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Recent Submissions
Test deposit 2 - 22/10/26
Devereux, T (UoM, 2026)
Test deposit 22/10
Devereux, T (UoM, 2026)
Investigation of antimicrobial resistance and its relation with mobile genetic elements among Australian equine Klebsiella isolates
Kawarizadeh, Amin (2026)
Antimicrobial resistance (AMR) is a global crisis that can threaten human and animal health. AMR can complicate the treatment and management of bacterial infections, leading to increased economic burden in veterinary settings. In addition, close contact between animals and humans may facilitate the transmission of resistant and potentially virulent bacterial strains across the animal-human interface. This study focuses on Klebsiella pneumoniae which is a Gram-negative bacterium with a great potential to acquire and spread antimicrobial resistance genes (ARGs). In this study the frequency of AMR among presumptive K. pneumoniae isolates in reproductive and non-reproductive samples from horses located in New South Wales, Australia between 2020 and 2022 was studied. Additionally, the genetic diversity and the potential role of mobile genetic elements (MGEs) in distribution and development of ARGs among these isolates were studied. The genome and AMR profile of a Raoultella terrigena isolate, which was initially misidentified as K. pneumoniae using conventional laboratory methods was thoroughly investigated. This isolate exhibited extensively drug-resistant (XDR) profile.
Clinical isolates were initially identified as presumptive K. pneumoniae in a private diagnostic laboratory based on the combination of colony morphology, biochemical and motility tests. Following transfer to the University of Melbourne, antimicrobial susceptibility testing was performed using broth microdilution method with the SensititreTM system, and the results were interpreted according to the guidelines of the Clinical & Laboratory Standards Institute (CLSI). All isolates were further characterized to assess their hypermucoviscosity phenotype, and their virulence was evaluated using a silk moth larvae infection model. Subsequently, all isolates underwent short-read sequencing using Illumina NovaSeq 6000 platform. The resulting sequencing data were used for taxonomic classification of the presumptive K. pneumoniae isolates. In addition, these sequencing data were used to identify ARGs and virulence-associated genes, and to perform capsule locus typing of the isolates. Furthermore, whole genome sequencing data were utilized for phylogenetic analysis to investigate the genetic relatedness between the isolates in this study and previously characterized strains available in public databases. Finally, a subset of multidrug-resistant (MDR) reproductive isolates was selected for long-read sequencing using Oxford Nanopore technology. These isolates were chosen based on their sequence type, ARGs profile, and plasmid content. Hybrid genome assemblies were generated by combining short- and long-read data, and the resulting assemblies were used to examine the association between ARGs and MGEs.
In this study, a total of 25,513 samples, including 23,772 reproductive and 1,741 non-reproductive samples were tested by the laboratory in NSW. From these, 120 isolates were recovered from reproductive samples, among them 117 presumptive K. pneumoniae isolates were available for further analysis. Furthermore, 24 isolates were recovered from non-reproductive isolates, among them 13 isolates were available for further analysis. Genomic analysis revealed that 14 of the reproductive isolates and one non-reproductive isolate were species other than K. pneumoniae. Antimicrobial susceptibility testing revealed that 55% of reproductive isolates and 70% of non-reproductive isolates were classified as MDR. Additionally, resistance to critically important antimicrobial, as defined by the World Health Organization, was observed, with rates among reproductive and non-reproductive isolates of 38% and 30% for ceftazidime, 52% and 50% for ceftiofur and 47% and 60% for enrofloxacin, respectively.
Among reproductive isolates from mares, over breeding season (August-December), a strong positive relationship between months and the isolation rate of MDR isolates (R2 = 0.960, p = 0.003) was observed.
Hypermucoviscosity phenotype was observed in 14% and 20% of reproductive and non-reproductive isolates, respectively. Among clinically relevant virulence loci, the most prevalent loci in reproductive and non-reproductive isolates were yersiniabactin (74% and 70%, respectively), followed by salmochelin (16% and 20%, respectively). Additionally, among reproductive isolates, a small subset of isolates carried colibactin (9%) and aerobactin (2%). No significant trend in mean virulence score over the month of breading season (R2 = 0.459, p = 0.209) was observed.
Genomic analysis revealed a high level of genetic diversity among the recovered isolates, particularly among reproductive isolates, in which 31 sequence types and 23 capsule locus types were identified. Among them, ST323 (29%) and ST145 (10%) were the most prevalent sequence types, while KL30 (42%) and KL22 (9%) were the most identified capsule locus types. Phylogenetic analysis of reproductive isolates revealed that 52 isolates belonging to eight sequence types in this study were closely related to equine isolates reported in horses from Australia and France in publicly available databases. Additionally, phylogenetic analysis of isolates belonging to ST323 demonstrated a high level of similarity to other equine isolates from Australia, as well as to a human-derived isolate reported in Australia. Among non-reproductive isolates, ST39 (30%) and KL149 (30%) were the most frequently identified sequence type and capsule locus type. Phylogenetic analysis demonstrated a substantial genetic divergence between isolates belonging to ST39 in this study and human-derived isolates of this sequence type from Australia.
