthcare infection-related factors correlated with the ESBL-E load, and demographic variables influenced the VRE load. In contrast, the healthcare infection-related factor mainly drove the CRE load. These findings demonstrate the potential of wastewater-based surveillance to understand the factors driving AMR distribution in the community. The subsequent thesis work covers the genomic characterisation of selected ESBL-E and CRE wastewater isolates to reveal their nature, origin, and underlying resistance mechanisms. Phylogenetic analysis showed that Escherichia coli isolates were related to high-risk human-associated pandemic clones and non-human-associated clones. The Klebsiella pneumoniae and K. variicola isolates were related to globally disseminated and emerging human-associated clones, and some were detected for the first time in Australia. Genomic analysis also indicated novel resistance mechanisms against nitrofurantoin in E. coli, and against piperacillin/tazobactam and ticarcillin/clavulanic acid in Klebsiella isolates. The virulence gene content indicated that some E. coli and Klebsiella isolates were likely associated with infections, while the asymptomatic carriage was suggested for other isolates. These results demonstrate a clear potential for wastewater-based surveillance to monitor the emergence and dissemination of resistance in non-clinical isolates, and in particular, isolates from the community and non-human sources. The findings of this study can complement healthcare infection surveillance to inform management strategies to mitigate the emergence and dissemination of AMR and important human pathogens in the general community.

  • (2023) Paul, Kishor Kumar
    Thesis
    The transmission of dengue fever is already being impacted by the changing climate. This phenomenon poses a considerable public health challenge for countries like Bangladesh, where regular seasonal outbreaks of dengue fever are already prevalent. This thesis aims to investigate how changing climate will impact long-term dengue epidemiology in Bangladesh as a whole and more specifically in Dhaka, the capital city of the country over the 21st Century. Several statistical models have been developed to estimate the short-term risk of dengue outbreaks as a function of climate variables but the underlying causal relationships that contribute to dengue transmission and the observed patterns of dengue epidemiology are not accounted for in these models. Initially, we determined the suitability of using climate projections for 21st Century from Global Climate Models (GCM) to assess the impact of changing climate on future dengue risk in Bangladesh setting. We then used the GCM output to assess the impact of changing climate on one aspect of dengue transmission by calculating the change in vectorial capacity (VC) of Aedes aegypti mosquitoes at a seasonal level for all regions in Bangladesh under two future climate change scenarios. The analysis indicates that the annual VC in all divisions of Bangladesh is expected to consistently exceed the threshold for dengue transmission throughout the 21st Century, regardless of the climate change scenarios considered. However, during the latter half of the century, there is a projected decline in the annual VC compared to the period between 1986 and 2005. Despite this, monthly VC variations reveal that the winter/dry season could see an increase in VC, potentially leading to a longer dengue season with outbreaks occurring year-round. The application of the VC calculation is limited by the fact that it only accounts for temperature and does not consider the impact of other climate variables such as rainfall and humidity, as well as the role of host immunity. To incorporate these factors, we then developed a mechanistic dengue transmission model that considers the influence of temperature, rainfall, and humidity on the transmission of two different dengue serotypes among human hosts and mosquito vectors. We calibrated and validated the model against observed dengue epidemiology data from Dhaka for 1995-2014 using observed climate data as input. We then used GCM output for two future climate change scenarios to simulate the model for two future periods (2030-2049 and 2080-2099) to assess the potential changes in dengue epidemiology in Dhaka. When utilizing observed climate data and climate projections from GCMs specific to Dhaka, our mechanistic model reasonably reproduced the observed dengue epidemiology in Dhaka between 1995 and 2014 in terms of the recurring annual dengue outbreaks, the seasonal pattern of transmission, and the increase in seroprevalence. Simulations for 2030-2049 indicate that dengue transmission is likely to increase regardless of the combination of initial seroprevalence, GCM, and climate change scenario, when compared to the baseline period of 1995-2014. However, for the period 2080-2099, the projected changes in dengue transmission vary, with some combinations of initial seroprevalence, GCM, and climate change scenario predicting a slight increase and others indicating a decrease. The simulations also suggest the seasonal pattern of dengue infections is likely to change in future, with more pronounced change projected for the 2080-2099 period, resulting in a lengthening of the dengue season. The primary contribution of this thesis is to present a modelling framework that considers the anticipated changes in the future climate and immunological factors to project the long-term risk of dengue epidemics. The model is flexible enough to be adapted to other settings and other pathogens transmitted by the same mosquito vector.

  • (2024) Koon, William
    Thesis
    Coastal areas including beaches, rock platforms, tidal bodies such as bays and harbours, and the open ocean itself, hold significant economic, social, and cultural value for many communities. While often associated with recreation, the coast also poses risks due to environmental hazards such as waves and dangerous currents. The interplay of these physical hazards with human and social factors creates a complex, ever-changing risk profile. In many communities, the majority of drowning deaths occur in coastal areas, resulting in thousands of lives lost each year. In Australia, approximately 40% of all drowning deaths occur at coastal sites, 2,303 between 2002 and 2022, and the prevention of these events has long been a social and civic priority. This thesis uses a mixed-methods, multi-disciplinary approach to expand the evidence base for the prevention of coastal drowning by presenting a series of studies that identify and subsequently address gaps in coastal drowning prevention science by advancing methods, thinking, and understanding of the issue to inform prevention efforts and ultimately, help keep people safe. In Chapter 1, I present an overview of drowning, coastal safety, the complex nature of risk in the coastal environment, and the structure and aims of the thesis guided by the Public Health Approach to Injury Prevention. Chapter 2 is a comprehensive scoping review of coastal drowning literature characterising the field by mapping 146 studies dating back to 1963. Chapter 2 serves as the foundation for the thesis as it identifies several gaps in the literature that subsequent chapters aimed to address, broadly grouped into a collection of epidemiology studies and prevention program focused studies. Chapter 3 is an epidemiological review of coastal drowning in Australia which, for the first time, comprehensively incorporates revised risk measurements based on exposure and a trend analysis on a national scale, showing drowning rates have not changed in 17 years. In Chapter 4, I present a comprehensive epidemiological analysis of all drowning deaths from my home state of California. This research guided a nascent multisectoral drowning prevention coalition and underpinned the recently released California Water Safety Strategy, the first such state-level strategy in the United States. This work represents one of the major impacts from my time as a PhD student as I was able to participate in and learn from the well-developed drowning prevention and coastal safety sectors in Australia and transfer some of that learning to a Californian context. Chapter 5 evaluates the relationship between tidal variables and risk of drowning on surf beaches. This study shows lower tidal water levels and time periods closer to low tide were associated with increased likelihood of fatal drowning, while tidal phase (rising vs falling), tide range, and the rate of change of falling or rising water levels were not – contrary to prevailing understanding by lifeguards. Chapter 6 examines pre-COVID-19 coastal fatalities of international visitors, establishing a risk profile distinct from residents. This study explores the tourism industry’s role in coastal safety, which is particularly important as tourism evolves and grows in the post COVID-19 era. In Chapter 7, I describe the co-design process of a high school beach safety program with ocean lifeguards and high school (year 7) students, challenging traditional educational approaches to beach safety education programs. Chapter 8 is a three-part, mixed-methods evaluation of a novel program that teaches surfers basic ocean rescue techniques and cardiopulmonary resuscitation (CPR). We found these programs improve skills and knowledge around safe rescue and further endorse the role surfers play as bystander rescuers, often in locations without lifeguards. Chapter 9 synthesizes the findings and recommendations from the thesis. This closing chapter includes a reflection on my personal learning from the thesis process and discusses implications of for the coastal safety field and future research.