Medicine & Health

Publication Search Results

Now showing 1 - 3 of 3
  • (2023) Zillur Rahman, Kazi Mohammad
    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.

  • (2020) Khan, Mahjabeen
    Pseudomonas aeruginosa causes both contact lens and non-contact lens-related keratitis (corneal infection). This opportunistic bacterium naturally has the ability to resist the mechanism of action of many antibiotics which are used for treatment. P. aeruginosa resistance patterns and the mechanism of resistance in isolates from keratitis are not well understood. This thesis described the phenotypic and genotypic patterns of antimicrobial resistance and compared these between ocular isolates of P. aeruginosa from Australia (contact lens) and India (non-contact lens). Changes in the antimicrobial susceptibility between isolates over time were also analysed. Susceptibility to antibiotics, multipurpose disinfecting solutions and disinfectants was analysed for twenty-seven Australian isolates from contact lens-related keratitis and forty non-contact lens-related isolated from India. The whole genomes of fourteen Australian (historical and recent) and twelve Indian isolates were sequenced using Illumina® MiSeq®. Computational analysis of the genomes was performed to analyse their core and pan genomes and these were examined for the presence of acquired resistance genes, virulence genes, gene mutations, and these compared to their phenotypic resistance to antibiotics. Indian isolates possessed large pan genomes with more acquired resistance (30) genes and larger numbers of genetic variations. The Indian isolates contained clones of three sequence types ST308, ST316 and ST491, whereas Australian isolates contained only one sequence type ST233. Isolates with larger gene variations had mutations in the DNA mismatch repair system. Most multi-drug resistant Indian (non-contact lens) isolates were exoU +. Indian isolates had large accessory genes compared to Australian isolates and this increased the pan genome size of the Indian isolates. The number of core genome mutations were larger in the Indian isolates a median of 50006 (IQR=26967-50600) compared to Australian isolates a median of 26317 (IQR=25681-33780). There were differences between isolates from Australia and India with respect to their antibiotic resistance and associated genes. Indian strains had more genetic diversity and were multi-drug resistant. However, there was no evidence of substantial genetic or phenotypic changes within isolates from their respective countries.

  • (2024) Koon, William
    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.