Additionally, all isolates that were initially misidentified as K. pneumoniae were susceptible to all tested antimicrobials, except for one isolate recovered from a uterine lavage of a mare. Following genomic analysis, this isolate was identified as R. terrigena and exhibited an XDR profile. Phylogenetic analysis of this isolate, together with other isolates of R. terrigena available in publicly accessible databases, revealed two distinct clades, with equine isolates clustering together with other animal-derived isolates.
Among reproductive MDR K. pneumoniae isolates, the genes conferring resistance to critically important antimicrobials were blaCTX-M-15 (68%), blaCTX-M-14 (16%) and blaCMY-2 (12%), associated with resistance to 3rd generation cephalosporins, as well as qnrB1(66%) and qnrS1(20%) associated with fluoroquinolone resistance. Among non-reproductive isolates blaCTX-M-15 (30%) and blaCTX-M-14 (20%), were linked to 3rd generation cephalosporin resistance, and qnrS1(30%) and qnrB1(30%) to fluoroquinolone resistance. In R. terrigena isolate, blaCTX-M-14 associated with 3rd generation cephalosporin resistance, was identified. However, despite the presence of qnrB6, no phenotypic resistance to fluoroquinolones was observed.
Analysis of the association between ARGs and MGEs demonstrated that, among reproductive MDR K. pneumoniae isolates, most acquired resistance determinants are in association with transposons, integrons and insertion sequences and were carried on IncC and hybrid and non-hybrid variants of IncF plasmids. Furthermore, multiple chromosomal regions linked to acquired resistance genes were identified. Among these, a chromosomal copy of blaCTX-M-14 associated with IS5075, IS903 and ISEcp1 elements was identified, not previously reported in K. pneumoniae. In the R. terrigena isolate, all acquired resistance genes (n=14), including blaCTX-M-14 and qnrB6 were identified within three mobile genetic element regions carried on an IncQ1/IncU plasmid.
This study represents the largest combined genomic and phenotypic investigation of reproductive K. pneumoniae isolates from horses worldwide, as well as the largest investigation of non-reproductive K. pneumoniae isolates from horses in Australia. The findings of this study indicated a high level of AMR, virulence and genetic diversity among K. pneumoniae isolates from horses. The identified resistance genes were frequently associated with MGEs, suggesting their potential role in the dissemination of resistance determinants. Furthermore, the close genetic relatedness between some isolates from this study and human-derived isolates suggests a potential risk for interspecies transmission of this bacterium. In addition, the presence of similar lineages of K. pneumoniae among horses in Australia and France may reflect their wider dissemination. These findings underscore the importance of continuous monitoring and antimicrobial stewardship programs in veterinary settings.
Loading Characteristics and Geotechnical Behaviour of Shared Caisson Anchors in Sandy Seabeds to Support Floating Offshore Wind Turbines
Yan, Bin (2026)
Floating offshore wind development is expanding into deeper waters and larger arrays. As water depth increases, fixed-bottom foundations become progressively less technically and economically viable, making floating systems an important option for exploiting deepwater wind resources. Floating turbines are held on station by mooring lines connected to seabed anchors. In conventional wind farm layouts, the number of anchors and the associated construction and installation costs increase with array size. Shared anchor systems reduce this demand by allowing mooring lines from several turbines to terminate at a common anchor. This arrangement, however, creates a more complex loading condition. Differences in turbine motion under wind, wave and current action result in mooring line tensions with different amplitudes and phases. Their vector sum at the shared anchor traces a load path whose magnitude and direction vary with time. Such path-dependent multidirectional loading is not adequately represented by conventional anchor assessments based on monotonic loading in a single direction.
This thesis investigates the geotechnical behaviour of shared caisson anchors in sandy seabeds. The research combines analytical load characterisation, three-dimensional finite element analysis, 1g biaxial model testing and mini-CPT measurements. The programme covers the generation of resultant load paths, changes in capacity under staged multidirectional loading, and anchor behaviour under unidirectional and rotational cyclic loading. The main findings are as follows.
(1) The analytical formulation relates environmental loads on an individual floating wind turbine to the corresponding mooring line tensions and derives the resultant load path at a shared anchor by vector superposition. Environmental load direction sets the principal orientation of the path, spatial phase differences between mooring line tensions determine its shape, and the equivalent load transfer angle governs the spatial components, mean value and fluctuation amplitude of the resultant load. Rotational paths, commonly taking eccentric elliptical forms, are representative of shared anchor loading. A fixed-direction cyclic path emerges only under specific conditions involving horizontal load transfer and ideal symmetry. The formulation provides representative load inputs for the subsequent numerical and physical investigations.
(2) The finite element analyses show that prior loading creates distinct zones of passive densification, shear dilation and active loosening around the caisson. When the loading direction changes, reloading capacity depends on which of these zones provides most of the resistance. Capacity is maintained or increases by no more than 5% when reloading mainly mobilises previously densified soil. When the mobilised soil has previously undergone shear dilation or active loosening, capacity decreases by a maximum of approximately 15%. A capacity modification factor is developed to account for the combined effects of prior load magnitude, change in loading direction and initial relative density of the sand.
(3) The unidirectional cyclic tests show how the mean load ratio and cyclic amplitude ratio affect accumulated displacement and rotation, unloading stiffness and hysteretic energy dissipation. Empirical expressions are developed for the initial unloading stiffness and initial hysteretic energy dissipation. Within the present test matrix, the post-cyclic capacity ratio exhibited an amplitude-dependent transition for reloading along the preceding loading direction, with an empirical critical cyclic amplitude ratio of 0.236. Mini-CPT measurements indicate that cyclic loading densifies the soil in front of the anchor while loosening the soil at its sides and rear. Frontal densification increases reloading stiffness, whereas loosening at the sides and rear reduces overall resistance. This contrast explains why reloading stiffness can increase even as post-cyclic capacity decreases.
(4) The rotational cyclic tests show that the phase difference between two orthogonal load components controls the geometry and extent of rotation of the resultant load path, as well as the in-plane response of the anchor. Within the test range, a phase difference of 90 degrees produces the largest transverse displacement and associated rotation amplitudes. Displacement increments are not generally aligned with the instantaneous resultant load, demonstrating a non-coaxial response. For comparable amplitudes of the resultant load, rotational cycling produces greater accumulated displacement and rotation than unidirectional cycling. Mini-CPT measurements show that the changes in soil state vary with azimuth after rotational loading. Post-cyclic reloading indicates that the capacity ratio measured in the prescribed reloading direction generally increases with phase difference. A mean path rotation index is introduced to quantify path rotation, and a quantitative relationship is established between this index and the corresponding post-cyclic capacity ratio.
Together, the findings show that shared anchor performance depends not only on load magnitude but also on load path geometry and loading history. The geotechnical assessment framework developed in this thesis connects system-level resultant loading with anchor serviceability, spatial redistribution of soil state and directional variations in subsequent capacity. The framework provides a basis for selecting representative load cases and evaluating the serviceability and bearing capacity of shared anchor systems in floating offshore wind farms.
Hygienic Citizenship: Shifting Practices and Infrastructures of Cleanliness, Hygiene and Sanitation
Mi, Dongyang (2025)
Over the past decades, China has undergone unprecedented processes of urbanisation, industrialisation, and demographic expansion, within which hygiene and cleanliness have occupied a critical intersection between public health, environmental transition, and resource sustainability. By positioning hygiene and cleanliness as central analytical axes within an interdisciplinary framework and by adopting an analytical lens of everydayness, this thesis interrogates the micro-politics embedded in the entanglements of infrastructures, discourses, and mundane practices across water, sanitation, and waste.
This thesis is inspired by Amity Doolittle’s (2015, p. 515) call for methodological pluralism, seeking to explore, in the context of Changsha, China, the potential of combining mixed qualitative and ethnographic approaches to understand the complexities of infrastructural realities and the everyday politics of hygiene and cleanliness in the city. This thesis undertakes an in-depth and systematic exploration at conceptual and theoretical levels, by advancing the theorisation of hygienic citizenship as a conceptual grammar and analytical device. Moreover, the thesis critically unpacks hygienic citizenship, grounding it in the Chinese urban context. Three interrelated themes respectively focus on water (heterogeneous urban water supply modalities), waste (household waste sorting initiatives), and hygiene and cleanliness (cross-sector practices concerning water, sanitation, and waste). Through a rich empirical analysis, it reflects on the theorisation of hygienic citizenship and elucidates how hygiene and cleanliness not only materialise uneven infrastructural landscapes but also function as moral and governmental technologies through which distinctions of civility, order, and morality are inscribed onto bodies, homes, and communities. In doing so, practices and infrastructures of cleanliness and hygiene contour the uneven everyday terrains through which power asymmetries, subjectivities, and citizenship are (re)produced, enacted, and experienced in contemporary urban China.
This thesis makes an innovative and timely contribution to debates on hygiene, cleanliness, and health emerging from the Chinese context—and, more broadly, to WaSH (water, sanitation and hygiene) and waste research in human geography and urban studies—by advancing new theoretical ground that rethinks citizenship through the entanglements of hygiene, infrastructures, and everyday practices. It pluralises the theorisation of citizenship, resources, and infrastructures through an everyday lens of hygiene; advances analyses of the politics of discourse and moral–ideological constructs of subjectivities; and promotes situated, embodied, and intersectional approaches to urban experience of citizenship, highlighting the enduring forms and burden of infrastructural labour and bodies that sustain hygiene and cleanliness. The thesis offers policy pathways and a practical orientation toward more equitable and just urban governance in China, while providing comparative insights for other rapidly industrialising and urbanising cities in the Global South. In particular, it contributes to an understanding of how hygienic citizenship is entangled in crises of resources, fragmented infrastructural landscapes, and exclusionary urban governance.